IN-VITRO REGULATION OF FC-EPSILON-RI-ALPHA EXPRESSION ON HUMAN BASOPHILS BY IGE ANTIBODY

In vivo studies suggested the possibility of an IgE-dependent regulati on of high-affinity (Fc epsilon RI) IgE receptor expression on basophi ls. 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 Fc epsilon RI expression decreased, as measured by flow cytometry using the anti- Fc epsilon RI alpha monoclonal antibody, 22E7, or by measuring Fc epsi lon RI alpha mass by Western blotting of whole-cell lysates. Culture o f basophils with IgE resulted in upregulation of Fc epsilon RI alpha e xpression by both flow cytometry and Western blotting of whole-cell ly sates, Upregulation followed a linear time course during 2 weeks of cu lture. The relative increase in Fc epsilon RI alpha density depended o n the starting density; with starting densities of Fc epsilon RI alpha of 10,000 to 170,000 per basophil, the upregulation varied 20- to 1.1 -fold, respectively. Upregulation occurred in high-purity basophils, w as not influenced by IgG at concentrations up to 1 mg/mL, and was inhi bited by dimeric IgE. Heat-inactivated IgE was less effective and the monoclonal antibody CGP51901 that prevents IgE binding to Fc epsilon R I alpha blocked the ability of IgE to induce upregulation. The dose-re sponse curve for IgE-induced upregulation had an effective concentrati ons(50) of 230 ng/mL. Although the receptor through which IgE induces this upregulation is not yet known, several characteristics suggest th at the upregulation is mediated by IgE interacting through Fc epsilon RI alpha itself. (C) 1998 by The American Society of Hematology.