title: Regulatory CD4+ T cells modulate the interaction between NK cells and hepatic stellate cells by acting on either cell type.
abstract: OBJECTIVE
  NK cells regulate liver fibrosis by killing activated hepatic stellate cells (HSCs) and are controlled themselves by immune cells and/or soluble factors. Here, we analysed if CD4(+) regulatory T cells (Tregs) modify the interaction between NK cells and HSCs.
  
  
  METHODS
  The modification of NK cell activity against HSCs was studied in CD56(high)CD16(-) NK cells, using a flow cytometric CD107a degranulation assay and co-cultures with Tregs from healthy donors and patients with hepatitis C, respectively. We studied the underlying mechanisms in detail, applying Treg supernatants, Treg pretreated HSCs, and recombinant IL-8, TGF-ß1, and IL-10 as well as blocking experiments with neutralizing antibodies and analysed Treg-associated changes in the expression of NK cell receptor ligands on HSCs.
  
  
  RESULTS
  Tregs suppressed NK cell activation during HSC co-culture in a cell-contact-dependent manner involving the cytotoxic T-lymphocyte antigen 4 (CTLA-4). NK cell degranulation was further reduced, when HSCs had been pretreated with Tregs (p=0.043), Treg supernatants (p=0.001) or recombinant IL-8 (R=0.630, p=0.001) and TGF-ß1 (R=0.608, p=0.002), respectively. This additional inhibitory effect corresponded to the IL-8/TGF-ß1-mediated downregulation of MIC-A/B and HLA class-I on HSCs. Tregs from hepatitis C likewise inhibited NK cell activity, which was reversed significantly in specific blocking experiments.
  
  
  CONCLUSIONS
  Our data indicate that Tregs interfere with NK cell regulation of fibrogenesis via both direct cell-contact-dependent inhibition of NK cells and release of soluble factors, downregulating activating NK cell receptor ligands on HSCs. Our data may be particularly relevant for the intrahepatic accumulation of Tregs in chronic hepatitis C because downregulated NK cell activity against HSCs may blunt their control of fibrogenesis.
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany. Electronic address: bettina.langhans@ukb.uni-bonn.de.
authors.forename: Bettina
authors.initials: B
authors.lastname: Langhans
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Abdel Wahed
authors.initials: AW
authors.lastname: Alwan
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Krämer
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Glässner
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Lutz
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Christian P
authors.initials: CP
authors.lastname: Strassburg
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Jacob
authors.initials: J
authors.lastname: Nattermann
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany; German Centre for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Spengler
mesh_terms: D000328:Adult; D000368:Aged; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology; D002478:Cells, Cultured; D018920:Coculture Techniques; D005260:Female; D055166:Hepatic Stellate Cells / Q000276:immunology* / Q000473:pathology; D019698:Hepatitis C, Chronic / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007111:Immunity, Cellular; D007694:Killer Cells, Natural / Q000276:immunology*; D008103:Liver Cirrhosis / Q000276:immunology* / Q000473:pathology; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
keywords: Fibrogenesis; Hepatic stellate cells; Hepatitis C virus; NK cells; Regulatory CD4(+) T lymphocytes