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, trinitrophenylated sheep red blood cells (TNP SRC), or the thymus independent antigen, TNP MRC (mouse). 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 produed higher anti TNP plaque forming cell responses after injection of TNP SRC than after TNP MRC whereas in older mice the reverse was 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 aged individuals.