Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-associated mortality in the United States and other countries. In most TRALI cases, human leukocyte antigen (HLA) class II antibodies are detected in implicated donors. However, the corresponding antigens are not present on the cellular key players in TRALI: neutrophils and endothelium. In this study, we identify monocytes as a primary target in HLA class II-induced TRALI. Monocytes become activated when incubated with matched HLA class II antibodies and are capable of activating neutrophils, which, in turn, can induce disturbance of an endothelial barrier. In an ex vivo rodent model, HLA class II antibody-dependent monocyte activation leads to severe pulmonary edema in a relevant period of time, whenever neutrophils are present and the endothelium is preactivated. Our data suggest that in most TRALI cases, monocytes are cellular key players, because HLA class II antibodies induce TRALI by a reaction cascade initiated by monocyte activation. Furthermore, our data support the previous assumption that TRALI pathogenesis follows a threshold model. Having identified the biologic mechanism of HLA class II antibodyinduced TRALI, strategies to avoid plasma from immunized donors, such as women with a history of pregnancy, appear to be justified preventive measures. (Blood. 2011;117(2):669-677) IntroductionTransfusion-related acute lung injury (TRALI) is the leading cause of transfusion-associated death in the United States and other countries. 1 It typically presents within 6 hours after transfusion as a clinical syndrome characterized by acute respiratory distress, hypoxemia, and a bilateral pulmonary edema on chest x-ray. 2 The incidence of TRALI has been estimated as 1/5000 for all blood components, and current mortality rates are in the range of 5%-25%. 3 All blood components have been implicated in TRALI, but those containing large amounts of plasma are mainly responsible. [3][4][5] A recently published literature review states that in 80% of all TRALI cases, white blood cell antibodies can be identified in the implicated blood donor, 6 and most implicated donors have been women with a history of pregnancy. Pregnancy results in alloimmunization against paternal white blood cell antigens in 21%-24% of women, 7,8 with 3 main antibody specificities: human leukocyte antigen (HLA) class I, HLA class II, and human neutrophil antigens (HNAs).The capability of antibodies recognizing either HNA 9-11 or HLA class I 12,13 to precipitate TRALI has been proved in different animal models. It is consensus opinion that neutrophil activation is the key mechanism by which antibodies to HNA and to HLA class I mediate TRALI, 4,14 be it by direct binding to the cognate antigen on the surface of the neutrophil [9][10][11]13 or, in the case of HLA class I antibodies, possibly by binding to HLA class I molecules on pulmonary endothelial cells, which leads to neutrophil trapping by the neutrophils' Fc receptors and subsequent neutrophil activation by receptor...

This study demonstrated that HEK293T cells expressing stable recombinant HNA-3 are suitable for the detection of HNA-3 alloantibodies allowing reliable screening of blood products.

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Most drugs causing immunocytopenias do not bind firmly to the affected cells. Consequently, the drug-dependent antibodies in such cases are completely removed from their binding sites by conventional cell washing. It has recently been shown that such cell-drug-antibody complexes do survive the washing procedure, if the drug (metabolite) was included in the wash medium. The study reported here used the microtube gel test to reexamine the reactivity of different drug-dependent red cell antibodies: cefotaxime (n = 1), carbimazole (n = 1), cianidanol (n = 1), diclofenac (n = 3), penicillin (n = 3), and nomifensine (n = 10). Whether the drug tested binds (penicillin, cianidanol, carbimazole, and diclofenac) or does not bind (cefotaxime and nomifensine) firmly to the cells, the resultant cell-drug-antibody complex could be recognized on and/or in the gel after it was separated from the mixture containing the drug by means of centrifugation alone and without washing. It is concluded that the gel test might be of value not only for the detection of drug-dependent antibodies, but also for the analysis of subtle drug--cell interactions.

These results suggested that rapid ELISA using recombinant neutrophil antigens may provide a valuable method for rapid screening of human alloantibodies against HNA-1a, -1b, and -1c in patients with neutropenia and in blood donors.