immunity

the way in which the body resists infection because of the presence of ANTIBODIES and white blood cells ( LEUCOCYTES ). Antibodies are generated in response to the presence of ANTIGENS of a disease. There are several types of immunity: active immunity is when the body produces antibodies and continues to be able to do so during the course of a disease, whether occurring naturally (also called acquired immunity) or by deliberate stimulation. Passive immunity is short-lived and is provided by the injection of ready-made antibodies from someone who is already immune.