Quantitative and qualitative analysis of the Fc receptor for IgE (FcɛRII) on human eosinophils

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Abstract
In order to characterize the Fc receptor for IgE (FcεRII) on human eosinophils, we have compared the binding of human IgE myeloma protein to that of a monoclonal antibody (mAb BB10) directed against a common antigenic determinant of the FcεRII present on eosinophils, platelets and macrophages. Scatchard analysis of the binding to human eosinophils of the BB10 mAb revealed a linear monophasic binding curve, with a binding affinity of 1.17 X 107 M-1' and a number of 105 binding sites per cell. Biochemical analysis of the human eosinophil FcεR, performed by immunosorbent chromatography with either BB10 mAb or IgE, showed under nonreducing conditions a major component of 200 kDa. Under reducing conditions, 3 peptide fragments were obtained, with molecular masses of 45-50, 23 and 15 kDa. Finally, comparative analysis suggested that the FCεRII of human eosinophils and of a human macrophage cell line (U937) are structurally related and differ from the high-affinity FcεRI present on basophilic granulocytes.