The binding of IgE to murine Fc epsilon RII is calcium-dependent but not inhibited by carbohydrate.
Despite extensive study, little is known about the functions of the moderate affinity IgE receptors (Fc epsilon RII) on B cells. Recent cDNA and genomic cloning studies have demonstrated that, in contrast to other FcR, Fc epsilon RII is not a member of the Ig gene superfamily. Moreover, it uniquely expresses a region that is highly homologous with a membrane-associated, calcium-dependent binding lectin, the asialoglycoprotein receptor. We now report that the interaction between IgE and the Fc epsilon RII of murine B cells and macrophages requires calcium. Furthermore, as might be expected of asialoglycoprotein lectins, this binding was pH-dependent and resulted in ligand internalization. However, although 125I-Fc epsilon RII bound in a calcium-dependent manner to monosaccharide-agarose beads, high concentrations of mono- and disaccharides did not inhibit the interaction between either 125I-IgE and intact B cells or 125I-Fc epsilon RII (from surface-labeled B cells) and IgE-Sepharose. These results suggest that although murine Fc epsilon RII is a lectin, it is not strictly dependent upon IgE oligosaccharides for its binding to IgE.
Richards
M L
ML
Division of Immunology, Medical Biology Institute, La Jolla, CA 92037.
Katz
D H
DH
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism; D001491:Basophils / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D050260:Carbohydrate Metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D007073:Immunoglobulin E / Q000378:metabolism*; D066298:In Vitro Techniques; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D051381:Rats; D011961:Receptors, Fc / Q000378:metabolism*; D017455:Receptors, IgE
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D011961:Receptors, Fc; D017455:Receptors, IgE; D007073:Immunoglobulin E; D004533:Egtazic Acid; D002118:Calcium