[Immunologic specificity, nature and properties of suppressor cells induced in mixed lymphocyte cultures].

Suppressor cells are generated in allogeneic or syngeneic one-way mixed lymphocyte culture (MLC) for 1 to 5 days, the suppressor activity being tested by inhibition of proliferation of 10 to 100-fold number responders in the fresh allogeneic MLC. In both allogeneic and syngeneic MLC the suppressors are found to be neither B cells, nor macrophages, resistant to mitomycin C, and their precursors are shown to be cyclophosphamide sensitive. Their properties differ from those previously shown for T killers or T suppressors generated in the lymphocyte monoculture. The allogeneic suppressors are T cells that are heterogeneous in respect to radiosensitivity and specificity. Generation of the nonspecific T suppressors is reduced if human or bovine serum is added to the MLC medium instead of fetal calf serum. The syngeneic suppressors are heterogeneous as well and differ from the allogeneic ones by greater stability to the effect of anti-T bodies and irradiation, and by greater resistance of their precursors to hydrocortisone.