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Biomedical subjects

B S Coller

Publications and source records attributed to B S Coller.

At least 127 records · Page 7Linked to original sources
PubMed1985

Inhibition of dog platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor.

To assess the potential of monoclonal antibodies that inhibit platelet function in vitro as in vivo therapeutic agents, F(ab')2 fragments (0.17 to 0.81 mg/kg) of a murine monoclonal antibody (7E3) that binds to platelet glycoproteins IIb and/or IIIa and blocks platelet aggregation induced by ADP were infused into three dogs. Soon after infusion, platelets recovered from the dogs showed a decreased aggregation response to adenosine diphosphate, with the highest dose producing nearly total inhibition. These platelets also showed decreased ability to bind 125I-7E3, which was assumed to reflect occupancy of the sites by the unlabeled F(ab')2 fragments. At the highest dose, the binding decreased by 85%, reflecting the binding of approximately 44,000 molecules of 7E3 F(ab')2 per platelet. Platelet counts decreased after antibody infusion by less than 20%, and none of the dogs showed spontaneous bleeding. Both the aggregation and binding results reverted toward normal within one day. We conclude that it is possible to profoundly inhibit platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antiplatelet antibody without producing spontaneous hemorrhage or significant thrombocytopenia.

Animals↗
PubMed1985

Related binding mechanisms for fibrinogen, fibronectin, von Willebrand factor, and thrombospondin on thrombin-stimulated human platelets.

Fibrinogen, fibronectin, von Willebrand factor, and thrombospondin are four large glycoproteins that bind to thrombin-stimulated platelets and influence cellular adhesive functions. The effects of five monoclonal antibodies that react with platelet membrane glycoproteins (GP) IIb and/or IIIa on the binding of these four molecules to stimulated platelets were assessed. Tab and PMI-1, antibodies recognizing GPIIb, had no effect, whereas 10E5 and 2G12, antibodies that immunoprecipitate both GPIIb and IIIa in the presence of calcium, inhibited binding of all four ligands by greater than 85%. T10, an antibody specific for the GPIIb-IIIa complex, produced partial inhibition (60% to 80%) of the binding of each ligand. Inhibitory antibodies were effective in the same dose range for all four proteins and also inhibited binding of fibrinogen, fibronectin, and von Willebrand factor to receptors fixed in an induced state (thrombin-stimulated platelets fixed with paraformaldehyde). Thrombospondin did not bind to these fixed cell preparations. The results suggest that these four adhesive proteins have a related mechanism of binding to thrombin-stimulated platelets. This related mechanism may entail the sharing of some, but not necessarily all, binding sites for the four ligands or a proximal relationship between these binding sites.

Antibodies, Monoclonal↗
PubMed1985

Platelet interaction with subendothelial extracellular matrix: platelet-fibrinogen interactions are essential for platelet aggregation but not for the matrix-induced release reaction.

Cultured endothelial cells produce an extracellular matrix (ECM) to which platelets adhere and spread, ultimately resulting in platelet aggregation, thromboxane B2 production, and serotonin release. We have investigated the role of fibrinogen binding to the platelet GPIIb/IIIa complex in these reactions by comparing normal platelet-rich plasma (PRP), PRP from patients with Glanzman's thrombasthenia (whose platelets lack the GPIIb/IIIa complex), PRP in the presence of a monoclonal antibody that blocks the binding of fibrinogen to the GPIIb/IIIa complex, platelets washed free of fibrinogen, and washed platelets to which fibrinogen was added. Although platelet aggregation was virtually completely inhibited in the samples in which the normal interaction between fibrinogen and GPIIb/IIIa was impaired, adhesion of platelets to the matrix, spreading, and release of [14C]-serotonin were not affected. All of the platelet preparations released significant amounts of T X B2 with time, but there was a decrease in the amount produced by both the thrombasthenic and antibody-treated platelets. We conclude that the interaction of fibrinogen with platelet GPIIb/IIIa is not required for platelet adhesion to ECM or for adhesion-induced shape change or serotonin release. On the other hand, the platelet-fibrinogen interaction may play some role in augmenting adhesion-induced T X B2 production, and it is absolutely required for adhesion-induced platelet aggregation.

Animals↗
PubMed1984

Evidence that glycocalicin circulates in normal plasma.

By using a combination of a heterologous antiserum to GPIb/glycocalicin and a radiolabeled monoclonal antibody to GPIb/glycocalicin, we were able to develop a sensitive and specific radioimmunoelectrophoretic assay that can distinguish small amounts of glycocalicin from GPIb. Normal plasmas were found to contain glycocalicin, even in samples treated with protease inhibitors and centrifuged extensively to remove platelets and platelet fragments. Confirmation that the plasma antigen had a relative molecular weight similar or identical to glycocalicin was obtained from studies employing gel chromatography and affinity chromatography. An immunoradiometric assay was developed to quantify plasma glycocalicin, and normal plasma was found to contain approximately 1-3 micrograms/ml. The plasma of a patient with severe thrombocytopenia due to aplastic anemia had less than 12.5% of the normal level of glycocalicin, whereas two patients with thrombocytopenia due to diseases of increased platelet destruction (idiopathic thrombocytopenic purpura and hemolytic-uremic syndrome) had normal levels. Thus, there appears to be ongoing catabolism of platelet GPIb in vivo, and we postulate that the plasma level of glycocalicin reflects a complex function of factors, including platelet count, platelet turnover, and the site of platelet destruction.

Blood Specimen Collection↗
PubMed1984

Fibrinogen competes with von Willebrand factor for binding to the glycoprotein IIb/IIIa complex when platelets are stimulated with thrombin.

Two monoclonal antibodies--one that blocks ristocetin-induced platelet binding of von Willebrand factor to glycoprotein Ib and one that blocks adenosine diphosphate-induced binding of fibrinogen to the glycoprotein IIb/IIIa complex--were used to assess the binding site(s) for von Willebrand factor when platelets are stimulated with thrombin or adenosine diphosphate (ADP). Neither agonist induced binding of von Willebrand factor to glycoprotein Ib. ADP and thrombin induced von Willebrand factor binding exclusively to the glycoprotein IIb/IIIa complex. The results of the site of binding of von Willebrand factor with thrombasthenic platelets were consistent with the data obtained with the monoclonal antibodies and normal platelets. Human fibrinogen caused complete inhibition of thrombin-induced von Willebrand factor binding to normal platelets at concentrations considerably below that found in normal plasma. We conclude that thrombin induces very little binding of exogenous von Willebrand factor to platelets at normal plasma fibrinogen levels.

Adenosine Diphosphate↗
PubMed1984

A murine monoclonal antibody that blocks fibrinogen binding to normal platelets also inhibits fibrinogen interactions with chymotrypsin-treated platelets.

We recently described a monoclonal antibody, 10E5 , that completely blocks adenosine diphosphate (ADP) induced fibrinogen binding to platelets and aggregation induced by ADP, epinephrine, and thrombin. Multiple lines of evidence indicate that 10E5 binds to platelet membrane glycoproteins IIb and/or IIIa. Because it has been reported that platelets treated with chymotrypsin aggregate when fibrinogen is added, we tested the effect of 10E5 antibody on chymotrypsin-induced fibrinogen binding and platelet aggregation. Aspirin-treated human platelets were washed in modified Tyrode's buffer (pH 7.5), incubated for 5 minutes at 22 degrees C with 300 micrograms/mL chymotrypsin, and washed again. The amount of 10E5 antibody bound to these platelets (37,232 +/- 2,928 molecules/platelet; mean +/- SEM, N=9) was similar to that bound to unstimulated control platelets (36,910 +/- 2,669) and did not differ significantly from the amount of antibody bound to ADP-treated platelets (P less than .01, N = 5). The amount of 10E5 bound to chymotrypsin-treated platelets correlated directly with the amount of fibrinogen bound to separate aliquots of the same platelet samples (r = .876, P less than .001). The 10E5 antibody caused virtually complete inhibition of both the binding of fibrinogen to chymotrypsin-treated platelets and the aggregation induced by exogenous fibrinogen. Immunoprecipitation studies of 125I-labeled chymotrypsin-treated platelets revealed that the 10E5 antibody bound proteins with molecular weights characteristic of glycoproteins IIb and IIIa. These data suggest that the fibrinogen receptor on chymotrypsin-treated platelets is identical to that on ADP-treated platelets and that this receptor is either near to, or on, the glycoprotein IIb/IIIa complex.

Animals↗
PubMed1983

Statistical analysis of repetitive subcloning by the limiting dilution technique with a view toward ensuring hybridoma monoclonality.

After empirically determining the adequacy of the Poisson equation for describing the distribution of particles in microtiter plate wells under the experimental conditions employed for subcloning hybridoma cells, an equation was developed for determining the probability of monoclonality after repetitive subclonings. A table derived from the equation and based on the percentage of wells showing growth allows the rapid evaluation of the likelihood of monoclonality.

Clone Cells↗
PubMed1983

A murine monoclonal antibody that completely blocks the binding of fibrinogen to platelets produces a thrombasthenic-like state in normal platelets and binds to glycoproteins IIb and/or IIIa.

To define better the role of the fibrinogen receptor in platelet physiology and to characterize it biochemically, a murine monoclonal antibody that completely blocks the binding of fibrinogen to the platelet surface was produced by the hybridoma technique with the aid of a functional screening assay. Purified F(ab')2 fragments and/or intact antibody completely blocked aggregation induced by ADP, thrombin, or epinephrine and the binding of radiolabeled fibrinogen to platelets induced by ADP. The antibody did not block agglutination of formaldehyde-fixed platelets by ristocetin or shape change induced by either ADP or thrombin. ADP- and epinephrine-induced release of ATP was completely inhibited by the antibody, but inhibition of release induced by collagen and thrombin was dose dependent and partial. The antibody also dramatically inhibited platelet retention in glass-bead columns, platelet adhesion to glass, and clot retraction. Thus, the antibody induced a thrombasthenic-like state. Immunofluorescent studies confirmed the specificity of the antibody for normal platelets and megakaryocytes and suggested that there is a marked decrease in detectable antigen in thrombasthenic platelets. Radiolabeled antibody bound to an average of approximately 40,000 sites on normal platelets but it bound to less than 2,000 sites on the platelets of a patient with thrombasthenia. The antibody immunoprecipitated both glycoproteins IIb and IIIa, and both glycoproteins bound to an affinity column of the antibody. These studies indicate that there is probably a single anatomic site that is crucial to the binding of all fibrinogen molecules and that this site is most likely on the glycoprotein IIb/IIIa complex. It also suggests that the thrombasthenic phenotype can be completely accounted for on the basis of the inhibition of fibrinogen binding to platelets.

Animals↗
PubMed1983

Studies with a murine monoclonal antibody that abolishes ristocetin-induced binding of von Willebrand factor to platelets: additional evidence in support of GPIb as a platelet receptor for von Willebrand factor.

A murine monoclonal antibody directed at or near a platelet membrane receptor for the von Willebrand factor was produced by the hybridoma technique. Purified F(ab')2 fragments and/or intact antibody completely blocked the agglutination of platelets induced by both ristocetin and bovine von Willebrand factor and the binding of von Willebrand factor antigen to platelets. The antibody also decreased platelet retention, prevented the reduction in platelet electrophoretic mobility caused by bovine von Willebrand factor, and decreased the serum prothrombin time. Radiolabeled F(ab')2 fragments bound to or approximately 2.5 X 10(4) sites on normal platelets with high affinity (KD or approximately 1.5 X 10(-8) M); there was no binding to platelets from 2 patients with the Bernard-Soulier syndrome. Immunoprecipitation and affinity chromatography studies indicated that the antibody binds to glycoprotein lb at a site contained on the externally oriented portion of the GPIb alpha chain (glycocalicin). An unidentified mol wt or approximately 20,000 molecule labeled by periodate/NaB3H4 coprecipitated and copurified with GPIb.

Antibodies, Monoclonal↗
PubMed1982

Severe von Willebrand's disease during labor and delivery.

In pregnant women with severe von Willebrand's disease, the prepartum period should include monitoring for a rise in factor VIII-related activities (factor VIII coagulant activity [factor VIII:C], factor VIII-related antigen [VIII R:Ag], and factor VIII ristocetin cofactor [factor VIII R:Cof]). Two women whose pregnancies were so monitored were delivered of normal infants: one by cesarean section and one by vaginal delivery. The failure of factor VIII:Ag or factor VIII R:Cof to rise above the level of 50% at term in the woman who delivered vaginally predicted hemostatic difficulty during the postpartum period. She was, therefore, treated with cryoprecipitate. In the woman who gave birth by cesarean section, although all factor VIII-related activities rose into the normal range, the additional surgical trauma anticipated in cesarean section prompted the use of cryoprecipitate as well.

Adult↗
PubMed1981

Normal pregnancy in a patient with a prior postpartum factor VIII inhibitor: with observations on pathogenesis and prognosis.

A 22-yr-old primigravada developed a hemorrhagic diathesis 6 days after delivering a normal female infant and was found to have an immunoglobulin inhibitor of factor VIII (15 Bethesda units). The patient was treated with prednisone and the bleeding stopped soon thereafter. Her inhibitor titer decreased over the next 8 mo, at which time no inhibitor was detectable. Nine months later she became pregnant again and proceeded to have an uneventful pregnancy and delivery of a normal female infant without evidence of a recurrence of the inhibitor. Studies of 3H-thymidine incorporation into the patient's lymphocytes in the presence of her own plasma or plasmas from her husband, normals, a von Willebrand patient, and a hemophilic patient yielded equivocal results. Analysis of VIII:CAg using 2 different antisera failed to discern immunologic differences between the VIII:CAg of the patient, her husband, or her first child. A review of the literature revealed that there were no recurrences with second pregnancies in any of the 8 patients with postpartum factor VIII inhibitors whose inhibitors had completely disappeared prior to delivery. While the pathogenesis of this disorder remains uncertain, the apparently favorable prognosis for such patients should be considered in counselling with regard to future pregnancies.

Adult↗
PubMed1981

Platelet membrane studies in the May-Hegglin anomaly.

Since studies of the giant platelets in the Bernard-Soulier syndrome have shown decreased electrophoretic mobility, decreased sialic acid, and an abnormality in a membrane glycoprotein, we performed similar studies on the giant platelets from two patients with the May-Hegglin anomaly. The patients' platelet electrophoretic mobilities did not differ from control. Although the total sialic acid contents of the patients' platelets were greater than control when calculated per platelet, they were very similar to control when normalized for differences in platelet volume and surface area. When platelet proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis there were no differences between the glycoproteins of control and patient platelets as judged by the patterns of periodic acid Schiff staining and fluorescein-labeled concanavalin A binding. Similarly, patterns of surface glycoprotein labeling by neuraminidase/galactose oxidase/KB3H4 were identical. We conclude that unlike the giant platelets in the Bernard-Soulier syndrome, those of the May-Hegglin anomaly are not associated with a membrane abnormality detectable by these techniques.

Adult↗