. Basic concepts of immunology Immunology is the study of immune system. This system protects an indvidual from various infective agents. It refers to all the mechanisms used by the body for protection from environmental agents that are foreign to the body.
When the immune system does not function efficiently in an individual, it leads to infection causing disease. The overall ability of body to fight against the disease causing pathogen is called immunity . It is also called disease resistance and the lack of immunity is known as susceptibility. Immunity is highly specific.
Normally many of the responses of the immune system initiate the destruction and elimination of invading organisms and any toxic molecules produced by them. These immune reactions are destructive in nature and are made in response only to molecules that are foreign to the host and not to those of host itself. This ability to distinguish foreign molecules from self is another fundamental feature of the immune system. However, occasionally, it fails to make its distinction and reacts destructively against the host's own molecules; such autoimmune diseases can be fatal to the organism.
Active (infection) Passive (maternal) Active (immunization) Passive (antibody transfer) Artificial Natural Innate Immunity Adaptive Immunity Immunity Fig. . Immune system XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Human Health and Diseases known as cell mediated immune response or cell mediated immunity. This is brought about by T cells, macrophages and natural killer cells.
. Antibody mediated immunity or humoral immunity When pathogens are destroyed by the production of antibodies, then it is known as antibody mediated or humoral immunity. This is brought about by B cells with the help of antigen presenting cells and T helper cells. Antibody production is the characteristic feature of vertebrates only.