Production of IgE‐potentiating factor in man by T cell lines bearing Fc receptors for IgE

Abstract The regulation of human IgE production in vitro by soluble T cell factors was examined. T cells were isolated from the peripheral blood of 2 patients with the hyper‐IgE syndrome on the basis of their expression of Fc receptors for human IgE (Fc ϵ R). The T cells were incubated with human myeloma IgE (10 μg/ml), washed, reacted with immunosorbent‐purified goat anti‐human IgE conjugated with fluorescein isothiocyanate, and then separated into Fc ϵ R and Fc ϵ R − T cells on the fluorescence‐activated cell sorter. Fc ϵ R T cells and Fc ϵ R − T cells were propagated in culture using supernatants of phytohemagglutinin‐stimulated peripheral blood mononuclear cells (PBMC) and irradiated autologous PBMC. Supernatants of Fc ϵ R T cell lines but not of Fc ϵ R − T cell lines selectively enhanced IgE synthesis in cultures of B cells obtained from patients with allergic rhinitis but not from normal nonallergic subjects. The surface phenotype of the Fc ϵ R T cell line was predominantly T3 − , T4, Ia with few (15%) T8 cells. Two T cell clones were grown from the Fc ϵ R − T cell line by limiting dilution (0.3 cells/well). These clones possessed the T4 − helper/inducer phenotype and secreted IgE‐enhancing factor(s). The IgE‐enhancing factor(s) which had affinity for insolubilized human IgE was sensitive to treatment with trypsin and neuraminidase, and had as its target an IgE‐bearing B cell. These results suggest that a subset of human T cells bearing an Fc ϵ R secretes an IgE‐binding glycoprotein which selectively enhances IgE synthesis by IgE‐bearing B cells.