ABSTRACT
The body’s system of defence against pathogenic micro-organisms can be subdivided into two principal categories. First, natural immunity that does not require previous exposure to the pathogen. Second, Specific or acquired immunity in which the immune system responds in a specific manner to the causative agent and retains a memory of the encounter. Old immunology was utilitarian, but based on simplistic concepts. The focus was on vaccines, antitoxins and serum-based factors. New immunology turned to the underlying structure and function of the immune system as a whole. Based upon rigorous scientific research extending over the last forty years, new immunology has yielded much understanding but this has not yet been translated into therapeutic benefits to match those of the old immunology. Antibody production (seroconversion) is initiated when a B lymphocyte encounters an antigen with a complementary structure. During the primary response to a new antigen of infective origin, the affected subject may develop an illness.
