Spontaneous or natural killer cytotoxicity of K562 erythroleukemic cells in normal patients.

Peripheral blood mononuclear cells from 200 normal individuals, ages 20 to 95 years, were evaluated for their capability to mediate spontaneous or natural killer (NK) cytotoxicity using the K562 erythroleukemic cells as targets. The results of a 4-hr 51Cr specific release assay demonstrated that the NK activity of normal individuals is independent of age, sex, and smoking habits. Although varying greatly among individuals, the NK activity of 25 persons restudied after a mean 20-month interval remained stable. Deficient NK lytic activity is not characteristic of elderly individuals.