Packed Red Blood Cell Transfusion Modulates Myeloid Dendritic Cell Activation and Inflammatory Response In Vitro

Transfusion of packed red blood cells (PRBCs) modulates patients' immune responses and clinical outcomes; however, the underpinning mechanism(s) remain unknown. The potential for PRBC to modulate myeloid dendritic cells (mDC) and blood DC antigen 3 was assessed using an in vitro transfusion model. In parallel, to model processes activated by viral or bacterial infection, toll-like receptor agonists polyinosinic:polycytidylic acid or lipopolysaccharide were added. Exposure to PRBC upregulated expression of CD83 and downregulated CD40 and CD80 on both DC subsets, and it suppressed production of interleukin (IL)-6, IL-8, IL-12, tumor necrosis factor-α, and interferon-gamma-inducible protein-10 by these cells. Similar effects were observed when modeling processes activated by concurrent infection. Furthermore, exposure to PRBC at date of expiry was associated with more pronounced effects in all assays. Our study suggests PRBC have an impact on recipient DC function, which may result in failure to establish an appropriate immune response, particularly in patients with underlying infection.