Azathioprine/hydroxyurea preconditioning prior to nonmyeloablative matched sibling donor hematopoietic stem cell transplantation in adults with sickle cell disease: A prospective observational cohort study.

Nonmyeloablative, matched sibling donor hematopoietic stem cell transplantation with alemtuzumab/total body irradiation (TBI) conditioning is a curative therapy with low toxicity for adults with sickle cell disease (SCD). However, relatively low donor chimerism levels and graft rejection remain important challenges. We hypothesized that adding azathioprine/hydroxyurea preconditioning will improve donor chimerism levels and reduce graft failure rate. In this prospective cohort study, we enrolled consecutive adult patients with SCD undergoing matched sibling donor transplantation at the Amsterdam UMC. Patients received azathioprine 150 mg/day and hydroxyurea 25 mg/kg/day for 3 months prior to alemtuzumab 1 mg/kg and 300 cGy TBI conditioning. Twenty patients with SCD (median age 26 years [range 19-49], 13 females) were transplanted. Median follow-up was 46.0 months (IQR 21.8-57.9). One-year overall survival and event-free survival (graft failure or death) were both 95% (95% confidence interval 86-100). Mean donor myeloid and T-cell chimerism 1-year post-transplant were 95.2% (SD ±10.6) and 67.3% (±15.3), respectively. One patient (5%) experienced graft failure without autologous regeneration, resulting in infections and death. All other patients had a corrected SCD phenotype and were able to discontinue sirolimus. Three patients were successfully treated with alemtuzumab (1 mg/kg) after the transplant because of declining donor chimerism and cytopenias to revert impending graft rejection. Toxicity was mostly related to sirolimus and alemtuzumab. One patient developed steroid-responsive grade II intestinal acute graft-versus-host disease. Collectively, preconditioning with azathioprine/hydroxyurea prior to nonmyeloablative matched sibling donor transplantation resulted in excellent event-free survival and robust donor T-cell chimerism, enabling the successful withdrawal of sirolimus. ClinicalTrials.gov: NCT05249452.

Presence of innate lymphoid cells in allogeneic hematopoietic grafts correlates with reduced graft-versus-host disease.

BACKGROUND: Allogeneic hematopoietic cell transplantation (HCT) can be devastating when graft-versus-host disease (GvHD) develops. GvHD is characterized by mucosal inflammation due to breaching of epithelial barriers. Innate lymphoid cells (ILCs) are immune modulatory cells that are important in the maintenance of epithelial barriers, via their production of interleukin (IL)-22 and their T cell suppressive properties. After chemo- and radiotherapy, ILCs are depleted, and recovery after remission-induction therapy and after allogeneic HCT is slow and incomplete in a significant number of patients, which is associated with an increased risk to develop acute GvHD. OBJECTIVE: To investigate whether the presence of mature ILCs within G-CSF-mobilized HCT grafts is correlated with the development of acute GvHD after allogeneic HCT. STUDY DESIGN: We analyzed ILCs in a cohort of 36 patients who received allogeneic HCT for a hematologic malignancy, by flow-cytometric immune-phenotyping of prospectively collected, cryopreserved peripheral blood mononuclear cells (PBMCs) and donor-derived HCT grafts collected for the same patients. Biased analysis, with ILCs defined as CD3-lineage-CD45+CD127+CD161+ lymphocytes, was performed using FlowJo version 10 software. Unbiased analysis was done using FlowSOM, which uses a self-organizing map (SOM) with a minimal spanning tree (MST) to define and visualize different clusters present in the samples. RESULTS: Remission-induction therapy significantly depleted ILCs from the blood, and patients who had a relatively low percentage of ILCs before allogeneic HCT were significantly more prone to develop acute GvHD, confirming previous findings in a separate cohort. Allogeneic HCT grafts, which were all obtained from the blood of G-CSF-mobilized healthy donors, contained ILCs at a frequency very similar to the peripheral blood of healthy individuals. The ILC subset composition was also comparable to that of the blood of healthy individuals, with the exception of NKp44+ ILC3s, which were significantly more abundant in HCT grafts. The relative ILC content of the graft tended to correlate with ILC reconstitution after allogeneic HCT, suggesting that peripheral expansion of transplanted mature ILCs may contribute to early ILC reconstitution after allogeneic HCT. Patients who received a relatively ILC-poor HCT graft had a significantly increased risk to develop acute GvHD, compared with patients who received relatively ILC-rich allogeneic HCT grafts. Unbiased phenotypic analysis with the FlowSOM algorithm confirmed that allogeneic HCT grafts of patients who developed acute GvHD contained a lower frequency of ILCs that clustered in NKp44+ ILC3 signature groups. CONCLUSION: The presence of ILCs in allogeneic HCT grafts is associated with a reduced risk to develop acute GvHD. These data suggest that enhancement of ILC reconstitution of ILC3s in particular, for example via adoptive transfer of ILCs, may prevent acute GvHD and has the potential to improve outcome of allogeneic HCT recipients.

DAMPS and complement activation in platelet concentrates that induce adverse reactions in patients.

BACKGROUND: Patients with severe thrombocytopenia due to bone marrow failure and after chemotherapy are still treated with platelet transfusions. Platelet concentrates (PC) are associated with a high incidence of adverse reactions (AR). Platelet-derived damage-associated molecular patterns (DAMPS) and complement were proposed to play a role in the pathology of AR. STUDY DESIGN AND METHODS: Single donor apheresis platelet concentrates (SDA PCs) were produced in a regional setting of the French Blood Establishment. After transfusion samples were collected from PC and possible AR in patients were recorded. Platelet activation markers, High mobility group box 1 (HMGB1) and complement activation products (CAP) were measured. The correlation between platelet activation, and HMGB1 and complement activation was analyzed. RESULTS: A total of 56 PC were included in the study. 30 PC induced no AR, and 26 induced AR (Febrile non-hemolytic transfusion reaction n = 16; Atypical Allergic Transfusion Reactions n = 11; hemodynamic instability n = 5) in the patients. The levels of P-selectin, sCD40L, HMGB1, C3b/c, and C4b/c were all significantly increased in PC that induced AR following transfusion in patients. Additionally, HMGB1, C3b/c, and C4b/c were positively correlated with P-selectin and sCD40L. CONCLUSION: In this study, we observed an association between HMGB1 and CAP and the incidence of AR. Furthermore, we demonstrated that both HMGB1 and complement activation were correlated to platelet activation.

Cell-free DNA levels are increased in acute graft-versus-host disease.

BACKGROUND: Cell-free DNA (cfDNA) and nucleosomes, consisting of cfDNA and histones, are markers of cell activation and damage. In systemic inflammation these markers predict severity and fatality. However, the role of cfDNA in acute Graft-versus-Host Disease (aGvHD), a major complication of allogeneic hematopoietic stem cell transplantation (HSCT), is unknown. OBJECTIVE: The aim of this study is to investigate the role of cfDNA as a marker of aGvHD. METHODS: We followed nucleosome levels in 37 allogeneic HSCT patients and an established xenotransplantation mouse model. We determined the origin of cfDNA with a species-specific polymerase chain reaction. RESULTS: In the plasma of aGvHD patients, nucleosome levels significantly increased around the time of aGvHD diagnosis compared to pretransplant, concurrently with a significant increase of known aGvHD markers ST2 and REG3α. In mice, we confirmed that nucleosomes were elevated during clinically detectable aGvHD. We found cfDNA to be mainly of human origin and to a lesser extent of mouse origin, indicating that cfDNA is released by (proliferating) human xeno-reactive PBMC and damaged mouse cells. CONCLUSION: We show increased cfDNA both in an aGvHD mouse model and in aGvHD patients. We also demonstrate that donor hematopoietic cells and to a lesser degree (damaged) host cells are the cellular source of cfDNA in aGvHD. We propose that nucleosomes and cfDNA might be an additive marker for aGvHD.

The relation between fibrinogen level, neutrophil activity and nucleosomes in the onset of disseminated intravascular coagulation in the critically ill.

BACKGROUND: Nucleosomes and neutrophil extracellular traps (NETs) are important in the pathophysiology of disseminated intravascular coagulation (DIC). Fibrinogen, as an acute phase reactant, may be protective by engaging neutrophils. We hypothesize that DIC can occur when NET formation becomes uncontrolled in relation to low fibrinogen levels. PATIENTS/METHOD: The ratio of both circulating nucleosomes and human neutrophil elastase alpha-1-antitrypsine complexes (HNE-a1ATc) to fibrinogen was correlated to thrombocytopenia, DIC and organ failure in 64 critically ill coagulopathic patients. RESULTS: A high nucleosome to fibrinogen ratio correlated with thrombocytopenia and organ failure (ρ -0.391, p 0.01 and ρ 0.556, p 0.01, respectively). A high HNE-a1ATc to fibrinogen ratio correlated with thrombocytopenia, DIC and organ failure (ρ -0.418, p 0.01, ρ 0.391, p 0.01 and ρ 0.477, p 0.01 respectively). CONCLUSION: These findings support the hypothesis that fibrinogen is protective against DIC by counterbalancing excessive neutrophil activation.

Mouse venous thrombosis upon silencing of anticoagulants depends on tissue factor and platelets, not FXII or neutrophils.

Tissue factor, coagulation factor XII, platelets, and neutrophils are implicated as important players in the pathophysiology of (experimental) venous thrombosis (VT). Their role became evident in mouse models in which surgical handlings were required to provoke VT. Combined inhibition of the natural anticoagulants antithrombin (Serpinc1) and protein C (Proc) using small interfering RNA without additional triggers also results in a venous thrombotic phenotype in mice, most notably with vessel occlusion in large veins of the head. VT is fatal but is fully rescued by thrombin inhibition. In the present study, we used this VT mouse model to investigate the involvement of tissue factor, coagulation factor XII, platelets, and neutrophils. Antibody-mediated inhibition of tissue factor reduced the clinical features of VT, the coagulopathy in the head, and fibrin deposition in the liver. In contrast, genetic deficiency in, and small interfering RNA-mediated depletion of, coagulation factor XII did not alter VT onset, severity, or thrombus morphology. Antibody-mediated depletion of platelets fully abrogated coagulopathy in the head and liver fibrin deposition. Although neutrophils were abundant in thrombotic lesions, depletion of circulating Ly6G-positive neutrophils did not affect onset, severity, thrombus morphology, or liver fibrin deposition. In conclusion, VT after inhibition of antithrombin and protein C is dependent on the presence of tissue factor and platelets but not on coagulation factor XII and circulating neutrophils. This study shows that distinct procoagulant pathways operate in mouse VT, dependent on the triggering stimulus.

Allogeneic hematopoietic cell transplantation in the management of GATA2 deficiency and pulmonary alveolar proteinosis.

Human hematopoiesis is critically dependent on the transcription factor GATA2. Patients with GATA2 deficiency typically present with myelodysplastic syndrome, reduced numbers of monocytes, NK cells and B cells, and/or opportunistic infections. Here, we present two families that harbor distinct GATA2 mutations with highly variable onset and course of disease. We discuss the use of allogeneic hematopoietic cell transplantation in these patients, especially as treatment for pulmonary alveolar proteinosis.

Peptidoglycan induces disseminated intravascular coagulation in baboons through activation of both coagulation pathways.

Anthrax infections exhibit progressive coagulopathies that may contribute to the sepsis pathophysiology observed in fulminant disease. The hemostatic imbalance is recapitulated in primate models of late-stage disease but is uncommon in toxemic models, suggesting contribution of other bacterial pathogen-associated molecular patterns (PAMPs). Peptidoglycan (PGN) is a bacterial PAMP that engages cellular components at the cross talk between innate immunity and hemostasis. We hypothesized that PGN is critical for anthrax-induced coagulopathies and investigated the activation of blood coagulation in response to a sterile PGN infusion in primates. The PGN challenge, like the vegetative bacteria, induced a sepsis-like pathophysiology characterized by systemic inflammation, disseminated intravascular coagulation (DIC), organ dysfunction, and impaired survival. Importantly, the hemostatic impairment occurred early and in parallel with the inflammatory response, suggesting direct engagement of coagulation pathways. PGN infusion in baboons promoted early activation of contact factors evidenced by elevated protease-serpin complexes. Despite binding to contact factors, PGN did not directly activate either factor XII (FXII) or prekallikrein. PGN supported contact coagulation by enhancing enzymatic function of active FXII (FXIIa) and depressing its inhibition by antithrombin. In parallel, PGN induced de novo monocyte tissue factor expression in vitro and in vivo, promoting extrinsic clotting reactions at later stages. Activation of platelets further amplified the procoagulant state during PGN challenge, leading to DIC and subsequent ischemic damage of peripheral tissues. These data indicate that PGN may be a major cause for the pathophysiologic progression of Bacillus anthracis sepsis and is the primary PAMP behind the pathogen-induced coagulopathy in late-stage anthrax.

Neutrophils mitigate the systemic host response during endotoxemia in mice.

Recent studies have suggested that neutrophils can exert anti-inflammatory effects. To determine the role of neutrophils in the acute response to lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, we challenged neutrophil-depleted and control mice with LPS and analyzed the plasma concentrations of biomarkers indicative of the cytokine and chemokine network, activation of coagulation and the vascular endothelium, and cellular injury. We here show that neutrophils serve an anti-inflammatory role upon LPS administration, as reflected by sustained elevations of multiple cytokines and chemokines, and enhanced release of nucleosomes in mice depleted of neutrophils, compared with control mice.

Anti-HLA antibodies with complementary and synergistic interaction geometries promote classical complement activation on platelets.

High titers of HLA antibodies are associated with platelet refractoriness, causing poor platelet increments after transfusions in a subset of patients with HLA antibodies. Currently, we do not know the biological mechanisms that explain the variability in clinical responses in HLA alloimmunized patients receiving platelet transfusions. Previously we showed that a subset of anti-HLA IgG-antibodies induces FcγRIIa-dependent platelet activation and enhanced phagocytosis. Here, we investigated whether anti-HLA IgG can induce complement activation on platelets. We found that a subset of anti-HLA IgG induced complement activation via the classical pathway, causing C4b and C3b deposition and formation of the membrane-attack complex. This resulted in permeabilization of platelet membranes and increased calcium influx. Complement activation also caused enhanced α-granule release, as measured by CD62P surface exposure. Blocking studies revealed that platelet activation was caused by FcγRIIa-dependent signaling as well as HLA antibody induced complement activation. Synergistic complement activation employing combinations of monoclonal IgGs suggested that assembly of oligomeric IgG complexes strongly promoted complement activation through binding of IgGs to different antigenic determinants on HLA. In agreement with this, we observed that preventing anti-HLA-IgG hexamer formation using an IgG-Fc:Fc blocking peptide, completely inhibited C3b and C4b deposition. Our results show that HLA antibodies can induce complement activation on platelets including membrane attack complex formation, pore formation and calcium influx. We propose that these events can contribute to fast platelet clearance in vivo in patients refractory to platelet transfusions with HLA alloantibodies, who may benefit from functional-platelet matching and treatment with complement inhibitors.

Survival of early posthematopoietic stem cell transplantation relapse of myeloid malignancies.

OBJECTIVE: Relapse of AML after allogeneic hematopoietic stem cell transplantation (HSCT) has a poor prognosis, and standard of care therapy is lacking. Early (<6 months) relapse is associated with dismal outcome, while the majority of relapses occur early after transplantation. A more precise indication which patients could benefit from reinduction therapy is warranted. METHODS: We retrospectively analyzed outcomes of 83 patients with postallogeneic HSCT relapse. Patients were divided based on intention to treat (curative vs supportive care). RESULTS: Of the 50 patients treated with curative intent, 44% reached complete remission (CR) upon reinduction chemotherapy, and of these patients, 50% survived. Two survivors reached CR after immunotherapy (donor lymphocyte infusion (DLI), without reinduction chemotherapy). Sixty-nine percent of the survivors had received high-intensity cytarabine treatment, followed by immunologic consolidation. Relapse <3 months after transplantation was predictive for adverse survival (P = .004), but relapse <6 months was not. In fact, >50% of the survivors had a relapse <6 months. CONCLUSION: We confirmed the dismal prognosis of postallogeneic HSCT relapse. Importantly, our data demonstrate that patients fit enough to receive high-dose chemotherapy, even when relapse occurred <6 months, had the best chance to obtain durable remissions, in particular when immunologic consolidation was performed after reaching CR.

Role of platelets, neutrophils, and factor XII in spontaneous venous thrombosis in mice.

Recently, platelets, neutrophils, and factor XII (FXII) have been implicated as important players in the pathophysiology of venous thrombosis. Their role became evident in mouse models in which surgical handling was used to provoke thrombosis. Inhibiting anticoagulation in mice by using small interfering RNA (siRNA) targeting Serpinc1 and Proc also results in a thrombotic phenotype, which is spontaneous (no additional triggers) and reproducibly results in clots in the large veins of the head and fibrin deposition in the liver. This thrombotic phenotype is fatal but can be fully rescued by thrombin inhibition. The mouse model was used in this study to investigate the role of platelets, neutrophils, and FXII. After administration of siRNAs targeting Serpinc1 and Proc, antibody-mediated depletion of platelets fully abrogated the clinical features as well as microscopic aspects in the head. This was corroborated by strongly reduced fibrin deposition in the liver. Whereas neutrophils were abundant in siRNA-triggered thrombotic lesions, antibody-mediated depletion of circulating Ly6G-positive neutrophils did not affect onset, severity, or thrombus morphology. In addition, absence of circulating neutrophils did not affect quantitative liver fibrin deposition. Remarkably, siRNA-mediated depletion of plasma FXII accelerated the onset of the clinical phenotype; mice were affected with more severe thrombotic lesions. To summarize, in this study, onset and severity of the thrombotic phenotype are dependent on the presence of platelets but not circulating neutrophils. Unexpectedly, FXII has a protective effect. This study challenges the proposed roles of neutrophils and FXII in venous thrombosis pathophysiology.

Complement Deposition and IgG Binding on Stored Red Blood Cells Are Independent of Storage Time.

BACKGROUND: In the Netherlands, red blood cells (RBCs) are allowed to be stored up to 35 days at 2-6 °C in saline-adenine-glucose-mannitol (SAGM). During storage, RBCs undergo several changes that are collectively known as storage lesion. We investigated to what extent complement deposition and antibody binding occurred during RBC storage and investigated phagocytic uptake in vitro. METHODS: RBCs were stored for different lengths of time at 2-6 °C in SAGM. Complement deposition and antibody binding were assessed upon storage and after incubation with serum. M1- and M2-type macrophages were generated from blood monocytes to investigate RBC phagocytosis. RESULTS: No complement deposition was directly observed on stored RBCs, while incubation of RBCs with serum resulted in variable donor-dependent C3 deposition and IgG binding, both independent of storage time. Only 1-4% phagocytosis of stored RBCs by macrophages was observed. CONCLUSION: RBCs are susceptible to complement deposition and antibody binding independent of storage time. Limited phagocytic uptake by macrophages was observed in vitro.

Toll-like receptor 9 enhances bacterial clearance and limits lung consolidation in murine pneumonia caused by methicillin resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in pneumonia, associated with severe lung damage. Tissue injury causes release of Damage Associated Molecular Patterns (DAMPs), which may perpetuate inflammation. DNA has been implicated as a DAMP that activates inflammation through Toll-like receptor (TLR)9. The aim of this study was to evaluate the role of TLR9 in MRSA pneumonia. Wild-type (Wt) and TLR9 knockout (tlr9-/-) mice were infected intranasally with MRSA USA300 (BK 11540) (5E7CFU) and euthanized at 6,24,48 or 72 hours for analyses. MRSA pneumonia was associated with profound release of cell-free host DNA in the airways, as reflected by increases in nucleosome and DNA levels in bronchoalveolar lavage fluid (BALF), accompanied by transient detection of pathogen DNA in MRSA-free BALF supernatants. In BALF, as compared to Wt -mice tlr9-/- mice showed reduced TNFα and IL-6 levels at 6 hours and reduced bacterial clearance at 6 and 24 hours post infection. Furthermore, tlr9-/- mice exhibited a greater influx of neutrophils in BALF and increased lung consolidation at 24 and 48 hours. This study demonstrates the release of host- and pathogen-derived TLR9 ligands (DNA) into the alveolar space after infection with MRSA via the airways and suggests that TLR9 has pro-inflammatory effects during MRSA pneumonia associated with enhanced bacterial clearance and limitation of lung consolidation.

Transfusion of 35-Day Stored RBCs in the Presence of Endotoxemia Does Not Result in Lung Injury in Humans.

OBJECTIVE: Transfusion-related acute lung injury is the leading cause of transfusion-related mortality. Preclinical studies have shown that aged RBCs can induce transfusion-related acute lung injury in the presence of a "first hit" (e.g., sepsis). Clinical studies, however, show conflicting results on this matter. We tested whether maximally stored RBCs are able to induce lung injury in the presence of a "first hit" in humans (Dutch Trial Register: NTR4455). DESIGN: Open-label, randomized controlled trial. PATIENTS: Healthy male volunteers. INTERVENTIONS: Eighteen healthy male volunteers donated one unit of autologous RBCs 2 or 35 days before the experiment. The experiment was started by infusion of 2 ng/kg lipopolysaccharide ("first hit"). After 2 hours, volunteers received normal saline (n = 6), 2-day stored transfusion (n = 6), or 35-day stored transfusion (n = 6) ("second hit"). Blood was sampled hourly. Six hours after transfusion, the diffusion capacity of the lungs for carbon monoxide was tested and volunteers underwent spirometry, chest x-ray study, and a bronchoalveolar lavage. MEASUREMENTS AND MAIN RESULTS: All volunteers fulfilled sepsis criteria after lipopolysaccharide injection. The stored blood transfusion did not result in significant changes in either hemodynamic or respiratory variables compared with the control groups. Furthermore, chest x-rays, lung function, and PaO2/FIO2 ratios did not differ between groups. Transfusion of stored autologous RBCs did not result in an increased level of protein in the lungs or neutrophil influx. CONCLUSIONS: Transfusion of 35-day stored autologous RBCs in the presence of endotoxemia does not result in lung injury in humans.

Are there any alternatives for transfusion of AB plasma as universal donor in an emergency release setting?

BACKGROUND: AB plasma is used as the universal donor plasma product in patients requiring massive transfusion. However, currently it is a recommended policy to transfuse plasma derived from male donors only as transfusion of plasma from HLA antibody-positive female donors is associated with an increased risk for transfusion-related acute lung injury. As a result, due to high demands, supplies of blood banks may run out of AB plasma, calling for alternatives. Therefore, the aim of this review was to investigate alternatives for emergency release of AB plasma as the universal donor. STUDY DESIGN AND METHODS: A systematic search was conducted in Embase and PubMed. Studies on adult patients, who were transfused with at least 1 unit of plasma, investigating the incidence of transfusion-related complications or mortality in patients transfused with ABO-identical, ABO-compatible, or ABO-incompatible plasma were eligible for inclusion. The primary outcomes were the incidence of transfusion-related complications and mortality. RESULTS: In total six studies were included. Transfusion of ABO-compatible plasma was associated with an increased incidence of lung injury and mortality (odds ratio, 1.10; 95% confidence interval, 1.04-1.15; p = 0.0003) compared to transfusion of ABO-identical plasma. No significant differences were observed regarding transfusion-related complications and mortality between patients transfused with ABO-compatible or ABO-incompatible plasma. DISCUSSION: Studies are insufficient to formulate advice about alternatives for transfusion of AB plasma as universal donor plasma in the emergency setting due to the small number of studies. The results of this review underline the need for further research.

HIV Coinfection Enhances Complement Activation During Sepsis.

BACKGROUND: Human immunodeficiency virus (HIV)-induced complement activation may play a role in chronic immune activation in patients with HIV infection and influence the complement system during acute illness. We determined the impact of HIV infection on the complement system in patients with asymptomatic HIV infection and HIV-infected patients with sepsis or malaria. METHODS: We performed a prospective observational study of 268 subjects with or without HIV infection who were asymptomatic, were septic, or had malaria. We measured complement activation products (C3bc and C4bc) and native complement proteins (C3 and C4). levels of mannose-binding lectin and C1q-C4 were measured to examine activation of the lectin and classical pathways, respectively. RESULTS: Asymptomatic HIV infection was associated with increased C4 activation, especially in patients with high HIV loads, and was accompanied by elevated C1q-C4 levels. Similarly, sepsis and malaria resulted in increased C4 activation and elevated C1q-C4 concentrations. HIV coinfection enhanced C4 activation and consumption in patients with sepsis; this effect was not detected in patients with malaria. Mannose-binding lectin deficiency (defined as a mannose-binding lectin level of <500 ng/mL) did not influence complement activation in any group. CONCLUSIONS: HIV activates the complement system, predominantly via the classical pathway, and causes increased C4 activation and consumption during sepsis. HIV-induced complement activation may contribute to tissue injury during chronic infection and acute intercurrent bacterial infections.

Activated protein C inhibits neutrophil migration in allergic asthma: a randomised trial.

Asthma patients show evidence of a procoagulant state in their airways, accompanied by an impaired function of the anticoagulant protein C system. We aimed to study the effect of recombinant human activated protein C (rhAPC) in allergic asthma patients.We conducted a randomised, double-blind, placebo-controlled, proof-of-concept study in house dust mite (HDM) allergic asthma patients. Patients were randomised to receive intravenous rhAPC (24 µg·kg(-1)·h(-1); n=12) or placebo (n=12) for 11 h. 4 h after the start of infusion, a first bronchoscopy was performed to challenge one lung segment with saline (control) and a contralateral segment with a combination of HDM extract and lipopolysaccharide (HDM+LPS), thereby mimicking environmental house dust exposure. A second bronchoscopy was conducted 8 h after intrabronchial challenge to obtain bronchoalveolar lavage fluid (BALF).rhAPC did not influence HDM+LPS induced procoagulant changes in the lung. In contrast, rhAPC reduced BALF leukocyte counts by 43% relative to placebo, caused by an inhibitory effect on neutrophil influx (64% reduction), while leaving eosinophil influx unaltered. rhAPC also reduced neutrophil degranulation products in the airways.Intravenous rhAPC attenuates HDM+LPS-induced neutrophil migration and protein release in allergic asthma patients by an effect that does not rely on coagulation inhibition.