Impaired CD4⁺ T Cell Stimulation of NK Cell Anti-Fibrotic Activity May Contribute to Accelerated Liver Fibrosis Progression in HIV/HCV Patients

J Hepatol. 2013 Sep;59(3):427-33. doi: 10.1016/j.jhep.2013.04.029. Epub 2013 May 9.

Abstract

Background & aims: HIV/HCV co-infection is characterized by a faster progression to liver fibrosis compared to HCV mono-infection. Epidemiologic studies found an association between low CD4(+) T cell counts and advanced stages of liver fibrosis. However, the mechanisms underlying this association remain unclear. CD4(+) T cells critically modulate NK cell activity. Of note, NK cells have been shown to display anti-fibrotic activity via killing of activated hepatic stellate cells (HSC). Thus, we speculated that CD4(+) T cells might modulate fibrosis progression by interacting with NK cells.

Methods: NK cells from HCV(+) (n=35), HIV(+)/HCV(+) (n=28), HIV(+) (n=8) patients, and healthy controls (n=30) were used in this study. NK cells were cultured in the presence or absence of supernatants from CD3/CD28-stimulated CD4(+) cells. Then, NK cells were co-incubated with activated HSC and studied for degranulation, IFN-γ secretion, and induction of HSC apoptosis.

Results: Following incubation with CD4(+) T cell supernatants, NK cells displayed a significantly increased activity against primary HSC as compared to unstimulated NK cells. This effect was, at least in part, mediated via an IL-2 dependent upregulation of NKG2D expression. HCV/HIV co-infection was associated with an impaired IL-2 secretion of CD4(+) T cells resulting in an ineffective stimulation of anti-fibrotic NK cell function.

Conclusions: Here, we show that CD4(+) T cells are able to stimulate anti-fibrotic NK cell activity via IL-2 mediated upregulation of NKG2D. HIV-induced loss of CD4(+) T cells together with an impaired activity of CD4(+) T cells may contribute to accelerate progression of liver fibrosis observed in co-infection.

Keywords: Apoptosis; CD4(+) T cells; FACS; FBS; HCV; HIV; HIV/HCV co-infection; HSC; Hepatic stellate cells; IFN; IL; IL-2; Liver fibrosis; NK cell; NK cells; NKG2D; PBMC; SIV; SteCM; TRAIL; fetal bovine serum; fluorescence-activated cell sorting; hepatic stellate cells; hepatitis C virus; human immunodeficiency virus; interferon; interleukin; natural killer cell; peripheral blood mononuclear cells; simian immunodeficiency virus; stellate cell medium; tumour necrosis factor related apoptosis inducing ligand.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Case-Control Studies
  • Coculture Techniques
  • Coinfection / immunology*
  • Coinfection / pathology
  • Culture Media, Conditioned
  • Disease Progression
  • Female
  • HIV Infections / complications*
  • HIV Infections / immunology*
  • Hepatic Stellate Cells / immunology
  • Hepatic Stellate Cells / pathology
  • Hepatitis C, Chronic / complications*
  • Hepatitis C, Chronic / immunology*
  • Hepatitis C, Chronic / pathology
  • Humans
  • Interleukin-2 / metabolism
  • Killer Cells, Natural / immunology*
  • Liver Cirrhosis / etiology*
  • Liver Cirrhosis / immunology*
  • Liver Cirrhosis / pathology
  • Male
  • Middle Aged
  • NK Cell Lectin-Like Receptor Subfamily K / metabolism
  • T-Lymphocytes / immunology*
  • Young Adult

Substances

  • Culture Media, Conditioned
  • IL2 protein, human
  • Interleukin-2
  • KLRK1 protein, human
  • NK Cell Lectin-Like Receptor Subfamily K