Stimulation of human NK cell activity by cultured cells. II Ingestion of aspirin by blood donors suppresses induced NK activity.

Incubation of mononuclear cells with a melanoma tumour cell. M4, induces a rapid increase in NK cell activity in both normal and tumour patient cells. A marked individual variation among the patient population can be attributed to the prior ingestion of aspirin. Single therapeutic doses of aspirin (two tablets, 660 mg) taken 12 hr prior to donation of the blood sample cause an 80-100% reduction in the NK cell activity induced by M4. Since many patients coming to cancer clinics take aspirin regularly, it is essential that they be questioned about their recent usage of this drug if their cells are to be used in assays for NK activity.