title: The receptor for IgE on blood platelets.
abstract: Highly purified blood platelets from man and rat could be induced into cytotoxic effectors against schistosome larvae by an IgE-dependent mechanism. Such a process implied the existence of a receptor for the Fc part of IgE on the surface of these blood elements. Normal platelets, incubated in the serum of infected individuals as well as in the IgE-rich serum from asthmatic patients, showed similar capabilities. Flow cytofluorometric analysis evidenced that the platelets bearing IgE receptors represented a subpopulation (20%), the percentage of which was significantly increased (up to 50%) in rats or patients with high levels of circulating IgE. Radiolabeled IgE, whose binding was specifically inhibited by an excess of unlabeled IgE or by anti-Fc epsilon receptor antibody, allowed the demonstration that the receptor for this isotype on the platelet surface was saturable. The binding of increasing amounts of IgE followed a bimodal curve, with less than 1000 sites per platelet showing an affinity coefficient of 3.3 X 10(7) M-1 at low concentrations, and a Ka of 7.8 X 10(5) M-1 for higher concentrations. Beyond their interest in the demonstration of cytotoxic properties of thrombocytes, these observations place emphasis on the potential role of the platelets in immediate-type allergic reactions by their direct interaction with IgE antibody molecules, through a specific receptor.
mesh_terms: D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D001249:Asthma / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology*; D005434:Flow Cytometry; D006790:Host-Parasite Interactions; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology*; D007814:Larva; D008163:Luminescent Measurements; D051381:Rats; D011961:Receptors, Fc / Q000032:analysis*; D017455:Receptors, IgE; D011971:Receptors, Immunologic / Q000032:analysis*; D012550:Schistosoma mansoni
chemical_list: D011961:Receptors, Fc; D017455:Receptors, IgE; D011971:Receptors, Immunologic; D007073:Immunoglobulin E