Tolerance of the lymphoid tissues to an antigen.
A failure of the body to distinguish between materials that are self, and therefore to be tolerated, and those that are ‘not self,’ against which antibodies are produced. For example, the body fails to produce antibodies against foreign materials if an antigen has previously been introduced into the body before the antibody-producing system is mature; apparently the presence of antigen within the growing cells inhibits antibody formation.
The state in which the immune system does not react to the body’s own antigens. It is caused by the destruction of lymphocytes that express receptors to self-antigens as they develop. Failure of these mechanisms may result in autoimmune disease.