Aggregation to Thrombin and Collagen of Platelets from a Glanzmann Thrombasthenic Patient Lacking Glycoproteins IIb and IIIa

SummaryThe aim of this study was to investigate the platelets of a Glanzmann thrombasthenic patient, which in citrated PRP failed to respond to various agonists, but aggregated and secreted to high concentrations of thrombin (0.36, 0.72 and 1 U/ml) and collagen (4, 10 and 20 μg/ml) when washed and resuspended in a Tyrode-albumin solution (containing 2 mM Ca2+). Aggregation of the patient platelets was not affected by anti-IIb/IIIa monoclonal antibody (P18) which strongly inhibits thrombin or collagen induced aggregation of normal platelets. Washed platelets of this patient did not aggregate to ADP (10-100 μM) in the presence of added fibrinogen (2 mg/ml) nor bind 125I-labelled fibrinogen (40 to 320 μg/ml) when thrombin-stimulated. Different anti-IIb/IIIa monoclonal antibodies (P2, P18) when used in binding or crossed immunoelectrophoretic studies showed a complete absence of the IIb-IIIa glycoprotein complex on the patient platelets. Moreover, glycoproteins IIb or IIIa were absent on silver-stained twodimensional (non-reduced/reduced) polyacrylamide gel separations of the patient platelets and were not detected by Western blots used in combination with anti-PLA1 (antigen present on Ilia), anti-Leka (antigen present on IIb). This study shows that platelets lacking glycoproteins IIb or IIIa can aggregate in response to high concentrations of collagen or thrombin when resuspended in the presence of physiological concentrations of calcium. Results obtained in this study could indicate the existence of other mechanisms (other than the IIb-IIIa glycoprotein complex) involving glycolipids, heparans, proteoglycans, and/or unknown membrane glycoproteins to mediate platelet aggregation of stimulated thrombasthenic platelets.

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PLATELETS OF A PATIENT LACKING GLYCOPROTEINS lib AND Ilia AGGREGATE TO HIGH CONCENTRATIONS OF THROMBIN OR COLLAGEN

10.1055/s-0038-1643863 ◽

1987 ◽

Author(s):

J L McGregor ◽

L McGregor ◽

M Hans ◽

A Sayegh ◽

M C Trzeeiak ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Polyclonal Antibodies ◽

Two Dimensional ◽

Binding Studies ◽

Western Blots ◽

Glycoprotein Complex ◽

Sds Page ◽

Bleeding Episodes ◽

High Concentrations ◽

Induced Aggregation

The aim of this study was to investigate the platelets of a patient having bleeding episodes that began in infancy. The patient’s platelets in citrated-PRP did not aggregate when stimulated with ADP (5 and 10 uM), collagen (2.5 ug/ml), or sodium arachidonate (1 uM). However, washed patient platelets, in the presence of 2mM calcium, aggregated and secreted when stimulated with high concentrations of thrombin (0.36, 0.72 and lU/ml) or collagen (2, 4, 10 ug/ml). Monoclonal antibodies (Mab) LYP18 (directed against the IIb-IIIa glycoprotein complex) and LYP8 (anti-thrombospondin) inhibited thrombin and collagen induced aggregation of control but not the patient platelets. Patient thrombin -stimulated platelets did not bind 125I-labelled fibrinogen (40 to 320 ug/ml). Moreover, stimulating the washed patient's platelets with ADP (10-100 uM), in the presence of fibrinogen (2mg/ml), did not result in aggregation. Binding studies using Mab 125I-LYP2 (directed against the IIb-IIIa glycoprotein complex) showed the absence of the complex on the patient's platelets. The absence of the IIb-IIIa complex on the patient's platelets was also observed using crossed immunoelectro -phoresis and Mab 125I-LYP2 or 125I-LYP18. Individual glycoproteins (lib or Ilia) were not detected on silver stained two-dimensional (non-reduced/reduced) SDS-PAGE. Moreover, Western blots of |he patients platelets used in combination with anti-PLA or anti-LEK polyclonal antibodies failed to detect the presence of these two glycoproteins. These results indicate that this patient has Glanzmann's thrombasthenia or a variant of this disease. Moreover, this study shows that platelets lacking the IIb-IIIa glycoprotein complex can aggregate in responseto collagen or thrombin in the presence of physiological concentrations of calcium.

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AN IMPORTANT ROLE OF CARBOHYDRATE MOIETIES ON CANCER CELL MEMBRANE GLYCOPROTEINS IN CANCER CELL-INDUCED PLATELET AGGREGATION

10.1055/s-0038-1644667 ◽

1987 ◽

Author(s):

H Kitagawa ◽

N Yamamoto ◽

G Kosaki ◽

H Yamazaki

Keyword(s):

Monoclonal Antibodies ◽

Platelet Aggregation ◽

Cell Membrane ◽

Western Blot ◽

Cancer Cells ◽

Cell Line ◽

Cancer Cell ◽

Target Cells ◽

Membrane Glycoproteins ◽

Induced Aggregation

Platelet aggregation induced by cancer cells may be an essential process in the development of hematogenous metastasis of cancers. A mechanism in HMV-I (human vaginal melanoma cell line)-induced platelet aggregation was studied by using monoclonal antibodies against membrane proteins of cancer cells or platelets. HMV-I cells or their membrana ractions induced platelet aggregation of human heparinized PRP, to which hirudin had no inhibitory effect. The platelet aggregation by HMV-I was completely lost after the pretreatment of the cells with 0.3U/ml neuraminidase for 60 min at 37°C. Preincubation of platelets with monoclonal antibodies against platelet GP lb or GP Ilb/lIIa inhibited HMV-I induced aggregation. A monoclonal antibody MB3 (igM) against another human melanoma (HMMB) which had been transplanted in nude mice was produced by hybridoma technique. Screening studies by cell binding ELISA revealed that MB3 antibody reacted with not only HMMB cells but also many other cells including HMV-I, M7609 (colon carcinoma cell line) and normal fibroblasts. Western-blot analyses showedthat MB3 antibody reacted with multiple, more than ten, proteins with molecular weights ranging from UO to 200 kDa in unreduced SDS-PAGE of HMV-I, HMMB or M7609. In contrast, when .these cells pretreated with neuraminidase were used in Western-blot, MB3 reactivity were all lost. MB3 reacted with at least three glycoproteins of human red cell membrane in Western-blot, but it did not react with human platelets. Immune adherent asgay with trypsin-treated HMV-I or HMMB cells as target cells showed negative reactivity. MB3 antibody inhibited HMV-I-induced aggregation of platelets, but did not inhibit M7609-induced aggregation which depended on thrombin generation.These results suggest that MB3 antibody may be against sialic acid-containing carbohydrate moieties of membrane glycoproteins on these cancercells and that the carbohydrate(s) may play a critical role in' cancer cell-platelet interaction.

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PLATELET ACTIVATION INDUCED BY A MONOCLONAL ANTIBODY AGAINST THE PLATELET GP Ilb/IIIa COMPLEX

10.1055/s-0038-1643514 ◽

1987 ◽

Author(s):

P W Modderman ◽

J G Huisman ◽

J A van Mourik ◽

A E G Kr ◽

v d Borne

Keyword(s):

Monoclonal Antibody ◽

Monoclonal Antibodies ◽

Platelet Aggregation ◽

Medical Research ◽

Platelet Activation ◽

Dense Granules ◽

Fibrinogen Binding ◽

Platelet Release ◽

Induced Aggregation ◽

Aggregation Of Platelets

A receptor for fibrinogen on the platelet GP Ila/lIIb complex is induced by ADP, thrombin and other agonists. To study functional domains on GP Ilb/IIIa, the effects of anti-GP Ilb/IIIa monoclonal antibodies (Mab’s) on platelet function were determined. One of these Mab’s, 6C9, induced platelet aggregation. The antibody binds to the intact GP Ilb/IIIa complex only, not to free GP lib or free GP Ilia. Its epitope is different from that of C17, a Mab that inhibits ADP-induced fibrinogen binding and platelet aggregation. 6C9 induces fibrinogen-mediated aggregation rather than agglutination since 6C9-induced platelet interactions were blocked by treatments that also inhibited the effects of ADP etc., without inhibiting binding of 6C9 itself. 6C9 induces binding of 125I-fibrinogen (35.000 ± 7.300 molecules/platelet, Kd = 1.3 ± 0.4 µM) to unstirred platelets. Binding of fibrinogen was 60 to 80% inhibited by apyrase, which indicates that 6C9-induced fibrinogen binding is largely mediated via ADP released from platelets. In addition, 6C9 induced aggregation of platelets in the absence of extracellular fibrinogen. Mediation of this process by platelet fibrinogen or other a-granule proteins, released upon activation by 6C9, was implicated by the finding that aggregation of washed platelets, but not of platelets to which fibrinogen was added, could be blocked by PGI2. Platelet release was also assessed directly by measuring β-thromboglobulin (α-granules) and (14C) serotonin (dense granules) in the medium of unstirred platelets incubated with 6C9. F(ab')2 fragments of 6C9 only aggregated platelets in the presence of fibrinogen and did not release (14C) serotonin. Moreover, release induced by intact 6C9 was inhibited by anti-GP Ilb/IIIa Mab C17 but not by C17 F(ab’)2, although the latter inhibited ADP-induced platelet aggregation. These data indicate that binding of antibodies to specific sites on GP Ilb/IIIa may induce Fc-dependent platelet activation.This study was supported by the Foundation for Medical Research MEDIGON (grant no. 900-526-057.

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Monoclonal antibodies against porcine platelet membrane glycoproteins Ib and IIb/IIIa

Blood ◽

10.1182/blood.v72.5.1740.1740 ◽

1988 ◽

Vol 72 (5) ◽

pp. 1740-1747 ◽

Cited By ~ 5

Author(s):

H Takami ◽

WL Nichols ◽

SE Kaese ◽

RS Miller ◽

JA Katzmann ◽

...

Keyword(s):

Monoclonal Antibody ◽

Monoclonal Antibodies ◽

Platelet Aggregation ◽

Polyacrylamide Gel Electrophoresis ◽

Sodium Dodecyl ◽

Human Platelets ◽

Platelet Membrane ◽

In Vivo Studies ◽

Membrane Glycoproteins ◽

Fab Fragments

Abstract We prepared murine monoclonal antibodies to porcine platelet membrane glycoprotein (GP) Ib and GP IIb/IIIa for further study of the porcine hemostatic mechanism. One monoclonal antibody, designated PP3–4C, blocked Ristocetin-induced platelet agglutination and caused 80% inhibition of Ristocetin-induced 125I-von Willebrand factor (vWF) binding to porcine platelets at a concentration of greater than or equal to 12 micrograms IgG/mL. PP3–4C did not affect adenosine diphosphate (ADP)- or collagen-induced platelet aggregation. Binding of 125I-Fab fragments of PP3–4C to platelets was saturable at 3.7 x 10(4) +/- 0.8 x 10(4) molecules per platelet. Another monoclonal antibody, designated PP3–3A, blocked ADP- or collagen-induced platelet aggregation at 6 micrograms IgG/mL. At a concentration of 10 micrograms IgG/mL, PP3–3A completely inhibited binding either of 125I-fibrinogen or of 125I-vWF to ADP-stimulated platelets. PP3–3A did not affect Ristocetin-induced platelet agglutination nor 125I-vWF binding to platelets in the presence of Ristocetin. Binding of 125I-Fab' fragments of PP3–3A to platelets was saturable at 9.8 x 10(4) +/- 1.2 x 10(4) molecules per platelet. PP3–4C antibody (anti-GP Ib) did not bind to human platelets; however, PP3–3A antibody (anti-GP IIb-IIIa) had partial cross-reactivity with human platelets. Immunoaffinity chromatography of solubilized surface-radiolabeled porcine platelets and subsequent sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis demonstrated that PP3–4C recognized a GP with an apparent molecular weight of 160,000 (nonreduced), and 140,000 (reduced). PP3–3A recognized GPs with apparent molecular weights of 130,000 and 80,000 (nonreduced), and 115,000 and 95,000 (reduced). These monoclonal antibodies to porcine platelet membrane GPs, which are structural and functional analogues of human GP Ib and GP IIb/IIIa, will be useful for in vitro and in vivo studies of the mammalian hemostatic mechanism.

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FAB FRAGMENTS OF MONOCLONAL ANTIBODIES SPECIFIC FOR PORCINE PLATELET MEMBRANE GLYCOPROTEINS GP IB ANDGP IIB/IIIA

10.1055/s-0038-1643513 ◽

1987 ◽

Author(s):

H Takami ◽

W L Nichols ◽

S E Kaese ◽

R S Miller ◽

J A Katzmann ◽

...

Keyword(s):

Monoclonal Antibody ◽

Monoclonal Antibodies ◽

Platelet Aggregation ◽

Platelet Membrane ◽

In Vivo Studies ◽

Membrane Glycoproteins ◽

Fab Fragments ◽

Igg1 Subclass ◽

Von Willebrand

For further study of the porcine hemostatic mechanism, we have prepared murine monoclonal antibodies, and F(ab')2 and Fab fragments, specific for porcine platelet membrane glycoproteins GP lb and GP Ilb/IIIa. To avoid production of antibodies to von Willebrand factor (vWF), mice were immunized with platelets obtained from pigs with severe von Willebrand,s disease. One monoclonal antibody (PP3-4C), of IgG1 subclass, caused 85% inhibition of Ristocetin-induced platelet binding of 125I-vWF (porcine) at ≥12 µg IgG/ml. PP3-4C did not affect ADP or collagen-induced platelet aggregation nor inhibit 125I-fibrinogen (porcine) binding. Pepsin and papain digestion, respectively, were used to prepare PP3-4C F(ab')2 and Fab fragments. PP3-4C F(ab')2 at concentrations ≥12 µg/ml caused 80% inhibition of washed platelet agglutination in the presence of vWF and Ristocetin, whereas Fab fragments at concentrations ≥10 µg/ml caused 60% inhibition. Another monoclonal antibody (PP3-3A), of IgG1 subclass, completely inhibited ADP or collagen-induced platelet aggregation at an IgG concentration of 6 µg/ml. At 10 µg IgG/ml PP3-3A completely inhibited binding either of 125I-fibrinogen or of 125I-vWF to ADP-stimulated porcine platelets. PP3-3A did not affect vWF-dependent Ristocetin-induced platelet agglutination, nor 125I-vWF binding to platelets in the presence of Ristocetin. PP3-3A did not bind to platelets which were treated with 10 mM EDTA at 37°C for 60 min. F(ab')2 and Fab fragments were isolated from PP3-3A pepsin or papain digests. Both types of PP3-3A fragments caused 100% inhibition of ADP-induced platelet aggregation, at concentrations ≥6 yg/ml. Immunoprecipitation of surface-radiolabeled porcine platelets and subsequent SDS-PAGE demonstrated that PP3-4C recognized a glycoprotein with molecular weight of 140,000 (under reducing conditions), and 165,000 (non-reduced). PP3-3A recognized glycoproteins with molecular weights of 115,000 and 100,000 (reduced), and 130,000 and 80,000 (non-reduced). Neither monoclonal antibody bound to human platelets. These monoclonal antibodies to porcine platelet membrane glycoproteins which are analogues of human GP lb and GP Ilb/IIIa will be useful for in vitro and in vivo studies to further understanding of mammalian hemostatic mechanisms.

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Monoclonal antibodies against porcine platelet membrane glycoproteins Ib and IIb/IIIa

Blood ◽

10.1182/blood.v72.5.1740.bloodjournal7251740 ◽

1988 ◽

Vol 72 (5) ◽

pp. 1740-1747

Author(s):

H Takami ◽

WL Nichols ◽

SE Kaese ◽

RS Miller ◽

JA Katzmann ◽

...

Keyword(s):

Monoclonal Antibody ◽

Monoclonal Antibodies ◽

Platelet Aggregation ◽

Polyacrylamide Gel Electrophoresis ◽

Sodium Dodecyl ◽

Human Platelets ◽

Platelet Membrane ◽

In Vivo Studies ◽

Membrane Glycoproteins ◽

Fab Fragments

We prepared murine monoclonal antibodies to porcine platelet membrane glycoprotein (GP) Ib and GP IIb/IIIa for further study of the porcine hemostatic mechanism. One monoclonal antibody, designated PP3–4C, blocked Ristocetin-induced platelet agglutination and caused 80% inhibition of Ristocetin-induced 125I-von Willebrand factor (vWF) binding to porcine platelets at a concentration of greater than or equal to 12 micrograms IgG/mL. PP3–4C did not affect adenosine diphosphate (ADP)- or collagen-induced platelet aggregation. Binding of 125I-Fab fragments of PP3–4C to platelets was saturable at 3.7 x 10(4) +/- 0.8 x 10(4) molecules per platelet. Another monoclonal antibody, designated PP3–3A, blocked ADP- or collagen-induced platelet aggregation at 6 micrograms IgG/mL. At a concentration of 10 micrograms IgG/mL, PP3–3A completely inhibited binding either of 125I-fibrinogen or of 125I-vWF to ADP-stimulated platelets. PP3–3A did not affect Ristocetin-induced platelet agglutination nor 125I-vWF binding to platelets in the presence of Ristocetin. Binding of 125I-Fab' fragments of PP3–3A to platelets was saturable at 9.8 x 10(4) +/- 1.2 x 10(4) molecules per platelet. PP3–4C antibody (anti-GP Ib) did not bind to human platelets; however, PP3–3A antibody (anti-GP IIb-IIIa) had partial cross-reactivity with human platelets. Immunoaffinity chromatography of solubilized surface-radiolabeled porcine platelets and subsequent sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis demonstrated that PP3–4C recognized a GP with an apparent molecular weight of 160,000 (nonreduced), and 140,000 (reduced). PP3–3A recognized GPs with apparent molecular weights of 130,000 and 80,000 (nonreduced), and 115,000 and 95,000 (reduced). These monoclonal antibodies to porcine platelet membrane GPs, which are structural and functional analogues of human GP Ib and GP IIb/IIIa, will be useful for in vitro and in vivo studies of the mammalian hemostatic mechanism.

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Functional Characterization of PM6/13, a β3-specific (GPIIIa/CD61) Monoclonal Antibody that Shows Preferential Inhibition of Fibrinogen Binding over Fibronectin Binding to Activated Human Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614247 ◽

1998 ◽

Vol 79 (01) ◽

pp. 177-185 ◽

Cited By ~ 10

Author(s):

Ashia Siddiqua ◽

Michael Wilkinson ◽

Vijay Kakkar ◽

Yatin Patel ◽

Salman Rahman ◽

...

Keyword(s):

Monoclonal Antibody ◽

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Functional Characterization ◽

Human Platelets ◽

Western Blots ◽

Activated Platelets ◽

Reducing Conditions ◽

Fibronectin Binding

SummaryWe report the characterization of a monoclonal antibody (MAb) PM6/13 which recognises glycoprotein IIIa (GPIIIa) on platelet membranes and in functional studies inhibits platelet aggregation induced by all agonists examined. In platelet-rich plasma, inhibition of aggregation induced by ADP or low concentrations of collagen was accompanied by inhibition of 5-hydroxytryptamine secretion. EC50 values were 10 and 9 [H9262]g/ml antibody against ADP and collagen induced responses respectively. In washed platelets treated with the cyclooxygenase inhibitor, indomethacin, PM6/13 inhibited platelet aggregation induced by thrombin (0.2 U/ml), collagen (10 [H9262]g/ml) and U46619 (3 [H9262]M) with EC50 = 4, 8 and 4 [H9262]g/ml respectively, without affecting [14C]5-hydroxytryptamine secretion or [3H]arachidonate release in appropriately labelled cells. Studies in Fura 2-labelled platelets revealed that elevation of intracellular calcium by ADP, thrombin or U46619 was unaffected by PM6/13 suggesting that the epitope recognised by the antibody did not influence Ca2+ regulation. In agreement with the results from the platelet aggregation studies, PM6/13 was found to potently inhibit binding of 125I-fibrinogen to ADP activated platelets. Binding of this ligand was also inhibited by two other MAbs tested, namely SZ-21 (also to GPIIIa) and PM6/248 (to the GPIIb-IIIa complex). However when tested against binding of 125I-fibronectin to thrombin stimulated platelets, PM6/13 was ineffective in contrast with SZ-21 and PM6/248, that were both potent inhibitors. This suggested that the epitopes recognised by PM6/13 and SZ-21 on GPIIIa were distinct. Studies employing proteolytic dissection of 125I-labelled GPIIIa by trypsin followed by immunoprecipitation with PM6/13 and analysis by SDS-PAGE, revealed the presence of four fragments at 70, 55, 30 and 28 kDa. PM6/13 did not recognize any protein bands on Western blots performed under reducing conditions. However Western blotting analysis with PM6/13 under non-reducing conditions revealed strong detection of the parent GP IIIa molecule, of trypsin treated samples revealed recognition of an 80 kDa fragment at 1 min, faint recognition of a 60 kDa fragment at 60 min and no recognition of any product at 18 h treatment. Under similar conditions, SZ-21 recognized fragments at 80, 75 and 55 kDa with the 55kDa species persisting even after 18 h trypsin treatment. These studies confirm the epitopes recognised by PM6/13 and SZ-21 to be distinct and that PM6/13 represents a useful tool to differentiate the characteristics of fibrinogen and fibronectin binding to the GPIIb-IIIa complex on activated platelets.

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Enhanced platelet aggregation and activation under conditions of hypothermia

Thrombosis and Haemostasis ◽

10.1160/th07-03-0189 ◽

2007 ◽

Vol 98 (12) ◽

pp. 1266-1275 ◽

Cited By ~ 41

Author(s):

Ruben Xavier ◽

Ann White ◽

Susan Fox ◽

Robert Wilcox ◽

Stan Heptinstall

Keyword(s):

Cardiac Surgery ◽

Platelet Aggregation ◽

Platelet Function ◽

Whole Blood ◽

Platelet Rich Plasma ◽

Baseline Levels ◽

Spontaneous Aggregation ◽

High Concentrations ◽

Induced Aggregation ◽

P2y12 Antagonist

SummaryThe effects on platelet function of temperatures attained during hypothermia used in cardiac surgery are controversial. Here we have performed studies on platelet aggregation in whole blood and platelet-rich plasma after stimulation with a range of concentrations of ADP, TRAP, U46619 and PAF at both 28°C and 37°C. Spontaneous aggregation was also measured after addition of saline alone. In citrated blood, spontaneous aggregation was markedly enhanced at 28°C compared with 37°C. Aggregation induced by ADP was also enhanced. Similar results were obtained in hirudinised blood. There was no spontaneous aggregation in PRP but ADP-induced aggregation was enhanced at 28°C. The P2Y12 antagonist AR-C69931 inhibited all spontaneous aggregation at 28°C and reduced all ADP-induced aggregation responses to small, reversible responses. Aspirin had no effect. Aggregation was also enhanced at 28°C compared with 37°C with low but not high concentrations of TRAP and U46619. PAF-induced aggregation was maximal at all concentrations when measured at 28°C, but reversal of aggregation was seen at 37°C. Baseline levels of platelet CD62P and CD63 were significantly enhanced at 28°C compared with 37°C. Expression was significantly increased at 28°C after stimulation with ADP, PAF and TRAP but not after stimulation with U46619. Overall, our results demonstrate an enhancement of platelet function at 28°C compared with 37°C, particularly in the presence of ADP.

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Antibodies Against Platelet Membrane Glycoproteins: Effect On Ristocetin-Induced Platelet Aggregation

10.1055/s-0038-1652644 ◽

1981 ◽

Author(s):

E F Ali-Briggs ◽

C S P Jenkins ◽

K J Clemetson

Keyword(s):

Platelet Aggregation ◽

Affinity Chromatography ◽

Platelet Membrane ◽

Receptor Activity ◽

Free Medium ◽

Membrane Glycoproteins ◽

Lectin Affinity Chromatography ◽

Lectin Affinity ◽

Fab Fragments ◽

Induced Aggregation

Some membrane glycoproteins (GPs) have been isolated by lectin-affinity chromatography and antibodies towards them have been raised. Platelets that have lost glycocalicin no longer respond to ristocetin-human VIII:WF, bovine VIIIR:WF, or to anti-glycocalicin or anti-GPs la and lb antibodies but are still agglutinated by anti-GPs lib and Ilia antibodies. Anti-GPs la and lb and anti-glycocalicin antibodies, IgG and Fab' fragments inhibited ristocetin- human VIIIR:WF- and bovine VIIIR:WF-induced aggregation of fixed, washed platelets and of platelets in plasma while anti-GPs Hb and Ilia antibodies were without effect.Crossed immunoelectrophorectic studies showed that glycocalicin was present on whole platelets in only trace amounts; anti-glycocalicin antibodies, however, recognized a slower migrating component. Platelets incubated in an EDTA-free medium no longer respond to ristocetin-human VIIIRrWF. Membranes isolated from such platelets contained glycocalicin which cross-reacted with a remnant of the slower migrating component. Anti-GPs la and lb antibodies gave more complex patterns but it was possible to identify the slower moving component recognized by the anti-glycocalicin antibodies.These results show that glycocalicin is not normally found as such on whole platelets but is present as a precursor which is most likely GP lb. On degradation of this precursor, glycocalicin is released from the membrane and VIIIRrWF-receptor activity is lost.

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ANALYSIS OF THE FUNCTIONAL ROLE OF PLATELET MEMBRANE GLYCOPROTEINS WITH MONOCLONAL ANTIBODIES

10.1055/s-0038-1643509 ◽

1987 ◽

Author(s):

H Nagata ◽

S Nomura ◽

K Oda ◽

T Kokawa ◽

K Yasunaga

Keyword(s):

Monoclonal Antibodies ◽

Lymphoblastic Leukemia ◽

Atp Release ◽

Platelet Membrane ◽

Calcium Flux ◽

Antibody Concentration ◽

Membrane Glycoproteins ◽

Induce Platelet Aggregation ◽

Platelet Surface ◽

Induced Aggregation

Eight monoclonal antibodies were obtained which recognized platelet surface antigens of these, 5 (NNKYl-32, NNKY2-5, NNKY2-6, NNKY2-11, NNKY2-18 ) recognized GP IIb-IIIa complex, 2 (NNKY5-4, NNKY5-5 ) recognized GP lb and 1 (NNKYl-19) recognized CD 9 antigen. They were used to research the platelet membrane antigens.Monoclonal antibodies that recognize CD 9 antigen, which exists on the surface of platelets, acute lymphoblastic leukemia cells, eosinophils and other tissue, are known to act as an aggregating agent to platelets and NNKYl-19 was fond to induce platelet aggregation accompanied by ATP release. NNKY5-4 had no effect on platelet functions. NNKY5-5 inhibited aggregation induced by ristocetin but had no effect on aggregation induced by ADP, collagen, thrombin, and NNKYl-19. NNKYl-32, 2-5, 2-6, 2-11, and 2-18 inhibited aggregation induced by ADP, collagen, thrombin, and NNKYl-19, although slight release of ATP was recognized when NNKYl-19-induced aggregation was completely inhibited by NNKYl-32. Mutual inhibition of binding to platelet membranes between the 3 groups of monoclonal antibodies was not recognizedNNKYl-19-induced aggregation was associated with a lag time that was plo-longed in inverse proportion to antibody concentration. Aspirin had almost no effect on NNKYl-19-induced aggregation. A TXA2 receptor antagonist, a calci-um-channel blocking drug and EDTA inhibited NNKYl-19-induced aggregation. These results indicate that GP I b, GP IIb-IIIa complex and the cyclooxygenase pathway are not involved in NNKYl-19-induced platelet activation, that the target of NNKYl-19 on the platelet membrane is same as that of TXA2, and that the mechanism of activation by NNKYl-19 is related to calcium flux.

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