In vitro regulation of FcεRIα expression on human basophils by IgE antibody

In vivo studies suggested the possibility of an IgE-dependent regulation of high-affinity (FcεRI) IgE receptor expression on basophils. The current studies extend these observations to in vitro cultures of human basophils. Incubation of basophils for 3 to 4 weeks resulted in a slow dissociation of IgE antibody, during which time FcεRI expression decreased, as measured by flow cytometry using the anti-FcεRIα monoclonal antibody, 22E7, or by measuring FcεRIα mass by Western blotting of whole-cell lysates. Culture of basophils with IgE resulted in upregulation of FcεRIα expression by both flow cytometry end Western blotting of whole-cell lysates. Upregulation followed a linear time course during 2 weeks of culture. The relative increase in FcεRIα density depended on the starting density; with starting densities of FcεRIα of 10,000 to 170,000 per basophil, the upregulation varied 20- to 1.1-fold, respectively. Upregulation occurred in high-purity basophils, was not influenced by IgG at concentrations up to 1 mg/mL, and was inhibited by dimeric IgE. Heat-inactivated IgE was less effective and the monoclonal antibody CGP51901 that prevents IgE binding to FcεRIα blocked the ability of IgE to induce upregulation. The dose-response curve for IgE- induced upregulation had an effective concentration⁵⁰ of 230 ng/mL. Although the receptor through which IgE induces this upregulation is not yet known, several characteristics suggest that the upregulation is mediated by IgE interacting through FcεRIα itself.