Lymphocyte mediated natural cytotoxicity in neoplasia.

Peripheral blood lymphoid cells from normal donors, patients with non-malignant diseases, and patients with malignant diseases were evaluated for cytotoxicity against a cultured carcinoma cell line, using a chromium release assay. The natural spontaneous lymphocyte-mediated cytotoxicity was significantly higher in tumor-free groups. The observed decreased response in patients with malignancies correlated with depressed responsiveness to phytohemagglutinin stimulation. Removal of cell subpopulations bearing Fc receptors significantly decreased the cytotoxicity, while depletion of phagocytic mononuclear cells did not. We suggest that natural cytotoxicity is a measure of cell membrane integrity of lymphocytes and should be included as a routine test for evaluation of general immune competence.