Pathogenesis Of Transfusion-related Acute Lung Injury Research Articles

Extracellular vesicles in fresh frozen plasma and cryoprecipitate: Impact on in vitro endothelial cell viability.

Transfusion-related acute lung injury (TRALI) remains a major contributor to transfusion-associated mortality. While the pathogenesis of TRALI remains unclear, there is evidence of a role for blood components. We therefore investigated the potential effects of fresh frozen plasma (FFP), cryoprecipitate, and extracellular vesicles (EVs) derived from these blood components, on the viability of human lung microvascular endothelial cells (HLMVECs) in vitro. EVs were isolated from FFP and cryoprecipitate using size-exclusion chromatography and characterized by nanoparticle tracking analysis, western blotting, and transmission electron microscopy. The potential effects of these blood components and their EVs on HLMVEC viability (determined by trypan blue exclusion) were examined in the presence and absence of neutrophils, either with or without prior treatment of HLMVECs with LPS. EVs isolated from FFP and cryoprecipitate displayed morphological and biochemical properties conforming to latest international criteria. While FFP, cryoprecipitate, and EVs derived from FFP, each reduced HLMVEC viability, no effect was observed for EVs derived from cryoprecipitate. Our findings demonstrate clear differences in the effects of FFP, cryoprecipitate, and their respective EVs on HLMVEC viability in vitro. Examination of the mechanisms underlying these differences may lead to an improved understanding of the factors that promote development of TRALI.

Crosstalk between neutrophil extracellular traps and immune regulation: insights into pathobiology and therapeutic implications of transfusion-related acute lung injury.

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-associated death, occurring during or within 6 hours after transfusion. Reports indicate that TRALI can be categorized as having or lacking acute respiratory distress syndrome (ARDS) risk factors. There are two types of TRALI in terms of its pathogenesis: antibody-mediated and non-antibody-mediated. The key initiation steps involve the priming and activation of neutrophils, with neutrophil extracellular traps (NETs) being established as effector molecules formed by activated neutrophils in response to various stimuli. These NETs contribute to the production and release of reactive oxygen species (ROS) and participate in the destruction of pulmonary vascular endothelial cells. The significant role of NETs in TRALI is well recognized, offering a potential pathway for TRALI treatment. Moreover, platelets, macrophages, endothelial cells, and complements have been identified as promoters of NET formation. Concurrently, studies have demonstrated that the storage of platelets and concentrated red blood cells (RBC) can induce TRALI through bioactive lipids. In this article, recent clinical and pre-clinical studies on the pathophysiology and pathogenesis of TRALI are reviewed to further illuminate the mechanism through which NETs induce TRALI. This review aims to propose new therapeutic strategies for TRALI, with the hope of effectively improving its poor prognosis.

Transfusion-Related Acute Lung Injury (TRALI): A Narrative Literature Review

Transfusion-related acute lung injury (TRALI) is defined as the onset of respiratory distress in a patient after receiving a blood component transfusion. So far, TRALI is considered a rare complication in the field of blood transfusion. However, in the last decade, there has been a shift in perspective. Currently, the US Food and Drug Administration recognizes the syndrome as the leading cause of transfusion-related death. This literature review aims to describe TRALI and its prevention strategies. Understanding the pathogenesis of TRALI drives prevention strategies from a blood bank perspective. A major breakthrough in efforts to reduce the incidence of TRALI was excluding female donors from the high plasma volume product, which resulted in an approximately two-thirds reduction in incidence. However, this strategy has not completely eliminated complications of transfusion. In recent years, research has identified patient-associated risk factors for the development of TRALI and empowered clinicians to take an individualized approach to patients requiring transfusion.

Are we missing reverse TRALI? – A real world experience from a tertiary care oncology centre in India

Transfusion related acute lung injury (TRALI) is a rare but potentially fatal pulmonary complication of transfusion that presents as acute hypoxemia and non-cardiogenic pulmonary oedema, developing during or within six hours of transfusion. Majority of the cases reported are due to transfusion of plasma rich blood components containing antibodies to human leukocyte antigen (anti-HLA) or human neutrophil antigen (anti-HNA). Rarely, anti-HLA or anti-HNA in recipients against transfused donor leukocyte antigens, cause TRALI by a reverse mechanism. Herein, we report three cases of suspected TRALI following transfusions of buffy coat derived granulocytes and peripheral blood stem cells. Three patients with hematological malignancies developed pulmonary symptoms after transfusions of leukocyte rich blood components. All cases showed findings of bilateral pulmonary infiltrates at chest radiography and patients were managed accordingly; however, all three expired within seven days of transfusion due to progressive respiratory deterioration. The patients were transfusion dependent for a long time and had received multiple non-leukoreduced blood components in the past. Clinical findings in all three cases indicate the possibility of reverse TRALI. Although, patients’ anti-HLA or anti-HNA antibodies concordance with donors’ cognate antigens (HLA and HNA) was not confirmed; yet these three cases suggest that reverse pathogenesis of TRALI is not as infrequent as reported in the literature. However, reverse TRALI has not been confirmed as the presence and nature of antibodies in the transfused recipient were not investigated due to the non availability of immunodiagnostic tests in India.

The Immune System in Transfusion-Related Acute Lung Injury Prevention and Therapy: Update and Perspective.

As an initiator of respiratory distress, transfusion-related acute lung injury (TRALI) is regarded as one of the rare complications associated with transfusion medicine. However, to date, the pathogenesis of TRALI is still unclear, and specific therapies are unavailable. Understanding the mechanisms of TRALI may promote the design of preventive and therapeutic strategies. The immune system plays vital roles in reproduction, development and homeostasis. Sterile tissue damage, such as physical trauma, ischemia, or reperfusion injury, induces an inflammatory reaction that results in wound healing and regenerative mechanisms. In other words, in addition to protecting against pathogens, the immune response may be strongly associated with TRALI prevention and treatment through a variety of immunomodulatory strategies to inhibit excessive immune system activation. Immunotherapy based on immune cells or immunological targets may eradicate complications. For example, IL-10 therapy is a promising therapeutic strategy to explore further. This review will focus on ultramodern advances in our understanding of the potential role of the immune system in TRALI prevention and treatment.

Advances in the Pathogenesis,Prevention,and Treatment of Transfusion-related Acute Lung Injury

Transfusion-related acute lung injury(TRALI)is a severe pulmonary complication of transfusion and has been one of the leading causes of transfusion-associated deaths.However,the pathogenesis of TRALI is still unclear,and treatment and prevention of this condition also face huge challenges.Many recent studies have explored the roles of various effector cells and effector molecules in TRALI and possible related mechanisms based on various hypotheses,in order to find the key factors that induce TRALI and the potential prevention measures.This article reviews the pathogenesis,prevention,and treatment of TRALI.

Update on the pathophysiology of transfusion-related acute lung injury.

The aim of this study was to discuss recent advances regarding the pathogenesis of transfusion-related acute lung injury (TRALI), which highlight the pathogenic role of macrophages. TRALI remains a leading cause of transfusion-related fatalities, despite the success of the mitigation strategy, and therapeutic approaches are unavailable. Neutrophils (PMNs) are recognized pathogenic cells in TRALI. Macrophages have previously also been suggested to be pathogenic in mice via binding of C5a to their C5a-receptor, producing reactive oxygen species (ROS), which damages the pulmonary endothelium. Recent work has further highlighted the role of macrophages in the TRALI-pathogenesis. It has been shown that the protein osteopontin (OPN) released by macrophages is critical for pulmonary PMN recruitment in mice suffering from TRALI and that targeting OPN prevents the occurrence of TRALI. Another recent study demonstrated the importance of M1-polarized alveolar macrophages in murine TRALI induction by showing that α1-antitrypsin (AAT) overexpression prevented TRALI in mice through decreasing the polarization of alveolar macrophages towards the M1 phenotype. Apart from PMNs, macrophages also appear to be important in the pathogenesis of TRALI. Targeting the pathogenic functions of macrophages may be a promising therapeutic strategy to explore in TRALI.

An animal model of transfusion-related acute lung injury and the role of soluble CD40 ligand.

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of transfusion and is one of leading causes of transfusion-associated fatalities. However, the pathogenesis of TRALI is still unclear. Soluble CD40 ligand (sCD40L) is a proinflammatory cytokine that accumulates during blood component storage and is involved in transfusion reactions. The objective of this study was to establish a clinically relevant TRALI animal model and to evaluate the role of sCD40L in TRALI. Rats' red-blood-cell (RBC) suspensions were prepared, and the quality of RBC was evaluated. A trauma-haemorrhage-transfusion strategy was applied to build the animal model. Lung oedema was evaluated by histopathology examination, total bronchoalveolar lavage fluid (BALF) protein concentration, Evans blue dye (EBD) leakage and inflammatory cytokines. The sCD40L concentrations were measured. Storage lesions of RBCs gradually increased over time. Obvious histological evidence of lung injury of rats transfused with a 35-day RBC was observed. The total BALF protein concentration, EBD leakage, inflammatory cytokines concentration were increased significantly in the Day 35 group. The sCD40L concentration increased significantly in the storage RBC suspension over time but was slightly elevated in rat plasma. These findings indicated successful establishment of a TRALI animal model with trauma-haemorrhage-transfusion, in which sCD40L may play a minor role in the development of TRALI.

Understanding the pathophysiology of transfusion-related acute lung injury (TRALI)

Transfusion-related acute lung injury (TRALI) is characterised by the onset of respiratory distress and acute lung injury within 6 hours of a blood transfusion. It is currently the leading cause of transfusion related mortality and no specific therapies are clinically available. The TRALI mortality rate has been estimated from 5 to 14% but the incidence and prevalence are difficult to ascertain because TRALI is probably the most underdiagnosed adverse event of transfusion. The pathogenesis of TRALI is not completely clear but it appears that induction of TRALI is controlled by a two-hit process where the first hit is a risk factor(s) present in the recipient and the second hit is the donor transfusion. The presence of alloimmune donor alloantibodies have been identified in the vast majority (approximately 85%) of TRALI reactions. It appears that in the antigen-positive recipient, neutrophils are opsonised with passively transfused donor antibodies which mediate agglutination, activation and compartmentalisation in the lung microvasculature. The remaining 15–20% of antibody-independent TRALI cases may be related to factors such as biological response modifiers, e.g., oxidised lipids generated during the storage of the transfused blood components. In this lecture, data from both human patients and animal models will be discussed and recent insights related to TRALI pathogenesis including potential therapies will be presented.

The Role of Complement in Transfusion-Related Acute Lung Injury.

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of acute respiratory distress occurring within 6 hours of blood transfusion. TRALI is one of the leading causes of transfusion-related fatalities and specific therapies are unavailable. Neutrophils are recognized as the major pathogenic cells, whereas T regulatory cells and dendritic cells appear to be important for protection against TRALI. The pathogenesis, however, is complex and incompletely understood. It is frequently postulated that the complement system plays an important role in the TRALI pathogenesis. In this article, we assess the evidence regarding the involvement of complement in TRALI from both human and animal studies. We hypothesize about the potential connection between the complement system and neutrophils in TRALI. Additionally, we draw parallels between TRALI and other acute pulmonary disorders of acute lung injury and acute respiratory distress syndrome regarding the involvement of complement. We conclude that, even though a role for complement in the TRALI pathogenesis seems plausible, studies investigating the role of complement in TRALI are remarkably limited in number and also present conflicting findings. Different types of TRALI animal models, diverse experimental conditions, and the composition of the gastrointestinal microbiota may perhaps all be factors which contribute to these discrepancies. More systematic studies are warranted to shed light on the contribution of the complement cascade in TRALI. The underlying clinical condition of the patient, which influences the susceptibility to TRALI, as well as the transfusion factor (antibody-mediated vs non–antibody-mediated), will be important to take into consideration when researching the contribution of complement. This should significantly increase our understanding of the role of complement in TRALI and may potentially result in promising new treatment strategies.

Osteopontin Mediates Murine Transfusion-Related Acute Lung Injury through Stimulation of Pulmonary Neutrophil Accumulation

Transfusion-related acute lung injury (TRALI) is a syndrome of respiratory distress which develops within 6 hours of blood transfusion. It is the leading cause of transfusion-related deaths and the pathogenesis is complex and incompletely understood. In the majority of the cases, anti-leukocyte antibodies present in the transfused blood product, in combination with recipient predisposing risk-factors such as inflammation, are implicated to be responsible for the onset of TRALI. Unfortunately, no therapies are available for TRALI.Osteopontin (OPN) is an extracellular matrix protein with multiple biological functions. OPN is involved in normal physiological processes, such as cell migration and adhesion, but has also been implicated in a wide range of disease states, including cancer, atherosclerosis, glomerulonephritis, and several chronic inflammatory diseases. Interestingly, OPN is upregulated at sites of inflammation and tissue remodeling. As inflammation is an important risk factor for TRALI development, and as neutrophils (PMNs) are known effector cells in the pathogenesis of TRALI which migrate and accumulate in the lungs during TRALI development, we investigated the potential contribution of OPN in the onset of antibody-mediated TRALI.We utilized a previously established murine TRALI model (Kapur et al, Blood 2017, Blood Advances 2018) in which C57BL/6 mice were first primed with a low dose of lipopolysaccharide (LPS) and depleted of their CD4+ T cells in vivo followed by injection of anti-major histocompatibility complex (MHC) class I antibodies (clones 34-1-2s and AF6-88.5.5.3). The TRALI response was analyzed after 90 minutes by analysis of pulmonary edema (lung wet-to-dry weight ratios, W/Ds) and the levels of pulmonary neutrophils. Wildtype (WT) mice suffered from antibody-mediated TRALI compared to untreated naïve mice, as was shown by their significantly increased lung W/Ds (4.72 vs 4.50, respectively, P<0.0001). This also corresponded to significantly increased levels of pulmonary PMNs compared to untreated naïve mice (34% vs 5%, P<0.0001). In contrast, C57BL/6 OPN knock-out mice were resistant to antibody-mediated TRALI induction as they did not display any significant increase in lung W/Ds levels or pulmonary PMNs compared to untreated naïve OPN knock-out mice (lung W/Ds 4.83 vs 4.75, and pulmonary PMNs 18% vs 16%, respectively). Strikingly, administration of purified recombinant OPN during TRALI induction in C57BL/6 OPN knock-out mice, significantly induced a TRALI reaction (lung W/Ds 5.12 vs 4.75 as compared to untreated naïve OPN knock-out mice, P<0.05). Mechanistically, this TRALI inducing effect of OPN administration to OPN knock-out mice was associated with increased levels of pulmonary PMNs (38% vs 16%, as compared to untreated naïve OPN knock-out mice, P<0.0001). In vivo blocking of OPN in WT mice with an anti-OPN antibody demonstrated decreased lung W/Ds as compared to treatment with an isotype antibody (4.48 vs 4.69, respectively, P<0.05). The OPN blocking response during TRALI was associated with a decreased level of pulmonary PMN accumulation as compared to treatment with an isotype antibody (14% vs 34%, respectively, P<0.0001). As the PMN-chemoattractant macrophage inflammatory protein (MIP)-2 has previously been described to be upregulated in murine antibody-mediated TRALI, we investigated if the OPN-associated pulmonary PMN accumulation and TRALI induction could be related to the levels of MIP-2. We found that plasma MIP-2 levels were increased in mice that were infused with anti-MHC class I antibodies as compared to naïve controls, but that addition or blocking of OPN did not affect these MIP-2 levels. This indicates that the OPN-related PMN responses in TRALI are independent of plasma MIP-2 levels.Collectively, these data indicate OPN as a novel pathogenic factor which enhances antibody-mediated murine TRALI through stimulation of PMN migration towards the lungs, independent of MIP-2. This may suggest that blocking OPN (using an anti-OPN antibody) may prevent TRALI by impairing pulmonary PMN accumulation and could be a therapeutic avenue to explore in combatting this serious adverse complication of blood transfusion. DisclosuresNo relevant conflicts of interest to declare.

Targeting Transfusion-Related Acute Lung Injury: The Journey From Basic Science to Novel Therapies.

Transfusion-related acute lung injury is characterized by the onset of respiratory distress and acute lung injury following blood transfusion, but its pathogenesis remains poorly understood. Generally, a two-hit model is presumed to underlie transfusion-related acute lung injury with the first hit being risk factors present in the transfused patient (such as inflammation), whereas the second hit is conveyed by factors in the transfused donor blood (such as antileukocyte antibodies). At least 80% of transfusion-related acute lung injury cases are related to the presence of donor antibodies such as antihuman leukocyte or antihuman neutrophil antibodies. The remaining cases may be related to nonantibody-mediated factors such as biolipids or components related to storage and ageing of the transfused blood cells. At present, transfusion-related acute lung injury is the leading cause of transfusion-related fatalities and no specific therapy is clinically available. In this article, we critically appraise and discuss recent preclinical (bench) insights related to transfusion-related acute lung injury pathogenesis and their therapeutic potential for future use at the patients' bedside in order to combat this devastating and possibly fatal complication of transfusion. We searched the PubMed database (until August 22, 2017). Using terms: "Transfusion-related acute lung injury," "TRALI," "TRALI and therapy," "TRALI pathogenesis." English-written articles focusing on transfusion-related acute lung injury pathogenesis, with potential therapeutic implications, were extracted. We have identified potential therapeutic approaches based on the literature. We propose that the most promising therapeutic strategies to explore are interleukin-10 therapy, down-modulating C-reactive protein levels, targeting reactive oxygen species, or blocking the interleukin-8 receptors; all focused on the transfused recipient. In the long-run, it may perhaps also be advantageous to explore other strategies aimed at the transfused recipient or aimed toward the blood product, but these will require more validation and confirmation first.

Platelet and TRALI: From blood component to organism

Even though used systematically with leukocyte reduction, platelet transfusions still cause adverse reactions in recipients. They include Transfusion-Related Acute Lung Injury (TRALI), respiratory distress that occurs within six hours of the transfusion. The pathophysiology of this transfusion complication brings complex cellular communication into play. The role, particularly inflammatory, played by blood platelets in TRALI pathophysiology has been demonstrated, but is still under debate. Blood platelets play a role in inflammation, particularly via the CD40/CD40L (sCD40L) immunomodulator complex. In this study, we examine in particular the specific involvement of the CD40/CD40L (sCD40L) complex in the inflammatory pathogenesis of TRALI. This molecular complex could be a major target in a TRALI prevention strategy. Improving the conditions in which the platelet concentrates (PC) are prepared and stored would contribute to controlling partly the risks of non-immune TRALI.

Elevation of C-reactive protein levels in patients with transfusion-related acute lung injury.

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related fatalities and is characterized by the onset of acute respiratory distress within six hours following blood transfusion. In most cases, donor antibodies are suggested to be involved, however, the pathogenesis is poorly understood. A two-hit model is generally assumed to underlie TRALI pathogenesis where the first hit consists of a patient predisposing factor such as inflammation and the second hit is due to donor antibodies present in the transfused blood. We recently demonstrated that the acute phase protein C-reactive protein (CRP) could enhance murine anti-major histocompatibility complex (MHC) class I-mediated TRALI. Whether CRP is increased in human TRALI patients which would support its role as a risk factor for human TRALI, is currently unknown. For that purpose, we measured CRP levels in the plasma of human TRALI patients and found CRP levels to be significantly elevated compared to transfused control patients. These data support the notion that CRP may be a novel first hit risk factor in human TRALI and that modulation of CRP levels could be an effective therapeutic strategy for this serious adverse event of transfusion.

Research progress of transfusion related acute lung injury and its prevention and control strategies

Transfusion-related acute lung injury (TRALI) which occurs acute lung injury (ALI) within 6 hours after transfusion is one of the leading causes of death in patients with blood transfusion. Several hypothesises have been proposed to explain the underlying pathologic mechanisms of TRALI, such astwo-eventandthreshold modelhypothesis, etc.. Immune-mediated TRALI accounts for over 80% of reported cases of TRALI which was mediated by HLA (human leucocyte antigen) or human neutrophil antigens (HNA) antibodies in transfused blood products. Immune-mediated TRALI is commonly associated with donor plasma transfusion or other blood products from multiparous women, which has led many countries to reduce or exclude women from donating high-volume plasma products. This policy has resulted in a decrease in the incidence of TRALI. This article reviews the definition, pathogenesis, diagnosis, prevention and control strategies of TRALI. Key words: Transfusion related acute lung injury; Pathogenesis; Mitigation strategies

Bioactive Lipids Are Generated to Micromolar Levels during RBC Storage, Even in Leukoreduced Units

Background: The transfusion of stored red blood cells (RBCs) has been linked to negative outcomes, such as Transfusion-Related Acute Lung Injury (TRALI) and Transfusion Related Immunomodulation (TRIM). Bioactive lipids have been implicated as playing an important role in TRALI pathogenesis, both as a "second hit" when anti-HLA antibodies are present and also in anti-HLA independent TRALI. Likewise, bioactive lipids have been suggested to play a role in TRIM.Methods: To further study bioactive lipids in RBC storage, we developed a targeted metabolomics approach, with isotope dilution, to accurately and precisely quantify concentrations of multiple poly-unsaturated fatty acids (PUFAs) and their related oxidation products (oxylipins) in stored RBC units. Analytes in RBC samples were extracted using methanol with isotopically-labeled internal standards and analyzed by liquid chromatography-tandem mass spectrometry using multiple reaction monitoring (LC-MS/MS-MRM). Eight units of leukoreduced (LR) and non-leukoreduced (NLR) RBCs were analyzed longitudinally from 6 to 42 days of storage.Results: LR RBCs had a significant increase in multiple PUFAs over storage, including: arachidonic acid (AA), linoleic acid (LA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), linolenic acid (ALA), dihomo-γ-linolenic acid (DGLA), adrenic acid (22:4), and docosapentaenoic acid (22:5). Only a modest increase was observed over the first 20 days of storage, followed by a rapid increase from day 20 to day 42. AA showed the biggest increase in concentration, from 1.0±0.4 µM at day 6 to 13.4±5.2 µM at day 42 in LR RBC units. Oxidative products of PUFA metabolism were also analyzed. The concentration of hydroxyeicosatetraenoic acids (HETEs), oxidation products of AA, including 5-, 8-, 9-, 11-, 12- and 15-HETEs increased 5 to 13 fold from day 6 to day 42 of storage in LR RBCs. The concentration of other oxylipins including hydroxyoctadecadienoic acids(9- and 13-HODEs)and dihydroxyoctadecenoic acids (, 9, 10- and 12,13-DiHOMEs), hydroxyl-DHA(14-, 16- and 17-HDoHEs) were also significantly increased during storage. If present, prostaglandins (PGE2 and PGD2) and Leukotriene (LTB4), were below the lower limits of detection. Juxta position of LR and NLR RBCs, showed that the concentrations of 12-HETE, 15-HETE, 14-HDoHE, and 17-HDoHE in NLR units were significantly higher at day 42 (p<0.01). Of particular note, the average concentration of 12-HETE reached 1.1±0.8 µM in NLR at day 42, which was 45 fold higher than that in LR units. No differences in LR and NLR RBCs were noted at day 6.Conclusions: We report significant generation of PUFAs and products of lipid metabolism/oxidation over RBC storage, with a particular increase in generation after day 20 of storage. LR decreased the generation of some lipid species (12-HETE in particular); however, accumulation of many bioactive lipids occurs robustly despite LR. Because variation from unit to unit was small at day 6 but substantial at day 42, these findings also support significant donor-to-donor differences in the process of bioactive lipid generation during storage. Exactly how the generation of bioactive lipids effects medical outcomes of transfusion remains undetermined; however, the quantitation allowed by the current methods demonstrates the generation of bioactive lipids up to µM levels, which are known to be sufficient to have significant physiological and/or pathological impacts in other settings. DisclosuresZimring:Immucor Inc.: Research Funding; BloodworksNW: Patents & Royalties: Patent Application filed on technology in this abstract - no royalties.

C-Reactive Protein (CRP) Enhances Murine Antibody-Mediated Transfusion Related Acute Lung Injury (TRALI)

Transfusion-related acute lung injury (TRALI), a syndrome characterized by respiratory distress triggered by blood transfusions, is the leading cause of transfusion-related mortality. Mostly, TRALI has been attributed to passive infusion of human leucocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies present in the transfused blood product. Several animal models have been developed to study the pathogenesis of antibody-mediated TRALI and various mechanisms for TRALI induction have been suggested, including involvement of endothelial cells, neutrophils and monocytes. In 2006, a murine of model of antibody-mediated TRALI was developed using a monoclonal MHC class I antibody (clone 34-1-2s). This antibody was shown to cause significant lung damage (excess lung water: pulmonary edema) within 2 hours of administration into BALB/c mice, which in follow-up studies was only reproducible after initial priming with the gram-negative endotoxin lipopolysaccharide (LPS). 34-1-2s was also shown to cause severe lung damage in severe combined immunodeficient (SCID) mice. We investigated 34-1-2s mediated TRALI in BALB/c mice, without LPS priming, and found no difference in TRALI severity when compared with injection with an control isotype antibody for 34-1-2s (Isotype Mouse IgG2a antibody), as examined by lung wet-to-dry ratios, a measure for pulmonary edema. Recently it was described that the acute phase protein C-reactive protein (CRP), heavily up-regulated during acute infections and also present at lower levels in healthy individuals, was able to enhance antibody-mediated platelet destruction both in vitro and in vivo via Fc-receptor mediated phagocytic responses. Considering the fact that TRALI has been shown to be mainly antibody-mediated, plus the fact that it has been suggested to be an Fc-dependent process as well, we investigated the effect of CRP in a murine antibody-mediated TRALI. We tested if CRP would be able to enhance antibody-mediated TRALI in the murine 34-1-2s based BALB/c TRALI model. For that purpose, we co-injected CRP together with 34-1-2s and compared that to co-injection of CRP together with control isotype mouse IgG2a or to injection with CRP alone. We found that CRP+34-1-2s injection resulted in significantly higher lung damage than CRP+isotype antibody, as well as than CRP alone, with at least 43% of the mice in the CRP+34-1-2s group having a lung wet-to-dry ratio of higher than 5, which is considered to represent severe lung damage. As the monocyte-derived neutrophil chemoattractant macrophage inflammatory protein 2 (MIP-2: murine equivalent of human IL-8) was recently shown to play a central role in murine (SCID) 34-1-2s-mediated TRALI induction, we measured MIP-2 values in our BALB/c TRALI model and found that CRP alone was capable of producing high levels of MIP-2, which were found to be even more increased when 34-1-2s was co-injected with CRP. We propose a mechanism in which CRP plays a synergistic role with 34-1-2s antibody to significantly increase the induction of antibody-mediated TRALI via enhanced stimulation of monocyte-derived MIP-2 secretion. DisclosuresNo relevant conflicts of interest to declare.

Human neutrophil antigen-3a antibodies induce neutrophil stiffening and conformational activation of CD11b without shedding of L-selectin.

HNA-3a antibodies induce severe transfusion-related acute lung injury (TRALI) in which neutrophils play a major role. As neutrophil passage through the pulmonary microvasculature is a critical step in the pathogenesis of TRALI, we investigated the impact of HNA-3a antibodies on two important factors that could impair granulocyte passage through lung capillaries: the elasticity of neutrophils and the expression and activation of adhesion molecules. The impact of HNA-3a antibodies on the elasticity of neutrophils was investigated using atomic force microscopy (AFM). Neutrophils were settled on poly-2-hydroxyethyl-methacrylate-coated glass slides before treatment with anti-HNA-3a plasma samples, control plasma, or control plasma containing formyl-methionyl-leucyl-phenylalanine (fMLP). Elasticity measurements were carried out in a temperature-controlled perfusion chamber using an atomic force microscopy (AFM) device. The impact of HNA-3a antibodies on the surface expression of total CD11b, activation of CD11b, and L-selectin (CD62L) shedding was investigated by flow cytometry. The functional impact of HNA-3a antibodies on neutrophil adhesion was assessed using fibrinogen-coated plates. HNA-3a antibodies induced stiffening of neutrophils (+24%-40%; p < 0.05) to a similar extent as fMLP. This effect was blocked by treatment of neutrophils with cytochalasin D. While total surface expression of CD11b and L-selectin on neutrophils was largely unaffected, HNA-3a antibodies induced alloantigen-specific activation of CD11b (+72%-107%; p < 0.05) and increased adhesion of neutrophils to fibrinogen. Accumulation of neutrophils in the pulmonary microvasculature during severe TRALI is likely mediated by increased rigidity and CD11b-mediated adhesion of neutrophils leading to retention of neutrophils.

Expression of co-stimulated molecule CD40 of macrophage on transfusion-related acute lung injury in Sprague Dawley rats

Objective To study the activation of alveolar macrophage β (AM) and the expression of co-stimulatory molecule CD40 in transfusion-related acute lung injury (TRALI) model in order to illustrate the pathogenesis of TRALI. Methods Sixty SD rats were randomly (random number) divided into normal control group (n=15) with sham operation using normal saline instead of LPS and plasma, positive control group (n=15) with ALI induced by intravenous infusion of 5 mg/kg lipopolysaccharide (LPS) in equivalent volume of whole blood drawn out) , and TRALI group (n=15) treated by intra-peritoneal injection of 2 mg/kg LPS 2 h before the transfusion of human plasma (1 mL whole blood about 10% of total blood volume drawn out and replaced with 1 mL plasma) , LPS control group (n=15) treated by intra-peritoneal injection of 2 mg/kg LPS 2 h before saline infusion in equivalent volume of blood drawn out. The pathologic changes of rat lung tissue were observed by HE staining. The expression of TLR4 was examined by RT-PCR. The activation of NF-кB in AM was measured by electrophoresis mobility shift assay (EMSA). The expression of CD40 mRNA and CD40 molecule were analyzed by Northern blot and flow cytometry respectively. ELISA was performed to detect the concentration of TNF-α, MIP-2 and IL-1β in broncho-alveolar lavage fluid (BALF). Results Broken alveolar septa, hyperemia, and massive infiltration of inflammatory cells including the neutrophils were observed in lung tissues of TRALI group. The expression of TLR4 gene was detected in activated macrophage phi (AMφ) of TRALI group rats. The activation of NF-кB was increased in TRALI group rats. The expression of CD40 in AMφ was higher in rats of TRALI group than that in rats of control group and LPS control group. The concentration of TNF-α, MIP-2 and IL-1β were enhanced significantly in BALF of TRALI group rats. Conclusion The activation of AM and up-regulation of co-stimulatory molecule CD40 induced release of some inflammatory cytokines. It suggested that AM activation may play an important role in the pathogenesis of TRALI. Key words: Acute lung injury; Macrophage; TLR4; CD4 molecule

Antibody-mediated transfusion-related acute lung injury; from discovery to prevention.

Transfusion-related acute lung injury (TRALI), a syndrome of respiratory distress caused by blood transfusion, is the leading cause of transfusion-related mortality. The majority of TRALI cases have been related to passive infusion of human leucocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies in donor blood. In vitro, exvivo and invivo animal models have provided insight in TRALI pathogenesis. The various classes of antibodies implicated in TRALI appear to have different pathophysiological mechanisms for the induction of TRALI involving endothelial cells, neutrophils, monocytes and, as very recently has been discovered, lymphocytes. The HLA and HNA-antibodies are found mainly in blood from multiparous women as they have become sensitized during pregnancy. The incidence of TRALI has decreased rapidly following the introduction of a male-only strategy for plasma donation. This review focuses on pre-clinical and clinical studies investigating the pathophysiology of antibody-mediated TRALI.