Fecal microbiota transplantation regulates TFH/TFR cell imbalance via TLR/MyD88 pathway in experimental autoimmune hepatitis.

Objective: Autoimmune hepatitis (AIH) is a chronic immune-mediated inflammatory liver disease. Intestinal flora disturbance in AIH is closely related to TFH/TFR cell imbalances. As a new method of microbial therapy, the role of fecal microbiota transplantation (FMT) in AIH remains elusive. Here, we attempted to verify the functional role and molecular mechanism of FMT in AIH. Methods: An experimental autoimmune hepatitis (EAH) mouse model was established to mimic the characteristics of AIH. H&E staining was used to detect histological features in mouse liver tissues. Serological tests were employed to identify several liver function biomarkers. Flow cytometry was utilized to examine the status of TFH/TFR cell subsets. Western blotting was used to evaluate TLR pathway-associated protein abundance. RT‒qPCR was applied to evaluate Treg cell markers and inflammation marker levels in mouse liver tissues. Results: There was significant liver inflammation and dysregulated TFR/TFH cells with elevated levels of liver inflammation-associated biomarkers in EAH mice. Interestingly, transferring therapeutic FMT into EAH mice dramatically reduced liver injury and improved the imbalance between splenic TFR and TFH cells. FMT treatment also reduced elevated contents of serum alanine transaminase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBIL) in EAH mice. Furthermore, therapeutic FMT reversed the increased levels of IL-21 while promoting IL-10 and TGF-β cytokines. Mechanistically, FMT regulated TFH cell response in EAH mice in a TLR4/11/MyD88 pathway-dependent manner. Conclusion: Our findings demonstrated that liver injury and dysregulation between TFR and TFH cells in EAH might be reversed by therapeutic FMT via the TLR4/11-MyD88 signaling pathway.