Siglec-H ablation in plasmacytoid dendritic cells alleviates acute liver injury by promoting IL-21⁺ CD4 T cells

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Presentation Time: 03:15 PM - 04:30 PM
Poster Board Number: B534
Abstract ID: 4463

Presenting Author:
James Ahodantin , Research Associate at Univ. of Maryland Sch. of Med.

Abstract:

Siglec-H is an immune receptor specifically expressed in plasmacytoid dendritic cells (pDCs) that inhibits IFN-α production and regulates pDC maturation. Although, the role of pDCs in autoimmune disorders is well-known, the effect of Siglec-H expression in pDCs in acute liver injury (ALI) remains elusive. To investigate Siglec-H/pDCs axis in ALI, BDCA2 transgenic and Siglec-H knockout (SH KO) mice were administrated with concanavalin A (ConA) to induce a T cell-mediated ALI in combination of either pDCs depletion with anti-BDCA2 antibody or anti-IL-21R and Stat3 blockade. Here, we report that specific depletion of pDCs in BDCA2 transgenic mice exacerbated ALI. Surprisingly, SH KO mice were resistant to ALI (lower ALT, hyaluronic acid, IL-6 and TNF-α). Th1/IFN-γ response and Stat1 signaling were both inhibited in the liver of SH KO mice while intrahepatic IL-21 and Stat3 signaling pathways were elevated. Mechanistically, we identified that Siglec-H-null pDCs exhibited immunosuppressive phenotypes (CD40^LowCCR9^Low), resulting in a defective CD4 T cell activation and a promotion of IL-21-producing CD4 T cells in the liver. Finally, IL-21R and Stat3 inhibitions in Siglec-H deficient mice restored ConA-induced ALI. We conclude that, Siglec-H-null pDCs mediate hepatic tolerance via induction of IL-21⁺CD4 T cells in the liver during ALI. These findings indicate that targeting Siglec-H/pDCs axis may provide a novel approach to modulate CD4 T cell polarization and liver disease.