Basic Concepts in Immunology

Immunity is the resistance of body against extraneous etiological factors of diseases, which is afforded by the interaction of chemical, humoral and cellular reactions in the body. Immunity can be classified as natural or paraspecific and acquired or specific immunity. Acquired immunity develops in the body as a result of prior stimulation with antigens. It can be classified as humoral and cell-mediated immunity. The antibody mediated immunity is called as humoral immunity and is present in body fluids mainly in the blood. Antigen is a foreign substance, which is able to stimulate the production of antibodies. Antibodies are protein in nature and are produced as a result of antigenic stimulation. Cell-mediated immunity is a form of immune response mediated by T-lymphocytes and macrophages. Cytokines are hormone like glycoproteins in nature with a molecular weight of 8–25 kDa and composed of a single chain.