Affinity-purified IgE-binding factors from the plasma of patients with the hyper IgE syndrome (HIE) were assessed for their capacity to enhance IgE synthesis by B cells derived from patients with allergic rhinitis or normal nonatopic donors. IgE-binding factors from three of four HIE patients enhanced IgE synthesis by B cells from patients with perennial allergic rhinitis, or with seasonal allergic rhinitis (SAR) and recent pollen exposure, but did not enhance IgE synthesis by B cells from nonatopic donors or from SAR patients with no recent pollen exposure. IgG synthesis was not affected by HIE IgE binding factors. In contrast, IgE binding factors from three of three nonatopic donors failed to enhance IgE or IgG synthesis. Plasma IgE-binding factors from the fourth patient with HIE contained a mixture of IgE-potentiating activity and IgE-suppressive activity. These two activities could be separated on concanavalin A Sepharose or peanut agglutinin agarose columns. Human IgE potentiating factor, but not IgE suppressive factor, had affinity for concanavalin A but not peanut agglutinin and fractionated into two peaks on gel filtration over Sephadex G-75: one peak with a molecular size of approximately 15,000 D and the other with a molecular size of approximately 60,000 D. The isolation of functional IgE binding factors which potentiate IgE synthesis from the plasma of patients with HIE suggests that IgE-binding factors play an important role in the in vivo regulation of IgE synthesis in man.
D Y Leung, R Frankel, N Wood, R S Geha