Hepatocyte-Specific Deficiency of Endoplasmic Reticulum-Associated Degradation Induces Coordinated Innate-Adaptive Immune Responses.

Hepatic inflammation is a defining feature of Metabolic Dysfunction-Associated Steatohepatitis (MASH), yet the specific contributions of individual immune cell populations and their reciprocal interactions remain incompletely understood. In this study, we combined flow cytometry with single-cell transcriptomic profiling to characterize the hepatic immune landscape in a novel model of spontaneous MASH caused by hepatocyte-specific deficiency of endoplasmic reticulum-associated degradation (ERAD). Hepatic ERAD deficiency led to the expansion of multiple immune cell populations in the liver, including CD8+ T cells, macrophages, monocytes, and dendritic cells, accompanied by extensive functional reprogramming of both innate and adaptive immune compartments. Myeloid cells exhibited enhanced phagocytic activity and increased antigen processing and presentation, whereas CD8+ T cells displayed elevated proliferation capacity, DNA repair activity and cytotoxicity. Notably, two functionally distinct triggering receptor expressed on myeloid cells 2 (TREM2)-expressing macrophage subsets emerged during the progression of ERAD deficiency-induced MASH. Depletion of CD8+ T cells increased monocyte infiltration and aggravated liver injury, suggesting that CD8+ T cells exert a previously unrecognized protective role by restraining monocyte recruitment. Collectively, these findings reveal highly coordinated interactions between innate and adaptive cells during MASH progression and identify CD8+ T cells as potential regulators of monocyte infiltration and hepatic injury.