title: Patients with acute-on-chronic liver failure have increased numbers of regulatory immune cells expressing the receptor tyrosine kinase MERTK.
abstract: OBJECTIVE
  Characteristics of decompensated cirrhosis and acute-on-chronic liver failure (ACLF) include susceptibility to infection, immuneparesis, and monocyte dysfunction. MER receptor tyrosine kinase (MERTK) is expressed by monocytes and macrophages and contributes to down-regulation of innate immune responses. We investigated whether MERTK expression is altered on monocytes from patients with liver failure.
  
  
  METHODS
  We analyzed blood and liver samples collected from patients admitted to the liver intensive therapy unit at King's College Hospital in London from December 2012 through July 2014. Patients had either ACLF (n = 41), acute decompensation of cirrhosis without ACLF (n = 9), cirrhosis without decompensation (n = 17), or acute liver failure (n = 23). We also analyzed samples from healthy individuals (controls, n = 29). We used flow cytometry to determine the level of innate immune function, and associated the findings with disease severity. We developed an assay to measure recruitment and migration of immune cells from the tissue parenchyma. Immunohistochemistry and confocal microscopy were used to determine levels of MERTK in bone marrow, liver, and lymph node tissues. We performed immunophenotype analyses and measured the production of tumor necrosis factor and interleukin 6 and intracellular killing of Escherichia coli by monocytes and peritoneal macrophages incubated with lipopolysaccharide, with or without an inhibitor of MERTK (UNC569).
  
  
  RESULTS
  The number of monocytes and macrophages that expressed MERTK was greatly increased in the circulation, livers, and lymph nodes of patients with ACLF, compared with patients with stable cirrhosis and controls. MERTK expression (mean fluorescence intensity) correlated with the severity of hepatic and extrahepatic disease and systemic inflammatory responses. Based on immunophenotype, migration, and functional analyses, MERTK-expressing monocytes migrate across the endothelia to localize into tissue sites and regional lymph nodes. Expression of MERTK reduced the response of cultured monocytes to lipopolysaccharide; the addition of UNC569 restored production of inflammatory cytokines in response to lipopolysaccharide.
  
  
  CONCLUSIONS
  Patients with ACLF have increased numbers of immunoregulatory monocytes and macrophages that express MERTK and suppress the innate immune response to microbes. The number of these cells correlates with disease severity and the inflammatory response. MERTK inhibitors restore production of inflammatory cytokines by immune cells from patients with ACLF, and might be developed to increase the innate immune response in these patients.
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Christine
authors.initials: C
authors.lastname: Bernsmeier
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Oltin T
authors.initials: OT
authors.lastname: Pop
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Arjuna
authors.initials: A
authors.lastname: Singanayagam
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom; Centre for Liver Research and National Institute for Health Research, Biomedical Research Unit, University of Birmingham, United Kingdom.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Triantafyllou
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Vishal C
authors.initials: VC
authors.lastname: Patel
authors.affiliation: Centre for Liver Research and National Institute for Health Research, Biomedical Research Unit, University of Birmingham, United Kingdom.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Weston
authors.affiliation: Centre for Liver Research and National Institute for Health Research, Biomedical Research Unit, University of Birmingham, United Kingdom.
authors.forename: Stuart
authors.initials: S
authors.lastname: Curbishley
authors.affiliation: Section of Hepatology, St. Mary's Hospital, Imperial College London, United Kingdom.
authors.forename: Fouzia
authors.initials: F
authors.lastname: Sadiq
authors.affiliation: Section of Hepatology, St. Mary's Hospital, Imperial College London, United Kingdom.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Vergis
authors.affiliation: Section of Hepatology, St. Mary's Hospital, Imperial College London, United Kingdom.
authors.forename: Wafa
authors.initials: W
authors.lastname: Khamri
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: William
authors.initials: W
authors.lastname: Bernal
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Georg
authors.initials: G
authors.lastname: Auzinger
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Heneghan
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Yun
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Wayel
authors.initials: W
authors.lastname: Jassem
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Heaton
authors.affiliation: Centre for Liver Research and National Institute for Health Research, Biomedical Research Unit, University of Birmingham, United Kingdom.
authors.forename: David H
authors.initials: DH
authors.lastname: Adams
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Alberto
authors.initials: A
authors.lastname: Quaglia
authors.affiliation: Section of Hepatology, St. Mary's Hospital, Imperial College London, United Kingdom.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Thursz
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom.
authors.forename: Julia
authors.initials: J
authors.lastname: Wendon
authors.affiliation: Institute of Liver Studies, King's College Hospital, King's College London, United Kingdom; Centre for Liver Research and National Institute for Health Research, Biomedical Research Unit, University of Birmingham, United Kingdom; Section of Hepatology, St. Mary's Hospital, Imperial College London, United Kingdom. Electronic address: c.antoniades@imperial.ac.uk.
authors.forename: Charalambos G
authors.initials: CG
authors.lastname: Antoniades
mesh_terms: D065290:Acute-On-Chronic Liver Failure / Q000276:immunology / Q000378:metabolism*; D000328:Adult; D000368:Aged; D058625:End Stage Liver Disease / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000276:immunology*; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000276:immunology / Q000378:metabolism*; D017114:Liver Failure, Acute / Q000276:immunology / Q000378:metabolism*; D008198:Lymph Nodes / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000378:metabolism; D000076202:c-Mer Tyrosine Kinase
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; D008070:Lipopolysaccharides; D011518:Proto-Oncogene Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D014409:Tumor Necrosis Factor-alpha; C000589254:UNC569; C097072:MERTK protein, human; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase
keywords: ALF; Bacterial Infection; Immune Regulation; SIRS