Frequency determination of K cells by a single cell cytotoxic assay.

This report describes a highly reproducible single cell cytotoxic assay which can measure the frequency of K cells in human peripheral blood lymphocytes. This assay is based on the ability of FcR-bearing lymphocytes to bind to antibody sensitized target cells via their FcR. Approximately 30% of lymphocytes which bound antibody sensitized target cells via their FcR. Approximately 30% of lymphocytes which bound antibody sensitized P815 cells (P815-AB) were K cells. Cytolysis of the conjugated P815-AB fulfilled all the criteria for ADCC. Furthermore, an excellent correlation was observed between the frequency of K cells and % cytotoxicity as measured by the ADCC 51Cr-release assay. The mean frequency of human k cells in peripheral blood lymphocytes from 20 volunteers was measured to be 3.2% of the total lymphocyte populations.