ristocetin and Bernard-Soulier-Syndrome

Topics: Adenosine Diphosphate; Antibodies, Monoclonal; Bernard-Soulier Syndrome; Blood Platelets; Cell Membrane; Collagen; Endothelium; Epitopes; Glycoproteins; Humans; Immunologic Techniques; Macromolecular Substances; Platelet Adhesiveness; Platelet Membrane Glycoproteins; Receptors, Cell Surface; Ristocetin; Thrombin; von Willebrand Diseases; von Willebrand Factor

Bernard-Soulier syndrome (BSS) is a rare severe autosomal recessive bleeding disorder. To date heterozygous carriers of BSS mutations have not been shown to have bleeding symptoms. We assessed bleeding using a semi-quantitative questionnaire, platelet parameters, PFA-100 closure times, ristocetin response, GP Ib/IX expression and VWF antigen in 14 BSS patients, 30 heterozygote carriers for related mutations and 29 controls. Eight mutations in GP1BA, GP1BB or GP9 were identified including four previously unknown pathogenic mutations. Subjects with BSS reported markedly more mucocutaneous bleeding than controls. Increased bleeding was also observed in heterozygotes. Compared to controls, patients with BSS had lower optical platelet counts (P < 0.001), CD61-platelet counts (P < 0.001) and higher mean platelet volume (17.7 vs. 7.8 fL, P < 0.001) and ristocetin response and closure times were unmeasurable. Heterozygotes had higher MPV (9.7 fL, P < 0.001) and lower platelet counts (P < 0.001) than controls but response to ristocetin and closure times were normal. The VWF was elevated in both BSS and in heterozygotes (P = 0.005). We conclude that heterozygotes for BSS mutations have lower platelet counts than controls and show a bleeding phenotype albeit much milder than in BSS. Both patients with BSS and heterozygote carriers of pathogenic mutations have raised VWF.

Topics: Adolescent; Adult; Aged; Bernard-Soulier Syndrome; Blood Coagulation; Blood Platelets; Child; Coagulants; Female; Gene Expression; Heterozygote; Homozygote; Humans; Male; Middle Aged; Mutation; Phenotype; Platelet Count; Platelet Glycoprotein GPIb-IX Complex; Ristocetin; Severity of Illness Index; Surveys and Questionnaires; von Willebrand Factor

Topics: Bernard-Soulier Syndrome; Child, Preschool; Diagnosis, Differential; Epistaxis; Female; Humans; Platelet Aggregation; Ristocetin; Thrombasthenia

Bernard-Soulier syndrome (BSS) is an inherited bleeding disorder caused by a defect in the platelet glycoprotein (GP) Ib/IX complex. The GPIX W127X mutation is the most common genetic defect in Japanese patients with BSS, which is often misdiagnosed as immune thrombocytopenic purpura, presumably due to residual expression of GPIbα. Neither the mechanism by which this mutation leads to a mild bleeding diathesis, nor whether functional GPIbα is expressed on platelet surfaces is known. We investigated GPIbα expression and function in platelets with a GPIX W127X mutation (GPIXW127X). GPIbα complexed with GPIbβ by disulfide bonding was expressed on GPIXW127X platelets and stable CHO-K1 cells lacking GPIX but expressing GPIbα and GPIbβ. Expression of GPIbα/β on GPIXW127X platelets was sufficient to support adhesion to immobilized von Willebrand factor and type III collagen and ristocetin-induced platelet agglutination. A residual amount of functional GPIbα/β heteromer expressed on GPIXW127X platelets partially compensates for the absence of the GPIb/IX complex. This may account for the mild bleeding phenotype of the BSS variant characterized by a non-sense mutation in GPIX.

Topics: Adult; Animals; Antibodies, Monoclonal; Bernard-Soulier Syndrome; Blood Platelets; CHO Cells; Codon, Nonsense; Collagen Type III; Cricetinae; Cystine; Diagnostic Errors; Female; Humans; Membrane Glycoproteins; Phenotype; Platelet Adhesiveness; Platelet Glycoprotein GPIb-IX Complex; Point Mutation; Pregnancy; Pregnancy Complications, Hematologic; Purpura, Thrombocytopenic, Idiopathic; Recombinant Fusion Proteins; Ristocetin; Transfection; von Willebrand Factor

To delineate the critical features of platelets required for formation and stability of thrombi, thromboelastography and platelet aggregation measurements were employed on whole blood of normal patients and of those with Bernard-Soulier Syndrome (BSS) and Glanzmann's Thrombasthenia (GT). We found that separation of platelet activation, as assessed by platelet aggregation, from that needed to form viscoelastic stable whole blood thrombi, occurred. In normal human blood, ristocetin and collagen aggregated platelets, but did not induce strong viscoelastic thrombi. However, ADP, arachidonic acid, thrombin, and protease-activated-receptor-1 and -4 agonists, stimulated both processes. During this study, we identified the genetic basis of a very rare double heterozygous GP1b deficiency in a BSS patient, along with a new homozygous GP1b inactivating mutation in another BSS patient. In BSS whole blood, ADP responsiveness, as measured by thrombus strength, was diminished, while ADP-induced platelet aggregation was normal. Further, the platelets of 3 additional GT patients showed very weak whole blood platelet aggregation toward the above agonists and provided whole blood thrombi of very low viscoelastic strength. These results indicate that measurements of platelet counts and platelet aggregability do not necessarily correlate with generation of stable thrombi, a potentially significant feature in patient clinical outcomes.

Topics: Adenosine Diphosphate; Adolescent; Arachidonic Acid; Base Sequence; Bernard-Soulier Syndrome; Blood Coagulation; Blood Platelets; Coagulants; DNA Mutational Analysis; Female; Humans; Male; Membrane Glycoproteins; Middle Aged; Molecular Sequence Data; Platelet Activation; Platelet Aggregation; Platelet Glycoprotein GPIb-IX Complex; Receptor, PAR-1; Ristocetin; Sequence Deletion; Thrombasthenia; Thrombelastography; Thrombin; Viscoelastic Substances; Young Adult

Bernard-Soulier syndrome is a severe bleeding disease due to a defect of GPIb/IX/V, a platelet complex that binds the von Willebrand factor. Due to the rarity of the disease, there are reports only on a few cases compromising any attempt to establish correlations between genotype and phenotype. In order to identify any associations, we describe the largest case series ever reported, which was evaluated systematically at the same center.. Thirteen patients with the disease and seven obligate carriers were enrolled. We collected clinical aspects and determined platelet features, including number and size, expression of membrane glycoproteins, and ristocetin induced platelet aggregation. Mutations were identified by direct sequencing of the GP1BA, GP1BB, and GP9 genes and their effect was shown by molecular modeling analyses.. Patients all had a moderate thrombocytopenia with giant platelets and a bleeding tendency whose severity varied among individuals. Consistent with expression levels of GPIbα always lower than 10% of control values, platelet aggregation was absent or severely reduced. Homozygous mutations were identified in the GP1BA, GP1BB and GP9 genes; six were novel alterations expected to destabilize the conformation of the respective protein. Except for obligate carriers of a GP9 mutation with a reduced GPIb/IX/V expression and defective aggregation, all the other carriers had no obvious anomalies.. Regardless of mutations identified, the patients' bleeding diathesis did not correlate with thrombocytopenia, which was always moderate, and platelet GPIbα expression, which was always severely impaired. Obligate carriers had features similar to controls though their GPIb/IX/V expression showed discrepancies. Aware of the limitations of our cohort, we cannot define any correlations. However, further investigations should be encouraged to better understand the causes of this rare and underestimated disease.

Topics: Adolescent; Adult; Amino Acid Sequence; Bernard-Soulier Syndrome; Blood Platelets; Cell Shape; Child; Child, Preschool; Female; Genetic Association Studies; Genetic Markers; Hemorrhage; Homozygote; Humans; Italy; Male; Membrane Glycoproteins; Middle Aged; Molecular Sequence Data; Platelet Aggregation; Platelet Count; Platelet Glycoprotein GPIb-IX Complex; Point Mutation; Polymerase Chain Reaction; Ristocetin; Thrombocytopenia; von Willebrand Factor; Young Adult

Platelets of patients suffering from Glanzmann's thrombasthenia (GT) and Bernard Soulier Syndrome (BSS) are defective in different membrane glycoproteins. Since these integrins can be identified by monoclonal antibodies, normal infused platelets could be distinguished from defective platelets and followed by using flow cytometry (FC). We studied this aspect in two recipients suffering, one from GT and the other one, who underwent splenectomy, from BSS. One hour after transfusion, normal platelets comprised 17% of the total platelet population in the patient with GT. Aggregation tests detected a measurable response to collagen (increase of 15% of transmittance). The presence of transfused platelets decreased progressively to 0.8% on day 4, which corresponded with a half-life of 2.6 days. Studies performed in the patient suffering from BSS found that 1 hour after transfusion, 53% of the platelet population corresponded to normal platelets. There was a progressive decay until day 6, which corresponded to a half-life of 4.6 days. Aggregation tests also detected a platelet response to ristocetin from 1 hour after transfusion (47% increase of transmittance) to day 3. FC is useful to measure platelet lifespan in these kinds of patients. We also report the first studies of platelet aggregation after platelet transfusion.

Topics: Bernard-Soulier Syndrome; Blood Platelets; Cell Survival; Child; Collagen; Female; Flow Cytometry; Humans; Middle Aged; Platelet Aggregation; Platelet Count; Platelet Membrane Glycoproteins; Platelet Transfusion; Ristocetin; Thrombasthenia

Sebastian syndrome is characterized by enlarged platelets and Döhle-like body leukocyte inclusions. This syndrome is an MYH-9-related disease, a group that also includes May-Hegglin anomaly and Fechtner syndrome. The differential diagnosis of the MYH-9 diseases requires ultrastructural studies. Certain in vitro aggregation responses may be abnormal in these conditions.. A 6-month-old boy presented with macrothrombocytopenia but no overt bleeding tendency. Giant platelets and Döhle-like body leukocyte inclusions were present in blood smears from both the patient and his mother. Electron microscopy confirmed ultrastructural features consistent with Sebastian syndrome. Platelet aggregation studies were normal except for an impaired response to the agonist ristocetin.. In this patient peripheral blood analyses and platelet aggregation studies revealed disease features shared with the Bernard-Soulier syndrome, but this syndrome was excluded by cellsurface glycoprotein analysis.

Topics: Bernard-Soulier Syndrome; Blood Platelets; Child, Preschool; Diagnosis, Differential; Humans; Male; Microscopy, Electron; Platelet Aggregation; Ristocetin; Syndrome; Thrombocytopenia

Four hundred and ninety seven patients were referred to our center for platelet aggregation studies because of spontaneous mucocutaneous bleeds. All these patients had normal complete blood count, platelet count and peripheral smears except in ten patients of Bernard Soulier Syndrome where platelet count was marginally reduced in the presence of giant platelets. Two hundred and eighty patients were found to have normal platelet aggregation to ADP, collagen, ristocetin and arachidonic acid. Out of the remaining 217 patients, 62 patients were diagnosed to have Glanzmanns thrombasthenia, 10 Bernard Soulier Syndrome, 6 storage pool deficiencies, 7 cyclooxygenase deficiencies and 72 von Willebrand disease. In all the patients with GT and BSS, diagnosis was confirmed with flow cytometry using multiple monoclonal antibodies to GPIIb-IIIa and GPIb-IX. There were sixty patients where initial platelet aggregation studies showed reduced (<30%) aggregation to either ADP, collagen, ristocetin or arachidonic acid in its various combination, however in 12 such patients (20%) the platelet aggregation studies were normal on repetition. All our platelet aggregation studies were done only after assuring that the patient is not taking any medicine for at least 7-10 days which may affect the platelet function tests. The present study shows that single atypically abnormal platelet aggregation studies should always be repeated. Finally in 48/217 patients (22%) some aggregation abnormality to one or more of the agonists persisted, although we could not categorize these patients into any clear-cut platelet disorder. None of these 48 patients platelet associated immunoglobulin was increased by flow cytometry. It is possible that large number of patients from that disorder will finally prove to be some form of platelet secretory defect. In north India similar group of defect in a large number of patients have been reported as isolated PF3 abnormality or thrombasthenic thrombopathy.

Topics: Adenosine Diphosphate; Arachidonic Acid; Bernard-Soulier Syndrome; Blood Coagulation Disorders; Blood Platelets; Collagen; Flow Cytometry; Humans; Platelet Aggregation; Prostaglandin-Endoperoxide Synthases; Reference Values; Ristocetin; Thrombasthenia; von Willebrand Diseases

To diagnose a patient with Bernard-Soulier syndrome (BSS) and investigate her gene abnormality.. Platelet size and structure were studied under light and electron microscopies. Platelet membrane glycoproteins (GP) were measured by flow cytometry. PCR and DNA sequencing were used to identify gene abnormality.. The patient had thrombocytopenia with giant platelets. Ristocetin-induced platelet agglutination was absent. GP I b/IX complex in the platelet membrane was significantly decreased, which was resulted from an Ala139 Thr substitution in the transmembrane domain of GPIX.. Ala139 Thr mutation of the GPIX gene in this patient is a novel missense mutation, which has not been reported in BSS.

Topics: Adult; Alanine; Bernard-Soulier Syndrome; Cell Size; Female; Humans; Membrane Proteins; Platelet Aggregation; Platelet Glycoprotein GPIb-IX Complex; Point Mutation; Protein Structure, Tertiary; Ristocetin; Threonine; Thrombocytopenia

Most proteolytic enzymes that cleave glycoprotein lb (GPlb) also cleave other glycoproteins or receptors on the surface of platelets. We have used an O-sialoglycoprotein endoprotease from Pasteurella haemolytica that selectively cleaves the heavily O-glycosylated GPlb, but does not cleave N-linked glycoproteins or unglycosylated proteins. Isolated, [14C]serotonin-labeled platelets in Tyrode-albumin solution were incubated with 10 microg/mL endoprotease for 60 minutes at 37 degrees C. These platelets did not release [14C]serotonin, had no detectable GPIb, and were unresponsive to ristocetin/von Willebrand factor. Compared with control platelets, aggregation and release of [14C]serotonin by the endoprotease-pretreated platelets were inhibited in response to low concentrations of thrombin, SFLLRN (the PAR-1-activating peptide), collagen, and U46619 (a thromboxane A(2) mimetic); aggregates were smaller in size. The presence of fibrinogen overcame the inhibition of responses induced by SFLLRN, collagen, and U46619. With fibrinogen, primary ADP-induced aggregation was scarcely affected by pretreatment with the endoprotease. Thus, the PAR-1 receptor for thrombin, and receptors for collagen, thromboxane A(2), fibrinogen (GPIIb/IIIa), and ADP appear to function normally on the endoprotease-pretreated platelets. Since only GPIb is cleaved by the endoprotease, these platelets seem to provide potential surrogates for Bernard-Soulier syndrome platelets for further studies of platelet functions in this condition.

Topics: Agglutination; Bernard-Soulier Syndrome; Blood Platelets; Carbon Radioisotopes; Coagulants; Fibrinogen; Humans; Mannheimia haemolytica; Metalloendopeptidases; Platelet Aggregation; Platelet Glycoprotein GPIb-IX Complex; Ristocetin; Serotonin

We describe a patient with positive antinuclear antibodies, polyclonal gammopathy and high level of circulating immunocomplexes, resulting in vascular purpura. In addition, the patient had a slightly prolonged bleeding time and an isolated defect of ristocetin-induced platelet aggregation (RIPA) in platelet-rich plasma (PRP). The patient's plasma also inhibited RIPA in normal PRP and in normal platelet suspension. The activity and multimeric structure of plasmatic von Willebrand factor showed no alteration. We could demonstrate an autoantibody against platelet membrane glycoprotein (GP) Ib, using an ELISA-type assay. These data suggest an acquired Bernard-Soulier syndrome. We suggest that the patient had an immunocomplex-mediated leukocytoclastic vasculitis accompanied by production of antinuclear autoantibodies as well as the presence of an autoantibody against GPIb. The titer of the anti-GPIb antibody, however, was too low to induce significant platelet-type bleeding tendency, only laboratory alterations were found. Moreover, in a later stage of her disease, she developed a severe necrotizing vasculitis which was followed by a deep venous thrombosis.

Topics: Antibodies, Antinuclear; Antibodies, Monoclonal; Antigens; Autoantibodies; Bernard-Soulier Syndrome; Bleeding Time; Enzyme-Linked Immunosorbent Assay; Female; Humans; Middle Aged; Plasma; Platelet Aggregation; Platelet Function Tests; Platelet Glycoprotein GPIb-IX Complex; Polyarteritis Nodosa; Ristocetin; Venous Thrombosis; von Willebrand Factor

Bernard-Soulier syndrome is a rare, congenital bleeding disorder caused by absent or defective GP Ib platelet membrane receptor for the von Willebrand factor (vWF). We studied two brothers with moderate bleeding symptoms. Bleeding time was prolonged and ristocetin-induced platelet aggregation was absent. Flow cytometric analysis showed that both boys had a subnormal expression of GP Ib. One antibody used (AN51) was bound only to 30% of the platelets and at a subnormal density. A second antibody (SZ2) also bound at a subnormal density but a normal fraction of the platelets were immunoreactive. Ristocetin stimulation of the patients' platelets in the presence of plasma resulted in a low binding of vWF, about 30% of healthy controls. On the other hand the expression of GP IIb/IIIa on the platelet membrane appeared to be supernormal even when the increased platelet size was taken into account as shown by the ratio between the density of GP IIIa and CD 9 structures. We conclude that these brothers have a variant of the Bernard-Soulier syndrome with a low expression of a GP Ib receptor.

Topics: Bernard-Soulier Syndrome; Bleeding Time; Child; Flow Cytometry; Humans; Male; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin

Topics: Bernard-Soulier Syndrome; Bleeding Time; Humans; Liver Cirrhosis; Male; Middle Aged; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin

To investigate the abnormality in platelet function in two patients with type I Gaucher's disease causing a chronic bleeding tendency despite normalisation of the platelet count after spleen removal.. Routine laboratory methods were used to assess baseline coagulation. Platelet aggregometry was used to assess platelet responses to a range of agonists, and abnormalities were further assessed in mixing experiments using washed platelets and patients' plasma.. Platelets from both patients with Gaucher's disease failed to agglutinate to ristocetin, despite normal platelet surface glycoprotein (GP) Ib and plasma von Willebrand factor activity. The agglutination of normal washed platelets was abolished by incubation in patient plasma. The inhibitory activity did not lie in the IgG fraction of patient plasma, and was found to be loosely associated with the patient platelet surface.. The inhibition of ristocetin induced platelet agglutination in patients with Gaucher's disease causes a prolonged skin bleeding time. This could be due to the accumulated glucocerebroside in the plasma coating the platelet membrane. It is suggested that the term pseudo-pseudo Bernard-Soulier syndrome would be appropriate, as on initial screening, the abnormality has the features of Bernard-Soulier syndrome, but further investigation shows normal plasma von Willebrand activity and platelet surface GP Ib concentrations. The inhibitory activity is not due to a platelet specific antibody as is the case in pseudo-Bernard Soulier syndrome.

Topics: Adult; Bernard-Soulier Syndrome; Cells, Cultured; Female; Gaucher Disease; Humans; Immunoglobulin G; Middle Aged; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin

We have previously shown that the platelet-aggregating activity of human MG-63 and HOS osteosarcoma cells depends at least in part upon tumor cell surface-associated thrombospondin, and suggested that platelet-osteosarcoma cell interactions could occur through interactions with specific platelet membrane receptors. In this study, the platelet-aggregating activity of MG-63 and HOS cells was studied by using a variety of platelet disorders. Both osteosarcoma cell lines induced a biphasic platelet aggregation response when added to normal platelet-rich plasma, while the second phase of aggregation was absent when added to gray platelets (deficiency in alpha-granule proteins) and to aspirin-treated platelets. Platelets from two unrelated patients with type I Glanzmann's thrombasthenia (deficiency in glycoprotein (GP) GPIIb/IIIa) did not aggregate at all with osteosarcoma cells. Using giant platelets from three patients with Bernard-Soulier syndrome (deficiency in GPIb/IX), the aggregation response induced by MG-63 and HOS cells was monophasic and reversible when compared to normal-sized platelets and to giant platelets from a patient with May-Hegglin anomaly (no membrane GP defect). Because GPIb serves as a receptor for von Willebrand factor during hemostasis, aggregation experiments were also conducted with the platelet-rich plasma of two patients with a low plasma von Willebrand factor concentration (type I von Willebrand's disease) before and after the infusion of deamino-D-arginine vasopressin. MG-63 and HOS cells induced biphasic platelet aggregation both before and after deamino-D-arginine vasopressin treatment, while the ristocetin-dependent binding of von Willebrand factor to platelets only occurred after deamino-D-arginine vasopressin treatment. Preincubation of normal platelet-rich plasma with monoclonal antibody SZ-2 directed against the von Willebrand binding domain of GPIb did not inhibit the platelet-aggregation activity of osteosarcoma cells, whereas anti-GPIb antibody SZ-2 did inhibit ristocetin-induced platelet agglutination. In addition, anti-GPIX antibodies did not affect platelet-osteosarcoma cell interactions. In conclusion, our data demonstrate that the first phase of the platelet-aggregating activity of human osteosarcoma cells is initiated by the interaction of these tumor cells with platelet membrane GPIIb/IIIa, whereas the second phase, even if plasma von Willebrand factor is deficient, involves platelet membrane GPIb and the partici

Topics: Antibodies, Monoclonal; Aspirin; Bernard-Soulier Syndrome; Blood Platelets; Cell Communication; Humans; In Vitro Techniques; Membrane Glycoproteins; Osteosarcoma; P-Selectin; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombasthenia; Thrombospondins; Tumor Cells, Cultured

The primary sequences of the three individual glycoprotein (GP) chains, GPIb alpha, GPIb beta, and GPIX, comprising the normal platelet GPIb/IX receptor for von Willebrand factor (vWF) have recently been determined, opening the possibility for characterization of disorders of this receptor at the molecular level. The presence of a leucine tandem repeat in each of these chains is of particular interest, because such repeats may be involved in associations between polypeptide segments. We now report an autosomal dominant variant of Bernard-Soulier disease associated with the heterozygous substitution of phenylalanine for a highly conserved leucine residue within the GPIb alpha leucine tandem repeat. Affected individuals experienced a moderate bleeding tendency, thrombocytopenia, and an increased mean platelet volume. Platelet aggregation was decreased only in response to ristocetin or to asialo-vWF. The kd for 125I-vWF binding to patients platelets was significantly increased over control values at 0.5 mg/mL ristocetin, but was normal at 1.0 or 1.5 mg/mL ristocetin. While sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed an essentially normal complement of all components of the GPIb/IX complex, a minor amount of a putative proteolytic fragment was identified that migrated faster than GPIb and was immunoreactive with polyclonal anti-GPIb alpha antibody, but not with a monoclonal antibody directed against the 45-Kd amino-terminal region of GPIb alpha. However, because the great majority of patient GPIb alpha comigrates with normal GPIb alpha, the major functional abnormalities of the patient platelets are most likely a consequence of the altered structure of the nonproteolyzed protein. Full concordance within the studied family between phenotypic expression and a heterozygous single nucleotide substitution in genomic DNA coding for a phenylalanine in place of the wild-type leucine at residue 57 of the mature GPIb alpha, absence of this substitution in 266 alleles from the normal population, and the lack of any other abnormality of patient DNA throughout the entire coding sequence for GPIb alpha provide strong support that this substitution may constitute a pathologic point mutation responsible for the observed phenotypic abnormalities. While the roles that leucine tandem repeats may normally play within the GPIb/IX complex are not yet known, the perturbation of such a repeat in GPIb alpha may impair interaction with other components of the comp

Topics: Adolescent; Bernard-Soulier Syndrome; Blood Platelets; DNA; Electrophoresis, Polyacrylamide Gel; Humans; Leucine; Male; Mutation; Nucleic Acid Hybridization; Pedigree; Phenylalanine; Platelet Membrane Glycoproteins; Polymerase Chain Reaction; Repetitive Sequences, Nucleic Acid; Ristocetin; von Willebrand Factor

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 Ib (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 Ib 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 fluorescein-labeled Fc fragments to intact platelets. We conclude that GP 210 functions as a platelet Fc receptor.

Topics: Antibodies; Antigen-Antibody Complex; Bernard-Soulier Syndrome; Blood Platelets; Chymotrypsin; Detergents; Humans; Molecular Weight; Platelet Membrane Glycoproteins; Receptors, Fc; Ristocetin

The Bernard-Soulier syndrome is an inherited bleeding disorder that is due to a deficiency in platelet glycoprotein Ib. Bernard-Soulier platelets fail to agglutinate in response to ristocetin despite normal levels of factor VIII:von Willebrand factor. We report a patient who developed severe refractory thrombocytopenia postsurgically while receiving procainamide therapy. Thrombocytopenia was immune mediated since the patient's platelets bore high levels of antiplatelet antibody. Radioimmunoprecipitation studies demonstrated that the autoantibodies had specificity for platelet glycoproteins Ib and V as well as platelet HLA. The patient's plasma as well as purified immunoglobulin G completely inhibited the ristocetin-induced aggregation of normal platelets but did not inhibit adenosine diphosphate-induced aggregation. The laboratory studies revealed that this patient suffered from antibody-mediated thrombocytopenia with unusual characteristics that we have called pseudo-Bernard-Soulier syndrome.

Topics: Aged; Antilymphocyte Serum; Autoantibodies; Bernard-Soulier Syndrome; Blood Platelet Disorders; Female; Humans; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; Thrombocytopenia