Question

autoimmunity

Answer 1

The process of acquired immunity would destroy the individual’s own body if a person became immune to his own tissues. The immune mechanism normally recognizes a person’s own tissues as being distinctive from bacteria or viruses, and the person’s immunity system forms few antibodies or activated T cells against his or her own antigens.Most tolerance is believed to develop during preprocessing of T lymphocytes in the thymus and of B lymphocytes in the bone marrow.It is believed that during the preprocessing of lymphocytes in the thymus and bone marrow, all or most of the clones of lymphocytes that are specific to damage the body’s own tissues are self-destroyed because of their
continual exposure to the body’s antigens.Failure of the tolerance mechanism causes autoimmune
diseases. Sometimes people lose immune tolerance of their own tissues. This phenomenon occurs to
a greater extent the older a person becomes. It usually occurs after destruction of some of the body’s own tissues, which releases considerable quantities of “self-antigens” that circulate in the body and presumably cause acquired immunity in the form of either activated T cells or antibodies.Several specific diseases that result from autoimmunity include (1) rheumatic fever, in which the body becomes immunized against tissues in the joints and heart, especially the heart valves, after exposure to a specific type of streptococcal toxin that has an epitope in its molecular structure similar to the structure of some of the body’s own self-antigens; (2) one type of glomerulonephritis, in
which the person becomes immunized against the basement membranes of glomeruli.(3) systemic lupus erythematosis (4) Myasthenia gravis.