PHENOTYPIC ANALYSIS OF NYLON-WOOL-ADHERENT SUPPRESSOR CELLS THAT INHIBIT THE EFFECTOR PROCESS OF TUMOR-CELL LYSIS BY LYMPHOKINE-ACTIVATED KILLER-CELLS IN PATIENTS WITH ADVANCED GASTRIC-CARCINOMA

The causes of down-regulation of cytotoxic immune responses in cancer patients have not been fully evaluated. We previously demonstrated that T-cell-growth-factor-activated peripheral blood lymphocytes (PBL) with the surface phenotype CD8(+) CD11b(-), from patients with widespread metastasis of gastric carcinoma, inhibited the effector process of lymphokine-activated-killer(LAK)-cell-mediated cytolysis. In this study, we examined suppressor cell activity in freshly prepared PBL from 18 patients with advanced gastric carcinoma, and 10 normal healthy individuals. The suppressor cell activity was assayed by recording whether or not PBL inhibited directly the effector process of LAK cell cytotoxicity. Most of the PBL suspensions from cancer patients showed that they contained a population of cells that can directly inhibit the effector phase of tumor cell lysis of the cytotoxic cells. To analyze further the PBL responsible for the suppression, the cells were passed over a nylon-wool column. Nylon-wool-adherent cells significantly augmented the suppression, while the cells passing through abrogated the suppressive effect. Most nylon-wool-adherent cells from 10 normal healthy controls did not inhibit the cytotoxic reaction. To determine further the suppresser-effector population in nylon-wool-adherent cells, negative-selection studies using CD8-, CD4- or CD11b-coated magnetic beads, and positive-selection studies using CD8- or CD4-coated magnetic beads were performed. Finally the results suggest that the suppressor-effector cells comprise at least two different surface phenotypes: CD8(+) T and CD8-CD11b(+) cells. The possible role of CD4(+) T cells and HLA-DR(+) LeuM3(+) macrophages as suppressor cells was ruled out in nylon-wool-adherent cells. CD8(+) T and possibly CD8(-)CD11b(+) cells apparently suppressed the efferent limb of the antitumor immunity. The selective immune suppression mediated by these cells may partly be concerned with escape mechanisms of gastric carcinoma from the host immune surveillance system.