Induction of Fc epsilon receptors on mouse macrophages and lymphocytes by homologous IgE.

Abstract

Normal mouse peritoneal macrophages express Fc gamma 2aR, Fc gamma 1/2bR, and Fc epsilon R, whereas B lymphocytes in mesenteric lymph nodes (MLN) bear Fc gamma 2bR, Fc gamma 1R, and Fc epsilon R. Rosette formation of Fc epsilon R+ macrophages and lymphocytes with IgE-coated ox erythrocytes was inhibited by rodent IgE but not by any other isotype of mouse immunoglobulins. In contrast, IgG1 rosettes and IgG2b rosettes of both macrophages and lymphocytes were inhibited not only by homologous isotype but also by IgE, suggesting that IgE has some affinity for Fc gamma 1/2bR on macrophages and for both Fc gamma 1R and Fc gamma 2bR on lymphocytes. Incubation of normal mouse macrophages with mouse IgE for 24 hr resulted in a twofold increase in the proportion of Fc epsilon R+ cells. Mouse IgE can induce Fc epsilon R on B cells as well. Incubation of MLN cells with mouse IgE for 2 to 4 hr, followed by culture of the cells in the absence of IgE, resulted in a 1.8- to 2.9-fold increase in Fc epsilon R+ cells. Determination of Fc gamma R+ cells in the same MLN cells revealed that induction of Fc epsilon R by IgE was accompanied by a substantial decrease in the expression of Fc gamma 1R and Fc gamma 2bR. Induction of Fc epsilon R by IgE on macrophages and lymphocytes requires protein synthesis. In MLN cells, cycloheximide inhibited not only the IgE-induced increase in Fc epsilon R+ cells but also the decrease in Fc gamma 1R+ cells and Fc gamma 2bR+ cells. It was also found that induction of Fc epsilon R by IgE on macrophages was completely inhibited if IgG1 or IgG2b was added to the cells together with IgE. In contrast, IgG2a did not affect the IgE-induced expression of Fc epsilon R on macrophages. In MLN cells, IgG2b but not IgG1 inhibited both IgE-induced increase in Fc epsilon R and decrease in Fc gamma 1R and Fc gamma 2bR. The results indicate that expression of various Fc receptors on lymphocytes is mutually regulated.