NKP-15: a monoclonal antibody reactive against purified human natural killer cells and granulocytes.

A monoclonal antibody of the isotype IgG1,k, NKP-15, was produced by immunizing Balb/c mice with highly purified suspensions of human natural killer (NK) cells. By indirect immunofluorescence, NKP-15 reacted with 15 +/- 5.0% of the peripheral blood lymphocytes, 90 +/- 3.0% of the granulocytes and was non-reactive with T-cells, B-cells, monocytes, platelets and erythrocytes. NKP-15 reacted with 90 +/- 6.0% of purified large granular lymphocytes (LGL), which displayed highly enriched NK cell activity. NKP-15, however, showed no reactivity with a panel of human tumor cell lines. Analysis of NK cell-K562 tumor cell conjugates and depletion by panning of NKP-15+ cells indicated that all functionally tumorlytic NK cells expressed the NKP-15 antigen. It was also determined by competitive blocking experiments that NKP-15 recognizes a new NK cell surface antigen not delineated by the NK-specific monoclonal antibody, Leu-7, and that the epitope for NKP-15 appears to be associated with the Fc-receptor of NK cells and granulocytes.