Regulation of surface Fc epsilon RI expression an human eosinophils by IL-4 and IgE

Background: Recent studies have demonstrated that eosinophils from allergic patients express low levels of Fc epsilon RI on their surface, but the reg ulatory mechanisms of eosinophil surface Fc epsilon RI expression are not f ully understood. We investigated whether IL-4 and IgE, which are reported t o regulate surface Fc epsilon RI expression on human mast cells, are able t o affect surface Fc epsilon RI expression in normal human eosinophils. Meth ods: Eosinophils purified from peripheral blood were cultured with IL-5 and with or without IL-4 and/or IgE, and surface Fc epsilon RI expression was analyzed by flow cytometry using an anti-Fc epsilon RI mAb, CRA-1. Results: Apparent Fc epsilon RI expression (similar to 1% of mast cell Fc epsilon R I levels) was observed in eosinophils cultured with both IL-4 and IgE. A co mbination of IL-4 (greater than or equal to 1 ng/ml) and IgE (greater than or equal to 0.5 mug/ml) was necessary for the maximal induction of surface Fc epsilon RI expression. In the presence of IL-4 and IgE, eosinophils cult ured for 2 days demonstrated low but statistically significant levels of su rface Fc epsilon RI, which reached a plateau after 7 days of culture. Howev er, cross-linkage of surface Fc epsilon RI molecules by CRA-1 or anti-IgE d id not induce any eosinophil activation. Conclusions: IL-4 and IgE can affe ct the levels of surface Fc epsilon RI on normal human eosinophils. Fc epsi lon RI expression on eosinophils may be regulated by a mechanism similar to that in mast cells. Copyright (C) 2001 S. Karger AG, Basel.