Background: In antibody-mediated nonhemolytic transfusion reactions, transfusion-related acute lung injury (TRALI) tends to occur typically within 2 hours after a blood transfusion. White cell antibodies or immune complexes have been frequently shown to be associated with the syndrome, although the mechanisms by which they induce TRALI are poorly understood. The aim of this study was to characterize soluble mediators that are released from cells at an early stage after immune stimulation.
Study design and methods: To explore the mechanism of TRALI, an in vitro whole-blood cell culture assay was established in which cells were stimulated by human antibodies and the activation of neutrophils was monitored by a cell surface marker (Mac-1) with flow cytometry and by measurement of the release of soluble factors, including perforin, interleukin-6, tumor necrosis factor-alpha, and heparin-binding protein (HBP) with enzyme-linked immunosorbent assays. In addition, the involvement of two neutrophil FcgammaRs (FcgammaRIIIb and FcgammaRIIa, also known as CD16 and CD32, respectively) was examined during antibody-induced cell activation with anti-FcgammaR blocking antibodies.
Results: Substantial amounts of HBP were released within 30 minutes of stimulation by human antibodies, although other soluble mediators were not released within the same period. Furthermore, the release of HBP was mediated via signals through both FcgammaRIIIb and FcgammaRIIa.
Conclusion: HBP appears to be one of the primary effector molecules of antibody-mediated nonhemolytic transfusion reactions including TRALI.