Autoimmunity and aging: the age-related response of mice of a long-lived strain to trinitrophenylated syngeneic mouse red blood cells.

Mice of 1.5, 9, 22, and 31 to 32 months of age were injected with the thymus-dependent antigen, TNP-SRC, or the thymus-independent antigen, TNP-SRC, TNP-MRC. The anti-SRC and TNP immune responses to TNP-SRC were markedly reduced in older mice, whereas the anti-TNP response to the TNP-MRC showed no substantial decline. Young mice produced higher anti-TNP plaque-forming cell responses after injection of TNP-SRC than after TNP-MRC, whereas in older mice the reverse obtained. Old mice but not young mice displayed a high anti-SRC cross-reactive response after injection of TNP-MRC. The avidity of anti-TNP antibody of young mice immunized with TNP-SRC was higher than that following immunization with TNP-MRC, whereas the avidities of anti-TNP antibodies from old mice injected with these two reagents were the same. Those individual mice which showed a poorly regulated immune response also displayed an autologous anti-MRC plaque-forming cell response after injection of either TNP-SRC or TNP-MRC. It is suggested that mechanisms mediated by suppressor T cells may be responsible for regulating the autoimmune response to modified self antigens, and that these are severely impaired in age individuals.