The Nlrp3 Inflammasome Does Not Regulate Alloimmunization to Transfused Red Blood Cells in Mice

Abstract

Red blood cell (RBC) transfusions are essential for patients with hematological disorders and bone marrow failure syndromes. Despite ABO matching, RBC transfusions can lead to production of alloantibodies against “minor” blood group antigens. Non-ABO alloimmunization is a leading cause of transfusion-associated mortality in the U.S. Despite its clinical importance, little is known about the immunological factors that promote alloimmunization. Prior studies indicate that inflammatory conditions place patients at higher risk for alloimmunization. Additionally, co-exposure to pro-inflammatory pathogen associated molecular patterns (PAMPs) promotes alloimmunization in animal models, suggesting that RBC alloimmunization depends on innate immune cell activation. However, the specific innate immune stimuli and sensors that induce a T cell-dependent alloantibody response to transfused RBCs have not been identified. The NLRP3 inflammasome senses chemically diverse PAMPs and damage associated molecular patterns (DAMPs), including extracellular ATP and iron-containing heme. We hypothesized that activation of the NLRP3 inflammasome by endogenous DAMPs from RBCs promotes the alloimmune response to a sterile RBC transfusion. Using genetically modified mice lacking either NLRP3 or multiple downstream inflammasome response elements, we ruled out a role for the NLRP3 inflammasome or any Caspase-1 or -11 dependent inflammasome in regulating RBC alloantibody production to a model antigen.

Type I IFN Is Necessary and Sufficient for Inflammation-Induced Red Blood Cell Alloimmunization in Mice

“…Treatment of recipient mice with poly(I:C), only during the peri-transfusion period, induced cDC activation and T cell—dependent alloimmunization to the human K1 Ag. These findings agree with prior studies demonstrating a critical role for cDC activation in T cell—dependent alloimmune responses to stored RBCs expressing the HOD Ag (18, 63). A recent study reported that the timing of poly(I:C) treatment influences alloantibody responses to transfused HOD RBCs (19).…”

“…These associations indicate that specific pathways activated in some inflammatory conditions, such as autoimmunity and viral infections, promote RBC alloimmunization. However, examination of these pathways, including inflammatory cytokine signaling, has only just begun (17, 18). …”

B cells require Type 1 interferon to produce alloantibodies to transfused KEL‐expressing red blood cells in mice

“…Mice were transfused 8 to 9 weeks after marrow reconstitution. For chimeras generated with Zbtb46‐DTR marrow, diphtheria toxin receptor (DTR)‐expressing cells were depleted with two intraperitoneal injections of diphtheria toxin (DT, Sigma‐Aldrich) 3 days (60 ng/g) and 1 day (40 ng/g) before transfusion as previously described . Doses of DT were titrated in Zbtb46‐DTR chimeras to achieve efficient conventional DC (cDC) depletion.…”

Transfusion-related immunomodulation: a reappraisal

“…RBC transfusions also affect innate immunity, with specific effects on macrophages, dendritic cells, and granulocytes [22, 23]. Of course, because of crosstalk mechanisms, it is not surprising that effects on innate immunity also influence adaptive immune responses [22, 24]. Finally, RBC transfusions, because of the delivery of the iron present in hemoglobin, influence nutritional immunity by enhancing pathogen virulence [15, 16, 25–27], by producing transfusion-induced iron overload with concomitant effects on immune responses [28], and by potentially reversing the defective immune responses seen in iron-deficiency anemia [29].…”