GATING OF THE SO-CALLED LYMPHOCYTIC CELL-POPULATION FOR THE QUANTIFICATION OF NATURAL-KILLER-CELLS (CD16+) BY FLOW-CYTOMETRY CAUSES LOSS OF CD16 POSITIVE CELLS

Natural killer cells can phenotypically be identified as CD16 positive witha specific monoclonal antibody (B73.1 = Leu-11c) by either immunofluorescence microscopy or by flow cytometry. The standard procedure in flow cytometry is to set a window or gate around the so called lymphocytic population, based on scatter characteristics. In this paper we demonstrate that a substantial part of the NK cell population is situated outside this gate in the total mononuclear cell population. We therefore recommend that the number of CD16+ cells is determined in the total mononuclear cell population. However, in the total mononuclear cell population, a group of dimly CD16 positive cells, probably monocytes, interferes with a clear separation of cells with a positive and negative fluorescence. We describe two methods to overcome this problem. © 1990.