Characterization of human T cell-derived IgE-potentiating factor

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Abstract
We have previously shown that Fcε receptor‐positive (FcεR+) T cell lines from patients with the hyper IgE syndrome secrete IgE‐binding factors which selectively enhance IgE but not IgG synthesis in cultures of B cells obtained from patients with allergic rhinitis but not from nonatopic subject. In the present study we have tested the effect of supernatants from FcεR+ T cell lines on a large panel of B cells from atopic patients (n = 20). We found that IgE synthesis was selectively enhanced only in B cell cultures in which there was ongoing spontaneous synthesis of IgE. The target of IgE‐potentiating factor(s) was a large low‐density B cell present in the circulation of responding atopic donors. In addition, we further characterized IgE‐potentiating factors derived from FcεR+ T cell lines. The factor(s) fractionated into 2 peaks on Sephadex G‐75 with approximate molecular masses of 15000 and 60000 kDa, and had affinity for lentil lectin but not for peanut agglutinin. Release of IgE‐potentiating factor(s) was enhanced by the addition of exogenous human IgE to FcεR+ T cell cultures and was inhibited by tunicamycin, an inhibitor of N‐glycosylation. These studies suggest a close homology between the physicochemical characteristics of human and rodent IgE‐potentiating factors and the immune signals which modulate production of these IgE regulatory factors.

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