title: Biology of the immunomodulatory molecule HLA-G in human liver diseases.
abstract: The non-classical human leukocyte antigen-G (HLA-G), plays an important role in inducing tolerance, through its immunosuppressive effects on all types of immune cells. Immune tolerance is a key issue in the liver, both in liver homeostasis and in the response to liver injury or cancer. It would therefore appear likely that HLA-G plays an important role in liver diseases. Indeed, this molecule was recently shown to be produced by mast cells in the livers of patients infected with hepatitis C virus (HCV). Furthermore, the number of HLA-G-positive mast cells was significantly associated with fibrosis progression. The generation of immune tolerance is a role common to both HLA-G, as a molecule, and the liver, as an organ. This review provides a summary of the evidence implicating HLA-G in liver diseases. In the normal liver, HLA-G transcripts can be detected, but there is no HLA-G protein. However, HLA-G protein is detectable in the liver tissues and/or plasma of patients suffering from hepatocellular carcinoma, hepatitis B or C, or visceral leishmaniasis and in liver transplant recipients. The cells responsible for producing HLA-G differ between diseases. HLA-G expression is probably induced by microenvironmental factors, such as cytokines. The expression of HLA-G receptors, such as ILT2, ILT4, and KIRD2L4, on liver cells has yet to be investigated, but these receptors have been detected on all types of immune cells, and such cells are present in liver. The tolerogenic properties of HLA-G explain its deleterious effects in cancers and its beneficial effects in transplantation. Given the key role of HLA-G in immune tolerance, new therapeutic agents targeting HLA-G could be tested for the treatment of these diseases in the future.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (Inserm), U.1085, Institut de Recherche Santé Environnement & Travail (IRSET), F-35043 Rennes, France; Université de Rennes 1, F-35043 Rennes, France; Fédération de Recherche BioSit de Rennes UMS 3480, F-35043 Rennes, France; Department of Biology, University Hospital Pontchaillou, CHU Pontchaillou, Rennes, France. Electronic address: laurence.amiot@univ-rennes1.fr.
authors.forename: Laurence
authors.initials: L
authors.lastname: Amiot
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (Inserm), U.1085, Institut de Recherche Santé Environnement & Travail (IRSET), F-35043 Rennes, France; Université de Rennes 1, F-35043 Rennes, France; Fédération de Recherche BioSit de Rennes UMS 3480, F-35043 Rennes, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vu
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (Inserm), U.1085, Institut de Recherche Santé Environnement & Travail (IRSET), F-35043 Rennes, France; Université de Rennes 1, F-35043 Rennes, France; Fédération de Recherche BioSit de Rennes UMS 3480, F-35043 Rennes, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Samson
mesh_terms: D001327:Autoimmune Diseases / Q000276:immunology; D015870:Gene Expression; D006087:Graft vs Host Reaction / Q000276:immunology; D059951:HLA-G Antigens / Q000235:genetics / Q000378:metabolism*; D006525:Hepatitis, Viral, Human / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance; D008099:Liver / Q000276:immunology; D008107:Liver Diseases / Q000276:immunology*; D008109:Liver Diseases, Parasitic / Q000276:immunology; D008113:Liver Neoplasms / Q000276:immunology; D016031:Liver Transplantation
chemical_list: D059951:HLA-G Antigens
keywords: HLA-G; Hepatocellular carcinoma; Liver failure; Transplantation; Viral hepatitis