A Human Natural Killer Cell‐Associated Antigen Defined by Monoclonal Antibody Anti‐Leu (NKP‐15): Functional and Two‐Color Flow Cytometry Analysis

A monoclonal antibody, anti‐Leu 11a (NPK‐15), was generated against human large granular lymphocyes (LGL). Anti‐Leu 11a reacted with the majority of Percoll gradient‐enriched LGL cells, a subpopulation of peripheral blood lymphocytes (PBL) approx (~10–20%), and most granulocytes, but not with a significant number of monocytes, T lymphocytes, or erythocytes. Cell sorting experiments demonstrated that the Leu 11a + population encompassed essentially all functional natural killer (NK) cells in the peripheral blood. Two‐color flow cytometry analysis of PBL populations stained with anti‐Leu 11a and anti‐Leu 7 revealed the existence of four distinct populations: Leu 11a –, 7 +; Leu 11a +, 7 –; Leu 11a +, 7 +; and Leu 11a –, 7 –. The Leu 11a + population did not appear to include cells marked with the T cell‐associated antigens Leu 1, Leu 2, or Leu 3. The existence of a cell surface antigen common to granulocytes and NK cells, which is capable of distinguishing subpopulations of Leu 7 + cells, provides a useful probe to analyze the nature of the NK lineage.