Fc receptors specific for IgE on subpopulations of human lymphocytes and monocytes

Abstract

Fc receptors for IgE (Fc ϵ) were detected on human lymphocytes and monocytes by rosette assays employing ox (E 0) or chicken (E c) erythrocytes coated with human myeloma IgE. Peripheral blood from normal donors contained 1.2 ± 0.6% Fc ϵ + lymphocytes and 23 ± 8% Fc ϵ + monocytes. Over 90% of the Fc ϵ + lymphocytes were B cells that did not have Fc receptors for IgG (Fcγ). Patients with severe atopic disease and highly elevated IgE levels had significantly higher percentages (7.0 ± 2.0%) of Fc ϵ + lymphocytes. Cells from 18 of 28 established human B lymphoblastoid cell lines were Fc ϵ + ; 16 of these were Fc γ − and only two were Fc ϵ + and Fc γ + . The affinity of monomeric IgE for Fc ϵ receptors on cultured lymphoblastoid cells was relatively low (10 6–10 7 L/M), and the IgE rapidly washed off the cells. Monocytes specifically phagocytosed and lysed IgE-coated 51Cr-labeled E c. These data provide evidence that Fc receptors for IgE are found not only on mast cells and basophilic granulocytes but also on lymphocytes and monocytes. The affinity of monomeric IgE to the Fc receptors of these cell types is much lower than that to mast cells and basophilic granulocytes. The function of Fc ϵ receptors on monocytes is most likely promotion of phagocytosis and lysis of IgE-coated target cells. Fc receptors for IgE on lymphocytes may play a role in the regulation of IgE synthesis.