The bacteroidal metabolite O-LysoPE facilitates hepatocyte-mediated immunosuppression in autoimmune hepatitis.

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease typically managed with broad-spectrum immunosuppressants that carry significant systemic side effects and often provide incomplete efficacy. While gut-microbiota-derived metabolites are known to influence AIH progression, the specific microbial drivers that maintain hepatic immune homeostasis remain poorly defined. Here, we show that Bacteroides acidifaciens (BA) and its metabolite 1-oleoyl-sn-glycero-3-phosphoethanolamine (O-LysoPE) are enriched in self-healing mouse models of hepatitis but markedly depleted in AIH patients. We demonstrate that O-LysoPE induces a 'hepatocyte-driven active immunosuppression' by targeting the Qa-1b (HLA-E): NKG2A immune checkpoint. Mechanistically, O-LysoPE selectively redirects the transcription factor Creb1 to the H2T23 promoter under inflammatory conditions, thereby upregulating hepatocytic Qa-1b expression. This elevation of Qa-1b engages the inhibitory receptor NKG2A on T cells, suppressing their overactivation and restoring a quiescent phenotype. Genetic disruption of H2T23 abrogates the hepatoprotective effects of O-LysoPE, confirming the central role of this metabolic-immune axis. Our findings reveal that the BA-O-LysoPE axis mobilizes the liver's intrinsic self-rescue mechanisms to restore immune quiescence. This study establishes a robust biological framework for liver-specific, targeted immunotherapy in AIH, offering a precision alternative to current systemic immunosuppression.