Induction of Systemic Autoimmunity by Xenobiotic Requires Endosomal TLR Trafficking and Signaling from the Late Endosome/Endolysosome but Not Type I IFN

摘要

Type I IFN and nucleic acid-sensing TLRs are both strongly implicated in the pathogenesis of lupus with most patients expressing IFN-induced genes in peripheral blood cells and with TLRs promoting type I IFNs and autoreactive B cells. About a third of SLE patients, however, lack the IFN signature suggesting the possibility of type I IFN-independent mechanisms. Here, we examined the role of type I IFN and TLR trafficking and signaling in a xenobiotic systemic autoimmunity induced by mercury (HgIA). Strikingly, autoAb production in HgIA was not dependent on the type I IFN receptor even in NZB mice that require type I IFN signaling for spontaneous disease, but was dependent on the endosomal TLR transporter UNC93B1 and the endosomal proton transporter, SLC15A4. HgIA also required the AP-3 complex, which transports TLRs from the early endosome to the late endolysosomal compartments. Examination of TLR signaling pathways implicated the canonical NF-κB pathway and the proinflammatory cytokine IL-6 in autoantibody production, but not IRF7. These findings identify HgIA as a novel type I IFN-independent model of systemic autoimmunity and implicate TLR-mediated NF-κB proinflammatory signaling from the late endocytic pathway compartments in autoAb generation.