On the association of the platelet-specific alloantigen, Pena, with glycoprotein IIIa. Evidence for heterogeneity of glycoprotein IIIa (original) (raw)
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Blood, 1992
The human platelet-specific alloantigens HPA-2a and HPA-2b (=Kob and KO") together constitute a biallelic antigen system. The HPA-2 antigens have not, to date, been located on a particular platelet membrane molecule. Here, we describe the localization of these antigens on platelet glycoprotein (GP) I b a Platelets from two patients with the Bernard-Soulier syndrome (BSS) were HPA-2(a-,b-) in the immunofluorescence test with HPA-2 alloantibodies on chloroquine-treated platelets. With monoclonal antibody (MoAb) immobilization of platelet antigen assay (MAIPA), positive reactions were obtained only when MoAbs against the platelet GPlb/lX complex were used in combination with anti-HPA-Pa or-2b alloantibodies and normal donor platelets. By immunoprecipitation under nonreducing and reducing conditions a protein of 160 Kd and 145 Kd, respectively, 0 DATE, eight platelet-specific alloantigen systems Platelet immunofluorescence test (PIFT).
European journal of biochemistry / FEBS, 1983
The specificity of five monoclonal antibodies (P1-P6) against platelet surface components was determined by immunoprecipitation of surface-labelled platelets from normal donors and patients with known platelet glycoprotein defects, followed by analysis by gel electrophoresis. Three (P2, P4 and P6) precipitated glycoproteins IIb and IIIa and, in addition, P2 precipitated glycoprotein Ia. P1 precipitated normally only glycoprotein Ib also Ia when the platelets were pretreated with neuraminidase. P3 precipitated principally glycoprotein Ia but glycoprotein Ib was also weakly precipitated. The effects of the monoclonals on platelet function were tested. P1 and P2 completely inhibited and P3 slightly inhibited thrombin-induced platelet aggregation. P2 also inhibited collagen-induced aggregation and partially inhibited ADP-induced platelet aggregation. P3, P4 and P6 partially inhibited ADP-induced platelet aggregation. None had any effect on ristocetin-induced aggregation despite P1 and P...
Platelet surface antigens: Analysis by monoclonal antibodies
Blut, 1984
Monoclonal antibodies were produced against human platetets. Four antibodies (PAl, PA2, PA3 and PA4) reacted specifically with platelets and megakaryocytes, but not with peripheral blood lymphocytes, granulocytes, erythrocytes or monocytes. The antibodies belonged to the mouse IgG subclass 2a (PAl, PA2, PA3), or 1 (PA4) respectively. PAl and PA4 did not precipitate, their antigens have not yet fully been characterized. PA3 was directed against the glycoprotein (Gp) complex IIb/IIIa; PA2 precipitated Gp IIb/IIIa, and, in addition, Gp Ia. PA4 revealed specificity against the human platelet alloantigen Zw (a).
Platelet specific alloantigens on the platelet glycoprotein Ia/IIa complex
British Journal of Haematology, 1989
The majority of platelet alloantigens are located on platelet glycoproteins IIb/IIIa. This report describes a codominant allelic system carried on the glycoprotein Ia/IIa complex. which we originally designated as Zava/Zavb but which is identical to the BP/Bfi system. Furthermore Zav" was found to be identical to Hc". The alloantigens could not be detected using a direct binding enzyme immunoassay (EIA) with intact platelets, but were readily detected using a glycoprotein capture EIA and by radioimmunoprecipitation techniques. The two index cases (designated as homozygous Zav" and Zavb) had alloantibodies against the corresponding antigen and did not react with their own platelets. Using these alloantibodies and a monoclonal antibody that reacts with the platelet glycoprotein Ia/IIa complex (1 2F1). we demonstrated that all Ia/IIa molecules carry either Zava or Zavb and we found that Zava and Zavb are on discrete populations of Ia/IIa. Following immunodepletion using either anti-Zava or anti-Zavb, all detectable Ia/IIa complexes from the respective homozygous platelets were removed. Immunodepletion of heterozygous Zava/Zavb with either anti-Zav" or anti-Zavb did not reduce the amount of Ia/IIa complexes precipitable using the alternate alloantiserum. Population studies ( n = 50) indicated the phenotypic frequency of Zava/Zava is less than 1%: Zava/Zavb is 18% and Zavb/Zavb is 82%. Four different alloantisera that had either anti-Zav" or anti-Zavb reactivity also carried reactivity against the Baka or Bakb antigens which may suggest an association in the immune response to these alleles.
Evidence that a 210,000-molecular-weight glycoprotein (GP 210) serves as a platelet Fc receptor
Journal of Clinical Investigation, 1987
We previously identified a 210,000-mol-wt platelet glycoprotein (GP 210) that is missing from Bernard-Soulier platelets, and found that an antibody against GP 210 inhibits ristocetin-induced platelet agglutination. We now show by immunoblotting that GP 210 binds heat-aggregated rabbit and human IgG, as well as keyhole limpet hemocyanin (KLH)anti-KLH and ovalbumin (OA)-anti-OA immune complexes. Immune complex binding to GP 210 was preserved on chymotrypsin-treated platelets that lacked glycoprotein lb (GP Ib). In contrast, ristocetin-induced platelet agglutination resulted in disappearance of immunologically detectable GP 210 and loss of immune complex binding, even though GP lb remained intact. Purified Fc fragments inhibited binding of anti-GP 210 antibody to intact platelets and to GP 210 on immunoblots. The Fc fragments also blocked immune complex binding to GP 210. Conversely, anti-GP 210 antiserum and F(ab)2 fragments inhibited binding of fluoresceinlabeled Fc fragments to intact platelets. We conclude that GP 210 functions as a platelet Fc receptor.
The isolation and characterisation of antiplatelet antibodies
European Journal of Haematology, 2006
The isolation and characterisation of antiplatelet antibodies Autoimmune thrombocytopenia purpura (ITP) is a disease characterised by antibody-mediated destruction of platelets (1, 2). The autoantibodies produced against platelet glycoproteins are able to bind to platelet membranes, initiating pathways that result in dysfunction and destruction of platelets. These include phagocytosis, lysis by complement activation, and decreased platelet production mediated by binding of antibody to megakaryocytes (3). Around 75% of platelet autoantigens lie on either the platelet GPIIb/IIIa or GPIb/IX complexes, and 25% are found on other membrane glycoproteins (4). Antiplatelet antibodies have been found in the sera of up to 80% of chronic ITP patients. However, despite many studies on antiplatelet antibodies, characterisation of binding and evaluation of antiplatelet autoantibodies remain poor (5). This study has investigated the isolation and characterisation of antiplatelet Fab antibodies, using the combinatorial phage library technique.