Suppressor cells in the thoracic duct lymph of tolerant, spleen-grafted rats.

Vascularized spleen allografts between two different inbred rat strains induce specific transplantation tolerance in vivo. Thoracic duct lymphocytes isolated from tolerant rats exhibited notable nonresponsiveness to donor stimulator cells in the mixed lymphocyte reaction. In-vitro co-culture experiments indicate that this nonresponsiveness reflects the activity of both specific and nonspecific suppressor cells. Since suppressor cells are present in tolerant animals, it is possible that the suppressor cells play an important role in maintaining spleen-induced transplantation tolerance.