The pivotal role of neutrophils in the pathology and investigation of TRALI

TRALI events are clinically diagnosed and laboratory investigations act to support the diagnosis. The two event or priming TRALI hypothesis proposes that the patient’s underlying illness induces activation of the pulmonary endothelium leading to the sequestration of primed neutrophils. Leukocyte antibodies or biological response modifiers (BRMs) in the transfused blood product activate the primed neutrophil producing an augmented respiratory burst response which causes injury to the microvasculature, resulting in the symptoms of ALI1. Hence neutrophils are a key effector cell in this pathology2. Current laboratory investigations are predominantly focussed on the antibody mediated TRALI. Both human neutrophil antigens (HNA) and human leukocyte antigens (HLA) have been associated and implicated in TRALI events. The combination of the granulocyte immunofluorescence tests (GIFT) and granulocyte agglutination test (GAT) have been recommended for the screening and detection of neutrophil reactive antibodies (i.e. HNA and HLA class I antibodies)3. HLA class II antibodies also have been implicated in severe TRALI, but HLA assays are needed to detect them4. Crossmatching of recipient neutrophils with donor sera by GIFT and GAT provide a useful means of confirming if an antibody is implicated. Otherwise only an association can be assumed. Although tedious and often protracted the laboratory investigation of TRALI events is needed so that blood donors with “risky” antibodies can be identified and removed from therapeutic use. There is not accepted method for investigating non-antibody mediated TRALI. The Granulocyte Immunobiology Working Party of the International Society of Blood Transfusion (ISBT) is a collective of the world’s granulocyte experts. They advice the ISBT on granulocyte immunobiology matters, have a granulocyte nomenclature sub-committee, conduct annual granulocyte immunobiology workshops and have made recommendations on TRALI investigations3. And thus are a useful resource for TRALI investigation