FcγRIIA/CD32A expression increases the activation of circulating neutrophils and platelets during antibody-mediated TRALI. LPS-sensitized (0.1 mg/kg, intraperitoneal) CD32A^– or CD32A⁺ mice were injected with the mAb hIgG1-34-1-2S (1.5 mg/kg, intravenous) or vehicle and examined 15 minutes later. (A) Blood plasma levels of myeloperoxidase (MPO) (CD32A^–, n = 5-11; CD32A⁺, n = 5-12). (B) Left: Neutrophil areas in the lungs of CD32A^– and CD32A⁺ mice (n = 3). Right: Representative lung sections from CD32A^– and CD32A⁺ mice immunolabeled with the anti-neutrophil mAb 1A8 (scale bar = 50 µm). (C) Circulating platelet counts before administration of LPS, 24 hours later, and 15 minutes after hIgG1-34-1-2S challenge (n = 8). (D) Percentage of CD62P-positive platelets (n = 6). (E) Left: Platelet areas in the lungs of CD32A^– and CD32A⁺ mice (n = 3). Right: Representative lung sections from CD32A^– and CD32A⁺ mice immunolabeled with the anti-platelet mAb RAM.1 (scale bar = 50 µm). Results are presented as the mean ± standard error of the mean. P > .05 (not significant [ns]), *P < .05, **P < .01, ***P < .001 by one-way analysis of variance (panels A and D), two-way analysis of variance (panel C), or a Student t test (panels B and E).