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Immunity and Immunology

IMMUNITY AND IMMUNOLOGY

CONCEPT

Immunity is the condition of being able to resist a specific disease, particularly through means that prevent the growth and development of disease-carrying organisms or counteract their effects. It is regulated by the immune system, a network of organs, glands, and tissues that protects the body from foreign substances. Immunology is the study of the immune system, immunity, and immune responses. Progress in immunology over the past two centuries has made inoculationthe prevention of a disease by the introduction to the body, in small quantities, of the virus or other microorganism that causes the diseasewidely accepted and practiced. Despite such progress, however, some diseases evade human efforts to counteract them through medicine or other forms of treatment. This is particularly the case with a disease in which the immune system shuts down entirely: a condition known as acquired immunodeficiency syndrome, or AIDS.

HOW IT WORKS

Immunity and the Immune System

The functioning of the immune system is considered in a separate essay, along with the means by which that system responds to foreign invasion. Also included in that essay is a discussion of allergies, which arise when the body responds to ordinary substances as though they were pathogens, or disease-carrying parasites. The body cannot know in advance what a pathogen will look like and how to fight it, so it creates millions and millions of different lymphocytes, a type of white blood cell. The principal types of lymphocyte are B cells and T cells. These cells recognize random antigens, or substances capable of requiring an immune response.

Certain researchers believe that while some B cells and T cells are directed toward fighting an infection, others remain in the bloodstream for months or even years, primed to respond to another invasion of the body. Such "memory" cells may be the basis for immunities that allow humans to survive such plagues as the Black Death of 1347-1351 (see Infectious Diseases). Other immunologists, however, maintain that trace amounts of a pathogen persist in the body and that their continued presence keeps the immune response strong over time.

Immunology

Immunology is the study of how the body responds to foreign substances and fights off infection and other disease-causing agents. Immunologists are concerned with the parts of the body that participate in this response, and this investigation takes them beyond looking merely at tissues and organs to studying specific types of cells or even molecules.

From ancient times, humans have recognized that some people survive epidemics, when the majority are dying. About 1,500 years ago in India, physicians even practiced a form of inoculation, as we discuss later. The modern science of immunology, however, had its beginnings only in 1798, when the English physician Edward Jenner (1749-1823) published a paper in which he maintained that people could be protected from the deadly disease smallpox by the prick of a needle dipped in the pus from a cowpox boil. (Cowpox is a related, less-lethal disease that, as its name suggests, primarily affects cattle.)

Later, the great French biologist and chemist Louis Pasteur (1822-1895) theorized that inoculation protects people against disease by exposing them to a version of the pathogen that is harmless enough not to kill them but sufficiently like the disease-causing organism that the immune system learns to fight it. Modern vaccines against such diseases as measles, polio, and chicken pox are based on this principle.

HUMORAL AND CELLULAR IMMUNITY.

In the late nineteenth century, a scientific debate raged between the German physician Paul Ehrlich (1854-1915) and the Russian zoologist Élie Metchnikoff (1845-1916) concerning the means by which the body protects against diseases. Ehrlich and his followers maintained that proteins in the blood, called antibodies, eliminate pathogens by sticking to them. This phenomenon and the theory surrounding it became known as humoral immunity. Metchnikoff and his students, on the other hand, had noted that certain white blood cells could swallow and digest foreign materials. This cellular immunity, they claimed, was the real way that the body fights infection. In fact, as modern immunologists have shown, both the humoral and cellular responses identified by Ehrlich and Metchnikoff, respectively, play a role in fighting disease.

REAL-LIFE APPLICATIONS

Inoculation and Vaccines

Inoculation is the prevention of a disease by the introduction to the body, in small quantities, of the virus or other microorganism that causes that particular ailment. It is a brilliant idea, yet one that seems to go against common sense. For that reason, it was a long time in coming: not until the time of Jenner, in about 1800, did the concept of inoculation become widely accepted in the West. Nonetheless, it had been applied more than 13 centuries earlier in India.

In the period between about 500 b.c. and a.d. 500, Hindu physicians made extraordinary strides in a number of areas, pioneering such techniques as plastic surgery and the use of tourniquets to stop bleeding. Most impressive of all was their method of treating smallpox, which remained one of the world's most deadly diseases until its eradication in the late 1970s. Indian physicians apparently took pus or scabs from the sores of a mildly infected patient and rubbed the material into a small cut made in the skin of a healthy person. The Indians' method was risky, and there was always a chance that the patient would become deathly ill, but the idea survived and gradually made its way west over the ensuing centuries.

SMALLPOX VACCINATION.

Smallpox, or variola, is carried by a virus that causes the victim's body to break out in erupting, pus-filled sores. Eventually, these sores dry up, leaving behind scars that may alter the appearance of the victim permanently, depending on the intensity of the disease. Such was the case with Lady Mary Wortley Montagu (1689-1762), a celebrated English writer and noblewoman. Known for her passionate relationships, romantic and otherwise, Lady Montagu had been scarred from youth by smallpox, and no doubt this experience gave her heightened concern for the victims of the disease. While she was in Turkey with her husband, Edward, an ambassador, she became aware of an inoculation method, probably based on the Hindu practice of many centuries before, used by local women. Lady Montagu arranged for her three-year-old son to be inoculated against smallpox in 1717, and after returning home, initiated smallpox inoculations in England.

Nonetheless, the problem remained that the inoculated person contracted a serious case of the disease and died, at least some of the time. More than 80 years later, in 1796, during a smallpox epidemic, Jenner decided to test a piece of folk wisdom to the effect that anyone who contracted cowpox became immune to human smallpox. He took cowpox fluid from the sores of a milkmaid named Sarah Nelmes and rubbed it into cuts on the arm of an eight-year-old boy, James Phipps, who promptly came down with a mild case of cowpox. Soon, however, James recovered, and six weeks later, when Jenner injected him with samples of the smallpox virus, the boy was unaffected.

Jenner, who published his findings after conducting additional tests, coined a new term for the type of inoculation he had used: vaccination, from the Latin word for cowpox, vaccinia. (The latter term comes from the Latin vacca, or "cow," the source of such terms as the French vache. ) With the success of his vaccine, Jenner was awarded a sum of money to continue his work, and he soon oversaw the vaccination of thousands of English citizens, including the royal family. The practice spread to Germany and Russia and then to the United States. In Lady Montagu's time, the American clergyman Cotton Mather (1663-1728) had been an advocate of vaccination, and now President Thomas Jefferson (1743-1826) became an ardent proponent of Jenner's methods.

RABIES AND POLIO INOCULATION.

The next advancement in the study of vaccines came almost 100 years after Jenner's discovery. In 1885 Pasteur saved the life of Joseph Meister, a nine-year-old boy who had been attacked by a rabid dog, by using a series of experimental rabies vaccinations. Pasteur's rabies vaccine, the first human vaccine created in a laboratory, was made from a version of the live virus that had been weakened by drying it over potash (sodium carbonateburnt wood ashes).

Exactly 70 years later, the American microbiologist Jonas Salk (1914-1995) created a vaccine for poliomyelitis (more commonly known as polio), in which the skeletal muscles waste away and paralysis and often permanent disability and deformity ensue. Although polio had been known for ages, the first half of the twentieth century had seen an enormous epidemic in the United States.

The most famous victim of this scourge was the future president Franklin D. Roosevelt (1882-1945), who contracted it while on vacation in 1921. Throughout the 1930s and 1940s, polio remained a threat, especially to children; at the peak of the epidemic, in 1952, it killed some 3,000 Americans in one year, while 58,000 new cases were reported. At the same time, Salk was working on his vaccine, which finally was declared safe after massive testing on school-children. In 1961 an oral polio vaccine developed by the Polish-born American virologist Albert Sabin (1906-1993) was licensed in the United States. Whereas the Salk vaccine contained the killed versions of the three types of poliovirus that had been identified in the 1940s, the Sabin vaccine used weakened live poliovirus. Because it was taken by mouth, the Sabin vaccine proved more convenient and less expensive to administer than the Salk vaccine, and it soon overtook the latter in popularity. By the early 1990s health organizations reported that polio was close to extinction in the Western Hemisphere.

TRIUMPHS AND CONTINUING CHALLENGES.

Thanks to these and other vaccines, many life-threatening infectious diseases have been forced into retreat. In the United States, children starting kindergarten typically immunized against polio, diphtheria, tetanus, measles, and several other diseases. Other vaccinations are used only by people who are at risk of contracting a disease, are exposed to a disease, or are traveling to an area (usually in the Third World) where particular diseases are common. Such vaccinations include those for influenza, yellow fever, typhoid, cholera, and hepatitis A.

Internationally, 80% of the world's children had been inoculated as of 1990 for six of the primary infectious diseases: polio, whooping cough, measles, tetanus, diphtheria, and tuberculosis. Smallpox was no longer on the list, because efforts against it had proved overwhelmingly successful. (See Infectious Diseases for more on the threat, or nonthreat, of smallpox as a form of biological warfare.) Despite these successes, however, each year more than two million children who have not received any vaccinations die of infectious diseases. Even polio has continued to be a threat in some parts of the world: as many as 120,000 cases are reported around the world each year, most in developing regions. And as if the threat from age-old diseases were not enough, in the last quarter of the twentieth century a new killer entered the fray: AIDS.

AIDS

A viral disease that is almost invariably fatal, AIDS destroys the immune systems of its victims, leaving them vulnerable to a variety of illnesses. No cure has been found and no vaccine ever developed. The virus that causes AIDS has proved to be one of the most elusive pathogens in history, and so far the only effective way not to contract the disease is to avoid sharing bodily fluid with anyone who has it. This means not having sex without condoms (and, to be on the truly safe side, not having sex outside a committed, fully monogamous relationship) and not engaging in intravenous drug use. But there are some people who have contracted the AIDS virus through no actions or fault of their own: people who have received it in blood transfusions or, even worse, babies whose AIDS-infected mothers have passed the disease on to them.

Within two to four weeks of being infected with the virus that causes AIDS (HIV, human immunodeficiency virus), a patient will experience what at first seems like flu: high fever, headaches, sore throat, muscle and joint pains, nausea and vomiting, open ulcers in the mouth, swollen lymph nodes, and perhaps a rash. As the immune system begins to fight the invasion, some cells produce antibodies to neutralize the viruses that are floating free in the bloodstream. Killer T cells destroy many other cells infected with the AIDS virus, and the patient enters a phase of the disease in which no symptoms are evident.

Although at this point it seems as though the worst is over, in fact, the AIDS virus is at work on the immune system, quietly destroying the body's protection by infecting those T cells that would protect it. With an immune system that gradually becomes more and more unresponsive, the patient is made vulnerable to any number of infections. Normally, the body would be able to fight off these attacks with ease, but with the immune system itself no longer functioning properly, infectious diseases and cancers are free to take over. The result is a long period of increasing misery and suffering, sometimes accompanied by dementia or mental deterioration caused by the ravaging of the brain by disease. Whatever the course it takes, the end result of AIDS is always the same: not just death but a miserable, excruciatingly painful death.

BIRTH OF A KILLER.

Believed to have originated in Africa, where the majority of AIDS cases still are found (see Infectious Diseases for statistics on AIDS), the disease first appeared in the United States in 1981. In that year two patients were diagnosed with an unusual form of pneumonia and with Kaposi's sarcoma, a type of cancer that previously had struck only people of Mediterranean origin aged 60 years and older. The appearance of that condition in younger persons of non-Mediterranean origin prompted an investigation by the United States Centers for Disease Control and Prevention (CDC).

Through the efforts of physicians both inside and outside the CDC, understanding of AIDSthe name and acronym appeared in 1982gradually emerged. In 1983 scientists at the Pasteur Institute in Paris, as well as a separate team in the United States, identified the virus that causes AIDS, a pathogen that in 1986 was given the name human immunodeficiency virus (HIV). Further research showed that HIV, a retrovirus (see Infectious Diseases for an explanation of retrovirus), is subdivided into two types: HIV-1 and HIV-2. In people who have HIV-2, AIDS seems to take longer to develop; however, neither form of HIV carries with it a guarantee that a person will contract the disease. At first it was believed that if someone were HIV-positive, meaning that the person had the virus, it was a virtual death sentence. Therefore in 1991, when the basketball superstar Earvin "Magic" Johnson (1959-) announced that he was HIV-positive, it was an extremely melancholy event. Fans and admirers all over the world assumed that Johnson shortly would contract AIDS and begin to wither away in the process of suffering an exceedingly panful, dehumanizing death.

The fact that Johnson was alive and healthy more than ten years after the diagnosis of his infection with HIV serves to indicate that there is a great deal of difference between being HIV-positive and having AIDS. It also says much about people's emerging understanding of the disease and the virus that causes it. So, too, does Johnson's experience as he attempted, twice, to make a return to the court after retiring in the wake of his HIV announcement. Before examining his experiences, let us look at the social climate engendered by this politically volatile immunodeficiency syndrome.

CHANGING VIEWS ON AIDS.

AIDS first was associated almost exclusively with the male homosexual community, which contracted the disease in large numbers. This had a great deal to do with the fact that male homosexuals were apt to have far more sexual partners than their heterosexual counterparts and because anal intercourse is more likely to involve bleeding and hence penetration of the skin shield that protects the body from infection. The association of AIDS with homosexuality led many who considered themselves part of the societal mainstream to dismiss AIDS as a "gay disease," and the fact that intravenous drug users also contracted the disease seemed only to confirm the prejudice that AIDS had nothing to do with heterosexual non-junkies. Some so-called Christian ministers even went so far as to assert, sometimes with no small amount of satisfaction, that AIDS was God's punishment for homosexuality.

Then, during the mid-1980s, AIDS began spreading throughout much of society: to heterosexuals, hemophiliacs (see Noninfectious Diseases) and others who received blood, and even babies. The fact that AIDS could be transferred through heterosexual intercourse proved that it was not just a disease of homosexuals. Nor were all homosexuals necessarily susceptible to it. In fact, the safest of all sexual groups was homosexual women, who often tended toward monogamy and whose form of sexual contact was least invasive.

As AIDS spread throughout society, so did paranoia. Rumors circulated that a person could catch the disease from a mosquito bite or from any contact with the bodily fluids of another personnot just semen or blood but even sweat or saliva. People with AIDS began to acquire the status lepers once had held (see Infectious Diseases). By the mid-1990s views had changed considerably, and society as a whole had a much more realistic view of AIDS. This came about to some extent because of increased education and awarenessand in no small part because of Johnson, who was by far the most widely knownand admired HIV-positive celebrity.

MAGIC COMES BACK.

After playing on the United States "Dream Team" that trounced all opponents at the 1992 Summer Olympics in Barcelona, Spain, Johnson attempted a comeback with the Lakers the following year. Owing to fears on the part of many other players that they might contract AIDS by coming into close contact with him on the court, however, he decided again to retire. In December 1991 Johnson had established the Magic Johnson Foundation to promote AIDS awareness, and he devoted himself to this and other AIDS-related causes as well as to other ventures. Raising money for AIDS led him out onto the basketball court again in October 1995, when he and the American All Stars faced an Italian team in a benefit game, with an unsurprisingly lopsided score of 135-81.

Then, in February 1996, Johnson made his second attempted comeback with the Lakers. He ended up retiring again four months later, this time for good, but because he had chosen to and not because he had been forced to do so. Thanks in part to his AIDS education programs, in his second comeback Johnson discovered that players realized that they were not likely to catch the virus on the court. As the New Jersey Nets' player Jayson Williams told one reporter, "You've got a better chance of Ed McMahon knocking on your door with $1 million than you have of catching AIDS in a basketball game."

WHERE TO LEARN MORE

Aaseng, Nathan. Autoimmune Diseases. New York: Franklin Watts, 1995.

American Autoimmune Related Diseases Association, Inc. (AARDA) (Web site). <http://www.aarda.org/>.

Benjamini, Eli, and Sidney Leskowitz. Immunology: A Short Course. New York: Liss, 1988.

Clark, William R. At War Within: The Double-Edged Sword of Immunity. New York: Oxford University Press, 1995.

Dwyer, John M. The Body at War: The Miracle of the Immune System. New York: New American Library, 1989.

Edelson, Edward. The Immune System. New York: Chelsea House, 1989.

How Your Immune System Works. How Stuff Works (Web site). <http://www.howstuffworks.com/immune-system.htm>.

"Infection and Immunity." University of Leicester Microbiology and Immunology (Web site). <http://www-micro.msb.le.ac.uk/MBChB/MBChB.html>.

"The Lymphatic System and Immunity." Estrella Mountain Community College (Web site). <http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookIMMUN.html>.

"Magic Johnson Retires Again, Saying It's on His Own Terms This Time." Jet , June 3, 1996, p. 46.

UNAids: The Joint UN Programme on HIV/AIDS (Web site). <http://www.unaids.org/>.

KEY TERMS

ALLERGY:

A change in bodily reactivity to an antigen as a result of a first exposure. Allergies bring about an exaggerated reaction to substances or physical states that normally would have little significant effect on a healthy person.

ANTIBODIES:

Proteins in the human immune system that help the body fight foreign invaders, especially pathogens and toxins.

ANTIGEN:

A substance capable of stimulating an immune response or reaction.

APC:

An antigen-presenting cella macrophage that has ingested a foreign cell and displays the antigen on its surface.

B CELL:

A type of white blood cell that gives rise to antibodies. Also known as a B lymphocyte.

EPIDEMIC:

Affecting or potentially affecting a large proportion of a population (adj. ) or an epidemic disease (n. )

HUMORAL:

Of or relating to the antibodies secreted by B cells that circulate in bodily fluids.

IMMUNE SYSTEM:

A network of organs, glands, and tissues that protects the body from foreign substances.

IMMUNITY:

The condition of being able to resist a particular disease, particularly through means that prevent the growth and development or counteract the effects of pathogens.

IMMUNOLOGY:

The study of the immune system, immunity, and immune responses.

INOCULATION:

The prevention of adisease by the introduction to the body, in small quantities, of the virus or other microorganism that causes the disease.

LYMPHOCYTE:

A type of white bloodcell, varieties of which include B cells and Tcells, or B lymphocytes and T lymphocytes.

MACROPHAGE:

A type of phagocyticcell derived from monocytes.

MONOCYTE:

A type of white blood cell that phagocytizes (engulfs and digests) foreign microorganisms.

MONOGAMOUS:

Having only one mate.

PATHOGEN:

A disease-carrying parasite, usually a microorganism.

PHAGOCYTE:

A cell that engulfs and digests another cell.

T CELL:

A type of lymphocyte, also known as a T lymphocyte, that plays a key role in the immune response. T cells include cytotoxic T cells, which destroy virus-infected cells in the cell-mediated immune response; helper T cells, which are key participants in specific immune responses that bind to APCs, activating both the antibody and cell-mediated immune responses; and suppressor T cells, which deactivate T cells and B cells.

VACCINE:

A preparation containing microorganisms, usually either weakened or dead, which are administered as a means of increasing immunity to the disease caused by those microorganisms.

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Immunity

IMMUNITY

Exemption from performing duties that the law generally requires other citizens to perform, or from a penalty or burden that the law generally places upon other citizens.

Sovereign Immunity

sovereign immunity prevents a sovereign state or person from being subjected to suit without its consent.

The doctrine of sovereign immunity stands for the principle that a nation is immune from suit in the courts of another country. It was first recognized by U.S. courts in the case of The Schooner Exchange v. M'Faddon, 11 U.S. (7 Cranch) 116, 3 L. Ed. 287 (1812). At first, courts espoused a theory that provided absolute immunity from the jurisdiction of a U.S. court for any act by a foreign state. But beginning in the early 1900s, courts relied on the political branches of government to define the breadth and limits of sovereign immunity.

In 1952, the U.S. state department reacted to an increasing number of commercial transactions between the United States and foreign nations by recognizing foreign immunity only in noncommercial or public acts, and not in commercial or private acts. However, it was easily influenced by foreign diplomats who requested absolute sovereign immunity, and the application of sovereign immunity became inconsistent, uncertain, and often unfair.

Complaints about inconsistencies led to the passage of the Foreign Sovereign Immunities Act of 1976 (28 U.S.C.A. §§ 1 note, 1330, 1332, 1391, 1441, 1602–1611). By that act, Congress codified the theory of sovereign immunity, listing exceptions for certain types of acts such as commercial acts, and granted the exclusive power to decide sovereign immunity issues to the courts, rather than to the State Department.

Indian tribes have been granted sovereign immunity status by the United States, and therefore they generally cannot be sued without the consent of either Congress or the tribe. This immunity is justified by two considerations: First, historically, with more limited resources and tax bases than other governments, Indian tribes generally are more vulnerable in lawsuits than are other governments. Second, granting sovereign nation status to tribes is in keeping with the federal policy of self-determination for Indians.

Indian tribes are immune from suit whether they are acting in a governmental or a proprietary capacity, and immunity is not limited to acts conducted within a reservation. However, individual members of a tribe do not receive immunity for their acts; only the tribe itself is immune as a sovereign nation.

Governmental Tort Immunity

Sovereign immunity may also apply to federal, state, and local governments within the United States, protecting these governments from being sued without their consent. The idea behind domestic sovereign immunity—also called governmental tort immunity—is to prevent money judgments against the government, as such judgments would have to be paid with taxpayers' dollars. As an example, a private citizen who is injured by another private citizen who runs a red light generally may sue the other driver for negligence. But under a strict sovereign immunity doctrine, a private citizen who is injured by a city employee driving a city bus has no cause of action against the city unless the city, by ordinance, specifically allows such a suit.

Governmental tort immunity is codified at the federal level by the federal tort claims act (28 U.S.C.A. § 1291 [1946]), and most states and local governments have similar statutes. Courts and legislatures in many states have greatly restricted, and in some cases have abolished, the doctrine of governmental tort immunity.

Official Immunity

The doctrine of sovereign immunity has its roots in the law of feudal England and is based on the tenet that the ruler can do no wrong. Public policy grounds for granting immunity from civil lawsuits to judges and officials in the executive branch of government survive even today. Sometimes known as official immunity, the doctrine was first supported by the U.S. Supreme Court in the 1871 case of Bradley v. Fisher, 80 U.S. 335, 20 L. Ed. 646. In Bradley, an attorney attempted to sue a judge because the judge had disbarred him. The Court held that the judge was absolutely immune from the civil suit because the suit had arisen from his judicial acts. The Court recognized the need to protect judicial independence and noted that malicious or improper actions by a judge could be remedied by impeachment rather than by litigation.

Twenty-five years later, in Spalding v. Vilas, 161 U.S. 483, 16 S. Ct. 631, 40 L. Ed. 780 (1896), the Court expanded the doctrine to include officers of the federal Executive Branch. In Spalding, an attorney brought a defamation suit against the U.S. postmaster general, who had circulated a letter that criticized the attorney's motives in representing local postmasters in a salary dispute. At that time, the postmaster general was a member of the president's cabinet. The Court determined that the proper administration of public affairs by the Executive Branch would be seriously crippled by a threat of civil liability and granted the postmaster general absolute immunity from civil suit for discretionary acts within the scope of the postmaster's authority. Federal courts since Spalding have continued to grant absolute immunity—a complete bar to lawsuits, regardless of the official's motive in acting—to federal executive officials, so long as their actions are discretionary and within the scope of their official duties.

Members of Congress and state legislators are absolutely immune from civil lawsuits for their votes and official actions. The U.S. Supreme Court, in Bogan v. Scott-Harris, 523 U.S. 44, 118 S. Ct. 966, 140 L. Ed. 2d 79 (1998), extended absolute immunity to local legislators (e.g., city council members, and county commissioners) when they act in their legislative, rather than administrative, capacities.

Prosecutors are absolutely immune for their actions during a trial or before a grand jury. However, during the investigatory phase, they are only granted qualified immunity. In Kalina v. Fletcher, 522 U.S. 118, 118 S. Ct. 502, 139 L. Ed. 2d 471 (1997), the U.S. Supreme Court ruled that a prosecutor was not entitled to absolute immunity with respect to her actions in making an allegedly false statement of fact in an affidavit supporting an application for an arrest warrant. Policy considerations that merited absolute immunity included both the interest in protecting a prosecutor from harassing litigation that would divert his or her time and attention from official duties and the interest in enabling him or her to exercise independent judgment when deciding which suits to bring and in conducting them in court. These considerations did not apply when a prosecutor became an official witness in swearing to a statement.

However, in Conn v. Gabbert, 526 U.S. 286, 119 S. Ct. 1292, 143 L. Ed. 2d 399 (1999), the U.S. Supreme Court held that prosecutors cannot be sued for having lawyers searched or for interfering with the ability to advise a client who is appearing before a grand jury. Prosecutors have a qualified immunity in this situation, based on the two-step analysis that the courts apply to qualified-immunity issues. Under this two-part test, an Executive Branch official will be granted immunity if (1) the constitutional right that allegedly has been violated was not clearly established; and (2) the officer's conduct was "objectively reasonable" in light of the information that the officer possessed at the time of the alleged violation. The qualified-immunity test is usually employed during the early stages of a lawsuit. If the standard is met, a court will dismiss the case.

Police and prison officials may be granted qualified immunity. In Hope v. Pelzer, 536 U.S. 730, 122 S. Ct. 2508, 153 L. Ed. 2d 666 (2002), the U.S. Supreme Court held that Alabama prison officials were not eligible for qualified immunity because they were on notice that their conduct violated established law even in novel factual circumstances. The officials were on notice that tying a prisoner to a hitching post in the prison yard constituted cruel and unusual punishment under the eighth amendment.Prior court rulings and federal prison policies also made clear that law banning the practice had been clearly established. Therefore, the officials were not qualified for immunity.

In Saucier v. Katz, 533 U.S. 194, 121 S. Ct. 2151, 150 L. Ed.2d 272 (2001), the U.S. Supreme Court applied the qualified-immunity test to a claim that a u.s. secret service agent had used excessive force in removing a protester. The Court reasserted its general belief that law officers must be given the benefit of the doubt that they acted lawfully in carrying out their day-today activities. Moreover, one of the main goals of qualified immunity is to remove the defendant from the lawsuit as quickly as possible, thereby reducing legal costs. Justice anthony kennedy restated the principle that immunity is not a "mere defense" to liability but an "immunity from suit." Therefore, immunity issues must be resolved as early as possible. As to the first step, Kennedy agreed that the case revealed a "general proposition" that excessive force is contrary to the fourth amendment. However, a more specific inquiry must take place to see whether a reasonable officer "would understand that what he is doing violates that right." As to this second step, Justice Kennedy rejected the idea that because the plaintiff and the officer disputed certain facts, there could be no short-circuiting of this step. He stated that the "concern of the immunity inquiry is to

acknowledge that reasonable mistakes can be made as to the legal constraints on particular police conduct." Officers have difficulty in assessing the amount of force that is required in a particular circumstance. If their mistake as to "what the law requires is reasonable, however, the officer is entitled to the immunity defense."

In Nixon v. Fitzgerald, 457 U.S. 731, 102 S. Ct. 2690, 73 L. Ed. 2d 349 (1982), the U.S. Supreme Court held that former U.S. president richard m. nixon was entitled to absolute immunity from liability predicated on his official acts as president. In Nixon, a weapons analyst, A. Ernest Fitzgerald, had been fired by the U.S. Air Force after he had disclosed to Congress certain cost overruns within the defense department. Fitzgerald sued Nixon and two former presidential aides for wrongful retaliatory termination.

The Court emphasized the singular importance of the duties of the president, and noted that the diversion of the president's energies over concern for private lawsuits "would raise unique risks to the effective functioning of government." It also observed that the president, in view of the visibility of the office, would be an easy target for civil lawsuits. The ensuing personal vulnerability and distraction would prove harmful to the nation.

Despite the Court's grant of absolute immunity to the president for official actions, a president does not have immunity from civil lawsuits for actions that allegedly occurred before becoming president. The Court, in Clinton v. Jones, 520 U.S. 681, 117 S. Ct. 1636, 137 L. Ed. 2d 945 (1997), ruled that President bill clinton had to defend himself in a sexual-harassment lawsuit that was based on his alleged actions while governor of Arkansas. Clinton had contended that the lawsuit could not proceed until he left office, but the Court disagreed. The Court pointed out that grants of official immunity are based on a functional analysis, and it would not extend immunity to actions outside of an office-holder's official capacities. Moreover, it concluded that defending the lawsuit would not divert Clinton's energies.

Immunity from Prosecution

State and federal statutes may grant witnesses immunity from prosecution for the use of their testimony in court or before a grand jury. Sometimes, the testimony of one witness is so valuable to the goals of crime prevention and justice that the promise of allowing that witness to go unpunished is a fair trade. For example, a drug dealer's testimony that could help law enforcement to destroy an entire illegal drug-manufacturing network is more beneficial to society than is the prosecution of that lone drug dealer. Although the fifth amendment to the U.S. Constitution grants witnesses a privilege against self-incrimination, the U.S. Supreme Court has permitted prosecutors to overcome this privilege by granting witnesses immunity. Prosecutors have the sole discretion to grant immunity to witnesses who appear before a grand jury or at trial.

States employ one of two approaches to prosecutorial immunity: Use immunity prohibits only the witness's compelled testimony, and evidence stemming from that testimony, from being used to prosecute the witness. The witness still may be prosecuted so long as the prosecutor can obtain other physical, testimonial, or circumstantial evidence apart from the witness's testimony. Transactional immunity completely immunizes the witness from prosecution for any offense to which the testimony relates.

Congressional committees have the power to grant testimonial immunity to witnesses who testify before members of Congress. Congressional investigations into allegations of misconduct—such as the watergate investigations in the 1970s and the iran-contra investigations in the 1980s—rely heavily on witness testimony. Whereas prosecutors simply decide whether to grant immunity to a witness, congressional committees must follow more formal procedures. Immunity may be granted only after a two-thirds majority vote by members of the committee. Ten days before the immunized testimony is given, the committee must advise the justice department or the independent counsel of its intention to grant immunity.

Family Immunity

At common law, a child could sue a parent for breach of contract and for torts related to property. An adult could sue his or her parent for any tort, whether personal or related to property. In 1891, the Mississippi Supreme Court, in Hewllette v. George, 9 So. 885 (1891), held that a child could not seek compensation for personal injury that was caused by a parent's wrongdoing, so long as the parent and child were obligated by their family duties to one another. The decision was based not on precedent but rather on public policy: The court found that such a lawsuit would undermine the "peace of society and of the families composing society." Criminal laws, the court found, were adequate to protect children.

Other states fell in step with Mississippi, adopting parental immunity of varying degrees. Some parental-immunity laws prohibited only claims of negligence, whereas others prohibited lawsuits for intentional torts such as rapes and beatings. The rationale supporting parental-immunity laws includes the need to preserve family harmony and, with the availability of liability insurance, the need to prevent parents and the children from colluding to defraud insurance companies.

Unjust results have led courts in many states that espouse parental immunity to carve out exceptions to the rule. For example, a child usually can sue a parent for negligence when the parent has failed to provide food or medical care, but not when the parent has merely exercised parental authority. Most courts have abolished the parental-immunity defense for car accident claims, and many allow children to sue their parents for negligent business or employment actions. Courts normally permit wrongful death suits to be brought by a child against a parent or by a parent against a child, because death terminates the parent-child relationship. Moreover, most states allow a child to sue a parent for injuries suffered in utero owing to the negligence of the mother.

further readings

Fox, Hazel. 2002. The Law of State Immunity. Oxford; New York: Oxford University Press.

Giuttari, Theodore R. 1970. The American Law of Sovereign Immunity; An Analysis of Legal Interpretation.New York: Praeger.

Sels, John van Loben. 1995."From Watergate to Whitewater: Congressional Use Immunity and Its Impact on the Independent Counsel." Georgetown Law Journal 83.

Stein, Theodore P. 1983. "Nixon v. Fitzgerald: Presidential Immunity as a Constitutional Imperative." Catholic University Law Review 32 (spring).

cross-references

Ambassadors and Consuls; Diplomatic Immunity; Feres Doctrine; Husband and Wife; Judicial Immunity.

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immunity

immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity. Mammals are protected by a variety of preventive mechanisms, some of them nonspecific (e.g., barriers, such as the skin), others highly specific (e.g., the response of antibodies).

Nonspecific Defenses

Nonspecific defenses include physical and chemical barriers, the inflammatory response, and interferons. Physical barriers include the intact skin and mucous membranes. These barriers are aided by various antimicrobial chemicals in tissue and fluids. An example of such a substance is lysozyme, an enzyme present in tears that destroys the cell membranes of certain bacteria.

Inflammatory Response

Another line of defense is the inflammatory response, in which white blood cells called monocytes and granulocytes (e.g., basophils and neutrophils) reach an injured area. Basophils release histamine, which results in increased local blood flow and increased permeability of the capillaries and allows phagocytizing cells, such as neutrophils and monocytes (macrophages), into the area. The same response sometimes results in fever. Leakage of the clotting protein fibrinogen and other substances into the injured area results in blockage of tissue by clots, which wall off the injured area to retard the spread of bacteria or their toxins.

Interferons

Interferons are proteins released by a virus-invaded cell that prompt surrounding cells to produce enzymes that interfere with viral replication. They are the reason that, in most instances, infection with one virus precludes infection by a second virus.

Nonsusceptibility

Nonsusceptibility is the inability of certain disease-carrying organisms to grow in a particular host species. Nonsusceptibility may be caused by such conditions as lack of availability of particular growth substances needed by the infecting microorganism or body temperature unsuitable for the invading microorganism. For example, chickens are nonsusceptible to anthrax because the bacteria cannot grow at the body temperature normal for that animal.

The Immune Response

The principal parts of the immune system are the bone marrow, thymus, lymphatic system, tonsils, and spleen. The lymph nodes, tonsils, and spleen act to trap and destroy antigens from the lymph, air, and blood, respectively. Antigens are molecules that the body reacts to by producing antibodies, highly specific proteins also known as immunoglobulins. Antigens include bacteria and their toxins, viruses, malignant cells, foreign tissues, and the like. Their destruction is accomplished by white blood cells (lymphocytes and the granulocytes and monocytes mentioned above), which are produced and constantly replenished by the stem cells of the bone marrow. The two types of lymphocytes are called B lymphocytes (B cells) and T lymphocytes (T cells). B cells are responsible for production of antibodies in what is called "humoral" immunity after the ancient medical concept of the body humors.

B Lymphocytes

The presence of antigens in contact with receptor sites on the surface of a B lymphocyte stimulates the lymphocyte to divide and become a clone (a line of descendant cells), with each cell of the clone specific for the same antigen. Some cells of the clone, called plasma cells, secrete large quantities of antibody; others, called memory cells, enter a resting state, remaining prepared to respond to any later invasions by the same antigen. Antibody secretion by lymphocytes can be stimulated or suppressed by such variables as the concentration of antigens, the way the antigen fits the lymphocyte's receptor regions, the age of the lymphocyte, and the effect of other lymphocytes.

According to the modified clonal selection theory originally postulated by the Australian immunologist Sir Macfarlane Burnet (for which he was awarded the 1960 Nobel Prize for Physiology or Medicine), a lymphocyte is potentially able to secrete one particular, specific humoral, or free-circulating, antibody molecule. It is believed that early in life lymphocytes are formed to recognize thousands of different antigens, including a group of autoimmune lymphocytes, i.e., cells recognizing antigens of the organism's own body. The immune system is self-tolerant; i.e., it does not normally attack molecules and cells of the organism's own body, because those lymphocytes that are autoimmune are inactivated or destroyed early in life, and the cells that remain, the majority, recognize only foreign antigens. Burnet's theory was confirmed with the development of monoclonal antibodies.

Antibodies

The antibodies produced by B cells are a type of globulin protein called immunoglobulins. There are five classes of immunoglobulins designated IgA, IgD, IgE, IgG, and IgM; gamma globulin (IgG) predominates. Antibody molecules are able to chemically recognize surface portions, or epitopes, of large molecules that act as antigens, such as nucleic acids, proteins, and polysaccharides. About 10 amino acid subunits of a protein may compose a single epitope recognizable to a specific antibody. The fit of an epitope to a specific antibody is analogous to the way a key fits a specific lock. The amino acid sequence and configuration of an antibody were determined in the 1960s by the biochemists Gerald Edelman, an American, and R. R. Porter, an Englishman; for this achievement they shared the 1972 Nobel Prize for Physiology or Medicine.

The antibody molecule consists of four polypeptide chains, two identical heavy (i.e., long) chains and two identical light (i.e., short) chains. All antibody molecules are alike except for certain small segments that, varying in amino acid sequence, account for the specificity of the molecules for particular antigens. In order to recognize and neutralize a specific antigen, the body produces millions of antibodies, each differing slightly in the amino acid sequence of the variable regions; some of these molecules will chemically fit the invading antigen.

Antibodies act in several ways. For example, they combine with some antigens, such as bacterial toxins, and neutralize their effect; they remove other substances from circulation in body fluids; and they bind certain bacteria or foreign cells together, a process known as agglutination. Antibodies attached to antigens on the surfaces of invading cells activate a group of at least 11 blood serum proteins called complement, which cause the breakdown of the invading cells in a complex series of enzymatic reactions. Complement proteins are believed to cause swelling and eventual rupture of cells by making holes in the lipid portion of the cell's membrane.

T Lymphocytes

After their production in the bone marrow, some lymphocytes (called T lymphocytes or T cells) travel to the thymus, where they differentiate and mature. The T cells interact with the body's own cells, regulating the immune response and acting against foreign cells that are not susceptible to antibodies in what is termed "cell-mediated immunity." Three classes of T lymphocytes have been identified: helper T cells, suppressor T cells, and cytotoxic T cells. Each T cell has certain membrane glycoproteins on its surface that determine the cell's function and its specificity for antigens.

One type of function-determining membrane glycoprotein exists in two forms called T4 or T8 (CD4 or CD8 in another system of nomenclature); T4 molecules are on helper T cells, T8 molecules are on suppressor and cytotoxic T cells. Another type of membrane glycoprotein is the receptor that helps the T cell recognize the body's own cells and any foreign antigens on those cells. These receptors are associated with another group of proteins, T3 (CD3), whose function is not clearly understood. T cells distinguish self from nonself with the help of antigens naturally occurring on the surface of the body's cells. These antigens are, in part, coded by a group of genes called the major histocompatibility complex (MCH). Each person's MCH is as individual as a fingerprint.

When a cytotoxic T lymphocyte recognizes foreign antigens on the surface of a cell, it again differentiates, this time into active cells that attack the infected cells directly or into memory cells that continue to circulate. The active cytotoxic T cells can also release chemicals called lymphokines that draw macrophages. Some (the "killer T cells" ) release cell-killing toxins of their own; some release interferon. Helper T cells bind to active macrophages and B lymphocytes and produce proteins called interleukins, which stimulate production of B cells and cytotoxic T cells. Although poorly understood, suppressor T cells appear to help dampen the activity of the immune system when an infection has been controlled.

Active and Passive Immunity

Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. Artificially acquired active immunity can be induced by a vaccine, a substance that contains the antigen. A vaccine stimulates a primary response against the antigen without causing symptoms of the disease (see vaccination).

Artificially acquired passive immunity is a short-term immunization by the injection of antibodies, such as gamma globulin, that are not produced by the recipient's cells. Naturally acquired passive immunity occurs during pregnancy, in which certain antibodies are passed from the maternal into the fetal bloodstream. Immunologic tolerance for foreign antigens can be induced experimentally by creating conditions of high-zone tolerance, i.e., by injecting large amounts of a foreign antigen into the host organism, or low-zone tolerance, i.e., injecting small amounts of foreign antigen over long periods of time.

Undesirable Immune Responses and Conditions

Immunity has taken on increased medical importance since the mid-20th cent. For instance, the ability of the body to reject foreign matter is the main obstacle to the successful transplantation of certain tissues and organs. In blood transfusions the immune response is the cause of severe cell agglutination or rupture (lysis) when the blood donor and recipient are not matched for immunological compatibility (see blood groups). An immune reaction can also occur between a mother and baby (see Rh factor). Allergy, anaphylaxis, and serum sickness are all manifestations of undesirable immune responses.

Many degenerative disorders of aging, e.g., arthritis, are thought to be disorders of the immune system. In autoimmune diseases, such as rheumatoid arthritis and lupus, individuals produce antibodies against their own proteins and cell components. Combinations of foreign proteins and their antibodies, called immune complexes, circulating through the body may cause glomerulonephritis (see nephritis) and Bright's disease (a kidney disease). Circulating immune complexes following infection by the hepatitis virus may cause arthritis.

At an extreme end of the spectrum of undesirable conditions is the lack of immunity itself. As a childhood condition, this absence can result from a congenital inability to produce antibodies or from severe disorders of the immune system, which leave individuals unprotected from disease. Such children usually die before adulthood. AIDS (Acquired Immune Deficiency Syndrome), which ultimately destroys the immune system, is caused by a retrovirus called the human immunodeficiency virus (HIV), which was identified in 1981. It infects the helper T cells, thereby disabling the immune system and leaving the person subject to a vast number of progressive complications and death.

Bibliography

See I. Cohen et al., ed., Auto-Immunity (1986); S. Sell, Immunology, Immunopathology, and Immunity (1987); R. Langman, The Immune System (1989); E. Sercarz, ed., Antigenic Determinants and Immune Regulation (1989); J. Kreier, Infection, Resistence, and Immunity (1990)

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immunity

immunity The state of relative insusceptibility of an animal to infection by disease-producing organisms or to the harmful effects of their poisons (toxins). Immunity depends on the presence in the blood of antibodies and white blood cells (lymphocytes), which produce an immune response. Inherited (natural or innate) immunity is that with which an individual is born. Acquired immunity is of two types, active and passive. Active immunity arises when the body produces antibodies against an invading foreign substance (antigen), either through infection or immunization; this type of immunity may be humoral, in which B lymphocytes produce free antibodies that circulate in the bloodstream (see B cell), or cell-mediated, caused by the action of T lymphocytes (see T cell). Passive immunity is induced by injection of serum taken from an individual already immune to a particular antigen; it can also be acquired by the transfer of maternal antibodies to offspring via the placenta or breast milk (see colostrum). Active immunity tends to be long-lasting; passive immunity is short-lived. See also autoimmunity.

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immunity

immunity (i-mewn-iti) n. the body's ability to resist infection, afforded by the presence of circulating antibodies and white blood cells. active i. immunity that arises when the body's own cells produce, and remain able to produce, appropriate antibodies following an attack of a disease or deliberate stimulation (see immunization). cell-mediated i. immunity resulting from the action of T-lymphocytes. humoral i. immunity resulting from the action of circulating antibodies produced by B lymphocytes. natural (or innate) i. immunity resulting from the activity of phagocytic cells, natural killer cells, and other mechanisms present before exposure to infection. passive i. temporary immunity that may be provided by injecting ready-made antibodies in antiserum taken from another person or an animal already immune. Babies have passive immunity, conferred by antibodies from the maternal blood and colostrum, to common diseases for several weeks after birth. See also herd immunity.

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immunity

im·mu·ni·ty / iˈmyoōnitē/ • n. (pl. -ties) the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells: immunity to typhoid seems to have increased spontaneously. ∎  protection or exemption from something, esp. an obligation or penalty: the rebels were given immunity from prosecution. ∎ Law officially granted exemption from legal proceedings. ∎  (immunity to) lack of susceptibility, esp. to something unwelcome or harmful: products must have an adequate level of immunity to interference | exercises designed to build an immunity to fatigue.

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immunity

immunity In medicine, protection or resistance to disease. Genetic factors and general health influence Innate immunity. Acquired immunity is the body's second line of defence. An infecting agent stimulates the immune system to respond to the presence of antigens. In cell-mediated immunity sensitized cells react directly with the antigen. This form of immunity is suppressed by human immunodeficiency virus (HIV). Immunity may be induced artificially by immunization.

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immunity

immunity The natural or acquired resistance of an organism to a pathogenic micro-organism or its products. Immunity may be active (see active immunity) or passive (see passive immunity).

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MICHAEL ALLABY. "immunity." A Dictionary of Ecology. 2004. Encyclopedia.com. 27 Aug. 2016 <http://www.encyclopedia.com>.

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immunity

immunity The resistance of an organism to a pathogenic micro-organism or its products. Immunity may be active (see ACTIVE IMMUNITY) or passive (see PASSIVE IMMUNITY).

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MICHAEL ALLABY. "immunity." A Dictionary of Zoology. 1999. Encyclopedia.com. 27 Aug. 2016 <http://www.encyclopedia.com>.

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immunity

immunity A natural or acquired resistance of an organism to a pathogenic micro-organism or its products.

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acquired immunity

acquired immunity See immunity.

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immunity

immunitybanditti, bitty, chitty, city, committee, ditty, gritty, intercity, kitty, nitty-gritty, Pitti, pity, pretty, shitty, slitty, smriti, spitty, titty, vittae, witty •fifty, fifty-fifty, nifty, shifty, swiftie, thrifty •guilty, kiltie, silty •flinty, linty, minty, shinty •ballistae, Christie, Corpus Christi, misty, twisty, wristy •sixty •deity, gaiety (US gayety), laity, simultaneity, spontaneity •contemporaneity, corporeity, femineity, heterogeneity, homogeneity •anxiety, contrariety, dubiety, impiety, impropriety, inebriety, notoriety, piety, satiety, sobriety, ubiety, variety •moiety •acuity, ambiguity, annuity, assiduity, congruity, contiguity, continuity, exiguity, fatuity, fortuity, gratuity, ingenuity, perpetuity, perspicuity, promiscuity, suety, superfluity, tenuity, vacuity •rabbity •improbity, probity •acerbity • witchetty • crotchety •heredity •acidity, acridity, aridity, avidity, cupidity, flaccidity, fluidity, frigidity, humidity, hybridity, insipidity, intrepidity, limpidity, liquidity, lividity, lucidity, morbidity, placidity, putridity, quiddity, rabidity, rancidity, rapidity, rigidity, solidity, stolidity, stupidity, tepidity, timidity, torpidity, torridity, turgidity, validity, vapidity •commodity, oddity •immodesty, modesty •crudity, nudity •fecundity, jocundity, moribundity, profundity, rotundity, rubicundity •absurdity • difficulty • gadgety •majesty • fidgety • rackety •pernickety, rickety •biscuity •banality, duality, fatality, finality, ideality, legality, locality, modality, morality, natality, orality, reality, regality, rurality, tonality, totality, venality, vitality, vocality •fidelity •ability, agility, civility, debility, docility, edibility, facility, fertility, flexility, fragility, futility, gentility, hostility, humility, imbecility, infantility, juvenility, liability, mobility, nihility, nobility, nubility, puerility, senility, servility, stability, sterility, tactility, tranquillity (US tranquility), usability, utility, versatility, viability, virility, volatility •ringlety •equality, frivolity, jollity, polity, quality •credulity, garrulity, sedulity •nullity •amity, calamity •extremity • enmity •anonymity, dimity, equanimity, magnanimity, proximity, pseudonymity, pusillanimity, unanimity •comity •conformity, deformity, enormity, multiformity, uniformity •subcommittee • pepperminty •infirmity •Christianity, humanity, inanity, profanity, sanity, urbanity, vanity •amnesty •lenity, obscenity, serenity •indemnity, solemnity •mundanity • amenity •affinity, asininity, clandestinity, divinity, femininity, infinity, masculinity, salinity, trinity, vicinity, virginity •benignity, dignity, malignity •honesty •community, immunity, importunity, impunity, opportunity, unity •confraternity, eternity, fraternity, maternity, modernity, paternity, taciturnity •serendipity, snippety •uppity •angularity, barbarity, bipolarity, charity, circularity, clarity, complementarity, familiarity, granularity, hilarity, insularity, irregularity, jocularity, linearity, parity, particularity, peculiarity, polarity, popularity, regularity, secularity, similarity, singularity, solidarity, subsidiarity, unitarity, vernacularity, vulgarity •alacrity • sacristy •ambidexterity, asperity, austerity, celerity, dexterity, ferrety, posterity, prosperity, severity, sincerity, temerity, verity •celebrity • integrity • rarity •authority, inferiority, juniority, majority, minority, priority, seniority, sonority, sorority, superiority •mediocrity • sovereignty • salubrity •entirety •futurity, immaturity, impurity, maturity, obscurity, purity, security, surety •touristy •audacity, capacity, fugacity, loquacity, mendacity, opacity, perspicacity, pertinacity, pugnacity, rapacity, sagacity, sequacity, tenacity, veracity, vivacity, voracity •laxity •sparsity, varsity •necessity •complexity, perplexity •density, immensity, propensity, tensity •scarcity • obesity •felicity, toxicity •fixity, prolixity •benedicite, nicety •anfractuosity, animosity, atrocity, bellicosity, curiosity, fabulosity, ferocity, generosity, grandiosity, impecuniosity, impetuosity, jocosity, luminosity, monstrosity, nebulosity, pomposity, ponderosity, porosity, preciosity, precocity, reciprocity, religiosity, scrupulosity, sinuosity, sumptuosity, velocity, verbosity, virtuosity, viscosity •paucity • falsity • caducity • russety •adversity, biodiversity, diversity, perversity, university •sacrosanctity, sanctity •chastity •entity, identity •quantity • certainty •cavity, concavity, depravity, gravity •travesty • suavity •brevity, levity, longevity •velvety • naivety •activity, nativity •equity •antiquity, iniquity, obliquity, ubiquity •propinquity

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