Heterogeneous expression of CD23 epitopes by eosinophils from patients. Relationships with IgE-mediated functions

The receptor for IgE (Fc epsilon RII) on human eosinophils presents some common characteristics with CD23, a differentiation marker of B cells. We have used flow cytometry for evaluating the expression of various epitopes of CD23 on purified eosinophils from patients with eosinophilia. A correlation was found between the binding of myeloma IgE protein and the binding of a monoclonal antibody (mAb 135), directed against the IgE-binding site of B cell CD23. Using two additional anti-CD23 mAb, directed (8-30) or not (3-5) against the IgE-binding site, a low expression of these CD23 epitopes was observed on eosinophils from different eosinophilic patients. Northern blot analysis of eosinophil RNA with the cDNA probe of CD23 revealed a low-abundance transcript in three of the six patients expressing membrane CD23. The inhibition by all anti-CD23 mAb of IgE-mediated cytotoxicity and IgE binding to eosinophils clearly indicated the participation of a CD23-related molecule in IgE-dependent eosinophil functions.