In vivo CAR-Tfh cell reprogramming restores tolerance in a mouse model of autoimmune hepatitis.

Autoimmune diseases involve the coordinated dysregulation of multiple types of immune cells, and single-cell targeted therapies often yield suboptimal results. Here, we developed chimeric antigen receptor (CAR)-engineered follicular helper T (Tfh) cells capable of simultaneously suppressing T cells, B cells, and dendritic cells (DCs) to restore immune homeostasis in an autoimmune hepatitis (AIH) mouse model. Using amino acid-derived lipid nanoparticles, we deliver self-amplifying RNA encoding Forkhead box protein P3 (Foxp3) and a cytochrome P4502D6 (CYP2D6)-specific CAR to Tfh cells, conferring stable regulatory features and antigen-dependent suppressive activity. Engineered CAR-Tfh cells preferentially localize to the liver, recognize CYP2D6-expressing hepatocytes, and suppress pathogenic T cell and B cell responses. In AIH-II mouse models, CAR-Tfh cell generation restores a tolerogenic hepatic immune environment and ameliorates autoimmune liver injury. These findings establish in situ Tfh cell reprogramming as a modular approach to coordinately modulate multiple immune compartments, providing a potential therapeutic framework for AIH and related autoimmune diseases.