im·mune / iˈmyoōn/ • adj. resistant to a particular infection or toxin owing to the presence of specific antibodies or sensitized white blood cells: they were naturally immune to hepatitis B. ∎  protected or exempt, esp. from an obligation or the effects of something: they are immune from legal action. ∎  not affected or influenced by something: no one is immune to his immense charm. ∎  Biol. of or relating to immunity: the body's immune system.

immune (i-mewn) adj. protected against a particular infection by the presence of specific antibodies against the organisms concerned. i. response the reaction of the body to the presence of antigens (foreign tissues, bacteria, etc.), which are attacked and destroyed by antibodies. See antibody, antigen, immunity. i. system the organs and tissues responsible for immunity, including the thymus, bone marrow, lymph nodes, spleen, and tonsils. See also lymphoid tissue.

immune †free, exempt XV; secure from contagion, etc. XIX. — L. immūnis exempt from a service or charge, f. IM-2 + mūnis ready for service (cf. COMMON).
So immunity exemption from service or liability XIV; non-susceptibility to contagion, etc. XIX.