EOSINOPHILS - FROM LOW-AFFINITY TO HIGH-AFFINITY IMMUNOGLOBULIN-E RECEPTORS

Several experimental approaches have been used to identify immunoglobu lin (IgE) binding molecules expressed by human eosinophils. After the description that Fc epsilon RII/CD23 identified on eosinophils could p articipate in IgE binding and IgE-mediated cytotoxicity, Mac2/epsilon binding proteins belonging to the S-type lectin family were also detec ted on human eosinophils. Anti-Mac2 monoclonal antibodies inhibited eo sinophil-dependent cytotoxicity towards parasitic targets. More recent ly, Fc epsilon RI was demonstrated on human eosinophils from hypereosi nophilic patients. The 3 components of Fc epsilon RI, alpha, beta and gamma chains, were detected in eosinophils. The alpha chain of Fc epsi lon RI was shown to be involved in IgE binding to eosinophils and in t he selective release of eosinophil peroxidase. The participation of Fc epsilon RI-bearing eosinophils in a protective immune response agains t a parasitic infection indicates a so far unsuspected function of Fc epsilon RI. The interactions between the different types of IgE bindin g molecules are discussed.