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Our understanding of the risks associated with perioperative anemia and transfusion, in terms of increased morbidity and mortality, has evolved over the past 2 decades. By contrast, our understanding of the potential mechanisms of injury and optimal treatment strategies remains incomplete. As such, the important role of effective patient blood management (PBM) programs, which address both the effective treatment of anemia and minimizes the need for red blood cell (RBC) transfusion, is of central importance to optimizing patient care and improving patient outcomes. We report on important clinical outcomes of the Ontario Transfusion Coordinator (ONTraC Program), a network of 25 hospital sites, working in coordination over the past 20 years. Transfusion nurse coordinators were assigned to apply multimodal best practice in PBM (including recommended changes in surgical approach; diagnosis, assessment, and treatment of anemia; and adherence to more restrictive RBC transfusion thresholds). Data were collected on various clinical parameters. We further described lessons learned and difficulties encountered in this multisite PBM initiative. A significant reduction in RBC transfusions was observed for numerous indexed surgeries. For example, RBC transfusion rates for knee arthroplasty decreased from 25% in 2002 to 0.4% in 2020. For coronary artery bypass graft (CABG) surgery, transfusion rates decreased from 60% in 2002 to 27% in 2020. We also observed a decrease in RBC units utilized per transfused patient for knee (2.1 ± 0.5 [2002] vs 1.0 ± 0.6 [2020] units per patient) and CABG surgery (3.3 ± 0.6 [2002] vs 2.3 ± 1.9 [2020] units per patient). These reductions were associated with favorable clinical outcomes, including reduced length of hospital stay (P = .00003) and a reduced rate of perioperative infections (P.001) for nontransfused versus transfused patients. These advances have been achieved with estimated savings in the tens of millions of dollars annually. Our experience and data support the hypothesis that instituting an integrated network of transfusion nurse coordinators can provide an effective provincewide PBM program, reduce RBC transfusions, improve some patient outcomes, and reduce health care costs, as an example of a "win-win-win" medical program.

While patient blood management (PBM) initiatives are increasingly adopted across the globe as part of standard of care, there is need for a clear and widely accepted definition of PBM. To address this, an expert group representing PBM organizations from the International Foundation for Patient Blood Management (IFPBM), the Network for the Advancement of Patient Blood Management, Haemostasis and Thrombosis (NATA), the Society for the Advancement of Patient Blood Management (SABM), the Western Australia Patient Blood Management (WAPBM) Group, and OnTrac (Ontario Nurse Transfusion Coordinators) convened and developed this definition: "Patient blood management is a patient-centered, systematic, evidence-based approach to improve patient outcomes by managing and preserving a patient's own blood, while promoting patient safety and empowerment." The definition emphasizes the critical role of informed choice. PBM involves the timely, multidisciplinary application of evidence-based medical and surgical concepts aimed at (1) screening for, diagnosing, and appropriately treating anemia; (2) minimizing surgical, procedural, and iatrogenic blood losses and managing coagulopathic bleeding throughout the care; and (3) supporting the patient while appropriate treatment is initiated. We believe that having a common definition for PBM will assist all those involved including PBM organizations, hospital administrators, individual clinicians, and policy makers to focus on the appropriate issues when discussing and implementing PBM. The proposed definition is expected to continue to evolve, making this endeavor a work in progress.

We report our 10-year experience of a multicenter hemoglobin optimization program with the aim to reduce red blood cell transfusion in patients undergoing coronary artery bypass grafting (CABG).From 2006 to 2016, patients undergoing CABG at 10 centers in Ontario were referred to the Ontario Transfusion Coordinators (ONTraC) program. Of these, we present data on the first 60 consecutive patients per center, per year (n = 6,145).Overall, 45.7% patients were assessed14 days preoperatively, 16.4% were assessed ≥14 days preoperatively, and 37.9% were not assessed by ONTraC preoperatively. Transfusion rates fell from 40.1% in 2006 to 26.2% in 2016 (p0.01). Patients undergoing assessment were more likely to be older (p0.01), female (p 0.01), and anemic (p0.01) versus nonassessed patients. Those patients assessed were more likely to be treated with iron (p0.01) and erythropoietin (p0.01) preoperatively versus nonassessed patients. Transfusion rates were 26%, 28%, and 28% for patients undergoing assessment ≥14 days prior to operation,14 days prior to operation, or not at all. After baseline covariate adjustment, patients assessed ≥14 days preoperatively had shorter length of stay (effect -0.83, 95% confidence interval [CI] -1.41 to -0.25; p0.01) and a trend towards lower risk of red blood cell transfusion (odds ratio [OR] 0.83, 95% CI 0.68 to 1.00; p = 0.06). Blood transfusion was independently associated with an increased risk of death (OR 1.49, 95% CI 1.37 to 1.60; p0.01), infection (OR 1.24, 95% CI 1.18 to 1.30; p0.01), and longer hospital length of stay (effect 1.49, 95% CI 1.35 to 1.62; p0.01).The results of this study suggest that preoperative hemoglobin optimization may be effective in reducing red blood cell transfusion after CABG, particularly for patients assessed ≥14 days preoperatively.

Platelets may selectively execute apoptosis (PL-Apo), activation (PL-Act), and both or no responses when exposed to different chemical agents, shear stresses, and stored under blood banking conditions. Appropriate diagnosis of PL-Apo is an important issue of platelet physiology investigations. However, in diagnosing PL-Apo, there is a risk of a false-negative or false-positive diagnosis. The goal of the current review is to present recommendations that may help to avoid incorrect PL-Apo diagnosis. Analyzing reported studies, we recommend (1) using platelet-rich plasma rather than isolated platelets to minimize artificial stimulation of PL-Apo during platelet isolation, (2) using established optimal conditions for stimulation of PL-Apo and/or PL-Act, (3) using a panel of PL-Apo and PL-Act markers, and (4) appropriate positive and negative controls for quantification of PL-Apo and PL-Act responses.

Miscarriage and intrauterine growth restriction (IUGR) are devastating complications in fetal/neonatal alloimmune thrombocytopenia (FNAIT). We previously reported the mechanisms for bleeding diatheses, but it is unknown whether placental, decidual immune cells or other abnormalities at the maternal–fetal interface contribute to FNAIT. Here we show that maternal immune responses to fetal platelet antigens cause miscarriage and IUGR that are associated with vascular and immune pathologies in murine FNAIT models. Uterine natural killer (uNK) cell recruitment and survival beyond mid-gestation lead to elevated NKp46 and CD107 expression, perforin release and trophoblast apoptosis. Depletion of NK cells restores normal spiral artery remodeling and placental function, prevents miscarriage, and rescues hemorrhage in neonates. Blockade of NK activation receptors (NKp46, FcɣRIIIa) also rescues pregnancy loss. These findings shed light on uNK antibody-dependent cell-mediated cytotoxicity of invasive trophoblasts as a pathological mechanism in FNAIT, and suggest that anti-NK cell therapies may prevent immune-mediated pregnancy loss and ameliorate FNAIT., Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a gestational disease caused by maternal immune responses against fetal platelets. Using a FNAIT mouse model and human trophoblast cell lines, here the authors show that uterine natural killer cell-mediated trophoblast apoptosis contributes to FNAIT pathogenesis.

Availability of universal marker for the diagnosis of platelet apoptosis is an important but currently unresolved goal of platelet physiology investigations. Mitochondrial inner transmembrane potential (▵Ψm) depolarization is frequently used as a marker of apoptosis in nucleated cells and anucleate platelets. Since ▵Ψm depolarization in platelets is also frequently associated with concurrent induction of other apoptotic responses, it may appear that ▵Ψm depolarization is a good universal marker of platelet apoptosis. However, data presented in the current study indicate that this is incorrect. We report here fundamental differences in the effects of potassium ionophore valinomycin and calcium ionophore A23187 on human platelet apoptosis. Although both A23187-triggered and valinomycin-triggered ▵Ψm depolarization are strongly induced, the former is dependent on the opening of mitochondrial permeability transition pore (MPTP) and the latter is MPTP-independent. Furthermore, effects of calcium and potassium ionophores on other apoptotic events are also basically different. A23187 induces caspase-3 activation, proapoptotic Bax and Bak protein expression, phosphatidylserine exposure, and microparticle formation, whereas valinomycin does not induce these apoptotic manifestations. Discovery of targeted ▵Ψm depolarization not associated with apoptosis in valinomycin-treated platelets indicates that this marker should not be used as a single universal marker of platelet apoptosis in unknown experimental and clinical settings as it may lead to a false-positive apoptosis diagnosis.

© 2018 AABB BACKGROUND: Tranexamic acid (TXA) therapy is effective in reducing postoperative red blood cell (RBC) transfusion in total joint arthroplasty (TJA), yet uncertainty persists regarding comparative efficacy and safety among specific patient subgroups. We assessed the impact of a universal TXA protocol on RBC transfusion, postoperative hemoglobin (Hb), and adverse outcomes to determine whether TXA is safe and effective in TJA, both overall and in clinically relevant subgroups. STUDY DESIGN AND METHODS: A retrospective observational study was performed on patients undergoing TJA at our institution spanning 1 year before and after the implementation of a universal protocol to administer intravenous (IV) TXA. The primary outcome was percentage of patients transfused, and secondary outcomes were perioperative Hb and occurrence of adverse events (death, myocardial infarction, stroke, seizure, pulmonary embolism, deep vein thrombosis, and acute kidney injury). Outcomes were compared in pre- and post-protocol groups with χ 2 analysis. Logistic regression compared risk of transfusion in pre- and post-protocol subgroups of patients with differing risk for transfusion (anemia, body mass index [BMI], and sex). RESULTS: No differences were found in baseline patient characteristics across pre- and post-protocol groups (n = 1084 and 912, respectively). TXA use increased from 32.3% to 92.2% while transfusion rates decreased from 10.3% to 4.8% (p < 0.001). Postoperative Day 3 Hb increased from 95.8 to 101.4 g/L (p < 0.001). Logistic regression demonstrated reduced transfusion in post-protocol subgroups regardless of sex, anemia, or BMI (p < 0.001). No increase in adverse events was observed (p = 0.8451). CONCLUSIONS: Universal TXA was associated with a reduction of RBC transfusion, overall and in clinically relevant subgroups, strengthening the rationale for universal therapy.

To determine whether a multidisciplinary, multimodal Patient Blood Management (PBM) program for patients undergoing surgery is effective in reducing perioperative complication rate, and thereby is effective in improving clinical outcome.PBM is a medical concept with the focus on a comprehensive anemia management, to minimize iatrogenic (unnecessary) blood loss, and to harness and optimize patient-specific physiological tolerance of anemia.A systematic review and meta-analysis was performed. Eligible studies had to address each of the 3 PBM pillars with at least 1 measure per pillar, for example, preoperative anemia management plus cell salvage plus rational transfusion strategy. The study protocol has been registered with PROSPERO (CRD42017079217).Seventeen studies comprising 235,779 surgical patients were included in this meta-analysis (100,886 pre-PBM group and 134,893 PBM group). Implementation of PBM significantly reduced transfusion rates by 39% [risk ratio (RR) 0.61, 95% confidence interval (CI) 0.55-0.68, P0.00001], 0.43 red blood cell units per patient (mean difference -0.43, 95% CI -0.54 to -0.31, P0.00001), hospital length of stay (mean difference -0.45, 95% CI -0.65 to -0.25, P0,00001), total number of complications (RR 0.80, 95% CI 0.74-0.88, P0.00001), and mortality rate (RR 0.89, 95% CI 0.80-0.98, P = 0.02).Overall, a comprehensive PBM program addressing all 3 PBM pillars is associated with reduced transfusion need of red blood cell units, lower complication and mortality rate, and thereby improving clinical outcome. Thus, this first meta-analysis investigating a multimodal approach should motivate all executives and health care providers to support further PBM activities.

John Freedman surveys the trends and important events in Russian theater from 2010 to 2015. Freedman pays particular attention to how changes in Russia's increasingly conservative political climate and cultural policy have resulted in increased censorship of, decreased funding for, and division among Russian artists. The article also discusses major milestones, such as the opening of the Gogol Center, the closing of Teatr.doc, and provocative productions by Konstantin Bogomolov and Timofei Kulyabin.

The existence of autoimmune diseases in humans has been known for almost 100 years. Currently, autoimmune pathogenesis has been attributed to more than 40 human diseases; yet it is still not clear what immune abnormalities conclusively prove underlying autoimmune pathogenesis. Hence, although much has been learned, research is still needed for complete elucidation of the mechanisms of the immune dysregulation in AIHA. Better understanding of the underlying mechanism(s) may allow for development of more specific therapies of these not uncommon and often difficult-to-treat disorders.

Background: Cardiac surgery requiring the use of cardiopulmonary bypass is frequently complicated by coagulopathic bleeding that, largely due to the shortcomings of conventional coagulation tests, is difficult to manage. This study evaluated a novel transfusion algorithm that uses point-of-care coagulation testing. Methods: Consecutive patients who underwent cardiac surgery with bypass at one hospital before (January 1, 2012 to January 6, 2013) and after (January 7, 2013 to December 13, 2013) institution of an algorithm that used the results of point-of-care testing (ROTEM®; Tem International GmBH, Munich, Germany; Plateletworks®; Helena Laboratories, Beaumont, TX) during bypass to guide management of coagulopathy were included. Pre- and postalgorithm outcomes were compared using interrupted time-series analysis to control for secular time trends and other confounders. Results: Pre- and postalgorithm groups included 1,311 and 1,170 patients, respectively. Transfusion rates for all blood products (except for cryoprecipitate, which did not change) were decreased after algorithm institution. After controlling for secular pre- and postalgorithm time trends and potential confounders, the posttransfusion odds ratios (95% CIs) for erythrocytes, platelets, and plasma were 0.50 (0.32 to 0.77), 0.22 (0.13 to 0.37), and 0.20 (0.12 to 0.34), respectively. There were no indications that the algorithm worsened any of the measured processes of care or outcomes. Conclusions: Institution of a transfusion algorithm based on point-of-care testing was associated with reduced transfusions. This suggests that the algorithm could improve the management of the many patients who develop coagulopathic bleeding after cardiac surgery. The generalizability of the findings needs to be confirmed.

Thrombopoietin (TPO), a hematopoietic growth factor produced predominantly by the liver, is essential for thrombopoiesis. Prevailing theory posits that circulating TPO levels are maintained through its clearance by platelets and megakaryocytes via surface c-Mpl receptor internalization. Interestingly, we found a two- to threefold decrease in circulating TPO in GPIbα-/- mice compared with wild-type (WT) controls, which was consistent in GPIbα-deficient human Bernard-Soulier syndrome (BSS) patients. We showed that lower TPO levels in GPIbα-deficient conditions were not due to increased TPO clearance by GPIbα-/- platelets but rather to decreased hepatic TPO mRNA transcription and production. We found that WT, but not GPIbα-/-, platelet transfusions rescued hepatic TPO mRNA and circulating TPO levels in GPIbα-/- mice. In vitro hepatocyte cocultures with platelets or GPIbα-coupled beads further confirm the disruption of platelet-mediated hepatic TPO generation in the absence of GPIbα. Treatment of GPIbα-/- platelets with neuraminidase caused significant desialylation; however, strikingly, desialylated GPIbα-/- platelets could not rescue impaired hepatic TPO production in vivo or in vitro, suggesting that GPIbα, independent of platelet desialylation, is a prerequisite for hepatic TPO generation. Additionally, impaired hepatic TPO production was recapitulated in interleukin-4/GPIbα-transgenic mice, as well as with antibodies targeting the extracellular portion of GPIbα, demonstrating that the N terminus of GPIbα is required for platelet-mediated hepatic TPO generation. These findings reveal a novel nonredundant regulatory role for platelets in hepatic TPO homeostasis, which improves our understanding of constitutive TPO regulation and has important implications in diseases related to GPIbα, such as BSS and auto- and alloimmune-mediated thrombocytopenias.

Integrins are a large family of heterodimeric transmembrane receptors differentially expressed on almost all metazoan cells. Integrin β subunits contain a highly conserved plexin-semaphorin-integrin (PSI) domain. The CXXC motif, the active site of the protein-disulfide-isomerase (PDI) family, is expressed twice in this domain of all integrins across species. However, the role of the PSI domain in integrins and whether it contains thiol-isomerase activity have not been explored. Here, recombinant PSI domains of murine β3, and human β1 and β2 integrins were generated and their PDI-like activity was demonstrated by refolding of reduced/denatured RNase. We identified that both CXXC motifs of β3 integrin PSI domain are required to maintain its optimal PDI-like activity. Cysteine substitutions (C13A and C26A) of the CXXC motifs also significantly decreased the PDI-like activity of full-length human recombinant β3 subunit. We further developed mouse anti-mouse β3 PSI domain monoclonal antibodies (mAbs) that cross-react with human and other species. These mAbs inhibited αIIbβ3 PDI-like activity and its fibrinogen binding. Using single-molecular Biomembrane-Force-Probe assays, we demonstrated that inhibition of αIIbβ3 endogenous PDI-like activity reduced αIIbβ3-fibrinogen interaction, and these anti-PSI mAbs inhibited fibrinogen binding via different levels of both PDI-like activity-dependent and -independent mechanisms. Importantly, these mAbs inhibited murine/human platelet aggregation in vitro and ex vivo, and murine thrombus formation in vivo, without significantly affecting bleeding time or platelet count. Thus, the PSI domain is a potential regulator of integrin activation and a novel target for antithrombotic therapies. These findings may have broad implications for all integrin functions, and cell-cell and cell-matrix interactions.

Purpose – To explain the Supreme Court’s recent decision in Halliburton Co. v. Erica P. John Fund, Inc. and its implications for private class action litigation under the federal securities laws. Design/methodology/approach – Explains the background on the Halliburton decision, including the prior case history and key precedents, analyzes the key reasoning and holdings of the decision, and discusses the implications of the decision and how it will impact private class actions brought under the securities laws. Findings – While there was considerable pontification in the bar that the Halliburton case might provide a vehicle to curtail many class actions brought under the securities laws, the Halliburton decision left prior law and practice largely intact, but provides defendants in such cases a tool to challenge viability of lawsuits in certain circumstances. Originality/value – Practical guidance from experienced securities litigators.

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related mortality and can occur with any type of transfusion. TRALI is thought to be primarily mediated by donor antibodies activating recipient neutrophils resulting in pulmonary endothelial damage. Nonetheless, details regarding the interactions between donor antibodies and recipient factors are unknown. A murine antibody-mediated TRALI model was used to elucidate the roles of the F(ab')2 and Fc regions of a TRALI-inducing immunoglobulin G anti-major histocompatibility complex (MHC) class I antibody (34.1.2s). Compared with intact antibody, F(ab')2 fragments significantly increased serum levels of the neutrophil chemoattractant macrophage inflammatory protein 2 (MIP-2); however, pulmonary neutrophil levels were only moderately increased, and no pulmonary edema or mortality occurred. Fc fragments did not modulate any of these parameters. TRALI induction by intact antibody was completely abrogated by in vivo peripheral blood monocyte depletion by gadolinium chloride (GdCl3) or chemokine blockade with a MIP-2 receptor antagonist but was restored upon repletion with purified monocytes. The results suggest a two-step process for antibody-mediated TRALI induction: the first step involves antibody binding its cognate antigen on blood monocytes, which generates MIP-2 chemokine production that is correlated with pulmonary neutrophil recruitment; the second step occurs when antibody-coated monocytes increase Fc-dependent lung damage.

Summary The cell plasma membrane is tightly coupled with the vital processes of apoptosis and activation. In the current study, we investigated exposure of the apoptosis marker phosphatidylserine (PS) and activation marker P-selectin (CD62) on the plasma membrane of anucleate platelets. We found that, depending on triggering stimuli, the plasma membrane of human platelets may exist in four states with predominant exposure of (i) PS but not CD62 (75·9 ± 2·8% of total cells), (ii) CD62 but not PS (86·2 ± 1·3%), (iii) both PS and CD62 (89·6 ± 1·0%) or (iv) neither PS nor CD62 (87·9–97·5%), when platelets were treated at optimal conditions with pro-apoptotic BH3 mimetic ABT-737, thrombin, calcium ionophore A23187 or control diluents, respectively. The dynamics of PS exposure induced by ABT-737 is a slow temperature-dependent process requiring 90 min treatment at 37°C rather than at room temperature for obtaining high levels of PS exposure. In contrast, thrombin-induced CD62 exposure and A23187-induced PS and CD62 exposure showed fast temperature-independent dynamics. This model of selective and concurrent stimulation of PS and/or CD62 transition to the platelet surface provides an experimental horizon for elucidating the roles of plasma membrane markers of platelet apoptosis and activation in platelet clearance.

Over the past decades, a wealth of information has been reported about the pathogenic features of immune thrombocytopenia (ITP). To this day, however, it is unclear whether the immune abnormalities associated with ITP play causative roles in the disease or are secondary epiphenomena brought on by the inflammatory processes that are associated with the disorder. Like the majority of all autoimmune diseases, ITP is an organ-specific disease and abnormalities in immune cell types, such as antigen-presenting cells (APC), T cells and B cells have been shown to play some sort of role in the initiation and/or perpetuation of the disease. This review will discuss recent advances in understanding three immune cells important in ITP pathophysiology: APC, T cells and B cells, and will review how they interact with each other to initiate and perpetuate ITP, particularly the chronic form of the disorder. It will also focus on new data related to the genetics of the disorder and discuss relevant animal models of ITP.

Summary Anucleate platelets perform two fundamental processes, activation and apoptosis. We elaborated an approach for selective and concurrent stimulation of platelet apoptosis and/or activation, processes important in haemostasis and platelet clearance. Human platelets were treated with BH3 mimetic ABT-737, thrombin, calcium ionophore A23187 and matched diluents. Apoptosis was determined as mitochondrial inner membrane potential (ΔΨm) depolarization and activation as P-selectin exposure. At optimal treatment conditions (90–180 min, 37°C), ABT-737 predominantly induced apoptosis, when 77–81% platelets undergo only ΔΨm depolarization. The ABT-737 impact on ΔΨm depolarization is strongly time- and temperature-dependent, and much higher at 37°C than at room temperature. In contrast, when platelets were treated with thrombin for 15–90 min at either temperature, activation-only was predominantly (79–85%) induced, whereas A23187 triggers both apoptosis and activation (73–81%) when platelets were treated for 15–60 min at 37°C or 15–90 min at room temperature. These data demonstrate that, depending on the triggering stimulus, platelets predominantly undergo ΔΨm depolarization-only, P-selectin exposure-only, or both responses, indicating that platelet apoptosis and activation are different phenomena driven by different mechanisms. The described model provides a basis for studying differential pharmacological manipulation of platelet apoptosis and activation and their role in haemostasis, thrombosis and platelet clearance.

Objectives Intravasation of bone marrow contents into venous circulation and pulmonary embolization after intramedullary nailing may be coupled with the activation of coagulation and fibrinolytic cascades. The objective of this study was to assess hemostatic response to pulmonary extravasated marrow contents. We hypothesize that activation of platelet activity and the coagulation cascade may occur after embolization of marrow contents in an experimental animal model of intramedullary nailing. Methods Fifteen New Zealand white male rabbits were randomly assigned to control or fat embolism (FE) groups. In the FE group (n = 8), femurs were surgically instrumented with retrograde intramedullary nails and pressurized with bone cement. In the control group (n = 7), a sham knee incision was made that was immediately closed without drilling, reaming, or pressurization. Fibrinogen, D-dimer latex screen assay, 1 stage prothrombin time, and activated partial thromboplastin time were analyzed. Results As the main platelet activation indicators, the marker Annexin-V percent binding increased in the FE group at 2 hours (P = 0.04) and 4 hours (P = 0.04), and the marker CD62P percent expression increased in the FE group at 2 hours (P = 0.04). Conclusions This preliminary study showed that pressurization of marrow and intravasation of fat and marrow products cause activation of platelets and the coagulation cascade, with or without tissue trauma. This may be relevant to the treatment of multiply injured patients with prior respiratory and coagulation abnormalities. A future larger study may be needed.

BACKGROUND: Treatment with human platelet antigen (HPA)-matched platelets (PLTs) is the optimal therapy for bleeding secondary to neonatal alloimmune thrombocytopenia. Recent advances in high-throughput DNA-based blood group and PLT antigen genotyping have made it possible to screen plateletpheresis donors for potential HPA-matched PLT transfusion. STUDY DESIGN AND METHODS: This prospective study evaluated genomic DNA from plateletpheresis donors for single-nucleotide polymorphisms (SNPs) associated with HPA-1, -2, -3, -4, -5, and -15 to determine whether high-throughput multiplex genomic DNA PCR and oligonucleotide extension technology can be used for mass-scale PLT antigen genotyping. Genotyping using SNP technology was confirmed using sequence-specific polymerase chain reaction (SSP-PCR). RESULTS: Of the 748 donors screened, 277 were found to be negative for antigens implicated in alloimmune thrombocytopenia. In addition, two donors were homozygous for HPA-1b/b and -2b/b, six donors for HPA-1b/b and -3b/b, one for HPA-2b/b and -3b/b, one for HPA-1b/b and -5b/b, 10 for HPA-1b/b and -15 b/b, four for HPA-5b/b and -15b/b, and one for HPA-2b/b and -15b/b. Retesting using SSP-PCR was conducted for 60 donors. Discrepant results occurred between SNP and SSP-PCR in less than 20% of samples for HPA-1b/1b/HPA-3b/3b, HPA-5b/5b, and HPA-15b/b. DISCUSSION: High-throughput multiplex PCR SNP and confirmatory molecular genotyping are useful for mass-scale screening of apheresis PLT donors to provide antigen-negative genotypes. Refinements to mass-scale multiplex analysis technology would reduce further the confirmatory testing needed.

Integrin αIIbβ3 plays key roles in thrombosis and hemostasis primarily through mediating platelet adhesion and aggregation. We recently reported that the active site of thiol-isomerase enzymes, CXXC motif, is expressed twice within the plexin-semaphorin-integrin (PSI) domain across all integrins and species, and the PSI domain of β3 integrin possesses endogenous thiol-isomerase activity, which may be a novel target for anti-thrombotic therapy (Blood, 2017). We developed four mouse anti-mouse β3 integrin PSI domain monoclonal antibodies (mAbs). These mAbs cross-react with β3 PSI domains of human, mouse, pig, rat, and rabbit tested but not other regions of β3 integrin, other integrins or other thiol-isomerase enzymes. They inhibit the thiol-isomerase activity of β3 PSI domain, decrease platelet adhesion/aggregation and thrombosis without increasing bleeding. Interestingly, the inhibitory effect of these mAbs on thrombosis in vivo (no anti-coagulant) was 10-20 times greater than their inhibitory effect on platelet aggregation in anti-coagulated platelet-rich plasma in vitro. This motivated us to explore whether this PSI domain contributes to blood coagulation. To asses blood clot formation and retraction, blood was incubated in non-stick tubes for two hours at 37°C in clot retraction assays. These assays showed less clot retraction and significantly lower dry clot weight in human and mouse whole blood treated with these anti-PSI mAbs compared to controls (p Disulfide bond exchanges are required for blood coagulation and thiol-isomerase enzymes play important roles in thrombosis. Given that blood coagulation is rapidly amplified on the platelet surface (i.e. cell-based coagulation), many coagulation factors are in close proximity to β3 integrin PSI domains (with thiol-isomerase activity). The study of interaction between β3 PSI domain and coagulation factors is currently being exploring. This is the first evidence of an allosteric therapeutic target of β3 integrin. This work suggests that a novel interaction exists between platelets and the coagulation cascade that requires the β3 integrin PSI domain and its thiol-isomerase activity. Importantly, the PSI domain can be targeted to partially block both platelet aggregation and coagulation, resulting in less bleeding while still providing a strong overall anti-thrombotic effect. Disclosures No relevant conflicts of interest to declare.