Natural killer (NK) activity in peripheral blood lymphocytes of patients with benign and malignant breast disease.

Previous studies of natural killer (NK) activity in the peripheral blood of breast cancer patients have failed to show a reduction in cytotoxicity, an observation at variance with results obtained in other malignancies. Interpretation of the data however is complicated by the presence of treated and post-mastectomy patients in the groups studied.In this study, lymphocytes from preoperative blood samples of untreated women with benign and malignant breast disease were tested at various effector-to-target ratios for cytotoxicity activity against the NK sensitive erythromyeloid cell line, K562.A significant reduction in NK activity was observed between carcinoma patients and the control group (P=0·02). When the carcinoma group was further divided into pre- and postmenopausal patients, the reduction was found to be a feature only of premenopausal women (P=0·002). The levels of NK activity in patients with benign breast disease were not significantly different from those in controls, irrespective of menstrual status. There was no correlation between NK activity and tumour size, oestrogen-receptor or lymph-node status in the carcinoma patients.A preliminary analysis of NK activities in the control group suggests that women donating blood in the first half of their menstrual cycle show significantly reduced NK activity in comparison with those in the second half (P=0·001). This finding, coupled with the variation in NK activity shown between pre- and postmenopausal breast carcinoma patients, suggests that hormonal effects in conjunction with malignancy determine the level of NK activity in breast cancer.