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Complement Deposition and IgG Binding on Stored Red Blood Cells Are Independent of Storage Time

Background: In the Netherlands, red blood cells (RBCs) are allowed to be stored up to 35 days at 2-6 °C in saline-adenine-glucose-mannitol (SAGM). During storage, RBCs undergo several changes that are collectively known as storage lesion. We investigated to what extent complement deposition and antibody binding occurred during RBC storage and investigated phagocytic uptake in vitro. Methods: RBCs were stored for different lengths of time at 2-6 °C in SAGM. Complement deposition and antibody binding were assessed upon storage and after incubation with serum. M1- and M2-type macrophages were generated from blood monocytes to investigate RBC phagocytosis. Results: No complement deposition was directly observed on stored RBCs, while incubation of RBCs with serum resulted in variable donor-dependent C3 deposition and IgG binding, both independent of storage time. Only 1-4% phagocytosis of stored RBCs by macrophages was observed. Conclusion: RBCs are susceptible to complement deposition and antibody binding independent of storage time. Limited phagocytic uptake by macrophages was observed in vitro.