The expression of Leu M4 on human NK cells

Previous studies have shown that the Leu M4 monoclonal antibody reacts strongly with human granulocytes in the peripheral blood, has a weak reactivity with monocytes but fails to react with platelets, eosinophils and K-562 cells. In the present study Leu M4 antibody was found to react with human NK cells. Immunofluorescent analysis indicated that about 12% of peripheral blood lymphocytes (PBL) are positive for this marker, and that the reactive cells are concentrated in the Percoll fraction known to display the strongest NK activity. Exposure of PBL to Leu M4 and complement resulted in a significant decrease of their NK activity. The relationship of Leu M4 to other monoclonal antibodies reactive with human neutrophils and NK cells remains to be elucidated.