Studies on the suppression of a one-way mixed lymphocyte reaction by mitomycin-C treated responder cells

We have investigated the suppression of lymphocyte proliferation in a one-way mixed lymphocyte culture by autologous mitomycin-C treated responder cells. The suppression was proportional to the number of mitomycin-C treated cells added. Irradiated cells suppressed in the same manner. Using subpopulations of peripheral blood mononuclear cells, it was shown that the 'suppressor activity' was not confined to a particular subpopulation, but was exhibited by all subpopulations tested. Cycloheximide-treated peripheral blood mononuclear cells and autologous erythrocytes also suppressed. These results suggest that 'suppression' in this system is due to mechanical interference by the added cells. The implications for the design of assays for spontaneous suppressor cell activity in man are discussed.