Human lymphocyte subpopulations identified by using three-color immunofluorescence and flow cytometry analysis: correlation of Leu-2, Leu-3, Leu-7, Leu-8, and Leu-11 cell surface antigen expression.

Three-color immunofluorescence has been used to determine the co-expression of cell surface antigens on human peripheral blood lymphocytes. Monoclonal antibodies or avidin were coupled to either FITC (green), phycoerythrin (orange), or Texas Red (red) fluorochromes. These three fluorochromes could be independently measured by using a dual laser FACS IV system equipped with an argon ion laser (488 nm) and a dye laser (600 nm). Human peripheral blood lymphocytes were stained with the following combinations of reagents: (1) FITC anti-Leu-11a + PE anti-Leu-2a + TR avidin/biotin anti-Leu-7; (2) FITC anti-Leu-11a + PE anti-Leu-3a + TR avidin/biotin anti-Leu-7; (3) FITC anti-Leu-8 + PE anti-Leu-2a + TR avidin/biotin anti-Leu-7; and (4) FITC anti-Leu-11a + PE anti-Leu-2 + TR avidin/biotin anti-Leu-8. The light scatter, green fluorescence, orange fluorescence, and red fluorescence signals for each sample were stored by a Consort 40 PDP/11 computer in list mode files. Sequential reanalysis of the data directly demonstrated the existence of several unrecognized subpopulations of lymphocytes. Previously, we reported that the anti-Leu-7 and anti-Leu-11 antibodies can be used to identify discrete subsets of human NK cells with distinct functional capacities. In this report, we show that these subsets can be further subdivided on the basis of Leu-8 and Leu-2 expression. Thus, these studies illustrate how multicolor and multiparameter flow cytometry can further our understanding of cellular heterogeneity within this group of lymphocytes.