Induction of CD8+ suppressor T cells by treatment with DMBA and TPA in vitro.

Antigen-nonspecific CD8+ T suppressor cells, which suppressed delayed-type hypersensitivity (DTH) against sheep red blood cells in BALB/c mice, were induced by incubating spleen cells from mice treated with 7,12-dimethylbenz[a]anthracene (DMBA), a tumor initiator, with 12-O-tetradecanoylphorbol 13-acetate (TPA), a tumor promoter. The optimal condition was incubation in 3.2 x 10(-8) mol/5 ml of TPA for 4 days. It was shown that induction of the suppressor cells required macrophages from mice treated with DMBA. These data were consistent with the results of previous work, in which CD8+ suppressor cells were induced by painting BALB/c mice with TPA following DMBA treatment. DTH was suppressed in the culture supernatants of spleen cells from mice treated with DMBA and TPA; the suppression was genetically unrestricted. The suppressor factor was resistant to trypsin and sensitive to heating at 56 degrees C for 30 min and had affinity for the macrophages.