active immunity definition
Active immunity. Definition. noun. A type of immunity or resistance developed in an organism by its own production of antibodies in response to an exposure to an antigen, a pathogen or to a vaccine.Supplement.ctive immunity is generally long-term and can be acquired by infection followed by B cells and T cells activation, or artificially acquired by vaccines, in a process called immunization. Thus, an active immunity often involves humoral immunity (B-cells) and cell-mediated immunity (T-cells).