USE OF A MONOCLONAL ANTIBODY TO MEASURE THE SURFACE EXPRESSION OF THROMBOSPONDIN FOLLOWING PLATELET ACTIVATION

1987 ◽  
Author(s):  
C Legrand ◽  
V Dubernard ◽  
N Kieffer ◽  
A T Nurden
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Activation ◽  
Surface Expression ◽  
Ionophore A23187 ◽  
Normal Range ◽  
Platelet Surface ◽  
Platelet Protein ◽  
Platelet Binding ◽  
Chloramine T ◽  
Gray Platelet Syndrome

A radiolabelled monoclonal antibody (mAb) against native thrombospondin (TSP) has been used to quantitatively assess the surface exposure of intracellular TSP following platelet stimulation. This mAb, designated 5G11, was purified from ascitic fluid by ammonium sulfate precipitation followed by chromatogloghy on DEAE Trisacryl. The isolated IgG were labelled with I by the chloramine T method (sp.act. 200-500 cpm/ ng). The specificity of the mAb was established by immunoblot-ting and crossed immunoelectrophoresis using platelet protein extracts. When the labelled IgG (20 μg/ml) were incubated with resting platelets in Tyrode's buffer binding was of the order of 2,000 molecules per platelet. Binding was increased 2 fold and 5-7 fold respectively upon ADP- and thrombin-(or ionophore A23187) stimulation. Unactivated platelets from 2 patients with the Gray Platelet Syndrome bound baseline levels of 5G11, but binding did not increase after platelet activation. In the presence of saturating concentrations of mAb 5G11, an average of 30,000 molecules of IgG were bound by normal platelets stimulated by thrombin. This binding was strongly reduced in the presence of EDTA. It was not significantly affected by AP-2, an anti-GP IIb-IIIa monoclonal antibody which inhibited by more than 85% the binding of plasma fibrinogen but which did not inhibit the surface expression of platelet fibrinogen. It was decreased but not prevented by the presence of an excess of rabbit anti-fibrinogen Fab fragments during the stimulation, while binding at the lower end of the normal range was observed on two different occasions using platelets isolated from an afibrinogenemic patient lacking platelet fibrinogen. These results suggest that while platelet fibrinogen may contribute to the surface organization of TSP other component(s) are required for the full expression of TSP on the platelet surface.

scholarly journals Investigation of the mechanisms of monoclonal antibody-induced platelet activation

Blood ◽  
1991 ◽  
Vol 78 (4) ◽  
pp. 1019-1026 ◽  
Author(s):  
P Horsewood ◽  
CP Hayward ◽  
TE Warkentin ◽  
JG Kelton
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Binding Sites ◽  
Fc Receptors ◽  
Secondary Antibody ◽  
Igg Antibodies ◽  
Platelet Surface ◽  
Platelet Protein ◽  
Platelet Binding ◽  
Protein Components

Abstract Antiplatelet antibodies can activate platelets causing platelet aggregation and the release reaction. However, the pathway of activation by these antibodies is unknown and several potential mechanisms are possible. In this report, we describe studies investigating potential pathways of platelet activation by IgG antibodies. We tested 16 different IgG monoclonal antibodies (MoAbs) against a variety of platelet surface components and found that six antibodies were capable of causing platelet aggregation and release. These included MoAbs against glycoprotein (GP) IIb/IIIa, CD9, GPIV, and two other not well-characterized platelet components. There was no relationship between the number of platelet binding sites and the ability of an MoAb to activate the platelets. By adding intact and F(ab')2 preparations of the MoAb to control or Fc receptor-blocked platelets, we found that in all instances the MoAbs initiated platelet activation via interacting with the platelet Fc receptors. Clustering of the platelet protein components using a secondary antibody did not cause activation. Studies into the pathway of Fc-dependent activation demonstrated that the MoAbs were capable of activating platelets by occupying Fc receptors on adjacent platelets (interplatelet activation), as well as on the same platelet (intraplatelet activation).

scholarly journals Investigation of the mechanisms of monoclonal antibody-induced platelet activation

Blood ◽  
1991 ◽  
Vol 78 (4) ◽  
pp. 1019-1026 ◽  
Author(s):  
P Horsewood ◽  
CP Hayward ◽  
TE Warkentin ◽  
JG Kelton
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Binding Sites ◽  
Fc Receptors ◽  
Secondary Antibody ◽  
Igg Antibodies ◽  
Platelet Surface ◽  
Platelet Protein ◽  
Platelet Binding ◽  
Protein Components

Antiplatelet antibodies can activate platelets causing platelet aggregation and the release reaction. However, the pathway of activation by these antibodies is unknown and several potential mechanisms are possible. In this report, we describe studies investigating potential pathways of platelet activation by IgG antibodies. We tested 16 different IgG monoclonal antibodies (MoAbs) against a variety of platelet surface components and found that six antibodies were capable of causing platelet aggregation and release. These included MoAbs against glycoprotein (GP) IIb/IIIa, CD9, GPIV, and two other not well-characterized platelet components. There was no relationship between the number of platelet binding sites and the ability of an MoAb to activate the platelets. By adding intact and F(ab')2 preparations of the MoAb to control or Fc receptor-blocked platelets, we found that in all instances the MoAbs initiated platelet activation via interacting with the platelet Fc receptors. Clustering of the platelet protein components using a secondary antibody did not cause activation. Studies into the pathway of Fc-dependent activation demonstrated that the MoAbs were capable of activating platelets by occupying Fc receptors on adjacent platelets (interplatelet activation), as well as on the same platelet (intraplatelet activation).

scholarly journals von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2011-2021 ◽  
Author(s):  
P Hourdille ◽  
HR Gralnick ◽  
E Heilmann ◽  
A Derlon ◽  
AM Ferrer ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Immunogold Staining ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin- induced platelet activation is a potential mechanism for regulating platelet adhesivity.

scholarly journals Factor XIIIa binding to activated platelets is mediated through activation of glycoprotein IIb-IIIa

Blood ◽  
1994 ◽  
Vol 83 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
AD Cox ◽  
DV Devine
Keyword(s):  
Monoclonal Antibody ◽  
Flow Cytometry ◽  
Platelet Activation ◽  
Factor Xiiia ◽  
Cross Linking ◽  
Platelet Surface ◽  
Activated Platelets ◽  
Fibrinogen Binding ◽  
A Chain ◽  
Functional Receptor

Abstract Stabilization of a clot is dependent on fibrin cross-linking mediated by the transglutaminase, factor XIIIa (FXIIIa). In addition to fibrin stabilization, FXIIIa acts on a number of platelet-reactive proteins, including fibronectin and vitronectin, as well as the platelet proteins, glycoprotein (GP) IIb-IIIa, myosin, and actin. However, conditions inducing the platelet-activation dependent binding of FXIIIa have not been characterized nor have the sites mediating FXIIIa binding been identified. The generation of FXIIIa and consequent detection of FXIIIa on the platelet surface were compared with other thrombin- induced activation events; the rate at which FXIIIa bound to activated platelets was much slower than platelet degranulation or fibrin(ogen) binding. Whereas platelets could be rapidly induced to express a functional receptor for FXIIIa, the rate of FXIIIa binding to platelets is limited by the rate of conversion of FXIII to FXIIIa. Immunoprecipitation of radiolabeled platelets using polyclonal anti- FXIII A-chain antibody identified two proteins corresponding to GPIIb and GPIIIa. Preincubation of intact platelets with 7E3, a monoclonal antibody that blocks the fibrinogen binding site, or GRGDSP peptide inhibited FXIIIa binding by about 95% when measured by flow cytometry; FXIIIa binding to purified GPIIb-IIIa was also inhibited by 7E3. The binding of FXIIIa to purified GPIIb-IIIa was enhanced by the addition of fibrinogen, but not by that of fibronectin or thrombospondin, suggesting that FXIIIa also binds to fibrinogen associated with the complex. These observations suggest that activated platelets bearing FXIIIa may enhance stabilization of platelet-rich thrombi through surface-localized cross-linking events.

Chemical Agonists and High Shear Stress Induce Apoptosis in Human Platelets.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3875-3875
Author(s):  
Valery Leytin ◽  
Sergiy Mykhaylov ◽  
David J. Allen ◽  
Lukasz Miz ◽  
Elena V. Lyubimov ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Activation ◽  
Caspase 3 ◽  
Calcium Ionophore ◽  
Shear Stresses ◽  
Ionophore A23187 ◽  
High Shear ◽  
Platelet Surface ◽  
Platelet Apoptosis ◽  
Chemical Stimuli

Abstract Apoptosis, or programmed cell death, is appreciated as the main physiologic mechanism that regulates cell life-span and serves for controlled deletion of unwanted cells. Since its discovery in 1972, apoptosis was long attributed exclusively to nucleate cells. It took more than 20 years to recognize apoptosis in enucleated cells cytoplasts and anucleate platelets. During the following years, apoptosis has been demonstrated in platelets treated with natural and artificial agonists, in platelet concentrates aged during storage under standard blood banking conditions, and in animal models of suppressed thrombopoiesis and thrombocytopenia. Other studies documented that mechanical forces (shear stresses) stimulate platelet activation and signaling in the absence of exogenous chemical stimuli. We analysed whether shear stresses can trigger platelet apoptosis, a question that has not yet been studied. Using a cone-and-plate viscometer (CAP-2000, Brookfield Engineering Labs, Inc., Middleboro, MA), we exposed human platelet-rich plasma to different shear stresses, ranging from physiologic arterial and arterioles levels (10–44 dynes/cm2) to pathologic high levels (117–388 dynes/cm2) occurring in stenosed coronary, peripheral or cerebral arteries. We found that pathologic shear stresses induce not only platelet activation (P-selectin upregulation and GPIb-alpha downregulation) but also trigger apoptosis events, including mitochondrial transmembrane potential depolarization, caspase 3 activation, phosphatidylserine exposure, and platelet shrinkage and fragmentation into microparticles, whereas physiologic shear stresses are not effective. Platelets subjected to pathologic shear stresses are characterized by impaired platelet function as shown by the absence of ADP-induced platelet aggregation. Apoptosis changes were also induced by the treatment of platelets with calcium ionophore A23187 (10 μM) and thrombin (1 U/mL). Thus, in the present work, we have demonstrated that platelet apoptosis can be induced by chemical stimuli and by mechanical rheological forces (pathologic high shear stresses). Most of shear-induced activation and apoptosis events occur inside of the platelet, including translocation of CD62 from alpha-granules to the platelet surface, depolarization of mitochondrial inner membrane potential, activation of cytosolic enzyme caspase 3, and translocation of phosphatidylserine from the inner to the outer plasma membrane leaflet. These data suggest that the effects of shear stress on platelet activation and apoptosis are mediated by mechanoreceptor(s) that transmit activation and apoptosis signals to the cell interior. The platelet paradigm of apoptosis induced by chemical agonists and shear stresses suggests that apoptotic cytoplasmic machinery may function without nuclear participation.

scholarly journals Alteration of platelet function in dogs mediated by interleukin-6

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 398-403
Author(s):  
J Peng ◽  
P Friese ◽  
JN George ◽  
GL Dale ◽  
SA Burstein
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Activation ◽  
Platelet Function ◽  
Interleukin 6 ◽  
Platelet Activating Factor ◽  
Platelet Surface ◽  
Thrombin Activation ◽  
Dog Blood ◽  
And Control ◽  
Twofold Decrease

To determine if interleukin-6 (IL-6) administration influences platelet function, platelet activation was analyzed sequentially in IL-6-treated (80 micrograms/kg/d) and control dogs. Platelet activation was determined in whole blood by flow cytometry by quantitating the binding of a monoclonal antibody to platelet surface P-selectin after stimulation with graded doses of thrombin. Administration of IL-6 resulted in a twofold decrease in the thrombin concentration required for induction of half-maximal P-selectin expression (ED50) compared with control animals. The ED50 returned to normal after cessation of IL- 6 administration. As measured by P-selectin expression, enhanced responsiveness to the strong agonist platelet activating factor (PAF) was also observed in the IL-6-treated dogs. IL-6 had no effect on the susceptibility of platelets to thrombin activation when incubated with anticoagulated dog blood. The data show that, in addition to augmenting the platelet count in normal dogs, IL-6 enhances the sensitivity of platelets to activation in response to thrombin and PAF.

scholarly journals Direct detection of activated platelets and platelet-derived microparticles in humans

Blood ◽  
1990 ◽  
Vol 75 (1) ◽  
pp. 128-138 ◽  
Author(s):  
CS Abrams ◽  
N Ellison ◽  
AZ Budzynski ◽  
SJ Shattil
Keyword(s):  
Flow Cytometry ◽  
Cardiopulmonary Bypass ◽  
Platelet Activation ◽  
Bleeding Time ◽  
Relative Proportion ◽  
Open Heart Surgery ◽  
Normal Range ◽  
In Vivo Models ◽  
Platelet Surface ◽  
Activated Platelets

Flow cytometry was used to determine whether activated platelets and platelet-derived microparticles can be detected directly in whole blood after a hemostatic insult. Two different in vivo models of platelet activation were examined: (1) a standardized bleeding time, and (2) cardiopulmonary bypass. Platelets and microplatelets were identified with a biotinylated anti-glycoprotein (GP)lb antibody and a fluorophore, phycoerythrin-streptavidin. Microparticles were distinguished from platelets by light scatter. Activated platelets were detected with three fluorescein-labeled monoclonal antibodies (MoAbs): (1) PAC1, which binds to the activated form of GPIIb-IIIa; (2) 9F9, a newly developed antibody that is specific for fibrinogen bound to the surface of activated platelets; and (3) S12, which binds to an alpha- granule membrane protein expressed on the platelet surface after granule secretion. In nine normal subjects, bleeding times ranged from 4.5 to 7.5 minutes. Over this time, there was a progressive increase in the amount of PAC1, 9F9, and S12 bound to platelets in blood emerging from the bleeding time wound. With all three antibodies, platelet activation was apparent as early as 30 seconds after the incision (P less than .03). Activation was accompanied by a progressive decrease in the concentration of platelets in blood from the wound, while the concentration of microparticles increased slightly. In nine patients undergoing open heart surgery, 1 hour of cardiopulmonary bypass caused a 2.2-fold increase in the relative proportion of microparticles in circulating blood (P less than .001). Moreover, bypass caused platelet activation as evidenced by a mean two- to threefold increase in PAC1 binding to platelets. Although this increase was significant (P less than .02), PAC1 binding exceeded the normal range for unstimulated control platelets in only 5 of 9 patients, and 9F9 and S12 binding exceeded the normal range in only two patients. Taken together, these studies demonstrate that it is now feasible using flow cytometry to evaluate the extent of platelet activation and the presence of platelet- derived microparticles in the circulation of humans.

scholarly journals Annexin V as a probe of aminophospholipid exposure and platelet membrane vesiculation: a flow cytometry study showing a role for free sulfhydryl groups

Blood ◽  
1993 ◽  
Vol 81 (10) ◽  
pp. 2554-2565 ◽  
Author(s):  
J Dachary-Prigent ◽  
JM Freyssinet ◽  
JM Pasquet ◽  
JC Carron ◽  
AT Nurden
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Annexin V ◽  
Cytoskeletal Proteins ◽  
Procoagulant Activity ◽  
Ionophore A23187 ◽  
Calpain Activity ◽  
Platelet Surface ◽  
Reactive Agents ◽  
Platelet Secretion

Annexin V, a protein with a high affinity and a strict specificity for aminophospholipids at physiologic calcium concentrations, was used to probe platelet activation and the development of procoagulant activity. Platelet secretion was studied in parallel using VH10, a murine monoclonal antibody specific for GMP-140, an alpha-granule membrane glycoprotein. Both proteins were labeled with fluorescein isothiocyanate and platelet activation was assessed by flow cytometry. Microparticles, which are shed from the platelet surface and also support procoagulant activity, were distinguished from platelets according to their associated light scattering signal. The relative ability of different inducers to trigger exposure of the procoagulant surface and microparticle formation was: ionophore A23187 = thrombin plus collagen = collagen = thrombin. The density of aminophospholipid on microparticles was higher than on remnant platelets. Platelet activation by these agonists was accompanied by GMP-140 exposure, both on platelets and microparticles. Here, thrombin was the most efficient agonist. The mechanisms responsible for the above processes were investigated using E-64-d, a specific membrane-permeable inhibitor of Ca(2+)-activated protease (calpain); tetracaine, an activator of calpain; and N-ethylmaleimide and diamide, two sulfhydryl-reactive agents. These agents were added to platelets alone or before stimulation by agonists. Calpain activity was assessed by the hydrolysis of cytoskeletal proteins as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results showed that calpain activity is not essential for aminophospholipid translocation or for secretion. In contrast, although sulfhydryl-reactive agents alone can trigger procoagulant activity, they inhibit microvesicle formation and platelet secretion induced by the above agonists, suggesting that different mechanisms account for these phenomena. The use of annexin V in flow cytometry is a rapid method to assess procoagulant activity in platelets and the loss of phospholipid asymmetry in cell membranes.

A Study of Platelet Activation during Human Cardiopulmonary Bypass and the Effect of S-Nitrosoglutathione

1997 ◽  
Vol 78 (06) ◽  
pp. 1516-1519 ◽  
Author(s):  
Edward J Langford ◽  
Andrew Parfitt ◽  
Adam J de Beider ◽  
Michael T Marrinan ◽  
John F Martin
Keyword(s):  
Nitric Oxide ◽  
Flow Cytometry ◽  
Cardiac Surgery ◽  
Cardiopulmonary Bypass ◽  
Platelet Activation ◽  
Surface Expression ◽  
Platelet Inhibition ◽  
Nitric Oxide Donor ◽  
Platelet Dysfunction ◽  
Platelet Surface

SummaryCardiac surgery is complicated by the occurrence of post-operative bleeding due to platelet dysfunction. This is largely caused by platelet activation and consumption during cardiopulmonary bypass. Patients undergoing cardiac surgery requiring cardiopulmonary bypass were studied to determine whether early platelet changes due to bypass could be inhibited using the platelet-selective nitric oxide donor S-nitroso-glutathione (GSNO). Flow cytometry was used to measure platelet surface expression of P-selectin (an α-granule protein) and glycoproteins (GP) IIb/IIIa and Ib (mediators of aggregation and adhesion) before and 5 and 10 min after commencing cardiopulmonary bypass, in 6 controls and 6 patients receiving GSNO 50 μg/min. Platelet P-selectin expression increased during bypass both in controls and patients receiving GSNO. Glycoproteins IIb/IIIa and Ib fell during bypass in control and GSNO-treated patients. There was no difference between control and GSNO-treated groups. Thus no significant platelet inhibition by S-nitrosoglutathione was demonstrated under these conditions.

Human Platelets Contain and Release an Active ADAMTS-13-Like Metalloprotease.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3527-3527
Author(s):  
Li Liu ◽  
Huiwan Choi ◽  
Bernardo Aubrey ◽  
Angila Bergeron ◽  
Leticia Nolasco ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Platelet Activation ◽  
Fluid Shear Stress ◽  
Vascular Endothelial Cells ◽  
Severe Infection ◽  
Surface Expression ◽  
Human Platelets ◽  
Platelet Surface ◽  
The Difference ◽  
Adhesion Ligand

Abstract The adhesion ligand von Willebrand factor (VWF) is synthesized and stored in vascular endothelial cells and megakaryocytes/platelets. These cells release VWF in response to similar stimulations. However, a longstanding observation stated that, unlike endothelial cells, platelets do not release the ultra-large form (UL) of VWF upon activation. The lack of ULVWF release may be attributed to the difference in multimerization process in the storage granules or the intrinsic proteolysis of the hyperreactive ULVWF. To examine these possibilities, we analyzed the multimer compositions of VWF stored in and released from platelets. We found that ULVWF was detected by immunobloting of washed platelet lysates in the presence, but not in the absence of 5 mM EDTA. Similarly, when stimulated with 5 μM of thrombin receptor-activating peptide (TRAP), platelets released only VWF that was similar in sizes to plasma VWF, suggesting that platelet ULVWF may have been cleaved before or during its release. In support of this hypothesis, we found that platelets expressed ADAMTS-13-like molecule by western blot of platelet lysates and flow cytometry using two different ADAMTS-13 antibodies. The surface expression of ADAMTS-13-like molecule increased significantly upon platelet activation by TRAP and ADP. Consistent with these observations, the Triton-X-100 lysates of washed platelets and supernatant of washed platelets activated by TRAP contained VWF-cleaving activity, as demonstrated by the cleavage of ULVWF strings formed on histamine-stimulated endothelial cells under fluid shear stress. Our finding is consistent with a previous report, but further showed that this ADAMTS-13-like molecule exists not only in cytoplasma, but also on the surface of platelets. More importantly, the ADAMTS-13-like molecule increased its expression on platelet surface and was released upon platelet activation. The ADAMTS-13-like molecule either in platelets or released upon activation was active in cleaving ULVWF. This intrinsic mechanism for ULVWF proteolysis may be physiologically important. It may prevent the sudden release of hyper-reactive ULVWF from platelets and serve as the second pool of ADAMTS-13 to encounter the increase in ULVWF release from endothelial cells during conditions such as severe infection. The role of the platelet membrane-bound ADAMTS-13 in hemostasis remains to be further determined.

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