Immunodeficiency and autoimmunity in aging.

In general, both cell-mediated and humoral immune activities decline with advancing age and, associated with this decline, is an increase in the incidence of certain types of autoimmune disease, cancer and infection. Not only may the relationship be causal, but the former may be a significant factor involved in the expression of the latter. Discussion is focused primarily on the relative contribution of extrinsic and intrinsic factors responsible for the immunodeficiency of aging individuals.