ABSTRACT
Nonalcoholic steatohepatitis (NASH) is a manifestation of systemic metabolic disease related to obesity, and causes liver disease and cancer1,2. The accumulation of metabolites leads to cell stress and inflammation in the liver3, but mechanistic understandings of liver damage in NASH are incomplete. Here, using a preclinical mouse model that displays key features of human NASH (hereafter, NASH mice), we found an indispensable role for T cells in liver immunopathology. We detected the hepatic accumulation of CD8 T cells with phenotypes that combined tissue residency (CXCR6) with effector (granzyme) and exhaustion (PD1) characteristics. Liver CXCR6+ CD8 T cells were characterized by low activity of the FOXO1 transcription factor, and were abundant in NASH mice and in patients with NASH. Mechanistically, IL-15 induced FOXO1 downregulation and CXCR6 upregulation, which together rendered liver-resident CXCR6+ CD8 T cells susceptible to metabolic stimuli (including acetate and extracellular ATP) and collectively triggered auto-aggression. CXCR6+ CD8 T cells from the livers of NASH mice or of patients with NASH had similar transcriptional signatures, and showed auto-aggressive killing of cells in an MHC-class-I-independent fashion after signalling through P2X7 purinergic receptors. This killing by auto-aggressive CD8 T cells fundamentally differed from that by antigen-specific cells, which mechanistically distinguishes auto-aggressive and protective T cell immunity.
Subject(s)
CD8-Positive T-Lymphocytes/immunology , Liver/immunology , Liver/pathology , Non-alcoholic Fatty Liver Disease/immunology , Non-alcoholic Fatty Liver Disease/pathology , Receptors, CXCR6/immunology , Acetates/pharmacology , Animals , CD8-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/pathology , Cell Death/drug effects , Cell Death/immunology , Diet, High-Fat/adverse effects , Disease Models, Animal , Humans , Interleukin-15/immunology , Interleukin-15/pharmacology , Liver/drug effects , Male , Mice , Mice, Inbred C57BLABSTRACT
Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are rare, autoimmune mediated cholestatic liver diseases. Other auto-immune diseases are often associated with PBC and PSC, and inflammatory bowel disease is present in the majority of PSC patients. In the course of disease, chronic inflammation in the liver leads to fibrotic restructuring and ultimately cirrhosis. The diagnosis of PBC is confirmed serologically and PSC is diagnosed via cholangiography, whereas MRCP is preferred over ERCP. For PBC, the first line therapy is ursodeoxycholic acid (UDCA). Prognosis is strongly dependent on the response to UDCA. The only approved second line therapy is obeticholic acid (OCA). Alternatively, Budesonide or Fibrates are often used off-label. In the management of PSC, prevention and adequate treatment of bacterial cholangitis play a major role. For both PBC and PSC novel treatments are currently being tested in clinical trials. Disease management should address compromising symptoms like pruritus and sicca as well as complications due to maldigestion and concomitant autoimmune diseases. The only curative treatment available is liver transplantation and should be considered at a MELD score of 15.