Laboratory approach for vaccine-induced thrombotic thrombocytopenia diagnosis in the Netherlands.

BACKGROUND AND OBJECTIVES: Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare adverse effect characterized by thrombocytopenia and thrombosis occurring after COVID-19 vaccination. VITT pathophysiology is not fully unravelled but shows similarities to heparin-induced thrombocytopenia (HIT). HIT is characterized by the presence of antibodies against platelet factor 4 (PF4)/heparin complex, which can activate platelets in an FcγRIIa-dependent manner, whereas IgG-antibodies directed against PF4 play an important role in VITT. MATERIALS AND METHODS: We characterized all clinically suspected VITT cases in the Netherlands from a diagnostic perspective and hypothesized that patients who developed both thrombocytopenia and thrombosis display underlying mechanisms similar to those in HIT. We conducted an anti-PF4 ELISA and a functional PF4-induced platelet activation assay (PIPAA) with and without blocking the platelet-FcγRIIa and found positivity in both tests, suggesting VITT with mechanisms similar to those in VITT. RESULTS: We identified 65 patients with both thrombocytopenia and thrombosis among 275 clinically suspected VITT cases. Of these 65 patients, 14 (22%) tested positive for anti-PF4 and PF4-dependent platelet activation. The essential role of platelet-FcγRIIa in VITT with mechanisms similar to those in HIT was evident, as platelet activation was inhibited by an FcγRIIa-blocking antibody in all 14 patients. CONCLUSION: Our study shows that only a small proportion of clinically suspected VITT patients with thrombocytopenia and thrombosis have anti-PF4-inducing, FcɣRIIa-dependent platelet activation, suggesting an HIT-like pathophysiology. This leaves the possibility for the presence of another type of pathophysiology ('non-HIT like') leading to VITT. More research on pathophysiology is warranted to improve the diagnostic algorithm and to identify novel therapeutic and preventive strategies.

Effect of alemtuzumab-based T-cell depletion on graft compositional change in vitro and immune reconstitution early after allogeneic stem cell transplantation.

BACKGROUND AIMS: To reduce the risk of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (alloSCT), T-cell depletion (TCD) of grafts can be performed by the addition of alemtuzumab (ALT) "to the bag" (in vitro) before transplantation. In this prospective study, the authors analyzed the effect of in vitro incubation with 20 mg ALT on the composition of grafts prior to graft infusion. Furthermore, the authors assessed whether graft composition at the moment of infusion was predictive for T-cell reconstitution and development of GVHD early after TCD alloSCT. METHODS: Sixty granulocyte colony-stimulating factor-mobilized stem cell grafts were obtained from ≥9/10 HLA-matched related and unrelated donors. The composition of the grafts was analyzed by flow cytometry before and after in vitro incubation with ALT. T-cell reconstitution and incidence of severe GVHD were monitored until 12 weeks after transplantation. RESULTS: In vitro incubation of grafts with 20 mg ALT resulted in an initial median depletion efficiency of T-cell receptor (TCR) α/ß T cells of 96.7% (range, 63.5-99.8%), followed by subsequent depletion in vivo. Graft volumes and absolute leukocyte counts of grafts before the addition of ALT were not predictive for the efficiency of TCR α/ß T-cell depletion. CD4pos T cells were depleted more efficiently than CD8pos T cells, and naive and regulatory T cells were depleted more efficiently than memory and effector T cells. This differential depletion of T-cell subsets was in line with their reported differential CD52 expression. In vitro depletion efficiencies and absolute numbers of (naive) TCR α/ß T cells in the grafts after ALT incubation were not predictive for T-cell reconstitution or development of GVHD post- alloSCT. CONCLUSIONS: The addition of ALT to the bag is an easy, fast and generally applicable strategy to prevent GVHD in patients receiving alloSCT after myeloablative or non-myeloablative conditioning because of the efficient differential depletion of donor-derived lymphocytes and T cells.

The association between haemorrhage and markers of endothelial insufficiency and inflammation in patients with hypoproliferative thrombocytopenia: a cohort study.

In daily haematological practice, predicting bleeding in thrombocytopenic patients is difficult, and clinicians adhere to transfusion triggers to guide patients through the aplastic phase of chemotherapy. Platelet count is not the only determinant of bleeding and additional mechanisms for impending haemostasis are likely. Beside clot formation, platelets are essential for the maintenance of integrity of vascular beds. We therefore prospectively investigated associations between biomarkers for endothelial damage (urine albumin excretion) and inflammation (C-reactive protein) and bleeding (WHO grading) in 88 patients with 116 on-protocol episodes. We found an increase in grade 2 bleeding with a higher urine albumin/creatinine ratio one day after the measurement [odds ratio (OR) 1·24 for every doubling of the ratio, 95% CI 1·05-1·46, P-value 0·01] and a 29% increase in the odds of grade 2 bleeding for every doubling of serum C-reactive protein (CRP) (95% CI 1·04-1·60, P-value 0·02) after correction for morning platelet count. The 24 h post-transfusion corrected count increment (CCI24 ) showed a significant association with these biomarkers: increasing urine albumin/creatinine ratio and CRP were associated with lower CCI24. We report two inexpensive and easy-to-apply biomarkers that could be useful in designing a prediction model for bleeding risk in thrombocytopenic patients.

Hemostatic efficacy of pathogen-inactivated vs untreated platelets: a randomized controlled trial.

Pathogen inactivation of platelet concentrates reduces the risk for blood-borne infections. However, its effect on platelet function and hemostatic efficacy of transfusion is unclear. We conducted a randomized noninferiority trial comparing the efficacy of pathogen-inactivated platelets using riboflavin and UV B illumination technology (intervention) compared with standard plasma-stored platelets (control) for the prevention of bleeding in patients with hematologic malignancies and thrombocytopenia. The primary outcome parameter was the proportion of transfusion-treatment periods in which the patient had grade 2 or higher bleeding, as defined by World Health Organization criteria. Between November 2010 and April 2016, 469 unique patients were randomized to 567 transfusion-treatment periods (283 in the control arm, 284 in the intervention arm). There was a 3% absolute difference in grade 2 or higher bleeding in the intention-to-treat analysis: 51% of the transfusion-treatment periods in the control arm and 54% in the intervention arm (95% confidence interval [CI], -6 to 11; P = .012 for noninferiority). However, in the per-protocol analysis, the difference in grade 2 or higher bleeding was 8%: 44% in the control arm and 52% in the intervention arm (95% CI -2 to 18; P = .19 for noninferiority). Transfusion increment parameters were ∼50% lower in the intervention arm. There was no difference in the proportion of patients developing HLA class I alloantibodies. In conclusion, the noninferiority criterion for pathogen-inactivated platelets was met in the intention-to-treat analysis. This finding was not demonstrated in the per-protocol analysis. This trial was registered at The Netherlands National Trial Registry as #NTR2106 and at www.clinicaltrials.gov as #NCT02783313.

What does cell therapy manufacturing cost? A framework and methodology to facilitate academic and other small-scale cell therapy manufacturing costings.

BACKGROUND AIMS: Recent technical and clinical advances with cell-based therapies (CBTs) hold great promise in the treatment of patients with rare diseases and those with high unmet medical need. Currently the majority of CBTs are developed and manufactured in specialized academic facilities. Due to small scale, unique characteristics and specific supply chain, CBT manufacturing is considered costly compared to more conventional medicinal products. As a result, biomedical researchers and clinicians are increasingly faced with cost considerations in CBT development. The objective of this research was to develop a costing framework and methodology for academic and other small-scale facilities that manufacture cell-based therapies. METHODS: We conducted an international multi-center costing study in four facilities in Europe using eight CBTs as case studies. This study includes costs from cell or tissue procurement to release of final product for clinical use. First, via interviews with research scientists, clinicians, biomedical scientists, pharmacists and technicians, we designed a high-level costing framework. Next, we developed a more detailed uniform methodology to allocate cost items. Costs were divided into steps (tissue procurement, manufacturing and fill-finish). The steps were each subdivided into cost categories (materials, equipment, personnel and facility), and each category was broken down into facility running (fixed) costs and operational (variable) costs. The methodology was tested via the case studies and validated in developer interviews. Costs are expressed in 2018 euros (€). RESULTS: The framework and methodology were applicable across facilities and proved sensitive to differences in product and facility characteristics. Case study cost estimates ranged between €23 033 and €190 799 Euros per batch, with batch yield varying between 1 and 88 doses. The cost estimations revealed hidden costs to developers and provided insights into cost drivers to help design manufacturing best practices. CONCLUSIONS: This framework and methodology provide step-by-step guidance to estimate manufacturing costs specifically for cell-based therapies manufactured in academic and other small-scale enterprises. The framework and methodology can be used to inform and plan cost-conscious strategies for CBTs.

Risk Factors, Treatment, and Immune Dysregulation in Autoimmune Cytopenia after Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients.

Autoimmune or alloimmune cytopenia (AIC) is a known rare complication of hematopoietic stem cell transplantation (SCT). AIC after SCT is considered difficult to treat and is associated with high morbidity and mortality. In this retrospective study in pediatric patients we evaluated incidence, outcome, potential risk factors, and current treatment strategies. A nested matched case-control study was performed to search for biomarkers associated with AIC. Of 531 consecutive SCTs at our center between 2000 and 2016, 26 were complicated by the development of AIC (cumulative incidence, 5.0%) after a median of 5 months post-SCT. Autoimmune hemolytic anemia was the most common AIC with 12 patients (46%). We identified nonmalignant disease, alemtuzumab serotherapy pre-SCT, and cytomegalovirus (CMV) reactivation as independently associated risk factors. The cytokine profile of patients at the time of AIC diagnosis appeared to skew toward a more pronounced Th 2 response compared with control subjects at the corresponding time point post-SCT. Corticosteroids and intravenous immunoglobulin as first-line treatment or a wait-and-see approach led to resolution of AIC in 35% of cases. Addition of step-up therapies rituximab (n = 15), bortezomib (n = 7), or sirolimus (n = 3) was associated with AIC resolution in 40%, 57%, and 100% of cases, respectively. In summary, we identified CMV reactivation post-SCT as a new clinical risk factor for the development of AIC in children. The cytokine profile during AIC appears to favor a Th 2 response. Rituximab, bortezomib, and sirolimus are promising step-up treatment modalities.

Detection of platelet autoantibodies to identify immune thrombocytopenia: state of the art.

Immune Thrombocytopenia (ITP) is diagnosed by exclusion of other causes for thrombocytopenia. Reliable detection of platelet autoantibodies would support the clinical diagnosis of ITP and prevent misdiagnosis. We optimized our diagnostic algorithm for suspected ITP using the direct monoclonal antibody immobilization of platelet antigens assay (MAIPA), which evaluates the presence of platelet autoantibodies on the glycoproteins (GP) IIb/IIIa, Ib/IX and V bound on the patient platelets. The direct MAIPA was shown to be a valuable technique for the detection of platelet autoantibodies and could possibly become a guide for optimizing therapy towards a more personalized treatment of ITP.

Second-line treatment for acute graft-versus-host disease with mesenchymal stromal cells: A decision model.

OBJECTIVE: No standard second-line treatment exists for acute graft-versus-host disease steroid-refractory (SR-aGvHD), and long-term outcomes remain poor. Mesenchymal stromal cells (MSCs) have been evaluated as treatment, but no disease model (DM) exists that integrates and extrapolates currently available evidence. The aim of this study was to develop such a DM to describe the natural history of SR-aGvHD and to predict long-term outcomes. METHOD: The DM was developed in collaboration with experts in haematology-oncology. Subsequently, a model simulation was run. Input parameters for transition and survival estimates were informed by published data of clinical trials on MSC treatment for SR-aGvHD. Parametric distributions were used to estimate long-term survival rates after MSCs. RESULTS: The newly developed DM is a cohort model that consists of eight health states. For the model simulation, we obtained data on 327 patients from 14 published phase II trials. Due to limited evidence, DM structure was simplified and several assumptions had to be made. Median overall survival was 3.2 years for complete response and 0.5 years for no complete response. CONCLUSION: The DM provides a comprehensive overview on the second-line treatment pathway for aGvHD and enables long-term predictions that can be used to perform a cost-effectiveness analysis comparing any treatment for SR-aGvHD.

MEIS1 regulates early erythroid and megakaryocytic cell fate.

MEIS1 is a transcription factor expressed in hematopoietic stem and progenitor cells and in mature megakaryocytes. This biphasic expression of MEIS1 suggests that the function of MEIS1 in stem cells is distinct from its function in lineage committed cells. Mouse models show that Meis1 is required for renewal of stem cells, but the function of MEIS1 in human hematopoietic progenitor cells has not been investigated. We show that two MEIS1 splice variants are expressed in hematopoietic progenitor cells. Constitutive expression of both variants directed human hematopoietic progenitors towards a megakaryocyte-erythrocyte progenitor fate. Ectopic expression of either MEIS1 splice variant in common myeloid progenitor cells, and even in granulocyte-monocyte progenitors, resulted in increased erythroid differentiation at the expense of granulocyte and macrophage differentiation. Conversely, silencing MEIS1 expression in progenitor cells induced a block in erythroid expansion and decreased megakaryocytic colony formation capacity. Gene expression profiling revealed that both MEIS1 splice variants induce a transcriptional program enriched for erythroid and megakaryocytic genes. Our results indicate that MEIS1 expression induces lineage commitment towards a megakaryocyte-erythroid progenitor cell fate in common myeloid progenitor cells through activation of genes that define a megakaryocyte-erythroid-specific gene expression program.

Antibodies against Platelet Glycoproteins in Clinically Suspected VITT Patients.

Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare but severe complication following COVID-19 vaccination, marked by thrombocytopenia and thrombosis. Analogous to heparin-induced thrombocytopenia (HIT), VITT shares similarities in anti-platelet factor 4 (PF4) IgG-mediated platelet activation via the FcγRIIa. To investigate the involvement of platelet-antibodies in VITT, we analyzed the presence of platelet-antibodies directed against glycoproteins (GP)IIb/IIIa, GPV and GPIb/IX in the serum of 232 clinically suspected VITT patients determined based on (suspicion of) occurrence of thrombocytopenia and/or thrombosis in relation to COVID-19 vaccination. We found that 19% of clinically suspected VITT patients tested positive for anti-platelet GPs: 39%, 32% and 86% patients tested positive for GPIIb/IIIa, GPV and GPIb/IX, respectively. No HIT-like VITT patients (with thrombocytopenia and thrombosis) tested positive for platelet-antibodies. Therefore, it seems unlikely that platelet-antibodies play a role in HIT-like anti-PF4-mediated VITT. Platelet-antibodies were predominantly associated with the occurrence of thrombocytopenia. We found no association between the type of vaccination (adenoviral vector vaccine versus mRNA vaccine) or different vaccines (ChAdOx1 nCoV-19, Ad26.COV2.S, mRNA-1273, BTN162b2) and the development of platelet-antibodies. It is essential to conduct more research on the pathophysiology of VITT, to improve diagnostic approaches and identify preventive and therapeutic strategies.

Intramyocardial injection of bone marrow mononuclear cells in chronic myocardial ischemia patients after previous placebo injection improves myocardial perfusion and anginal symptoms: an intra-patient comparison.

BACKGROUND: We recently demonstrated in a randomized, double-blind, placebo-controlled trial that intramyocardial bone marrow cell (BMC) injection is associated with improvements in myocardial perfusion and anginal symptoms in chronic myocardial ischemia patients. In the present study the results of the crossover phase of this trial, in which patients previously treated with placebo received autologous BMC injections are reported. This allows a unique intra-patient comparison on the effect of BMC versus placebo injection with elimination of patient-related confounding factors. METHODS: In 16 patients (14 male, 64 ± 10 years), who previously received intramyocardial placebo injections in the setting of a randomized trial, 100 × 10(6) BMC were injected using the NOGA-system. Canadian Cardiovascular Society angina score and quality of life were evaluated at baseline, 3 and 6 months. Tc-99m single photon emission computed tomography and magnetic resonance imaging were performed at baseline and 3 months to assess myocardial perfusion and left ventricular (LV) function. RESULTS: Canadian Cardiovascular Society score and quality of life improved significantly after BMC injection as compared to placebo (P = 0.01 and P = 0.02, respectively). Single photon emission computed tomography revealed a significant greater improvement (P = 0.03) in summed stress score after BMC injection as compared to placebo. LV end-systolic volume significantly decreased after BMC injection but not after placebo injection. LV end-diastolic volume and LV ejection fraction did not change. CONCLUSION: Intramyocardial BMC injection in patients with chronic myocardial ischemia who previously received intramyocardial placebo treatment resulted in significant improvement in angina symptoms and myocardial perfusion. These results confirm the outcome of our previously reported randomized trial.

The haemostatic effect of deep-frozen platelets versus room temperature-stored platelets in the treatment of surgical bleeding: MAFOD-study protocol for a randomized controlled non-inferiority trial.

BACKGROUND: The Netherlands Armed Forces have been successfully using deep-frozen (- 80 °C) thrombocyte concentrate (DTC) for the treatment of (massive) bleeding trauma patients in austere environments since 2001. However, high-quality evidence for the effectiveness and safety of DTCs is currently lacking. Therefore, the MAssive transfusion of Frozen bloOD (MAFOD) trial is designed to compare the haemostatic effect of DTCs versus room temperature-stored platelets (RSP) in the treatment of surgical bleeding. METHODS: The MAFOD trial is a single-blinded, randomized controlled non-inferiority trial and will be conducted in three level 1 trauma centres in The Netherlands. Patients 12 years or older, alive at hospital presentation, requiring a massive transfusion including platelets and with signed (deferred) consent will be included. The primary outcome is the percentage of patients that have achieved haemostasis within 6 h and show signs of life. Haemostasis is defined as the time in minutes from arrival to the time of the last blood component transfusion (plasma/platelets or red blood cells), followed by a 2-h transfusion-free period. This is the first randomized controlled study investigating DTCs in trauma and vascular surgical bleeding. DISCUSSION: The hypothesis is that the percentage of patients that will achieve haemostasis in the DTC group is at least equal to the RSP group (85%). With a power of 80%, a significance level of 5% and a non-inferiority limit of 15%, a total of 71 patients in each arm are required, thus resulting in a total of 158 patients, including a 10% refusal rate. The data collected during the study could help improve the use of platelets during resuscitation management. If proven non-inferior in civilian settings, frozen platelets may be used in the future to optimize logistics and improve platelet availability in rural or remote areas for the treatment of (massive) bleeding trauma patients in civilian settings. TRIAL REGISTRATION: ClinicalTrials.gov NCT05502809. Registered on 16 August 2022.

A functional spleen contributes to afucosylated IgG in humans.

As a lymphoid organ, the spleen hosts a wide range of immune cell populations, which not only remove blood-borne antigens, but also generate and regulate antigen-specific immune responses. In particular, the splenic microenvironment has been demonstrated to play a prominent role in adaptive immune responses to enveloped viral infections and alloantigens. During both types of immunizations, antigen-specific immunoglobulins G (IgGs) have been characterized by the reduced amount of fucose present on N-linked glycans of the fragment crystallizable (Fc) region. These glycans are essential for mediating the induction of immune effector functions. Therefore, we hypothesized that a spleen may modulate humoral responses and serve as a preferential site for afucosylated IgG responses, which potentially play a role in immune thrombocytopenia (ITP) pathogenesis. To determine the role of the spleen in IgG-Fc glycosylation, we performed IgG subclass-specific liquid chromatography-mass spectrometry (LC-MS) analysis of Fc glycosylation in a large cohort of individuals splenectomized due to trauma, due to ITP, or spherocytosis. IgG-Fc fucosylation was consistently increased after splenectomy, while no effects for IgG-Fc galactosylation and sialylation were observed. An increase in IgG1- and IgG2/3-Fc fucosylation level upon splenectomy has been reported here for the first time, suggesting that immune responses occurring in the spleen may be particularly prone to generate afucosylated IgG responses. Surprisingly, the level of total IgG-Fc fucosylation was decreased in ITP patients compared to healthy controls. Overall, our results suggest a yet unrecognized role of the spleen in either the induction or maintenance of afucosylated IgG responses by B cells.

Generation and infusion of multi-antigen-specific T cells to prevent complications early after T-cell depleted allogeneic stem cell transplantation-a phase I/II study.

Prophylactic infusion of selected donor T cells can be an effective method to restore specific immunity after T-cell-depleted allogeneic stem cell transplantation (TCD-alloSCT). In this phase I/II study, we aimed to reduce the risk of viral complications and disease relapses by administrating donor-derived CD8pos T cells directed against cytomegalovirus (CMV), Epstein-Barr virus (EBV) and adenovirus antigens, tumor-associated antigens (TAA) and minor histocompatibility antigens (MiHA). Twenty-seven of thirty-six screened HLA-A*02:01pos patients and their CMVpos and/or EBVpos donors were included. Using MHC-I-Streptamers, 27 T-cell products were generated containing a median of 5.2 × 106 cells. Twenty-four products were administered without infusion-related complications at a median of 58 days post alloSCT. No patients developed graft-versus-host disease during follow-up. Five patients showed disease progression without coinciding expansion of TAA/MiHA-specific T cells. Eight patients experienced CMV- and/or EBV-reactivations. Four of these reactivations were clinically relevant requiring antiviral treatment, of which two progressed to viral disease. All resolved ultimately. In 2/4 patients with EBV-reactivations and 6/8 patients with CMV-reactivations, viral loads were followed by the expansion of donor-derived virus target-antigen-specific T cells. In conclusion, generation of multi-antigen-specific T-cell products was feasible, infusions were well tolerated and expansion of target-antigen-specific T cells coinciding viral reactivations was illustrated in the majority of patients.

Intramyocardial bone marrow cell injection for chronic myocardial ischemia: a randomized controlled trial.

CONTEXT: Previous studies have suggested that bone marrow cell injection may improve myocardial perfusion and left ventricular (LV) function in patients with chronic myocardial ischemia. OBJECTIVE: To investigate the effect of intramyocardial bone marrow cell injection on myocardial perfusion and LV function in patients with chronic myocardial ischemia. DESIGN, SETTING, AND PATIENTS: Randomized, double-blind, placebo-controlled trial at a Netherlands university hospital, May 1, 2005-March 3, 2008 (6-month follow-up ended September 2008) of 50 patients with chronic myocardial ischemia (mean age [SD], 64 [8] years; 43 men). INCLUSION CRITERIA: severe angina pectoris despite optimal medical therapy and myocardial ischemia. All patients were ineligible for conventional revascularization. INTERVENTIONS: Intramyocardial injection of 100 x 10(6) autologous bone marrow-derived mononuclear cells or placebo solution. MAIN OUTCOME MEASURES: Primarily, the summed stress score, a 17-segment score for stress myocardial perfusion assessed by Tc-99m tetrofosmin single-photon emission computed tomography (SPECT). Secondary included LV ejection fraction (LVEF), Canadian Cardiovascular Society (CCS) class, and Seattle Angina Questionnaire quality-of-life score (mean difference >5% considered clinically significant). RESULTS: After 3-month follow-up, the summed stress score (mean [SD]) improved from 23.5 (4.7) to 20.1 (4.6) (P < .001) in the bone marrow cell group, compared with a decrease from 24.8 (5.5) to 23.7 (5.4) (P = .004) in the placebo group. In the bone marrow cell-treated patients who underwent magnetic resonance imaging (MRI), a 3% absolute increase in LVEF was observed at 3 months (95% CI, 0.5% to 4.7%; n = 18), but the placebo group showed no improvement. CCS angina score improved significantly in the bone marrow cell group (6-month absolute difference, -0.79; 95% CI, -1.10 to -0.48; P < .001) compared with no significant improvement in the placebo group. Quality-of-life score increased from 56% (9%) to 64% (12%) at 3 months and 69% (12%) at 6 months in bone marrow cell-treated patients, compared with a smaller increase in the placebo group from 57% (11%) to 61% (14%) to 64% (17%). The improvements in CCS class and quality of life score were significantly greater in bone marrow cell-treated patients than in placebo-treated patients (P = .03 and P = .04, respectively). CONCLUSIONS: In this short-term study of patients with chronic myocardial ischemia refractory to medical treatment, intramyocardial bone marrow cell injection resulted in a statistically significant but modest improvement in myocardial perfusion compared with placebo. Further studies are required to assess long-term results and efficacy for mortality and morbidity. TRIAL REGISTRATIONS: trialregister.nl Identifier: NTR400 and isrctn.org Identifier: ISRCTN58194927.

Reporting transfusion-related acute lung injury by clinical and preclinical disciplines.

BACKGROUND: Disciplines involved in diagnosing transfusion-related acute lung injury (TRALI) report according to a "one-hit" theory. However, studies showed that patients with an underlying condition are at increased risk of the development of TRALI. We investigated whether accumulating evidence on the "two-hit" theory has changed the practice of reporting TRALI. MATERIALS AND METHODS: Departments of haematology, haemovigilance, transfusion medicine, intensive care and anaesthesiology from all Dutch hospitals with at least five beds equipped for mechanical ventilation were invited to participate in an online survey. Using clinical vignettes with conjoint analysis we investigated the effect of patients' age, admission diagnosis, type and number of transfusions and presence of risk factors for acute lung injury on TRALI reporting. A positive ß-coefficient indicated a higher likelihood of reporting TRALI. RESULTS: We received 129 questionnaires (response rate 74%). Respondents were more likely to report TRALI in younger patients, if symptoms developed within 2 hours of transfusion and if patients had received multiple transfusions. Sepsis and the presence of a risk factor for acute lung injury reduced the inclination to report. Transfusion medicine physicians and haemovigilance staff no longer took the age of transfusion products into account in their diagnostic considerations on TRALI. DISCUSSION: We conclude that the multidisciplinary team involved in TRALI reporting, still considers TRALI a "one-hit" event, despite accumulating evidence that supports the "two-hit" theory. These results suggest that the patients most at risk of developing TRALI are not reported to the blood bank.

Activation of inflammation and coagulation after infusion of C-reactive protein in humans.

C-reactive protein (CRP) has been postulated to play a causal part in atherosclerosis and its acute complications. We assessed the effects of CRP-infusion on coagulation and inflammatory pathways to determine its role in atherothrombotic disease. Seven male volunteers received an infusion on two occasions, containing 1.25 mg/kg recombinant human CRP (rhCRP) or diluent, respectively. CRP-concentrations rose after rhCRP-infusion from 1.9 (0.3 to 8.5) to 23.9 (20.5 to 28.1) mg/L, and subsequently both inflammation and coagulation were activated. This sequence of events suggests that CRP is not only a well known marker of cardiovascular disease, but is also probably a mediator of atherothrombotic disease.

Platelet binding to monocytes increases the adhesive properties of monocytes by up-regulating the expression and functionality of beta1 and beta2 integrins.

Human monocytes adhere to activated platelets, resulting in the formation of platelet-monocyte complexes (PMC). Complex formation depends on the interaction between platelet-displayed P-selectin and the specific ligand for P-selectin on leukocytes, P-selectin glycoprotein ligand-1 (PSGL-1). We have recently shown that monocytes within PMC have increased adhesive capacity to the activated endothelium. To better understand the effect of platelet binding on the capacity of monocytes to adhere to activated endothelium, the P-selectin-PSGL-1 interaction-induced changes in integrin functionality were studied. The binding of platelets to monocytes via P-selectin-PSGL-1 interactions was shown to increase expression and activity of alpha4beta1 and alphaMbeta2integrin, with a concomitant decrease in L-selectin expression. Furthermore, the binding of platelets to monocytes resulted in increased monocyte adhesion to intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and fibronectin. Platelet binding was also responsible for an increase in monocyte transendothelial migration. Similar effects were observed after engagement of PSGL-1 with specific antibodies or with P-selectin immunoglobulin protein. Our data suggest that platelets, by binding via P-selectin to PSGL-1 on monocytes, induce up-regulation and activation of beta1 and beta2integrins and increased adhesion of monocytes to activated endothelium. Hence, monocytes within PMC are in a higher state of activation and may have, therefore, an increased atherogenic capacity.