"Cross-wiring" of the immune response in old mice: increased autoantibody response despite reduced antibody response to nominal antigen.

Older humans and experimental animals have been repeatedly found to have higher titers of autoantibodies than do younger individuals despite the impaired responses of older individuals to foreign antigens. The studies reported here were designed to examine the relationship between these two age-related changes in antibody responses. Antibody response to foreign antigen was measured concurrently with autoantibody response in the same mice. Old mice (18-24 months old) had decreased responses to foreign antigens and increased responses to bromelain-treated syngeneic erythrocytes, compared to young mice (2 months old). In vitro mixing experiments were consistent with the possibility that suppressor cell activity in spleen cells from old mice reduce the antibody response to foreign antigen but not to autologous antigen. The results support an emerging view that age-associated changes in immune responses are the result of dysregulation rather than exhaustion of the immune system.