Immune function in aged mice. V. Role of suppressor cells.

Suppressor cells were identified in the lymphoid system of old CBA mice by means of an adoptive transfer system in which old cells were mixed with a corresponding number of cells from young syngeneic donors. Inhibition of the primary antibody response to DNP.KLH and HRC (T-dependent antigens) and DNP. Ficoll (a T-independent antigen) and of the secondary antibody response to DNP.HGG was observed, indicating that suppression was not antigen specific. The effect was mediated by a T-T interaction between Ly-1+ and Ly-2+ T cells rather than by a single Ly-2+ or Ly-1,2,3+ T cell subset. In addition, suppression was abrogated by pretreatment of cells with anti-la serum plus C, which led to the conclusion that the actual effector cell responsible was most likely to bear the phenotype Ly-1−, 2+, Ia+. The suppressor cells were widely distributed, being found in the spleen, lymph nodes, and bone marrow. On the other hand, induction of antigen- (HGG) specific suppressor cells was not impaired in old mice, which is in contrast to the loss of activity of most other lymphoid components of the immune system. Taken together, these results suggest that suppressor cells play a role in the loss of immune competence with age but do not provide an explanation for the high incidence of autoimmunity in old animals.