Reducing the incidence of TRALI in the UK: the results of screening for donor leucocyte antibodies and the development of national guidelines

Kidney transplant outcomes in patients with antibodies to human neutrophil antigen 3a

BACKGROUND

Antibody mediated rejection (ABMR) of kidney transplants has been shown to occur in the absence of a known donor specific antibody to human leucocyte antigen (HLA). Antibodies to the human neutrophil antigen (HNA) system have been detected in kidney transplant recipients and linked to ABMR in the absence of an HLA donor specific antibody (DSA), but there remains limited literature regarding this.

METHODS

Case series analysis was carried out examining three cases of HNA-3a antibody positive flow cytometry cross match (FC-XM) from two transplant centres in Scotland.

RESULTS

All patients included were female and had been sensitised as a result of pregnancy. One live donor recipient with HNA-3a antibodies identified prior to transplant received ATG induction and has had a good outcome. The remaining two patients received deceased donor transplants. HNA-3a antibodies were indicated following a retrospective flow cytometry crossmatch. Both patients received Basiliximab induction and both have experienced ABMR requiring supplementary immunosuppression.

CONCLUSIONS

The predicted rate of HNA-3a antibodies amongst patients awaiting kidney transplant in the UK is <1%. However, with increasing evidence to support a role for HNA-3a antibodies in the development of ABMR there may be value in screening at risk groups to allow for augmented immunosuppression to be considered at the time of kidney transplant.

Prevalence of leucocyte antibodies in non-transfused male and female platelet apheresis donors

OBJECTIVES

In our study group of Thai PLT apheresis donors, we assessed the prevalence of anti-leucocyte antibodies.

BACKGROUND

Antibodies against human leucocyte antigens (anti-HLA), neutrophil antigens (anti-HNA), and major histocompatibility complex class I related chain A (anti-MICA) in blood products can lead to transfusion-related acute lung injury (TRALI). To reduce the risk of TRALI, some blood centres are implementing strategies based on screening platelet (PLT) apheresis donors for the presence of anti-leucocyte antibodies.

METHODS/MATERIALS

Blood samples were collected from non-transfused individuals, 340 males and 63 females (50 nulliparous and 13 parous). Anti-HLA class I and II and anti-MICA were analysed using the Luminex assay, and anti-HNA-3 was detected using the granulocyte agglutination test.

RESULTS

Anti-HLA was found in 14 of 403 subjects (3.5%). Ten subjects (2.5%) tested positive for HLA class I, 2 (0.5%) for HLA class II, and 2 (0.5%) for both HLA class I and HLA class II. Anti-HLA class I or II were detected in 2 of 13 (15.4%) parous females and only anti-HLA class I was found in 4 (8.0%) nulliparous females. Six of 327 subjects tested (1.8%), all males, were positive for anti-MICA. Anti-HNA-3 was not found in any of the 403 individuals.

CONCLUSIONS

Screening for anti-HLA class I and II should be implemented for Thai PLT apheresis donors. Although immunisation against HNA and MICA seems to be a rare event in Thais, further work is necessary to decide whether our PLT apheresis donors should be screened for HNA and MICA antibodies.

Antikörper gegen humane Leukozytenantigene (HLA) bei männlichen Apheresespendern ohne klassische Alloimmunisierung

Im Rahmen von Präventivmaßnahmen zur Vermeidung von TRALI (transfusionsassoziierte akute Lungeninsuffizienz) wurden in einer Studie 15 523 männliche und weibliche Apheresespenderinnen und -spender mit und ohne positiver Immunisierungsanamnese (IA) auf HLA-Klasse-I-, HLA-Klasse-II- und HNA-Antikörper (AK) untersucht. Unsere Ergebnisse zeigten, dass bei 3,85% der männlichen Spender ohne IA HLA-AK und bei 0,10% HNA-AK auftraten. Diese Beobachtung stellt die seit Beginn der HLA-Ära vor 50 Jahren klar bewiesene Aussage infrage, dass HLA-AK nur durch eine Alloimmunisierung infolge von Schwangerschaften, Transfusionen oder Transplantationen entstehen können. Wir diskutieren mehrere mögliche Kausalitäten dieser positiven Reaktionen:

Große Aufmerksamkeit richteten wir auf den Ausschluss möglicher falsch positiver Reaktionen, da der LABScreen Multi als höchst sensitiv eingeschätzt wird. Nach Validierung eines neuen positiven Normalized-Background-Cut-offs (NBG: Normalized Background) und der Nachtestung von Rückstellproben der als positiv getesteten männlichen Spender konnten 50% der HLA-Klasse-I- und 43% der HLA-Klasse-II-AK nicht bestätigt werden. Dennoch blieben 1,5% der getesteten männlichen Spender für HLA-Klasse I und 0,5% für HLA-Klasse II positiv. Handelt es sich hier ausschließlich um HLA-spezifische oder um heterophile AK? Welche klinische Bedeutung haben diese AK bei der Prävalenz von TRALI oder für die Transplantationsimmunologie?

Human neutrophil antigens: Nature, clinical significance and detection

Granulocytes are an essential part of both the innate and adaptive immune systems. Human neutrophil antigens (HNAs) are a family of epitopes that are located on glycoproteins that are mostly expressed on human granulocytes. Antibodies that recognize these epitopes have been associated with neutropenia, transfusion complications, haematopoietic stem cell transplant nonengraftment and renal transplant rejection. Currently, there are fourteen recognized HNA alleles across five antigen systems (HNA-1 through HNA-5), the molecular basis of which are located on the genes FCGR3B, CD177, SLC44A2, ITGAM and ITGAL, respectively. Elucidation of the associated genes has permitted the development of testing strategies for HNA typing and aided understanding of the associated epitopes. This review will outline the associated clinical conditions that require HNA investigation and how these are performed in specialized laboratories. Investigations provided are both reactive for patients with a variety of existing or suspected neutropenias and proactive in the testing of blood component donors in order to reduce the potential risk to patients who require transfusion.

Acute Respiratory Distress Syndrome in Cancer Patients

Acute respiratory distress syndrome (ARDS) is a heterogeneous form of acute, diffuse lung injury that is characterized by dysregulated inflammation, increased alveolar-capillary interface permeability, and non-cardiogenic pulmonary edema. In the general population, the incidence and mortality associated with ARDS over the last two decades have steadily declined in parallel with optimized approaches to pneumonia and other underlying causes of ARDS as well as increased utilization of multimodal treatment strategies that include lung-protective ventilation. In the cancer settings, significant declines in the incidence and mortality of ARDS over the past two decades have also been reported, although these rates remain significantly higher than those in the general population. Epidemiologic studies identify infection, including disseminated fungal pneumonias, as a major underlying cause of ARDS in the cancer setting. More than half of cancer patients who develop ARDS will not survive to hospital discharge. Those who do survive often face a protracted and often incomplete recovery, resulting in significant long-term physical, psychological, and cognitive sequelae. The residual organ dysfunction and poor functional status after ARDS may delay or preclude subsequent cancer treatments. As such, close collaboration between the critical care physicians and oncology team is essential in identifying and reversing the underlying causes and optimizing treatments for cancer patients with ARDS. This chapter reviews the diagnosis and common causes of ARDS in cancer and gives an update on the general management principles for cancer patients with ARDS in the ICU.

TACO and TRALI: biology, risk factors, and prevention strategies

Transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are the leading causes of transfusion-related morbidity and mortality. These adverse events are characterized by acute pulmonary edema within 6 hours of a blood transfusion and have historically been difficult to study due to underrecognition and nonspecific diagnostic criteria. However, in the past decade, in vivo models and clinical studies utilizing active surveillance have advanced our understanding of their epidemiology and pathogenesis. With the adoption of mitigation strategies and patient blood management, the incidence of TRALI and TACO has decreased. Continued research to prevent and treat these severe cardiopulmonary events is focused on both the blood component and the transfusion recipient.

Granulocyte antibodies in male blood donors: can they trigger transfusion-related acute lung injury?

BACKGROUND

White blood cell-associated antibodies can lead to transfusion-related acute lung injury (TRALI). Female donors with a history of pregnancies have been identified as a main cause for these antibodies. Male or female donors without a history of pregnancy are considered as safe donors.

STUDY DESIGN AND METHODS

Following the identification of two TRALI cases associated with blood products from male donors, we investigated the frequency of granulocyte-specific and human leukocyte antigen (HLA) antibodies in the entire blood donor population using a high throughput automated flow-cytometry-based granulocyte immunofluorescence test (Flow-GIFT). We investigated sera from 14,343 whole blood donors (female, n = 6974, 48.7%; male, n = 7369, 51.3%) using automated Flow-GIFT. Of the female blood donors, 60.4% had a history of pregnancy. Positive sera were retested by the standard granulocyte immunofluorescence test and granulocyte agglutination test. For the detection of HLA Class I and II immunoglobulin G antibodies, we used a commercial screening enzyme-linked immunosorbent assay.

RESULTS

We detected in 924 (21.9%) of the 4212 females with a history of pregnancy antibodies against granulocyte antigens (n = 62, 1.5%), HLA Class I and/or II antigens (n = 864, 20.5%). Notably, in 3.5% (n = 96) of 2762 females without a history of pregnancy and in 2.1% (n = 154) of 7369 males antibodies against granulocyte antigens (n = 13, 0.47% and n = 45, 0.6%), HLA Class I and/or II (n = 83, 3% and n = 109, 1.4%, respectively), were also detected.

CONCLUSION

Human neutrophil antigen antibodies are rare in male and females without a history of pregnancy compared to females with a history of pregnancy, but their relevance is not negligible.

Transfusion-Related Acute Lung Injury (TRALI) in two Thalassaemia Patients Caused by the Same Multiparous Blood Donor

We report two separate episodes of transfusion-related acute lung injury (TRALI) in two thalassaemia patients who received red blood cell transfusions from the same multiparous donor. Both cases had the same symptomatology and occurred within 60 minutes of transfusion. The patients presented dyspnoea, sweating, fatigue, dizziness, fever, and sense of losing consciousness. The chest x-ray showed a pulmonary oedema-like picture with both lungs filled with fluid. The patients were treated in the intensive therapy unit. They were weaned off the ventilator and discharged following hospitalization 7 and 9 days respectively. The TRALI syndrome was diagnosed to be associated with HLA-specific donor antibodies against mismatched HLA-antigens of the transfused patients. Haemovigilance improvements are essential for reducing the morbidity and mortality in transfused patients. Blood from multiparous donors should be tested for the presence of IgG HLA-Class I and -Class II antibodies before being transfused in thalassaemia and other chronically transfused patients.

Transfusion-related acute lung injury risk mitigation: an update

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of transfusion. Greater understanding of the pathophysiology of this syndrome has much improved during the last two decades. Plasma-containing components from female donors with leucocyte antibodies were responsible for the majority of TRALI fatalities before mitigation strategies were implemented. Over the past 15 years, measures to mitigate risk for TRALI have been implemented worldwide and they continued to evolve with time. The AABB requires that all plasma containing components and whole blood for transfusion must be collected from men, women who have not been pregnant, or women who have tested negative for human leucocyte antigen antibodies. Although the incidence of TRALI has decreased following the institution of TRALI mitigation strategies, TRALI is still the most common cause of transfusion-associated death in the United States. In this review, we focus on TRALI risk mitigation strategies. We describe the measures taken by blood collection facilities to reduce the risk of TRALI in the United States, Canada and European countries. We also review the literature for the effectiveness of these measures.

Evaluation of a new microbeads assay for granulocyte antibody detection

BACKGROUND

To reduce the risk of transfusion-associated acute lung injury (TRALI), a high number of plasma donors were tested for human leukocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies. For HNA antibody detection, the gold standard is a combination of the granulocyte immunofluorescence test (GIFT) and the granulocyte agglutination test (GAT). However, these tests are not suitable for a high-throughput of samples.

STUDY DESIGN AND METHODS

To evaluate the new generation of the LABScreen MULTI assay (One Lambda, Inc.), which has special new beads for all the known HNA specificities, including HNA-3a, 97 sera samples containing well-defined HNA antibodies were used. For background testing, we used 91 samples from plasma donors previously identified by GAT, GIFT, and the monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) assay.

RESULTS

Compared with previous tests, the new LABScreen MULTI assay was highly specific for the HNA-1a, HNA-1b, HNA-2, and HNA-3a antibody specificities required to prevent TRALI. Ninety-eight percent of the HNA-1a, HNA-1b, and HNA-2 antibodies could be detected as true positive; and 90% of the HNA-3a antibodies were recognized correctly as positive. False-positive reactions were identified in 5.5% of samples that previously tested negative.

CONCLUSION

The detection of HNA-3a antibody specificities could be integrated into the new LABScreen MULTI assay; however, we detected only 90%. In addition, we detected further HNA antibodies, such as HNA-1c, HNA-1d, and some HNA-3b and HNA-4a antibodies. The new generation of LABScreen MULTI is a great step toward feasible high-throughput testing for HNA antibodies. Nevertheless, GIFT and GAT remain the gold-standard methods for the differentiation of rare and currently unknown HNA specificities.

The prevalence of leucocyte alloantibodies in blood donors from South China

BACKGROUND

Several studies had demonstrated that leucocyte antibodies including anti-human leucocyte antigen (anti-HLA) antibodies (class I and class II) and anti-human neutrophil antigen (anti-HNA) antibodies (HNA-1, -2 and -3) present in the blood products are responsible for transfusion-related acute lung injury (TRALI). Therefore, selection of blood products exclusive of anti-HLA and anti-HNA antibodies may lower the risk of TRALI reaction. However, the prevalence of leucocyte antibodies among blood donors in China is currently not known.

STUDY DESIGN AND METHODS

Blood samples were collected from 454 male and 560 female donors (143 nulliparous and 417 multiparous female). HLA class I and II antibodies were analyzed by bead assays. Anti-HNA-1 and -2 antibodies were screened by the LABScreen assay (One Lambda Inc.), and HNA-3 were detected by antigen capture assay, and confirmed by the granulocyte agglutination test (GAT).

RESULTS

Screening of the total cohort showed higher prevalence of HLA antibodies in female compared with male donors (19.64 vs. 4.63%). We found antibodies against HLA class I (13.21%) and HLA class II (11.43%) in 560 female donors. The most frequent antibodies against HLA class I and II in parous females (n = 69) reacted with were A*11 (28.81%), B*07 (42.37%), Cw*07 (20.34%) and DRB1*04 (40.43%) molecules. Among 778 donors (randomly selected from 1014 donors), we found three donors with neutrophil reactive antibodies, two against HNA-2 and one without known specificity. Anti-HNA-3 antibodies were not found so far.

CONCLUSION

In this study, we found alloimmunization against HLA class I, II and HNA in 4.63, 24.70 and 0.39%, respectively, in our female blood donors, indicating that the use of plasma containing blood products from parous female blood donors without HLA antibodies pre-testing may increase the risk of TRALI reaction. Although immunization against HNA seems to be a rare event in China, further observation is necessary to decide the necessity of HNA antibodies screening in our blood donors.

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, ex vivo and in vivo 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.

Split Blood Products

The last 20 years have seen many advances in transfusion therapy and safety. Blood products are biological products engendering complex interactions with the immune system. Prestorage leukoreduction results in a reduced risk of febrile reactions, CMV transmission, and immune modulation, proving to be safer for patients than non-leuko reduced products.

Simple patient identification issues and clerical error continue to be the primary causes of ABO-incompatible transfusions. Rigorous donor screening as well as serologic and nucleic acid testing for transfusion transmitted infection have brought the blood supply to a very safe level, although transmission of these agents continues to be a problem in underdeveloped countries. Emerging infectious diseases, beyond current laboratory detection capabilities, combined with global travel, pose unknown imminent risks everywhere. We also briefly discuss the current risks of transfusion-transmitted infections.

We review currently available hemostatic blood products, their compositions, and their clinical indications; we mention product modifications currently in development; and we touch upon the hemostatic properties and drawbacks of whole blood, which is currently gaining popularity as an alternative to split blood products. We conclude with an in-depth overview of the risks associated with transfusion, including incompatibility, hemolytic transfusion reactions, transfusion-associated circulatory overload (TACO), and transfusion-related acute lung injury (TRALI).

Anemia, bleeding, and blood transfusion in the intensive care unit: causes, risks, costs, and new strategies

The definition of anemia is controversial and varies with the sex, age, and ethnicity of the patient. Anemia afflicts half of hospitalized patients and most elderly hospitalized patients. Acute anemia in the operating room or intensive care unit is associated with increased morbidity as well as other adverse outcomes, including death. The risks of anemia are compounded by the added risks associated with transfusion of red blood cells, the most common treatment for severe anemia. The causes of anemia in hospitalized patients include iron deficiency, suppression of erythropoietin and iron transport, trauma, phlebotomy, coagulopathies, adverse effects of and reactions to medications, and stress-induced gastrointestinal bleeding. The types and causes of anemia and the increased health care utilization and costs associated with anemia and undetected internal bleeding are described. The potential benefits and risks associated with transfusion of red blood cells also are explored. Last, the strategies and new tools to help prevent anemia, allow earlier detection of internal bleeding, and avoid unnecessary blood transfusions are discussed.

Approach of using established and new laboratory tests to more comprehensively investigate noninfectious and nonhemolytic transfusion reactions--along with the experience in Japan

BACKGROUND AND OBJECTIVES

Noninfectious and nonhaemolytic transfusion reactions are the most common type of transfusion reactions. Several new tests have been made, helping diagnosis and understanding of their pathogenesis. This manuscript provides a review of the literature on currently available tests in association with the approach in Japan.

MATERIALS & METHODS

Primarily by using key words, more than 100 pertinent articles in the Medline database were identified and reviewed.

RESULTS

Numbers of laboratory tests are available including those for plasma protein levels, plasma protein antibodies, leucocyte and platelet antibodies, serum N-terminal-pro-brain natriuretic peptide levels, serum tryptase levels and genetic microchimerism. Cross-match tests, such as basophil activation test and neutrophil activation test, are also available to determine a causal relationship between the reaction and transfusion.

CONCLUSIONS

Several tests should help to confirm diagnosis and determine causal relationship between adverse reactions and transfusion and to gain an insight into the mechanism of the reaction in some cases, although some of the recently developed tests have not been completely validated.

External quality assessment of human neutrophil antigen (HNA)-specific antibody detection and HNA genotyping from 2000 to 2012

Since 2000, Quality Assurance (QA) exercises for the detection and identification of granulocyte antibodies and DNA typing for human neutrophil antigens (HNA) have been distributed within the International Granulocyte Immunobiology Workshops, which are linked to International Society of Blood Transfusion. The exercises were standardised at the outset to enable laboratory performance to be monitored. Between 2000 and 2012, nine exercises were distributed to 20 laboratories. Overall, 45 examples of 42 unique samples containing defined granulocyte reactive antibodies were distributed for serological analysis together with 20 samples for HNA genotyping. The level of satisfactory serological performance was initially set at 50% and later increased to 70%, while the 'cut-off' for HNA genotyping was set at 100% after 2008. Failure to achieve the minimum score in the QA exercises in consecutive years resulted in temporary exclusion. In 2000, the 15 participating laboratories had a mean score of 56.1% for serological analysis and 13 laboratories attempted HNA-1a and -1b genotyping, while 11 attempted HNA-1c typing. Steady improvements in proficiency for serological testing and HNA typing occurred in subsequent exercises. In 2012, the mean score for serology was 88.5% and 12/13 laboratories scored 100% for HNA-1a, -1b, -1c, -3a, -3b, -4a, -4bw, -5a and -5bw genotyping. These QA exercises have provided an invaluable tool to monitor and improve the standard of granulocyte immunology investigations for participating laboratories, thereby enhancing performance for both clinical investigations and donor screening programmes to reduce the incidence of TRALI.

Luminex(®) and its applications for solid organ transplantation, hematopoietic stem cell transplantation, and transfusion

SUMMARY

The detection of antibodies against the human leukocyte antigen (HLA) complex has become indispensable in every clinical practice. The development of solid-phase assays like the Luminex allows the standardized measurement of anti-HLA antibodies (HLAab) with high sensitivity, albeit the relevance for some clinical settings remains a matter of debate. In this review we aim to describe the principle of Luminex-based antibody detection, including two modifications that allow identifying solely complement-activating antibodies. We then describe three applications for Luminex: i) detection of HLAab preceding solid-organ transplantation and monitoring of donor-specific antibodies posttransplant as a risk factor for antibody-mediated rejection; ii) presence of HLAab in recipients as a risk for graft failure in hematopoietic stem cell transplantation, especially in haploidentical or mismatched transplantations; iii) role of HLAab in blood transfusion including refractory thrombocytopenia and selection of suitable platelet donors, transfusion-related lung injury after plasma transfusion, and immunization against HLA after red blood cell transfusion despite leukodepletion. Although the Luminex platform constitutes a potent technology for HLA antibody detection, some drawbacks require the well-educated analysis and interpretation of data in critical cases. In addition, Luminex has become an important tool to identify clinically relevant antibodies.

Pulmonary complications of transfused blood components

Three transfusion complications are responsible for the majority of the morbidity and mortality in hospitalized patients. This article discusses the respiratory complications associated with these pathophysiologic processes, including definitions, diagnosis, mechanism, incidence, risk factors, clinical management, and strategies for prevention. It also explores how different patient populations and different blood components differentially affect the risk of these deadly transfusion complications. Lastly, the article discusses how health care providers can risk stratify individual patients or patient populations to determine whether a given transfusion is more likely to benefit or harm the patient based on the transfusion indication, risk, and expected result.

An International reference reagent for the detection of anti-human neutrophil antigen-1a

BACKGROUND AND OBJECTIVES

Testing for neutrophil antibodies has become more common as awareness of transfusion-related acute lung injury (TRALI) has increased. However, unlike other areas of blood cell antibody testing, there are no certified reference reagents available with which laboratories can determine the sensitivity of detection of their assays. This report describes the production and evaluation of a freeze-dried preparation of human plasma, code 09/284, containing anti-human neutrophil antigen-1a (anti-HNA-1a) for use as a minimum sensitivity reagent.

MATERIALS AND METHODS

One-millilitre of aliquots of plasma containing anti-HNA-1a were freeze-dried in glass ampoules. To characterize the material, 24 laboratories took part in an international collaborative study. The participants evaluated doubling dilutions of the material using their in-house routine assays and recorded the highest dilution in which the antibody could be detected.

RESULTS

When diluted 1 in 4, most laboratories were able to detect the anti-HNA-1a in the material, and the participants agreed that this was an appropriate level to set as the minimum sensitivity required.

CONCLUSIONS

In October 2011, the WHO Expert Committee on Biological Standardization approved the material 09/284 as an International Reference Reagent for the detection of anti-HNA-1a.

Transfusion-related acute lung injury: Current understanding and preventive strategies. Transfus Clin Biol. 2012;19:117-124. [PMID: 22682310 DOI: 10.1016/j.tracli.2012.03.001]

Transfusion-related acute lung injury (TRALI) is the most serious complication of transfusion medicine. TRALI is defined as the onset of acute hypoxia within 6 hours of a blood transfusion in the absence of hydrostatic pulmonary oedema. The past decades have resulted in a better understanding of the pathogenesis of this potentially life-threating syndrome. The present notion is that the onset of TRALI follows a threshold model in which both patient and transfusion factors are essential. The transfusion factors can be divided into immune and non-immune mediated TRALI. Immune-mediated TRALI is caused by the passive transfer of human neutrophil antibodies (HNA) or human leukocyte antibodies (HLA) present in the blood product reacting with a matching antigen in the recipient. Non-immune mediated TRALI is caused by the transfusion of stored cell-containing blood products. Although the mechanisms behind immune-mediated TRALI are reasonably well understood, this is not the case for non-immune mediated TRALI. The increased understanding of pathways involved in the onset of immune-mediated TRALI has led to the design of preventive strategies. Preventive strategies are aimed at reducing the risk to exposure of HLA and HNA to the recipient of the transfusion. These strategies include exclusion of "at risk" donors and pooling of high plasma volume products and have shown to reduce the TRALI incidence effectively. This review discusses the current understanding of TRALI and preventive strategies available.