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Patient Platelets (patient + platelet)
Selected AbstractsCompromised ITAM-based platelet receptor function in a patient with immune thrombocytopenic purpuraJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2008E. E. GARDINER Summary.,Background:,Receptors on platelets that contain immunoreceptor tyrosine-based activation motifs (ITAMs) include collagen receptor glycoprotein (GP) VI, and Fc,RIIa, a low affinity receptor for immunoglobulin (Ig) G. Objectives:,We examined the function of GPVI and Fc,RIIa in a patient diagnosed with immune thrombocytopenic purpura (ITP) who had unexplained pathological bruising despite normalization of the platelet count with treatment. Methods and Results:,Patient platelets aggregated normally in response to ADP, arachadonic acid and epinephrine, but not to GPVI agonists, collagen or collagen-related peptide, or to Fc,RII-activating monoclonal antibody (mAb) 8.26, suggesting ITAM receptor dysfunction. Plasma contained an anti-GPVI antibody by MAIPA and aggregated normal platelets. Aggregating activity was partially (,60%) blocked by Fc,RIIa-blocking antibody, IV.3, and completely blocked by soluble GPVI ectodomain. Full-length GPVI on the patient platelet surface was reduced to ,10% of normal levels, and a ,10-kDa GPVI cytoplasmic tail remnant and cleaved Fc,RIIa were detectable by western blot, indicating platelet receptor proteolysis. Plasma from the patient contained ,150 ng mL,1 soluble GPVI by ELISA (normal plasma, ,15 ng mL,1) and IgG purified from patient plasma caused Fc,RIIa-mediated, EDTA-sensitive cleavage of both GPVI and Fc,RIIa on normal platelets. Conclusions:,In ITP patients, platelet autoantibodies can curtail platelet receptor function. Platelet ITAM receptor dysfunction may contribute to the increased bleeding phenotype observed in some patients with ITP. [source] WASP plays a novel role in regulating platelet responses dependent on ,IIb,3 integrin outside-in signallingBRITISH JOURNAL OF HAEMATOLOGY, Issue 3 2010Anna Shcherbina Summary The most consistent feature of Wiskott Aldrich syndrome (WAS) is profound thrombocytopenia with small platelets. The responsible gene encodes WAS protein (WASP), which functions in leucocytes as an actin filament nucleating agent ,yet, actin filament nucleation proceeds normally in patient platelets regarding shape change, filopodia and lamellipodia generation. Because WASP localizes in the platelet membrane skeleton and is mobilized by ,IIb,3 integrin outside-in signalling, we questioned whether its function might be linked to integrin. Agonist-induced ,IIb,3 activation (PAC-1 binding) was normal for patient platelets, indicating normal integrin inside-out signalling. Inside-out signalling (fibrinogen, JON/A binding) was also normal for wasp-deficient murine platelets. However, adherence/spreading on immobilized fibrinogen was decreased for patient platelets and wasp-deficient murine platelets, indicating decreased integrin outside-in responses. Another integrin outside-in dependent response, fibrin clot retraction, involving contraction of the post-aggregation actin cytoskeleton, was also decreased for patient platelets and wasp-deficient murine platelets. Rebleeding from tail cuts was more frequent for wasp-deficient mice, suggesting decreased stabilisation of the primary platelet plug. In contrast, phosphatidylserine exposure, a pro-coagulant response, was enhanced for WASP-deficient patient and murine platelets. The collective results reveal a novel function for WASP in regulating pro-aggregatory and pro-coagulant responses downstream of integrin outside-in signalling. [source] A Val193Met mutation in GPIIIa results in a GPIIb/IIIa receptor with a constitutively high affinity for a small ligandBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2001John Fullard We have identified a patient designated as (GTa) with Glanzmann's Thrombasthenia (GT) diagnosed on the basis of a prolonged bleeding time and failure of the patient's platelets to aggregate. The number of glycoprotein (GP)IIb/IIIa receptors on the platelet surface was 37% of normal and those receptors displayed a defect in soluble fibrinogen binding. Nevertheless, GTa platelets showed increased adhesion to solid-phase fibrinogen and binding affinity for the RGD-mimetic 3H-SC52012, a non-peptide GPIIb/IIIa antagonist. Dithiothreitol (DTT) and ADP enhanced the affinity for [3H]-SC52012 in normal platelets, but had little effect in GTa platelets. These findings suggested that GTa platelets were locked in an altered affinity state. Genetic analysis showed that GTa was a compound heterozygote for the GPIIIa gene. One allele showed a deletion at the 3, end of exon 3 resulting in a premature stop codon. The second GPIIIa allele had a G to A transition at nucleotide 577, resulting in a Val193Met substitution. HEK 293T cells transfected with mutant GPIIb/IIIaV193M bound [3H]-SC52012 with a higher affinity than wild-type GPIIb/IIIa, and this was not increased by DTT. The mutant receptor distinguishes between platelet adhesion and aggregation, and demonstrates the phenotype that may be expected when platelet aggregation alone is inhibited. [source] Peripheral blood stem cell collection in multiple myeloma: A retrospective analysis of 6 years leukapheresis activity in 109 patients treated at the Istituto Nazionale dei Tumori of MilanJOURNAL OF CLINICAL APHERESIS, Issue 4 2009Paola Coluccia Abstract Double autologous stem cell transplantation is the standard treatment in newly diagnosed multiple myeloma (MM) patients younger than 65 years; therefore, optimization of leukapheresis is crucial. We performed a retrospective analysis of 297 leukaphereses comparing semiautomated (V4.7 in 20% of collections) versus automated (V6.0 in 80%) Caridian (COBE) Spectra versions and analyzing the influence of M-protein on the outcome. Both methods gave comparable collection efficiencies (CE%) (53.4% vs. 55.7% in V6.0 and V4.7, respectively) with similar leukapheresis time and processed volume. Harvest volume was higher in V4.7 (P < 0.0001) with similar contamination of red blood cells (RBCs) (P = 0.77) and platelets (P = 0.09) when compared with V6.0. In patients with higher peripheral white blood cells (WBCs), V6.0 with adjusted harvest volume (<700 mL), achieved similar CD34+ CE% (P = 0.39) and better enrichment of nucleated cells (P < 0.0,002) but higher RBCs (P < 0.0,001) and platelets contamination (P = 0.001), when compared with a larger cycle volume in patients with lower WBCs. In hard to mobilize patients, CD34+ CE% was significantly more efficient with V4.7 than V6.0 (P < 0.0,001). CD34+ CE% was unaffected by serologic M-protein, but platelet CE% was higher in the absence of M-protein (P = 0.0,003), without any reduction in peripheral patients platelets. We, therefore, conclude that in the setting of MM patients with a high WBCs count and/or low percentage of peripheral CD34+ cells, collections with V4.7 or adjusted cycle volume V6.0 gave comparable result in CD34+ CE%. RBCs and platelets contamination is higher if low cycle volume is chosen. In hard to mobilize patients, V4.7 is advisable. J. Clin. Apheresis, 2009. © 2009 Wiley-Liss, Inc. [source] A novel Phe171Cys mutation in integrin ,IIb causes Glanzmann thrombasthenia by abrogating ,IIb,3 complex formationJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2004N. Rosenberg Summary.,Background: Glanzmann thrombasthenia (GT) is an autosomal recessive bleeding disorder characterized by lack of platelet aggregation induced by most agonists. The disease is caused by mutations in either ,IIb[glycoprotein (GP) IIb] or ,3 (GPIIIa) genes that lead to a lack or dysfunction of the integrin ,IIb,3 which serves as a fibrinogen receptor. Patients Mucocutaneous bleeding manifestations and platelet dysfunction consistent with GT were observed in three members of a Cypriot family: a 3-year-old proband, her father and her paternal uncle. Objective: To determine the molecular basis of GT in this family and to characterize possible biochemical and structural defects. Results: Analysis of the patients' platelets by fluorescence-activated cell sorting demonstrated trace amounts of ,3, no ,IIb and no ,IIb,3 on the membrane. Sequence analysis revealed a novel T607G transversion in exon 5 of the ,IIb gene predicting a Phe171Cys alteration that created a PstI recognition site. All three patients were homozygous for the mutation, the mother and paternal grandparents of the proband were heterozygous, whereas 110 healthy subjects lacked this transversion. Chinese hamster ovary cells cotransfected with cDNAs of mutated ,IIb and wild-type ,3 failed to express ,IIb,3 as shown by immunoprecipitation and immunohistochemistry experiments. Structural analysis of the ,IIb,3 model, which was based on the crystal structure of ,v,3, indicated that Phe171 plays an essential role in the interface between the ,-propeller domain of ,IIb and the ,A domain of ,3. Conclusions: A novel Phe171Cys mutation in the ,IIb gene of patients with GT is associated with abrogation of ,IIb,3 complex formation. [source] | ||||||||||