Targeting pathogenic CD8⁺ tissue-resident T cells with chimeric antigen receptor therapy in murine autoimmune...

Primary biliary cholangitis (PBC) is a cholestatic autoimmune liver disease characterized by autoreactive T cell response against intrahepatic small bile ducts. Here, we use Il12b^-/-Il2ra^-/- mice (DKO mice) as a model of autoimmune cholangitis and demonstrate that Cd8a knockout or treatment with an anti-CD8α antibody prevents/reduces biliary immunopathology. Using single-cell RNA sequencing analysis, we identified CD8⁺ tissue-resident memory T (Trm) cells in the livers of DKO mice, which highly express activation- and cytotoxicity-associated markers and induce apoptosis of bile duct epithelial cells. Liver CD8⁺ Trm cells also upregulate the expression of several immune checkpoint molecules, including PD-1. We describe the development of a chimeric antigen receptor to target PD-1-expressing CD8⁺ Trm cells. Treatment of DKO mice with PD-1-targeting CAR-T cells selectively depleted liver CD8⁺ Trm cells and alleviated autoimmune cholangitis. Our work highlights the pathogenic role of CD8⁺ Trm cells and the potential therapeutic usage of PD-1-targeting CAR-T cells.