Induction of suppressor cell mechanism in antilymphocyte serum-induced skin allograft tolerance in mice.

In the B10.D2 leads to B10.D2(M504) strain combination (H-2D incompatibility), 20--40% of skin allografts survive for more than 100 days in ALS-treated recipients. Allograft tolerance in ALS-treated recipients could not be abolished by adoptively transferred normal or immune syngeneic spleen cells, but it could be adoptively transferred by spleen or lymph node cells to sublethally irradiated syngeneic mice. The suppressive activity of transferred cell population markedly declined after treatment with anti Thy-1.2 serum and complement. Cells with suppressor activity could be demonstrated by adoptive transfers as early as 5 days after skin grafting and ALS treatment. The results showed that the long-term allograft-promoting effect of ALS was caused not only by a decrease in the graft-rejection cell potential of the recipients (as demonstrated by other authors earlier) but also by the activation of a T cell-mediated suppressor mechanism.