IgE receptors on human lymphocytes. II. Detection of cells bearing IgE receptors in unstimulated mononuclear cells by means of a monoclonal antibody.

A monoclonal antibody (mAb) specific for lymphocyte IgE receptors (ER) was employed in a rosette assay for the detection of cells bearing IgE receptors (Fc epsilon R). The specificity of the assay was documented by inhibition studies with soluble immunoglobulins (Ig) and anti-Ig antibodies. Moreover, similar results were obtained by employing the F(ab')2 fragment of mAbER instead of intact molecule. Circulating mononuclear cells isolated from normal or allergic adults and from umbilical cord blood contained approximately 8% of Fc epsilon R-bearing cells with values ranging from 0.3 to 17%. Tonsillar lymphocytes contained about 30% of Fc epsilon R+ cells. After the removal of adherent cells, there was a small but significant reduction of the proportion of Fc epsilon R+ cells. When mononuclear cells were separated into T and B cell fractions by two-cycle rosetting with 2-aminoethylisothiouronium bromide hydrobromide-treated sheep red blood cells, most of the Fc epsilon R+ cells were in the B cell fraction; however, a small proportion of Fc epsilon R+ was also found in the enriched T cells and double-labeling experiments confirmed that these cells were indeed T lymphocytes. Fc epsilon R+ cells were purified by rosetting with mAbER-coated erythrocytes and their phenotype was compared to that of Fc epsilon R- cells; Fc epsilon R+ cells contained about 90% of B cells (B1+) together with a small proportion of OKT3+, Leu 7+ and Mo2+ cells. The bulk of T cells, macrophages and natural killer (NK) cells was found in the Fc epsilon R- cells which contained fewer B cells than the fraction of Fc epsilon R+ cells. These data thus indicated that the great majority of Fc epsilon R-bearing cells are B cells but that a small proportion of NK cells, macrophages and T lymphocytes also express Fc epsilon R. Upon incubation at 37 degrees C, B cells lost their Fc epsilon R and this phenomenon was selectively inhibited by IgE; however, purified T cells seemed to express more Fc epsilon R after overnight incubation at 37 degrees C and this was not influenced by IgE. It is finally shown that the expression of Fc epsilon R is cyclic and that Fc epsilon R-bearing B cells do not represent a functionally distinct subpopulation of B lymphocytes.