Microparticles in red cell concentrates prime polymorphonuclear neutrophils and cause acute lung injury in a two-event mouse model

Red cell-derived microparticles (RMPs) are potential mediators of transfusion-related acute lung injury (TRALI). The aim of this study was to investigate the effects of microparticles present in red cell concentrates (RCC) on polymorphonuclear neutrophil (PMN) respiratory burst and acute lung injury (ALI) in mice. Microparticles (MPs) in RCC supernatant were quantified using flow cytometry. The priming activity of either isolated MPs or RCC supernatant toward human PMN was measured in vitro. Mice were injected with lipopolysaccharide (LPS), followed by an infusion of either isolated MPs or heat-treated RCC supernatant. The lungs were harvested to assess myeloperoxidase (MPO) activity, histology and pulmonary edema. Protein content in bronchoalveolar lavage fluid (BALF) was measured. The number of RMPs increased significantly during storage. Both isolated MPs and the supernatants from RCCs that had been stored for 28 and 35 days effectively primed the PMN respiratory burst. The infusion of isolated MPs or supernatants that had been stored for > 28 days into LPS-treated mice caused ALI. The filtered supernatant resulted in significantly ameliorated mouse ALI. MPs that accumulate during RCC storage prime the PMN respiratory burst and cause ALI in a two-event mouse model.