Francesca Saffioti

Autoimmune liver diseases (AILDs) are chronic liver pathologies characterized by fibrosis and cirrhosis due to immune-mediated liver damage. In this study, we addressed the question whether mucosal-associated invariant T (MAIT) cells, innate-like T cells, are functionally altered in patients with AILD and whether MAIT cells can promote liver fibrosis through activation of hepatic stellate cells (HSCs). We analyzed the phenotype and function of MAIT cells from AILD patients and healthy controls by multicolor flow cytometry and investigated the interaction between human MAIT cells and primary human hepatic stellate cells (hHSCs). We show that MAIT cells are significantly decreased in peripheral blood and liver tissue of patients with AILD. Notably, MAIT cell frequency tended to decrease with increasing fibrosis stage. MAIT cells from AILD patients showed signs of exhaustion, such as impaired interferon-γ (IFN-γ) production and high ex vivo expression of the activation and exhaustion markers CD38, HLA-DR, and CTLA-4. Mechanistically, this exhausted state could be induced by repetitive stimulation of MAIT cells with the cytokines interleukin (IL)-12 and IL-18, leading to decreased IFN-γ and increased exhaustion marker expression. Of note, repetitive stimulation with IL-12 further resulted in expression of the profibrogenic cytokine IL-17A by otherwise exhausted MAIT cells. Accordingly, MAIT cells from both healthy controls and AILD patients were able to induce an activated, proinflammatory and profibrogenic phenotype in hHSCs in vitro that was partly mediated by IL-17. CONCLUSION: Our data provide evidence that MAIT cells in AILD patients have evolved towards an exhausted, profibrogenic phenotype and can contribute to the development of HSC-mediated liver fibrosis. These findings reveal a cellular and molecular pathway for fibrosis development in AILD that could be exploited for antifibrotic therapy. (Hepatology 2018;68:172-186).

Abstract Increasing rates of autoimmune and inflammatory disease present a burgeoning threat to human health 1 . This is compounded by the limited efficacy of available treatments 1 and high failure rates during drug development 2 , highlighting an urgent need to better understand disease mechanisms. Here we show how functional genomics could address this challenge. By investigating an intergenic haplotype on chr21q22—which has been independently linked to inflammatory bowel disease, ankylosing spondylitis, primary sclerosing cholangitis and Takayasu’s arteritis 3–6 —we identify that the causal gene, ETS2 , is a central regulator of human inflammatory macrophages and delineate the shared disease mechanism that amplifies ETS2 expression. Genes regulated by ETS2 were prominently expressed in diseased tissues and more enriched for inflammatory bowel disease GWAS hits than most previously described pathways. Overexpressing ETS2 in resting macrophages reproduced the inflammatory state observed in chr21q22-associated diseases, with upregulation of multiple drug targets, including TNF and IL-23. Using a database of cellular signatures 7 , we identified drugs that might modulate this pathway and validated the potent anti-inflammatory activity of one class of small molecules in vitro and ex vivo. Together, this illustrates the power of functional genomics, applied directly in primary human cells, to identify immune-mediated disease mechanisms and potential therapeutic opportunities.

UNLABELLED: There is a need to determine biomarkers reflecting disease activity and prognosis in primary sclerosing cholangitis (PSC). We evaluated the prognostic utility of the enhanced liver fibrosis (ELF) score in Norwegian PSC patients. Serum samples were available from 305 well-characterized large-duct PSC patients, 96 ulcerative colitis patients, and 100 healthy controls. The PSC patients constituted a derivation panel (recruited 1992-2006 [n = 167]; median age 41 years, 74% male) and a validation panel (recruited 2008-2012 [n = 138]; median age 40 years, 78% male). We used commercial kits to analyze serum levels of hyaluronic acid, tissue inhibitor of metalloproteinases-1, and propeptide of type III procollagen and calculated ELF scores by the previously published algorithm. Results were also validated by analysis of ELF tests using the ADVIA Centaur XP system and its commercially available reagents. We found that PSC patients stratified by ELF score tertiles exhibited significantly different transplant-free survival in both panels (P < 0.001), with higher scores associated with shorter survival, which was confirmed in the validation panel stratified by ELF test tertiles (P = 0.003). The ELF test distinguished between mild and severe disease defined by clinical outcome (transplantation or death) with an area under the curve of 0.81 (95% confidence interval [CI] 0.73-0.87) and optimal cutoff of 10.6 (sensitivity 70.2%, specificity 79.1%). In multivariate Cox regression analysis in both panels, ELF score (hazard ratio = 1.9, 95% CI 1.4-2.5, and 1.5, 95% CI 1.1-2.1, respectively) was associated with transplant-free survival independently of the Mayo risk score (hazard ratio = 1.3, 95% CI 1.1-1.6, and 1.6, 95% CI 1.2-2.1, respectively). The ELF test correlated with ultrasound elastography in separate assessments. CONCLUSION: The ELF score is a potent prognostic marker in PSC, independent of the Mayo risk score.