Cell-mediated immune response in vitro. I. The development of suppressor cells and cytotoxic lymphocytes in mixed lymphocyte cultures.

During the in vitro development of cytotoxic lymphocytes (CL), suppressor cells also develop. Spleen cells or lymph node cells harvested from mixed lymphocyte cultures (MLC) on day 2 (day-2 MLC) and added to a fresh MLC suppressed the development of CL. This suppressive effect was sensitive to treatment with anti-theta and C. The suppressive effect of day-2 MLC was not due to cytotoxic effects nor to altered kinetics of the development of both suppressor cells and CL. Although CL develop from hydrocortisone-treated spleen cells, day-2 MLC of hydrocortisone-treated spleen cells did not suppress the development of CL. These studies suggest that suppressor cells and CL are derived from different T cell subpopulations.