RBC alloimmunization in patients with sickle cell disease (SCD) can lead to potentially fatal hemolytic events.
Patients with SCD have the highest incidence of RBC alloimmunization, compared to all other disease
populations including those with similar transfusion burdens. Factors explaining this high incidence are poorly
understood. Identifying such factors would allow for identification of patients with SCD who may benefit from
personalized transfusion protocols and rare antigen-matched units. Inflammation in the transfusion recipient has
been shown to promote RBC alloantibody responses. We previously reported that proinflammatory type 1
interferons (IFNa/ß) induced by viral infection or autoimmunity promote RBC alloimmunization in pre-clinical
transfusion models. Recent studies, including preliminary data included in this application, have revealed that
many patients with SCD have an IFNa/ß gene signature, defined by leukocyte expression of IFNa/ß stimulated
genes. However, mechanisms leading to IFNa/ß activation, including signaling pathways, receptors, and ligands,
are poorly understood. Nearly all IFNa/ß-inducing receptors are intracellular receptors for nucleic acids. Thus,
phagocytosis of nucleic acid containing cells, including reticulocytes which are elevated in SCD, has the potential
to activate IFNa/ß pathways. Anti-RBC autoantibodies facilitate erythrophagocytosis, with alloimmunized
patients with SCD having an increased incidence of such autoantibodies. While the RBC alloantibody/RBC
autoantibody association is poorly understood, our preliminary data indicate that reticulocyte counts correlate
with IFNa/ß gene scores and erythrophagocytosis of autoantibody-opsonized reticulocytes from patients with
SCD induces IFNa/ß activation in human macrophages. Preliminary data also show that anti-RBC autoantibodies
induce IFNa/ß activation and RBC alloimmunization in a pre-clinical transfusion model.
In this proposal, we aim to test the hypothesis that RBC autoantibodies promote IFNa/ß-mediated RBC
alloimmunization in SCD by identifying inflammatory pathways that induce IFNa/ß (Aim 1) and determining the
effects of autoantibody-induced IFNa/ß inflammation on RBC alloimmunization in SCD mice (Aim 2). In Aim 1,
IFNa/ß pathways induced by autoantibodies will be identified in co-cultures of human macrophages and
reticulocytes from patients with and without SCD, and the extension of findings will be tested in pre-clinical murine
models. Identified pathways and receptors will inform ligands that induce IFNa/ß in SCD. Aim 2 represents the
first investigation of IFNa/ß-regulated RBC alloimmunization in pre-clinical models of SCD and has the potential
to reveal a mechanism that may contribute to the elevated incidence of RBC alloimmunization.
Long term goals of this project include improved understanding of proinflammatory interferons in SCD, with the
possibility that targeted IFNa/ß-modulated therapy may be beneficial. Findings may also have applicability
beyond SCD, with inflammatory interferons playing a critical role in autoimmunity and other disease processes.