Spontaneous development of an autoimmune hepatitis - primary biliary cholangitis overlap syndrome in dnTGFβRII...

Autoimmune regulator (Aire) and TGF-β signaling play important roles in central tolerance and peripheral tolerance, respectively, by eliminating or suppressing the activity of autoreactive T cells. We previously demonstrated that dnTGFβRII mice develop a defect in peripheral tolerance and a primary biliary cholangitis (PBC)-like disease. We hypothesized that by introducing the Aire gene to this model, we would observe a more severe PBC phenotype. Interestingly, however, we demonstrated that, while dnTGFβRII Aire^-/- mice do manifest key histological and serological features of autoimmune cholangitis, they also develop mild to moderate interface hepatitis and show high levels of alanine transaminase (ALT) and antinuclear antibodies (ANA), characteristics of autoimmune hepatitis (AIH). To further understand this unique phenotype, we performed RNA sequencing (RNA-seq) and flow cytometry to explore the functional pathways and immune cell pathways in the liver of dnTGFβRII Aire^-/- mice. Our data revealed enrichments of programmed cell death pathways and predominant CD8⁺ T cell infiltrates. Depleting CD8⁺ T cells using an anti-CD8α antibody significantly alleviated hepatic inflammation and prolonged the life span of these mice. Finally, RNA-seq data indicated the clonal expansion of hepatic CD8⁺ T cells. In conclusion, these mice developed an autoreactive CD8⁺ T-cell-mediated autoimmune cholangitis with concurrent hepatitis that exhibited key histological and serological features of the AIH-PBC overlap syndrome, representing a novel model for the study of tolerance and autoimmune liver disease. © 2023 The Pathological Society of Great Britain and Ireland.