title: Activation of human platelets through gp140, the C3d/EBV receptor (CR2).
abstract: gp140, the C3d/EBV receptor (CR2), previously isolated and characterized from human B lymphocytes, was identified on human platelets: by measuring the specific binding of either polyclonal anti-gp140 IgG and monoclonal anti-C3d/EBVR antibodies, as OKB-7 and HB-5, or human C3d; by isolating gp140 from solubilized platelet components with polyclonal anti-gp140 IgG or monoclonal OKB-7, using immunoprecipitation and electro-immunoblotting assays; by inducing specific activation of human platelets. Cross-linking of this receptor by polyclonal anti-gp140 IgG induced aggregation of human platelets and stimulated ATP release. Absence of lactate dehydrogenase release and inhibition by EDTA and prostacyclin of anti-gp140-induced aggregation, support strongly active aggregation and absence of lysis. Platelet aggregation by anti-gp140 required metabolic activities and was modulated by fibrinogen, paf-acether or thrombin. OKB-7 triggered human platelet aggregation when cross-linked by anti-mouse second-step antibodies. In the same way, platelet activation by C3d fragment was detected, in presence of fibrinogen, only when C3d was cross-linked on the cell surface by anti-C3d F(ab')2 fragments.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000937:Antigen-Antibody Reactions; D001792:Blood Platelets / Q000032:analysis / Q000502:physiology*; D002462:Cell Membrane / Q000032:analysis; D003176:Complement C3 / Q000378:metabolism; D003179:Complement C3b / Q000378:metabolism; D015933:Complement C3d; D006801:Humans; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000302:isolation & purification / Q000502:physiology*; D011951:Receptors, Complement / Q000302:isolation & purification / Q000502:physiology*; D017464:Receptors, Complement 3d
chemical_list: D003176:Complement C3; D010980:Platelet Membrane Glycoproteins; D011951:Receptors, Complement; D017464:Receptors, Complement 3d; D003179:Complement C3b; D015933:Complement C3d; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase