Abstract
Red blood cell (RBC) transfusion exposes recipients to hundreds of non-ABO antigens that are not matched between donors and recipients. Alloantibodies formed against these antigens can cause potentially fatal hemolytic events and limit availability of compatible blood products, resulting in anemia-associated morbidity and mortality. Multiple studies have established that certain autoimmune diseases and inflammatory disorders are associated with an increased frequency of alloimmunization. However, underlying molecular mechanisms are poorly understood. A recent study reported that pre-treatment of the transfusion recipient with a pro-inflammatory stimulus (poly(I:C), a double-stranded RNA), induces type 1 interferons (IFNα/β) that promote RBC alloimmunization in mice. This finding suggests that IFNα/β-inducing infections may increase the risk of alloimmunization in transfusion recipients. Here, we hypothesized that infection with influenza, known to induce multiple cytokines including IFNα/β, may promote RBC alloimmunization. Wildtype mice were infected with 10 plaque forming units of PR8 influenza A virus 3 days prior to transfusion with transgenic RBCs expressing the KEL antigen (KEL RBCs). Anti-KEL IgM and IgG responses were measured by flow cytometry 5 and 14-28 days, respectively, following transfusion. Although mock-infected transfused wildtype mice produced low baseline levels of anti-KEL antibodies (IgG peak response mean MFI = 18.5 ± 5.7, standard error), influenza-infected mice produced significantly elevated levels of anti-KEL IgM and IgG (IgG, MFI = 675.7 ± 150.5, p<0.05) in 3 out of 3 (3/3) experiments. The influenza-induced anti-KEL antibody response was associated with increased KEL RBC clearance 1 hr post-transfusion (% of KEL RBCs remaining = 73.5% ± 0.06, p<0.05) compared to mock-infected transfused mice (98.6% ± 0.01). Influenza infection prior to transfusion also led to enhanced RBC-specific T cell proliferation and T follicular helper (Tfh) cell differentiation (% of RBC-specific T cells, Tfh = 8.9% ± 0.9, p<0.05) compared to mock-infected transfused controls (Tfh = 4.1% ± 1.1). To determine whether IFNα/β signaling contributes to influenza-induced alloimmunization, the alloimmune response to KEL RBCs was examined in influenza-infected mice lacking the receptor for IFNα/β (IFNAR1-/-) or transcription factors required for IFNα/β production (IRF3-/- IRF7-/-). As shown in Figure 1a, both IFNAR1-/- and IRF3-/- IRF7-/- mice produced significantly lower levels of anti-KEL IgG following transfusion, compared to infected wildtype mice, in 3/3 experiments. Finally, treatment of infected wildtype mice with an IFNAR1-blocking antibody 1 day prior to infection and 1 day prior to KEL-RBC transfusion profoundly inhibited anti-KEL IgG production, compared to isotype control treated mice in 3/3 experiments (Figure 1b). Collectively, these results indicate that influenza infection of mice promotes alloimmunization to an RBC antigen by an IFNα/β dependent mechanism. These data contribute to a growing appreciation of the role that IFNα/β plays in RBC alloimmunization in animal models, and suggest that an investigation into the role of type 1 interferons in human alloimmunization may be informative.
No relevant conflicts of interest to declare.
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