Murine natural killer cells express functional Fcγ receptor II encoded by the FcγRα gene

Abstract

We report evidence that murine NK cells express a functional FcγRII encoded by the FcγRIIα gene. Several lines of indirect evidence indicate that freshly obtained NK cells from mice of several strains bear a functional FcγRII: (1) anti-FcγRII antibody 2.4G2 detects a small but significant proportion of sIg- cells and a smal proportion of the 2.4G2+ cells are included in the Thy-1+ population; (b) sIg- lymphocytes contain 2.4G2+ and FcγR-bearing cells in similar proportions; (c) binding of particulate immune complexes by sIg- lymphocytes is completely inhibited by 2.4G2; (d) 2.4G2+ cells mediate >50% of the spontaneous cytotoxicity in sIg- splenic lymphocytes. Direct evidence for the presence of FcγRII on murine NK cells is provided by the results of two-color immunofluorescence studies performed on splenic lymphocytic from C56BL/6 mice showing coexpression of NK-1.1 and 2.4G2. Studies of in vitro propagated homogeneous NK cell populations confirm that murine NK cells express only FcγRII and that this FcγR is functional, as shown in experiments of inhibition of ADCC by the anti-FcγRII antibody 2.4G2. The results of studies at the molecular level show that an FcγRIIα transcript identical to that expressed in macrophage is the only molecule encoding FcγRIII in murine NK cells.