Role of Suppressor Cells in Depression of In Vitro Lymphoproliferative Responses of Lung Cancer and Breast Cancer Patients2

Abstract

Lung and breast cancer patients previously shown to have depressed in vitro lymphocyte proliferation (LP) responses to mitogens and alloantigens were further studied for the presence of suppressor cells. Patients' peripheral blood mononuclear leukocytes (PBL's) were tested for LP responses to phytohemagglutinin and in mixed lymphocyte cultures, with or without depletion of adherent cells by passage over Sephadex G-10 columns. Mitomycin C-blocked PBL's, PBL's passed over Sephadex G-10 columns, and the cells recovered from the Sephadex G-10 beads (80–95% esterase-positive) were also tested for their ability to inhibit LP responses of PBL's from normal donors. Of 38 cancer patients tested, 15 (40%) were found to have suppressor cells in their PBL's. Adherent suppressor cells were assumed to be present if G-10 column-passed cells showed a significant enhancement of LP responses and/or were no longer able to suppress LP responses of normal PBL's. Adherent and/or phagocytic suppressor cells accounted for the inhibition of LP in most lung cancer patients with suppression (5 of 8), but 3 patients had nonadherent suppressor cells. Of the 6 breast cancer patients found to have suppressor cells, 2 had adherent suppressor cells and the other 4 had nonadherent suppressor cells. Cells that were adhering to the G-10 column and were from patients thought to have adherent suppressor cells were able to suppress normal PBl responses, which further indicated the suppressor activity of these cells. In contrast, adherent cells recovered from patients thought to have nonadherent suppressor cells and adherent cells from normal individuals did not detectably suppress normal PBL responses at the concentrations used. This study provides evidence that in some cancer patients with in vitro immunodepression, suppressor cells are detectable and may mediate the noted immunodepression.