A role for glycoprotein IIb-IIIa complex in the binding of IgE to human platelets and platelet IgE-dependent cytotoxic functions.
A possible relationship between binding sites for Immunoglobulin E (IgE) on human platelets, involved in IgE-dependent cytotoxic functions of platelets against helminth parasites, and well-characterized platelet constituents involved in haemostasis, was investigated. We first explored the interaction with IgE of platelets from patients with rare inherited deficiencies of defined platelet constituents and functions: Glanzmann's thrombasthenia, Bernard-Soulier and grey platelet syndromes. We report that only type I and II thrombasthenic platelets, which lack the membrane glycoproteins (GP) IIb and IIIa, failed to bind IgE and to exhibit IgE-dependent effector functions. Since thrombasthenic monocytes, however, showed normal interaction with IgE, this defect appeared restricted to platelets. Polyclonal and monoclonal antibodies directed against GP IIb-IIIa complex, but not monoclonal antibody directed against GP Ib, inhibited the binding of IgE to normal platelets, and their IgE-dependent cytotoxicity. Taken together, these findings indicate a relation between the GP IIb-IIIa complex and the expression of IgE binding sites and IgE-dependent effector functions in human platelets.
D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism; D009000:Monocytes / Q000276:immunology; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D013915:Thrombasthenia / Q000097:blood
D007074:Immunoglobulin G; D010980:Platelet Membrane Glycoproteins; D007073:Immunoglobulin E