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

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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 (FcϵR). 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 FcϵR and FcϵR− T cells on the fluorescence-activated cell sorter. FcϵR T cells and FcϵR− T cells were propagated in culture using supernatants of phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMC) and irradiated autologous PBMC. Supernatants of FcϵR T cell lines but not of FcϵR− 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 FcϵR T cell line was predominantly T3−, T4, Ia with few (15%) T8 cells. Two T cell clones were grown from the FcϵR− 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 FcϵR secretes an IgE-binding glycoprotein which selectively enhances IgE synthesis by IgE-bearing B cells.

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