Autophagy Sustained the Activation and Survival of Liver-infiltrating CD8+ T Cells in Primary Biliary Cholangitis.

BACKGROUND

Primary biliary cholangitis (PBC) fundamentally manifests as an immune-mediated disorder where T cell-driven autoreactivity persists as the principal pathogenic mechanism. Despite this understanding, immunosuppressive therapies have failed to halt PBC. This underscores the imperative to identify novel mechanisms for immunoregulation in PBC treatment. Here, we investigated the activity and role of autophagy in liver-infiltrating T lymphocytes of PBC.

METHODS

Liver tissues from PBC patients and a well-established PBC mouse model (dnTGFβRII, Tg) were analyzed by immunohistochemistry and immunofluorescence. Hepatic and splenic mononuclear cells and CD8+ T cells were isolated from Tg and wild-type mice. LC3BII, p62, and phospho-mTOR was detected by western blotting. Autophagic activity was assessed using CytoID staining and LC3BII turnover assay. Mitochondrial reactive oxygen species (mROS), T cell activation (IFN-γ, Granzyme B), and cell apoptosis were evaluated using flow cytometry.

RESULTS

Our findings revealed the elevated expression of autophagic marker LC3B in hepatic-infiltrating T lymphocytes, particularly CD8+ T lymphocytes, from PBC patients and PBC mice. We observed a significant increase of autophagic flux in liver-infiltrating T lymphocytes, suggesting the functional activation of autophagy. Furthermore, we found that autophagy activation exhibits an inverse correlation with mROS generation. The mTOR signaling disruption may contribute to autophagy upregulation in liver-infiltrating T lymphocytes of PBC. Pharmacological inhibition of T lymphocyte autophagy yielded three principal outcomes: substantial attenuation of pro-inflammatory cytokine production, decreased CD8+ effector differentiation, and concomitant induction of mROS-mediated apoptosis.

CONCLUSION

Our study indicates autophagy is a critical survival mechanism for intrahepatic T lymphocytes such as CD8+ T cells, functioning through mROS quenching to maintain cellular viability and sustains liver inflammation. This evidence suggests that modulation of T lymphocyte autophagic processes within the hepatic microenvironment may disrupt immune activation, potentially decelerating PBC progression.