title: IFN-γ production by human natural killer cells in response to HCV-infected hepatoma cells is dependent on accessory cells.
abstract: OBJECTIVE
  Interferon-γ (IFN-γ), a cytokine produced by activated natural killer cells (NK) and T lymphocytes, is an important regulator of innate and adaptive immunity during hepatitis C virus (HCV) infection. However, the cellular sources and mechanisms of IFN-γ induction in HCV-infection are not fully understood.
  
  
  METHODS
  We cultured normal human peripheral blood mononuclear cells (PBMCs) with different populations of immune cells and JFH-1 HCV-infected HuH7.5 (JFH-1/HuH7.5) cells.
  
  
  RESULTS
  We found that PBMCs produced large amounts of IFN-γ after co-culture with JFH-1/HuH7.5 cells. Using intracellular cytokine staining, we confirmed that NK cells and NKT cells (to a lesser extent) were the major IFN-γ producers within PBMCs. Purified NK/NKT cells did not produce IFN-γ in response to JFH-1/HuH7.5 cells and depletion of accessory (HLA-DR(+)) cells prevented IFN-γ induction in PBMCs. Through selective cell depletion of dendritic cells or monocytes from PBMCs, we determined that plasmacytoid dendritic cells (pDCs) were indispensable for NK-IFN-γ induction and the presence of monocytes was needed for maximal NK-IFN-γ induction. We further revealed that NK-IFN-γ induction depended on pDC-derived IFN-α while other IFN-γ inducing cytokines, IL-12, and IL-18, played minimal roles. Close contact between JFH-1/HuH7.5 cells and NK cells was required for IFN-γ production and monocyte-derived IL-15 significantly augmented IFN-γ induction.
  
  
  CONCLUSIONS
  We discovered a novel mechanism where NK cells interact with pDCs and monocytes, efficiently producing IFN-γ in response to HCV-infected cells. This indicates that co-operation between NK cells and accessory cells is critical for IFN-γ production and regulation of immunity during HCV infection.
authors.affiliation: University of Massachusetts Medical School, Worcester, MA 10605, United States.
authors.forename: Shuye
authors.initials: S
authors.lastname: Zhang
authors.forename: Banishree
authors.initials: B
authors.lastname: Saha
authors.forename: Karen
authors.initials: K
authors.lastname: Kodys
authors.forename: Gyongyi
authors.initials: G
authors.lastname: Szabo
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology; D016174:Hepacivirus / Q000276:immunology* / Q000472:pathogenicity*; D006526:Hepatitis C / Q000276:immunology; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D007370:Interferon Type I / Q000096:biosynthesis; D007371:Interferon-gamma / Q000096:biosynthesis*; D007694:Killer Cells, Natural / Q000276:immunology*; D008114:Liver Neoplasms, Experimental / Q000276:immunology / Q000821:virology; D009000:Monocytes / Q000276:immunology
chemical_list: D007370:Interferon Type I; D007371:Interferon-gamma
keywords: DC; ELISA; HCV; IFN; IFN-α; ISG; Monocyte; NK; NKT; PAMPs; PBMC; PCR; TLR; dendritic cell; enzyme-linked immunosorbent assay; hepatitis C virus; interferon; interferon stimulated gene; mDC; myeloid dendritic cell; natural killer; natural killer T; pDC; pathogen associated molecular patterns; peripheral blood mononuclear cell; plasmacytoid dendritic cell; polymerase chain reaction; toll-like receptor