Double-negative T cells in combination with ursodeoxycholic acid ameliorates immune-mediated cholangitis in mice

BACKGROUND: Primary biliary cholangitis (PBC) is a liver-specific autoimmune disease. Treatment of PBC with ursodeoxycholic acid (UDCA) is not sufficient to prevent disease progression. Our previous study revealed that the number of hepatic double-negative T cells (DNT), which are unique regulatory T cells, was reduced in PBC patients. However, whether replenishment of DNT can prevent the progression of PBC remains unclear. METHODS: DnTGFβRII (Tg) mice and 2OA-BSA-immunized mice received DNT alone or in combination with oral UDCA. After 6-12 weeks of treatment, these mice were assessed for serological changes, liver pathological manifestations and intrahepatic immune responses. RESULTS: Adoptive transfer of DNT alone significantly decreased serum levels of alanine transaminase (ALT), aspartate transaminase (AST), antimitochondrial antibody M2 (AMA-M2) and immunoglobulin M (IgM) in both Tg and 2OA-BSA-immunized PBC mouse models. In addition, DNT exhibited a strong killing effect on liver T cells and strong inhibition of their proliferation, but did not significantly improve the histology of PBC liver. However, combination therapy with DNT and oral UDCA predominantly ameliorated liver inflammation and significantly inhibited hepatic T and B cells. In vitro further study revealed that UDCA up-regulated the proliferation of DNT, increased the expression of the functional molecule perforin, and reduced the expression of NKG2A and endothelial cell protein C receptor (EPCR) through the farnesoid X receptor (FXR)/JNK signaling pathway in both mice and human DNT. CONCLUSIONS: A single transfer of DNT ameliorated PBC in mice, while combination therapy of DNT with oral UDCA displayed a better efficacy, with stronger inhibition of hepatic T and B cells. This study highlights the potential application of DNT-based combination therapy for PBC, especially for UDCA non-responders.