[Natural killer activity in patients with malignant melanoma].

Thirty-three malignant melanoma patients were tested for NK cytotoxicity of peripheral blood lymphocytes in a Cr-release assay. NK activity was significantly lower in patients as compared with controls. In eight patients no cytotoxicity whatsoever could be detected. We tried to understand this NK impairment by using further assays such as the removal of plastic adherent cells or of carbonyl-iron phagocytizing cells and by mixing experiments. Only three patients showed the presence of NK activity suppressing cells and one patient had suppressive factors in his serum. No correlation was seen between NK activity values and clinical-biological parameters such as thickness of tumor, stage of disease, rate of recurrences or hystological findings.