A loss of tolerance in discriminating between cells of the self and nonself can lead to antibody synthesis against the body’s own cells or commensal microbes, resulting in autoimmune disease.
Circulating body components in a fetus that reach the lymphoid system are remembered as “self,” creating a permanent unresponsiveness to these protein patterns. This self-tolerance is not absolute. Autoimmune disorders may have many causes and conditions (multifactorial etiology).
Genetic predispositions facilitate onset of autoimmune diseases, but even good genes can succumb to neglect by a body’s occupant. Diabetes and arthritis are autoimmune diseases. A healthy body keeps potentially harmful anti-self lymphocytes in check.