Murine splenocyte migration inhibition assay. II. Characterization of splenic suppressor cells in mice bearing P388/ADR tumor.

Suppressor cells in the spleens of mice bearing i.p. transplants of adriamycin-resistant P388/ADR tumors were detected by their ability to abrogate the response of splenocytes from syngeneic mice bearing i.p. transplants of the parental adriamycin-sensitive P388 tumors, in a mixed splenocyte migration assay system. In further experiments the suppressor cells were found to be enriched after removal of nylonwool-adherent cells. Complete loss of the suppressive activity after exposure of the nylonwool-nonadherent splenocytes to monoclonal antithy 1.2 antibody and complement indicated the T-lineage of the suppressor cells. Furthermore, intracellular synthesis of proteins, but not DNA, was found to be essential for manifestation of the suppressive activity. In addition, the suppressor cells associated with P388/ADR tumors were found to be sensitive to gamma-radiation (5 Gy) and hydrocortisone (3 micrograms/ml).