Thrombospondin-induced adhesion of human platelets.
Washed human unactivated platelets attached and spread on thrombospondin (TSP)-coated microtiter plates. Platelet adhesion was promoted by divalent cations Mn2+, Mg2+, and Ca2+ as compared to buffer having all divalent cations complexed with EDTA. TSP-dependent adhesion was inhibited by anti-TSP fab fragments, an anti-TSP monoclonal antibody, an RGD-containing peptide, complex-specific anti-glycoprotein (GP)IIb-IIIa monoclonal antibodies (A2A9 or AP-2) and anti-VLA-2 monoclonal antibodies (6F1 and Gi9), but not by rabbit preimmune fab fragments, mouse IgG, an anti-GPIIIa monoclonal antibody, or monoclonal antibodies against either the human vitronectin receptor, glycocalicin, or GPIV. At saturating concentrations, anti-GPIIb-IIIa inhibited adhesion by 40-60%. Glanzman's thrombasthenic platelets, which lack GPIIb-IIIa, adhered to TSP to the same extent as anti-GPIIb-IIIa-treated normal platelets or 40-60% as well as untreated normal platelets. Antibody 6F1 (5-10 micrograms/ml) inhibited platelet adhesion of both normal and thrombasthenic platelets by 84-100%. Both VLA-2 antibodies also inhibited collagen-induced platelet adhesion, but had no effect on fibronectin-induced adhesion of normal platelets. These data indicate that platelets specifically adhere to TSP and that this adhesion is mediated through GPIIb-IIIa and/or VLA-2.
Tuszynski
G P
GP
Department of Medicine, Medical College of Pennsylvania, Philadelphia 19129.
Kowalska
M A
MA
D000911:Antibodies, Monoclonal / Q000276:immunology; D001792:Blood Platelets / Q000648:ultrastructure; D002413:Cations, Divalent / Q000494:pharmacology; D005353:Fibronectins / Q000502:physiology; D006487:Hemostasis; D006801:Humans; D007158:Immunologic Techniques; D008345:Manganese / Q000494:pharmacology; D008854:Microscopy, Electron; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism* / Q000494:pharmacology*; D011971:Receptors, Immunologic / Q000378:metabolism; D018000:Receptors, Peptide; D016029:Receptors, Very Late Antigen / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D013915:Thrombasthenia / Q000503:physiopathology; D019699:Thrombospondins
D000911:Antibodies, Monoclonal; D002413:Cations, Divalent; D005353:Fibronectins; D010980:Platelet Membrane Glycoproteins; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D016029:Receptors, Very Late Antigen; D019699:Thrombospondins; C051382:arginyl-glycyl-aspartic acid directed cell adhesion receptor; D012701:Serotonin; D008345:Manganese