scholarly journals Evaluation of Platelet Function Defects in Patients with Immune Thrombocytopenia

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1021-1021
Author(s):  
Elena Monzón Manzano ◽  
María Teresa Alvarez Román ◽  
Andres Ramirez Lopez ◽  
Elena G Arias-Salgado ◽  
Paula Acuña ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Sialic Acid ◽  
Platelet Function ◽  
Research Funding ◽  
Immune Thrombocytopenia ◽  
Healthy Controls ◽  
Activation Markers ◽  
Platelet Production ◽  
Neuraminidase Activity ◽  
Fibrinogen Receptor

Abstract Background: Primary immune thrombocytopenia (ITP) is a megakaryocytic (MK)/platelet-specific autoimmune disorder characterized by platelet count <100×10 9/L with or without bleeding manifestations, and diagnosed by exclusion of other causes of thrombocytopenia. It is widely accepted the involvement of platelet autoantibodies on deterioration of platelets from patients with ITP. Moreover, an enhanced activity of neuraminidase may also reduce sialic acid from glycoside residues on platelet surface, especially from the highly glycosylated von Willebrand factor (vWF) receptor. Because controversial results regarding the functionality of platelets from ITP patients can be found in literature, we aimed to determine platelet ability to be stimulated by agonists. Moreover, we aimed to determine the way anti-platelet auto- antibodies (abs) and neuraminidase activity may affect the function of platelets derived from MKs of healthy controls. Methods: This observational, prospective and transversal study included 42 patients with chronic primary ITP and 55 healthy controls. Platelet fibrinogen and vWF receptors and activation markers (PAC1 binding to activated fibrinogen receptor and exposure of P-selectin after agonists treatment), were evaluated by flow cytometry. Presence of Antibodies (abs) against platelet's glycoproteins in ITP serum was analysed with a Luminex based assay (LifecodesPak Lx). Neuraminidase (NEU) activity in serum was determined with the substrate 20-(4-methylumbelliferyl)-a-D-N-(MUNANA). Human CD34 + cell-enriched population was obtained with CliniMACS (MiltenyiBiotec) from G-CSF mobilized peripheral blood of a healthy donor. For MK differentiation, CD34 + cells were cultured 12 days in StemSpan™ Serum-Free Expansion Medium II (SFEM II) with 50ng/ml of recombinant human thrompoietin. Then, 10% of serum from healthy controls (4) or ITP patients (4) were added to the culture of mature MKs and incubated for 3 days. Phenotypic analysis of MKs and culture derived-platelets was carried out using abs against CD34, CD41, CD42a and CD42b.Platelet-like particles were considered as CD41-positive events with a size (FSC) and granularity (SSC) scatter properties similar to blood platelets. Culture-derived platelets were stimulated with 100 µM TRAP and 10 µM ADP and activation markers were analyzed by flow cytometry. Results: Expression of fibrinogen receptor on platelets from ITP patients were similar to those from healthy controls but showed a reduced capacity to be activated. Impairment in platelet degranulation measured as exposition of P-selectin after agonist's stimulation was also observed in platelets from these patients (Figure 1). Of note, surface content of CD42b subunit of vWF receptor was reduced (Figure 1). To determine whether diminished platelet function might be due to a plasma component, we induced platelet production from MK of healthy controls as referred in Methods. Abs against platelets and neuraminidase activity were determined in serum samples. Serum from 4 healthy controls or from 4 ITP patients (1 with anti-CD42b, 1 with anti-GPIa-IIa and 2 with undetectable abs) were added to MKs culture. No differences existed in MK differentiation and platelet production between MKs incubated with serum from healthy controls or from ITP patients, but similarly as observed in platelets from ITP patients, MK-derived platelets had an impaired ability to be activated (Table 1). Platelets derived from MKs incubated with ITP serum with anti-platelet abs had also a diminished exposure of CD42b (73±8% of controls). Moreover, neuraminidase content of these samples was slightly higher than that from ITP samples without abs (130 vs 100 % of controls). Conclusion: Platelets from ITP patients had a diminished ability to be stimulated. In vitro study showed that megakaryopoiesis was normal in presence of ITP serum, but released platelets had a lower ability to be activated. Involvement of abs in this effect cannot be ruled out despite we detected abs only in 2 of the tested sera because efficiency of method to detect these abs is ~ 50%. On the other hand, reduced levels of CD42b might be due to the increased activity of neuraminidase. Reduction of sialic acid from CD42b might initiate its metalloproteinase-mediated cleavage or change affinity of the ab used for its detection. Research funded by ISCIII-Fondos FEDER PI19/00772 and Platelet Disorder Support Association Figure 1 Figure 1. Disclosures Alvarez Román: Pfizer: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Sobi: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding; Biomarin: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; CSL-Behring: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Novo-Nordisk: Consultancy, Honoraria, Research Funding. García Barcenilla: Roche: Speakers Bureau; Takeda: Speakers Bureau; Bayer: Speakers Bureau; SOBI: Speakers Bureau. Canales: Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria; Gilead/Kite: Consultancy, Honoraria; Eusa Pharma: Consultancy, Honoraria; Incyte: Consultancy; Karyopharm: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Sanofi: Consultancy; iQone: Honoraria; Sandoz: Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau. Jiménez-Yuste: Grifols: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; BioMarin: Consultancy; Sobi: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding. Butta: Novo-Nordisk: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Roche: Speakers Bureau; CSL-Behring: Research Funding.

Detection of Anti-Thrombopoietin Antibodies in Patients with Immune Thrombocytopenia

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4187-4187
Author(s):  
Takashi Satoh ◽  
Koji Miyazaki ◽  
Naoki Shimada ◽  
Koki Nagane ◽  
Tomoya Inukai ◽  
...  
Keyword(s):  
Plasma Levels ◽  
Research Funding ◽  
Immune Thrombocytopenia ◽  
Healthy Controls ◽  
Plasma Samples ◽  
Elevated Plasma ◽  
Competition Assay ◽  
Platelet Production ◽  
Healthy Control ◽  
Control Plasma

Abstract Background: Immune thrombocytopenia (ITP) is an autoimmune disease characterized by the presence of autoantibodies against platelet membrane glycoproteins, which cause the autoantibody-mediated destruction of platelets and impaired platelet production. Thrombopoietin (TPO) binds to its receptor on the surface of hematopoietic stem cells and megakaryocytes and induces their maturation and proliferation. Patients with thrombocytopenia due to aplastic anemia have drastically elevated plasma levels of TPO, whereas patients with ITP have normal or slightly elevated plasma levels of TPO despite their low platelet count. Furthermore, based on the existence of a multitude of autoantibody reactivities in ITP, including antibodies against platelets and TPO receptors, the presence of anti-TPO antibodies in patients with ITP may be suspected. Objective: We developed assay systems to detect plasma anti-TPO antibodies and screen patients with ITP. We examined the clinical characteristics associated with anti-TPO antibodies and their pathogenic roles in patients with ITP. Methods: Plasma anti-TPO antibodies from 101 patients with ITP and 72 healthy controls were measured by enzyme-linked immunosorbent assay (ELISA) using recombinant human TPO (rhTPO) as an antigen. The specificity of anti-TPO antibody reactivity was confirmed by ELISA competition assay. The presence of anti-TPO antibodies was further examined using immunoprecipitation and immunoblotting using rhTPO. To investigate whether anti-TPO antibodies inhibited functional interactions between TPO and TPO receptors, we examined extracellular signal-regulated kinases (ERKs), downstream signals induced by TPO. The binding of TPO to TPO receptors induced the phosphorylation of ERK in TPO receptor-expressing UT-7/TPO cells. Results: The level of anti-TPO antibodies measured by ELISA was significantly greater in the samples from patients with ITP than in those from healthy controls (2.91 ± 3.64 units versus 1.45 ± 0.67 units, P < 0.001). Samples were classified as positive or negative for anti-TPO antibody, as determined by immunoprecipitation and immunoblotting. Thus, the ELISA positive-cutoff value was considered to be the mean plus 3.5 standard deviation (SD) of 72 healthy control plasma samples. Plasma anti-TPO antibodies were detected in twenty-four ITP patients (23.8%), but in none of the healthy controls. By ELISA competition assay, anti-TPO antibody reactivity was inhibited dose-dependently by preincubation of patient plasma with rhTPO. In addition, anti-TPO antibody-positive plasma samples inhibited the phosphorylation of ERK in UT-7/TPO cells. In contrast, healthy control plasma had no inhibitory effect. Furthermore, the number of megakaryocytes was decreased relatively in the anti-TPO antibody-positive ITP patients. There was no difference in the TPO levels in plasma between ITP patients with anti-TPO antibodies and patients without anti-TPO antibodies (63.6 ± 79.7 pg/ml versus 45.2 ± 49.3 pg/ml). Conclusion: Our results have thus demonstrated the presence of anti-TPO autoantibodies in patients with ITP. The ELISA using rhTPO was specific for the detection of anti-TPO antibodies and thus allows their easy and rapid measurement in clinical settings. These findings suggest that functional anti-TPO antibodies cause impaired megakaryocyte proliferation and platelet production in patients with ITP. Disclosures Higashihara: Bristol-Myers Squibb: Research Funding; Baxter: Research Funding; Teijin: Research Funding; Pfizer: Research Funding; Astellas: Research Funding; Yakurt: Honoraria; KyowaHakkoKirin: Honoraria, Research Funding; Chugai: Honoraria, Research Funding; Eisai: Honoraria; GlaxoSmithKline: Honoraria, Research Funding; Nippon Shinyaku: Research Funding; Shionogi: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria; Takeda: Honoraria; Janssen　pharma: Honoraria, Research Funding; Alexion: Honoraria; Dainippon Sumitomo: Research Funding; Taisho Tomiyama: Research Funding.

scholarly journals Glycoside Residues on Platelet's Surface Regulate Platelet Function, Apoptosis and Binding of Coagulation Complexes in Patients with Immune Thrombocytopaenia

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 10-11
Author(s):  
Nora V. Butta ◽  
María Teresa Alvarez Román ◽  
Elena Monzón Manzano ◽  
Paula Acuña ◽  
Mónica Martín ◽  
...  
Keyword(s):  
Platelet Count ◽  
Sialic Acid ◽  
Platelet Function ◽  
Research Funding ◽  
Platelet Rich Plasma ◽  
University Hospital ◽  
Activation Markers ◽  
Platelet Surface ◽  
Prothrombinase Complex ◽  
Platelet Disorder

Introduction: Platelet surface glycoproteins (GPs) are highly glycosylated and are key elements for platelet function since most of them constitute receptors for adhesion ligands. However, exact role of their glycan composition is not clear. Under normal conditions, platelets contain sialic acid in the carbohydrate side chains of their GPs, and it has been described that alterations in the degree of their sialinization can affect the clearance of platelets. This mechanism has been proposed as involved in etiopathogenesis of immune thrombocytopaenia (ITP), mainly in those patients who do not respond to treatments. Thus, after the loss of sialic acid, there would be a greater exposure of galactose and of N-acetyl-glucosamine residues on the surface of circulating platelets to hepatic Ashwell-Morell receptors, which could induce their phagocytosis and platelet clearance. On the other hand, procoagulant platelets, defined as the platelet subpopulation that binds functional prothrombinase, exposed on their surface increased levels of P-selectin and GPIb, two glycan rich GPs. So, it is tempting to speculate that changes in glycan residues on platelet surface may induce changes in their function. Aim: We aimed to assess in ITP patients whether changes in platelet glycosylation, mainly the loss of sialic acid, may condition platelet function, apoptosis and binding of prothrombinase complex. Methods: This is an observational, prospective and transversal study approved by Ethics Committee from La Paz University Hospital. One hundred and eight patients with chronic primary ITP (68 with a platelet count ≥30x103 platelets/µL and 40 with a platelet count &lt;30x103 platelets/µL) and 132 healthy controls were included after signing the informed consent. Platelet activation markers were determined in platelet rich plasma; whereas platelet glycosylation, binding of prothrombinase, annexin V and caspase's activities were assayed in washed platelets. Samples were analyzed by flow cytometry. Table 1 shows lectins tested and their sugar-binding specificity. Data were analyzed with GraphPad Prism 6.0 software. Results: Platelets from ITP patients with a platelet count &lt;30x103/µL exposed less sialic acid in correspondence to an enhanced binding of lectins to non-sialylated residues. Moreover, levels of α1,6-Fucose, a glycan residue which could directly regulate antibody-dependent cellular cytotoxicity, and of α-Mannose, which could be recognized by the mannose binding lectin and activate complement pathway, were increased in platelets from these ITP patients. In accordance, sialic acid loss and consequent platelet surface exposure of other glycoside residues were inversely related to platelet count and ability to be activated (Table 1). These differences in glycosylation observed in ITP patients with a platelet count &lt;30x103/µL were accompanied by a less ability of platelets to be activated (Figure 1), an increased exposure of phosphatidylserine and higher caspase activites (Figure 2). Moreover, increased exposure of phosphatidylserine and of N-acetyl-glucosamine residues (measured through the binding of WGA) enhanced binding of prothrombinase complex (Figure 3). Conclusion: Changes in glycoside composition of GPs on platelet's surface impaired their functional capacity, increases their apoptosis and modifies conditions for the binding of coagulation proteins. These modifications in platelet's glycoside residues seem to be related to severity of ITP. This work was supported by grants from FIS-FONDOS FEDER (PI19/00772) and and Platelet Disorder Support Association. EMM holds a predoctoral fellowship from Fundación Española de Trombosis y Hemostasia (FETH-SETH). Disclosures Butta: Grifols: Research Funding; Novartis: Speakers Bureau; ROCHE: Research Funding, Speakers Bureau; Pfizer: Speakers Bureau; SOBI: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; NovoNordisk: Speakers Bureau. Alvarez Román:Grifols: Research Funding; Bayer: Consultancy; Novartis: Speakers Bureau; Roche: Speakers Bureau; Pfizer,: Research Funding, Speakers Bureau; SOBI,: Consultancy, Research Funding, Speakers Bureau; Takeda: Research Funding, Speakers Bureau; NovoNordisk,: Research Funding, Speakers Bureau. Martín:SOBI: Research Funding; Pfizer: Research Funding, Speakers Bureau; Roche: Speakers Bureau; Novartis: Speakers Bureau; NovoNordisk: Speakers Bureau. Rivas Pollmar:Novartis: Speakers Bureau; Roche: Speakers Bureau; Pfizer: Speakers Bureau. Justo Sanz:Takeda: Current Employment. García Barcenilla:NovoNordisk: Research Funding, Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Pfizer,: Speakers Bureau; Roche: Speakers Bureau; Bayer: Speakers Bureau; Novartis: Speakers Bureau. Canales:Celgene: Honoraria; Janssen: Speakers Bureau; Novartis: Honoraria; Roche: Honoraria; Gilead: Honoraria; Sandoz: Honoraria; iQone: Honoraria; Takeda: Speakers Bureau; Sandoz: Speakers Bureau; Roche: Speakers Bureau; Janssen: Speakers Bureau; Sandoz: Honoraria; Roche: Honoraria; Takeda: Speakers Bureau; Novartis: Honoraria; Sandoz: Speakers Bureau; Karyopharm: Honoraria; Roche: Speakers Bureau; Janssen: Honoraria; Karyopharm: Honoraria; Janssen: Honoraria. Jimenez-Yuste:F. Hoffman-La Roche Ltd, Novo Nordisk, Takeda, Sobi, Pfizer, Grifols, Octapharma, CSL Behring, Bayer: Honoraria; F. Hoffman-La Roche Ltd, Novo Nordisk, Takeda, Sobi, Pfizer: Consultancy; Grifols, Novo Nordisk, Takeda, Sobi, Pfizer: Research Funding.

Procoagulant Profile of Platelets from Immune Thrombocytopenia Patients

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1370-1370
Author(s):  
María Teresa Álvarez Román ◽  
Raul Justo Sanz ◽  
Elena Monzon Manzano ◽  
Monica Martín Salces ◽  
Ihosvany Fernandez Bello ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Count ◽  
Immune Thrombocytopenia ◽  
Conflicts Of Interest ◽  
Annexin V ◽  
Compensatory Mechanism ◽  
Healthy Controls ◽  
Hepes Buffer ◽  
Prothrombinase Complex ◽  
Fibrinogen Receptor

Abstract Introduction: Immune thrombocytopenia (ITP) is an autoimmune disorder in which both increased platelet destruction and insufficient platelet production are involved. Patients can have a range of bleeding manifestations from none to severe at a similar platelet count. In some cases, patients have fewer bleeding symptoms than expected considering the low platelet count that they might have. Objective: The aim of this study was to determine the procoagulant profile of platelets from ITP patients in order to determine whether any of their features may explain this observation. Methods: Twenty-five patients with chronic ITP [(68±100)x109 platelets/L, mean age: 59.6 ± 16.1 years old, 56% female)] and thirty-five healthy controls [(256±36)x109 platelets/L, mean age: 41.6 ± 13.5 years old, 51% female) were included. Platelet counts were determined with a Coulter Ac. T Diff cell counter (Beckman Coulter, Madrid, Spain). Citrated blood was centrifuged at 152 g 10 min at 23°C for obtaining platelet rich plasma (PRP). To obtain washed platelets, the top two-thirds volumes of PRP were collected and centrifuged (650 g for 10 min at 23°C) after the addition of acid-citrate-dextrose (ACD, 1:10) and the pellet was resuspended in an equal volume of HEPES buffer. Platelet activation was determined by flow cytometry through binding of FITC-PAC1 (a mAb that recognizes activated conformation of fibrinogen receptor) to quiescent and 100 micromol/L thrombin receptor-activating peptide 6 (TRAP, Bachem, Switzerland) or 20 micromol/L ADP. Apoptosis was determined by flow cytometry analysis through FITC-annexin V binding to phosphatidylserine (PS) exposed on platelet membrane under basal conditions. To characterize platelet ability to bind coagulation factors, washed platelets (1x108/mL) were activated with 100 micromol/L TRAP and then incubated with FVa and/or FXa (5nM each, 10 min, ambient temperature). After fixation with 2% paraformaldehyde to cross-link the platelet-bound factors Va and Xa, platelets were washed two times with Hepes Buffer. Non-specific binding sites were blocked with 8% bovine serum albumin (30 min, room temperature). Following centrifugation, platelets were first incubated with anti-CD41-PE, anti-FVa and/or anti-FXa and then with a secondary FITC-goat anti-mouse IgG and stored at 4°C until flow cytometry analyses. Results: Platelets from ITP patients showed a basal expression of activated fibrinogen receptor similar to controls and a reduced ability for being activated by agonists (% of positive platelets for TRAP-induced PAC1 binding: 60±20 % in controls and 35±23 % in ITP, p<0.01; ADP-induced PAC1 binding: 63±14 % in controls and 50±23 % in ITP, p<0.05). Diminished responses to activation were not due to a reduction in surface expression of fibrinogen receptor in platelets from ITP patients. Platelets from ITP patients expressed more PS than controls under basal conditions [mean fluorescence (MF) for FITC-annexin V binding was: 336±128 in controls, 588±25 in ITP, p<0.05]. Since the PS is the anchor site of the prothrombinase complex, we studied the binding of FVa and FXa at baseline and after activating platelets with TRAP. The binding of these factors in both conditions was higher in the group of patients with ITP (MF for basal FVa binding: 41.4±14.4 in controls, 58.1±24 in ITP, p <0.02; MF for TRAP-induced FVa binding: 44.1±11.4 in controls, 81.4±38 in ITP, p<0.001; MF for basal FXa binding: 45.7±18.4 in controls, 58.1±24 in ITP, p <0.005; MF for TRAP-induced FXa binding: 46.1±16.4 in controls, 72.0±24 in ITP, p<0.05). The lower the platelet count the higher increase in PS exposure (Spearman r =-0,518, p <0.001) and the union of FVa (Spearman r = -0.8571, p <0.001) and FXa (Spearman r = -0.7455, p<0.05). Conclusions: Platelets from ITP patients, despite having less capacity of activation by agonist stimulation, have an increased procoagulant surface with greater ability to bind prothrombinase complex (FXaVa) than those from healthy controls. This feature might be a procoagulant compensatory mechanism that could reduce the risk of bleeding in patients with ITP. This work was supported by a grants from the FIS-FEDER, PI12/01831 and PI15/01457 Disclosures No relevant conflicts of interest to declare.

scholarly journals The Importance of Platelet Glycoside Residues in the Haemostasis of Patients with Immune Thrombocytopaenia

2021 ◽  
Vol 10 (8) ◽  
pp. 1661
Author(s):  
Andrés Ramírez-López ◽  
María Teresa Álvarez Román ◽  
Elena Monzón Manzano ◽  
Paula Acuña ◽  
Elena G. Arias-Salgado ◽  
...  
Keyword(s):  
Platelet Count ◽  
Sialic Acid ◽  
Healthy Controls ◽  
Caspase Activity ◽  
Antibody Dependent Cellular Cytotoxicity ◽  
Activation Markers ◽  
Platelet Surface ◽  
Mannose Binding ◽  
Transversal Study ◽  
Binding Lectin

Loss of sialic acid from the carbohydrate side chains of platelet glycoproteins can affect platelet clearance, a proposed mechanism involved in the etiopathogenesis of immune thrombocytopaenia (ITP). We aimed to assess whether changes in platelet glycosylation in patients with ITP affected platelet counts, function, and apoptosis. This observational, prospective, and transversal study included 82 patients with chronic primary ITP and 115 healthy controls. We measured platelet activation markers and assayed platelet glycosylation and caspase activity, analysing samples using flow cytometry. Platelets from patients with ITP with a platelet count <30 × 103/µL presented less sialic acid. Levels of α1,6-fucose (a glycan residue that can directly regulate antibody-dependent cellular cytotoxicity) and α-mannose (which can be recognised by mannose-binding-lectin and activate the complement pathway) were increased in the platelets from these patients. Platelet surface exposure of other glycoside residues due to sialic acid loss inversely correlated with platelet count and the ability to be activated. Moreover, loss of sialic acid induced the ingestion of platelets by human hepatome HepG2 cells. Changes in glycoside composition of glycoproteins on the platelets’ surface impaired their functional capacity and increased their apoptosis. These changes in platelet glycoside residues appeared to be related to ITP severity.

scholarly journals Platelet and Immune Characteristics of Patients with Immune Thrombocytopaenia Non Responders to Therapeutic Treatments

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1089-1089
Author(s):  
Elena Monzón Manzano ◽  
Raul Justo Sanz ◽  
Diana Hernández ◽  
Teresa Álvarez Roman ◽  
Ihosvany Fernandez-Bello ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Immune Response ◽  
Sialic Acid ◽  
Research Funding ◽  
Caspase 3 ◽  
Mononuclear Cells ◽  
Ricinus Communis ◽  
The Other ◽  
Control Group ◽  
Platelet Surface

Introduction: Mechanisms leading to diminished platelet counts in immune thrombocytopaenia (ITP) appear to be multifactorial: autoantibodies, autoreactive CD8+ cytotoxic T cells, enhanced apoptosis and loss of sialic acid which mediates platelet clearance through the Ashwell-Morell receptors present in hepatocytes. Differential involvement of each of them might condition the ability of patients with ITP to respond to treatments. We aimed to examine platelet features and the immunological state of patients with ITP who do not respond to any treatment to detect the unique characteristics of this group. Methods: This was an observational, prospective and transversal study. Patients with chronic primary ITP were included: 28 ITP patients without treatment for at least 6 months (UT-ITP); 36 responders to agonists of thrombopoietin receptors (TPO-RA); and 14 ITP patients who did not respond to first- and second-line treatments (NR-ITP). A healthy control group (n=104) was also included in the study. Active caspase-3, -7, -8 or -9 were determined by flow cytometry using CaspaTag kits (Millipore, Madrid, Spain) in PRP diluted with HEPES-buffer containing 2 mM Ca2+ and 2 mM Gly-Pro-Arg-Pro (Sigma-Aldrich, Madrid, Spain) to prevent fibrin formation . Platelet surface glycan exposure was analysed by determining the binding of lectins by flow cytometry. To do so, washed platelets were incubated with 1 μg/ml Alexa fluor 488-conjugated wheat germ agglutinin lectin (WGA, Invitrogen, Spain) or with 1 μg/ml FITC-conjugated Ricinus communis agglutinin (RCA, Vector Labs, UK). WGA binds to sialic acid and N-acetylglucosaminyl residues, and RCA is a galactose-specific legume lectin which binding serves as an indirect measurement of the loss of sialic acid. Peripheral blood mononuclear cells (PBMCs) subsets were analysed by flow cytometry using specific antibodies. Experimental data was analysed using SPSS 9.0 software (SPSS Inc., Chicago, IL). Results: Platelets from TPO-RA treated and from NR-ITP patients had increased caspase-3, -7, -8 and -9 activities (Figure 1A). Platelets from NR-ITP patients exposed less sialic acid and more N-acetylglucosaminyl residues than the other groups (Figure 1B). Binding of WGA and RCA correlated with caspase activities (Table 1). Distribution of lymphocytes, monocytes and natural killer cells is shown in Table 1. NR-ITP patients had an increased proportion of B lymphocyte (LB), maybe due to a significant rise in the fraction of naive LB cells, and a diminution in LTreg subset. Whereas classical monocytes was increased, nonclassical monocyte fraction was decreased in the UT-ITP and NR-ITP groups. NR-ITP patients also presented an increased CD16+CD56bright cells fraction and a diminished NK CD16+CD56dim subset. TPO-RA-treated patients seemed to recover an immune homeostasis similar to healthy controls (monocyte and NK cells subset distribution and LTreg count similar to control group). It is of interest to note the relationship between loss of sialic acid from platelet surface glycans and Tregs count: the most reduced surface exposure of sialic acid, the less Treg count (Figure 2). Conclusions: Platelets from NR-ITP patients had more signs of apoptosis and a different composition of surface glycans, accompanied by a diminished LTreg population, a higher LB naïve percentage, and an increased CD16+CD56bright cells fraction in circulation, indicating a severe deregulation of the immune system. Since an inverse correlation was observed between loss of sialic acid and LTreg count, a potential relationship between glycan composition on the platelet surface and immune response is suggested, positing terminal sugar moieties of the glycan chains as aetiopathogenic agents in ITP. On the other hand, TPO-RA appears to have a beneficial effect on immune response. Nevertheless, one of the limitations of our study was that patients were recruited once the response to TPO-RA was achieved; therefore, a longitudinal study would provide more information regarding TPO-RA effects. This work was supported by grants from the FIS-FONDOS FEDER (PI15/01457, NB). NVB holds a Miguel Servet tenure track grant from FIS-FONDOS FEDER (CP14/00024). Disclosures Álvarez Roman: Roche: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Takeda: Research Funding; NovoNordisk: Consultancy, Speakers Bureau; CSL Behring: Consultancy, Speakers Bureau; Sobi: Consultancy, Speakers Bureau. Fernandez-Bello:Novartis, Pfizer, ROCHE, Stago: Speakers Bureau. Martín:SOBI: Research Funding; Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau. Rivas Pollmar:Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau; SOBI: Research Funding. Canales:Novartis: Honoraria; Takeda: Speakers Bureau; iQone: Honoraria; Sandoz: Honoraria; Celgene: Honoraria; SOBI: Research Funding; Karyopharm: Honoraria; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau; Gilead: Honoraria; Janssen: Honoraria, Speakers Bureau. Jimenez-Yuste:Bayer, CSL Behring, Grifols, Novo Nordisk, Octapharma, Pfizer, Roche, Sobi, Shire: Consultancy, Honoraria, Other: reimbursement for attending symposia/congresses , Research Funding, Speakers Bureau. Butta:Novartis: Consultancy; Roche, Pfizer: Speakers Bureau.

Impact of Pathogen Reduction Technology Treatment and Storage in New Generation Platelet Additive Solutions (PAS) on Platelet Function.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2115-2115
Author(s):  
Gines Escolar ◽  
Miguel Lozano ◽  
Patricia Molina ◽  
Susanne Marschner ◽  
Raymond Goodrich ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Function ◽  
Research Funding ◽  
Ex Vivo ◽  
Quality Parameters ◽  
Slight Reduction ◽  
Flow Cytometry Analysis ◽  
Adhesive Properties ◽  
Pathogen Reduction ◽  
New Generation

Abstract Abstract 2115 Poster Board II-92 New strategies for preparing platelet concentrates (PCs) are investigating the combination of pathogen reduction technologies (PRT) with storage of platelets in additive solutions (PAS) containing phosphate buffer. While these approaches have several advantages by reducing adverse effects, improving biological safety and increasing plasma availability, there is a reasonable concern on how these strategies could affect platelet function. In the present study we have evaluated the effect of Marisol® PRT treatment (CaridianBCT Biotechnologies, LLC) in combination with storage in PAS-III (Intersol; Baxter Healthcare Corp) or PAS-IIIM (SSP+; MacoPharma) on analytical and functional characteristics of apheresis PCS. PCs (2.5-3.4×109plts/ml) were split into three aliquots. One was kept untreated and stored in plasma as a control (CON-PPP). One was PRT-treated and stored in the corresponding PAS (PRT-PASIII or PRT-IIIM) with a 35% plasma carryover to achieve a final concentration of 0.7-1.5 × 109 plt/ml. The last aliquot was stored in the corresponding PAS (CON-PASIII or CON-PASIIIM), not subjected to PRT treatment. PCs were stored under standardized conditions and evaluations were performed on days 0, 5 and 7. Cell quality parameters (pH, swirl, lactate and glucose), flow cytometry analysis of major platelet glycoproteins and activation dependent antigens were assessed. Adhesive and aggregating functions of platelets were evaluated using an ex vivo perfusion model with flowing reconstituted blood recirculating through damaged vascular segments. A slight reduction in platelet counts was noticed on day 7 compared to day 0 in PRT-treated PCs (p<0.05), however no statistical differences were observed between the different study groups. All measured cell quality parameters were within ranges previously published. Flow cytometry analysis revealed comparable levels of the analyzed glycoproteins for all conditions evaluated. Only moderate reductions in the expression of GPIb were observed on day 7 of storage in all groups except for CON-PASIIIM. A progressive increase in the expression of P-selectin was observed in both controls and PRT-treated PCs during storage. Lysosomal integral membrane protein (LIMP) expression was increased in PRT-PASIII and PRT-PASIIIM and CON-PASIII, but not CON-PASIIIM PCs. PRT-PASIII PCs showed the highest levels of annexin V binding after 7 days of storage. Studies under flow conditions showed comparable levels of adhesion and aggregation to subendothelium for PRT-treated platelets stored in PAS solutions at 5 days of storage. A detailed morphometric analysis revealed slightly enhanced adhesive functions in CON-PASIII on day 0 and moderate reductions in adhesive properties in PRT-PASIII, but not PRT-PASIIIM PCs after 7 days of storage. Our investigations show that cell quality parameters, glycoproteins levels and platelet functions were preserved in PRT-treated concentrates and stored in new generation PAS for up to 5 days. The relevance of our experimental data on the in vivo performance of PCs exposed to PRT and stored in new generation PAS deserve further investigation in the clinical setting. Disclosures: Escolar: Caridian BCT Technologies: Consultancy, Research Funding. Marschner:Caridian BCT Technologies: Employment. Goodrich:Caridian BCT Technologies: Employment. Galan:Caridian BCT Technologies: Research Funding.

Iron Overload Diminishes the Effectiveness of the Innate Immune Response in Thalassemia Major: a Possible Mechanism for Increased Infection Risk.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4071-4071
Author(s):  
Patrick B Walter ◽  
Paul R Harmatz ◽  
Annie Higa ◽  
David Killilea ◽  
Nancy Sweeters ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Immune Response ◽  
Iron Overload ◽  
Board Of Directors ◽  
Innate Immune Response ◽  
Research Funding ◽  
Innate Immune ◽  
Healthy Controls ◽  
Advisory Committees ◽  
Fluorescent Intensity

Abstract Abstract 4071 Poster Board III-1006 Introduction Infection is the second most common cause of death in thalassemia. The innate immune system provides a first line of defense against infection and specificity depends on pattern recognition receptors (PRRs) specific to microbial pathogens. One class of PRR called the toll-like receptors (TLRs) are important for transducing the signal for bacterial Lipopolysaccharide (LPS), resulting not only in cytokine production, but also in the control of extracellular iron levels through production of neutrophil gelatinase associated Lipocalin (NGAL). However, the exact role that NGAL plays and the expression level of PRRs are unknown in thalassemia. Thus, the goal in these studies is to investigate the relationship of iron overload to the innate immune cell expression of PRRs and NGAL in thalassemia. Patients and Methods Fifteen transfusion dependent thalassemia patients (11 – 29 yrs old) participating in the combination trial of deferasirox (an oral iron chelator) and deferoxamine were enrolled (Novartis sponsored CICL670AUS24T). Fasting blood samples were obtained i) at baseline after a 72 hr washout of chelator, and ii) at 6 and 12 months on study. Five healthy controls (13 - 18 yrs old) were also enrolled. Fresh monocytes were isolated using antibody-linked magnetic microbeads (Miltenyi Biotec Inc). Highly enriched populations of CD14+ monocytes were verified by flow cytometry. The expression of TLR4, also examined by flow cytometry is reported as the mean fluorescent intensity (MFI). In patients with thalassemia, liver iron concentration (LIC) was analyzed by biomagnetic susceptibility (“SQUID”, Ferritometer®). The plasma levels of NGAL were analyzed by ELISA. Results At baseline the expression of monocyte TLR4 (mean 18.8 ± 3.5 MFI) was reduced 30% compared to the healthy controls (mean 26.9 ± 7.6 MFI, p<0.05). The expression of TLR4 over the follow-up period of 52 weeks in patients receiving intensive combination chelator therapy significantly increased 27% / year (7 MFI / year, p=0.005). Interestingly the expression of monocyte TLR4 was negatively correlated with LIC (r=-0.6, p=0.04). Finally, thalassemia patients at baseline have significantly higher levels of NGAL (80 ± 20 ng/ml) compared to controls (42 ± 15 ng/ml, p=0.01). Conclusions These preliminary studies support the hypothesis that iron burden has a negative impact on the innate immune response in thalassemia as demonstrated by the decreased expression of TLR4. After intensive chelation, the levels of TLR4 increased, indicating that decreased iron overload with chelation may improve innate immune responsiveness. Finally, the iron transport protein NGAL is significantly elevated in thalassemia possibly acting to prevent essential iron uptake by pathogenic bacteria. Disclosures: Harmatz: Novartis: Research Funding; Apotex : Membership on an entity's Board of Directors or advisory committees; Ferrokin: Membership on an entity's Board of Directors or advisory committees. Vichinsky:Novartis: Consultancy, Research Funding.

Association Of Platelet Function Markers, Independent Of Platelet Count, With Bleeding Score In Patients With Immune Thrombocytopenia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3534-3534
Author(s):  
Andrew L. Frelinger ◽  
Anja J Gerrits ◽  
Michelle A. Berny-Lang ◽  
Travis Brown ◽  
Sabrina L. Carmichael ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Activation ◽  
Platelet Function ◽  
Research Funding ◽  
Immune Thrombocytopenia ◽  
Univariate Analysis ◽  
Blood Draw ◽  
Platelet Surface ◽  
Platelet Counts ◽  
Bleeding Score

Abstract Background Immune thrombocytopenia (ITP) patients with similarly low platelet counts differ in their tendency to bleed. Aim To determine if differences in platelet function in ITP patients with similarly low platelet counts partly account for the variation in bleeding tendency. Methods The relationship between bleeding scores and platelet function markers was investigated in a single center cross-sectional study of pediatric patients with ITP. Following informed consent, blood was collected from ITP patients and bleeding was graded using the Buchanan and Adix Score (J Pediatr 2002) at routine clinic visits or while admitted to the hospital. Bleeding scores were obtained by one of three hematologists blinded to platelet function results, and investigators performing platelet function tests were blinded to clinical results. Platelet function was assessed by whole blood flow cytometric measurement of unstimulated, ADP- or TRAP-stimulated platelet surface activated GPIIb-IIIa (as measured by PAC1 binding), P-selectin, and GPIb and by unstimulated, convulxin-, or ADP plus TRAP-stimulated platelet surface phosphatidylserine expression (as determined by annexin V binding). Platelet count, immature platelet fraction (IPF) and mean platelet volume (MPV) were determined by a Sysmex XE-2100, and platelet forward angle light scatter (FSC) was measured by flow cytometry. Results Platelet function and bleeding scores were evaluated in 34 consecutive consenting pediatric ITP patients (16 female, 18 male, age 9.7 ± 5.7 years [mean ± SD]). ITP was newly diagnosed (< 3 months) in 10 patients, persistent (3 -- 12 months) in 7 patients, and chronic (>12 months) in 17 patients. Platelet count at the time of the blood draw was 47 ± 55 x 109/L. The median bleeding score on day of blood draw was 1 (range 0 to 4). By univariate analysis, higher IPF, and lower platelet count were significantly associated with a higher bleeding score (odds ratio [OR] >1, p<0.05) but MPV was not. Multiple measures of platelet function were associated with bleeding scores by univariate analysis: higher levels of platelet FSC (a measure affected by multiple variables including size) surface GPIb on unstimulated, ADP- or TRAP-stimulated platelets, surface P-selectin on unstimulated platelets, and platelet FSC were associated with increased odds for higher bleeding scores (ORs each >1, p<0.05), while higher ADP- and TRAP-stimulated platelet surface activated GPIIb-IIIa and P-selectin were associated with reduced odds of higher bleeding scores (ORs each <1, p<0.05). After adjustment for platelet count, higher levels of platelet surface P-selectin on unstimulated platelets, GPIb on TRAP-stimulated platelets, and FSC remained significantly associated with increased odds for higher bleeding scores (Figure), but IPF did not. Similarly, after adjustment for platelet count, higher TRAP-stimulated percentage of P-selectin and activated GPIIb-IIIa positive platelets remained significantly associated with reduced odds of higher bleeding scores (Figure). These findings were independent of recent ITP-related treatment. Conclusions In this study of pediatric ITP patients, we identified selected platelet function markers which, independent of platelet count, are associated with increased (platelet FSC, platelet surface P-selectin on unstimulated platelets, and GPIb on TRAP-stimulated platelets) or decreased (TRAP-stimulated percent P-selectin and GPIIb-IIIa positive platelets) odds of high bleeding scores. Possible hypotheses to explain these associations are as follows: 1) Increased P-selectin on unstimulated platelets demonstrates in vivo platelet activation, possibly as a consequence of the recent bleeding. 2) Because platelet activation results in a reduction in platelet surface GPIb and increases in platelet surface activated GPIIb-IIIa and P-selectin, the ORs associated with all of these markers could be explained by reduced ability of platelets in patients with higher bleeding scores to respond to agonists. 3) While platelet FSC is partly related to size, the finding that MPV and IPF, adjusted for platelet count, were not associated with bleeding score suggests that factors other than size account for the association of platelet FSC with higher bleeding scores. Further study is required to validate these findings and determine if differences in platelet function are associated with future risk for bleeding. Disclosures: Off Label Use: Eltrombopag was given to WAS/XLT patients for treatment of thrombocytopenia. Neufeld:Shire: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Apopharma: Consultancy. Michelson:Sysmex: Honoraria.

Abnormalities of Bone Marrow Immune Micro-Environment in Patients with Immune Thrombocytopenia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3464-3464
Author(s):  
Yang Song ◽  
Yu-tong Wang ◽  
Xiao-jun Huang ◽  
Yuan Kong
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
T Cells ◽  
Endothelial Cells ◽  
Th17 Cells ◽  
Immune Thrombocytopenia ◽  
Perivascular Cells ◽  
Platelet Production ◽  
Cd34 Cells ◽  
Significant Difference

Abstract Background: Immune thrombocytopenia (ITP) is an immune-mediated disease that is characterized by excessive platelet destruction and decreased platelet production. Although antiplatelet antibodies are considered as the primary immunologic defect in ITP, dysfunctional cellular immunity is also important in the pathophysiology of ITP. The current publications have observed excessive activation and proliferation of platelet auto-antigen-reactive CTLs, production abnormal Th cells, abnormal numbers and function of Tregs in peripheral blood of ITP, but no one focus on the bone marrow (BM) micro-environment in ITP patients. Many cell types including osteoblastic, perivascular, endothelial cells, and various mature immune cells contribute to the BM micro-environment. We have recently reported that the impaired BM vascular micro-environment may affect the thrombopoiesis of CD34+ cells by disrupting the interaction between megakaryocytes and BM endothelial cells (BMECs), resulting in the delayed platelet engraftment in allotransplant patients with prolonged isolated thrombocytopenia (Kong Y, et al. Biol Blood Marrow Transplant. 2014; 20:1190-1197). In mice model, the cross-talk between megakaryocytes and BMECs in BM vascular micro-environment regulates the megakaryocyte maturation and thrombopoiesis. Therefore, we hypothesized that the abnormal BM vascular micro-environment and immune micro-environment may operate in the occurrence of ITP. Aims: To investigate whether abnormal BM vascular and immune micro-environment are involved in ITP patients. Methods: The compartments of BM immune micro-environment were analyzed by flow cytometry in 26 untreated ITP patients and 26 healthy donors (HD). The fractions of T cells, including Th1, Tc1,Th2, Tc2 ,Th17 and Treg were identified as CD3+ CD8- IFN-gama+, CD3+ CD8- IFN-gama+, CD3+ CD8+ IL4+, CD3+ CD8+ IL-4+, CD3+ CD8- IL17A+ and CD3+ CD4+ CD25+ Foxp3+, respectively. The BMECs and perivascular cells, acting as key elements of vascular micro-environment, were identified as CD45- CD34+ VEGFR2+ and CD45- CD34- CD146+, respectively. Hematoxylin-eosin (H&E) staining and immunohistochemistry (IHC) using rabbit anti-human CD34 and CD146 primary antibodies were performed on each BM trephine biopsies (BMB) derived from the patients and controls. Results: The proportion of Th1 cells and Tc1 cells among the bone marrow mononuclear cells (BMMNCs) was significantly increased in ITP patients compared to HD (27.7% ± 11.6% vs. 16.3% ± 7.7%, P<0.001; 39.8%±17.7% vs. 24.1%±11.8%, P<0.005), whereas there was no significant difference in the percentages of Th2 and Tc2 cells. In addition, the proportion of Th17 cells in ITP patients was remarkable higher than HD (3.2%±0.51%1.5%vs 1.7%±1.0%, P<0.0001). We also found the significantly decreased percentage of Treg in ITP patients compared to HD (2.5%±2.0% vs 3.7%±2.6%, P<0.001). However, the frequency of CD34+ cells as well as BMECs and perivascular cells were similar in BM between the ITP patients and HD. Consistent with our flow cytometry data, histological analysis of the recipient BMBs in situ showed no significant differences in CD34-positive BMECs and CD146-positive perivascular cells between ITP patients and HD. Summary/Conclusion: The BM CD34+ cells and vascular micro-environment were normal in ITP patients. However, the abnormal BM immune micro-environment, including the excessive polarization of Th1, Tc1 and Th17 cells and a remarkable decrease of Treg cells were observed in ITP patients. Our data indicated that the desregulated T cells responses in BM may abrogate the thrombopoiesis through the impaired megakaryocytes maturation and decreased platelet production, and eventually contributing to the occurrence of ITP. Acknowledgment: Supported by the National Natural Science Foundation of China (grant nos. 81370638&81230013), and the Beijing Municipal Science and Technology Program (grant nos. Z141100000214011& Z151100004015164& Z151100001615020). Disclosures No relevant conflicts of interest to declare.

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