Analysis of Fc (IgG) receptors on human peripheral blood leukocytes by dual fluorescence flow microfluorometry. II. Quantitation of receptors on cells that express the OKM1, OKT3, OKT4, and OKT8 antigens.

Human peripheral blood mononuclear cells were analyzed for the expression of Fc(IgG) receptors (FcR) by a quantitative dual fluorescence flow microfluorometric (FMF) technique. Mononuclear cells from all donors tested were distributed into three distinct subsets on the basis of FcR expression: cells expressing high, intermediate, or background levels of FcR. To characterize these subsets, cells were doubly labeled for FcR and with OKM1, OKT3, OKT4, or OKT8 hybridoma antibodies by using nonoverlapping red and green fluorophores. Each cell was then analyzed for the presence of both labels with a dual laser flow cytometer. Cells that did not express FcR were heterogeneous for OKT3, OKT4, and OKT8, did not express OKM1, and were primarily T cells on the basis of rosette formation with sheep erythrocytes (E+ cells). Most of the cells that expressed intermediate levels of FcR (an average of 1.3 x 10(4) FcR/cell) also expressed high levels of OKM1 but did not bind OKT3, OKT4, or OKT8 hybridoma antibodies. These cells were characterized as monocytes because they were removed by passage over Sephadex G-10 columns and because they were larger than the other cells as judged by light scatter. The majority of cells with the highest FcR density (an average of 4.5 x 10(4) FcR/cell) formed rosettes with E and were, by definition, T gamma cells. These cells expressed negligible levels of OKT4 and intermediate levels of OKM1, levels that clearly distinquished them from monocytes. The T gamma cells were heterogeneous in the expression of both OKT3 and OKT8, with approximately 20% being positive for OKT3 and OKT8. The level of OKT3 expression for the OKT3 and OKT8. The level of OKT3 expression for the OKT3+ T gamma cells was about the same as for as for OKT3+ T nongamma cells. In contrast, the OKT8 T nongamma cells expressed lower levels of OKT8 than did the OKT8+ T nongamma cells. By compaing our results with those obtained by other invesigators, we tentatively assigned functions to the subsets of cells that we describe here.