Natural killer cells are polarized toward cytotoxicity in chronic hepatitis C in an interferon-alfa-dependent manner.
OBJECTIVE
Patients with chronic hepatitis C virus (HCV) infection display great variability in disease activity and progression. Although virus-specific adaptive immune responses have been characterized extensively and found to be impaired in chronic hepatitis C, the role of innate immune responses in disease activity and progression of chronic hepatitis C is not well understood.


METHODS
We studied 42 HCV-infected patients and 12 healthy uninfected controls.


RESULTS
We found an increased frequency of natural killer (NK) cells expressing tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), NKp44, NKG2C, and CD122 in chronic hepatitis C as compared with healthy controls (P < .05 for all markers) and stronger activation of NK cells in the liver than in the blood (P < .05). This NK cell phenotype was associated with polarization of NK cell function toward CD107a expression as a marker of degranulation, but with not increased interferon (IFN)-gamma production of CD56(dim) NK cells. The polarized NK cell phenotype correlated with alanine aminotransferase levels (r(2) = 0.312, P = .03). To investigate whether in vivo exposure of NK cells to HCV-induced type I IFN was causing this NK cell phenotype, peripheral blood mononuclear cells from 10 healthy controls and 8 HCV-infected patients were stimulated in the presence of IFN-alfa, which resulted in increased NK cell expression of TRAIL and CD107a (P < .001), but not IFN-gamma.


CONCLUSIONS
Collectively, these results describe a polarized NK cell phenotype induced by chronic exposure to HCV-induced IFN-alfa. This phenotype may contribute to liver injury through TRAIL expression and cytotoxicity, whereas the lacking increase in IFN-gamma production may facilitate the inability to clear HCV.
Ahlenstiel
Golo
G
Immunology Section, National Institute for Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-1800, USA.
Titerence
Rachel H
RH
Koh
Christopher
C
Edlich
Birgit
B
Feld
Jordan J
JJ
Rotman
Yaron
Y
Ghany
Marc G
MG
Hoofnagle
Jay H
JH
Liang
T Jake
TJ
Heller
Theo
T
Rehermann
Barbara
B
D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology; D016764:Cell Polarity / Q000276:immunology; D002478:Cells, Cultured; D018450:Disease Progression; D005434:Flow Cytometry; D019698:Hepatitis C, Chronic / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D016898:Interferon-alpha / Q000276:immunology / Q000494:pharmacology*; D007371:Interferon-gamma / Q000378:metabolism; D053646:Interleukin-2 Receptor beta Subunit / Q000378:metabolism; D007694:Killer Cells, Natural / Q000166:cytology / Q000378:metabolism* / Q000821:virology*; D008099:Liver / Q000276:immunology / Q000821:virology; D055654:NK Cell Lectin-Like Receptor Subfamily C / Q000378:metabolism; D055629:Natural Cytotoxicity Triggering Receptor 2 / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism
D016898:Interferon-alpha; D053646:Interleukin-2 Receptor beta Subunit; C527059:KLRC2 protein, human; C112837:NCR2 protein, human; D055654:NK Cell Lectin-Like Receptor Subfamily C; D055629:Natural Cytotoxicity Triggering Receptor 2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D007371:Interferon-gamma