Influence and fate of T lymphocytes in autoimmunity

Many T cells with autoaggressive potential are deleted in the thymus but some escape to the general circulation. They do not damage organs such as the insulin-producing tissue of the pancreas, unless some or all of the following conditions are met: high affinity of the antigen receptor on T cells (TCR) for the target self antigen, priming by environmental antigens which mimic the target antigen, and some inflammatory reaction in the target site. When the liver expresses the antigen, any circulating T cells specific for this are deleted in the liver. This suggests that the liver may play a role in preventing autoimmune aggression by T cells specific for antigens expressed on liver cells. Recent experimental models have been set up to test the possibility that an immunoregulatory T cell may exist and exert some type of preventive influence on the autoaggressive potential of self-reactive T cells. (C) 1996 Academic Press Limited