Fine characterization of intrahepatic NK cells expressing natural killer receptors in chronic hepatitis B and C☆
Introduction
Hepatitis C virus (HCV) and hepatitis B virus (HBV) are preferentially hepatotropic, not directly cytopathic, capable of provoking acute and chronic necroinflammatory liver injury and are the most common causes of liver disease worldwide [1].
The various strategies that many viruses have evolved to evade natural killer (NK) cell effector functions illustrate the central role for these cells in early host defense against viral infections [2], [3]. It is known that both HCV and HBV impair human and murine NK cell activity [4], [5]. HCV may inhibit the activation of Interferon Regulatory Factor (IRF) [6] and can interfere with PKR kinase function [7] which can activate NK cells. In the case of HBV, both IRF and PKR appear to mediate signals that modulate viral replication in IRF(−/−) or PKR(−/−) transgenic mice [8]. In contrast to other viruses, HCV and HBV induce sustained HLA class I expression on infected cells [9], [10]. The inhibitory effect of NK cells on HCV replication in cultured human hepatocytes [11] suggests that NK cells might be able to contribute to the control of these infections. In the early phase of HBV infection, the host’s response to HBV mediates the activation of NK cells which produce IFN-α and are able to lyse infected cells by TRAIL-mediated death of hepatocytes [12].
Despite multiple studies on the functional potential of NK cells in persistent HCV and HBV infections [13], [14], [15], evidence of a role for NK cell defects in these chronic infections remains open to debate. It is established that NK cell frequencies in HCV-infected patients are lower than those observed in the uninfected population [14], [15], [16]. According to the surface expression level of CD56, NK cells can be divided into two subsets with important functional distinctions. The vast majority of NK cells displays a moderate level of CD56 (CD56dim) with a marked cytotoxicity potential, while, a small proportion harbors a high CD56 expression level (CD56bright) having a greater capacity to secrete cytokines [17], [18]. Recently, it was reported that the frequency of peripheral blood cytolytic CD56dim NK cells is decreased in HCV-infected patients [15]. Less is known about expression of HLA class I specific NK receptors (NKRs). NKRs are subdivided into two major families. The first family is composed of killer immunoglobulin-like receptors (KIR), such as CD158 molecules and LIR1/ILT2 (leukocyte Ig-like receptor 1/Ig-like transcript 2) which recognize classical HLA-A, -B and -C class I molecules. The second family includes C type lectin-like molecules, such as, NKG2A that associate with CD94 to form inhibitory heterodimer that recognize non-classical HLA-E molecules.
Here, we have performed flow cytometry analyses and detailed histological studies on liver biopsies to quantify and localize the CD56+ cells in the different histological areas. Furthermore, we investigated the perforin contents of different NK cells subset as markers of their cytotoxicity. Then, we searched for relationship between NK cells subset distribution and the clinical parameters.
Section snippets
Patients
Chronic hepatitis C (n = 28) and B patients (n = 19) seen in the Grenoble University Hospital between 2005 and 2007, were included in this study. Their main characteristics were analyzed as previously described [19] and are summarised in Table 1. For immunohistochemical studies, HCV (n = 6) and HBV (n = 6) patients were classed as have low necroinflammatory grading (Metavir-A1, 3 patients) and high necroinflammatory grading (Metavir-A3, 3 patients) by the French Metavir Scoring System. Blood samples
Decreased frequency of blood and intrahepatic NK cells in HCV patients
The flow cytometric gating strategy used to identify the different subsets of NK cells is depicted in Fig. 1. Phenotypic analysis of PBMCs from HCV patients demonstrated that the proportion of CD3−CD56+ NK cells relative to lymphocyte populations was significantly decreased as compared to healthy donors (8.6% vs 13.3%, p < 0.05) (Fig. 2A). Examination of the CD3−CD56dim and CD3−CD56bright cells distribution revealed that the frequency of CD3−CD56bright cells was significantly increased (10.0% vs
Discussion
Our data confirm a significant reduction in NK cell frequency and a quantitative imbalance of the CD56bright and CD56dim subsets within the total NK cell population in HCV- and HBV-infected patients [14], [16]. In HCV infections, under proinflammatory conditions, it has also been reported that CD3−CD56dim NK cells are more susceptible to apoptosis compared to CD3−CD56bright NK cells, under inflammatory conditions and that this can contribute to altered maintenance of CD3−CD56dim NK cells in
Acknowledgements
We are grateful to the patients who enrolled in this study for their cooperation. This work was supported by grants from INSERM, from the Agence Nationale pour la Recherche sur le Sida (ANRS) and from Pole de compétitivité LyonBiopole. P.B. was supported by ANRS; M.R. from Higher Education Commission of Pakistan and X.C. by Région-Rhône Alpes “Cluster 10”. The authors thank Dr. Mary Callanan for reading this manuscript.
References (27)
- et al.
Human natural killer cells: a unique innate immunoregulatory role for the CD56(bright) subset
Blood
(2001) - et al.
Phenotypic and functional characterization of intrahepatic T lymphocytes during chronic hepatitis C
Hepatology
(2003) - et al.
T lymphocytes infiltrating the liver during chronic hepatitis C infection express a broad range of T-cell receptor beta chain diversity
J Hepatol
(2003) - et al.
Expression of inhibitory receptors in natural killer (-)CD56(+) cells and CD3(+)CD56(+) cells in the peripheral blood lymphocytes and tumor infiltrating lymphocytes in patients with primary hepatocellular carcinoma
Clin Immunol
(2001) - et al.
Immunobiology and pathogenesis of viral hepatitis
Annu Rev Pathol
(2006) NK cell recognition
Annu Rev Immunol
(2005)- et al.
Viral evasion of natural killer cells
Nat Immunol
(2002) - et al.
Inhibition of natural killer cells through engagement of CD81 by the major hepatitis C virus envelope protein
J Exp Med
(2002) - et al.
Binding of the hepatitis C virus envelope protein E2 to CD81 inhibits natural killer cell functions
J Exp Med
(2002) - et al.
Regulation of interferon regulatory factor-3 by the hepatitis C virus serine protease
Science
(2003)
Inhibition of the interferon-inducible protein kinase PKR by HCV E2 protein
Science
Interferon-regulated pathways that control hepatitis B virus replication in transgenic mice
J Virol
Upregulation of major histocompatibility complex class I on liver cells by hepatitis C virus core protein via p53 and TAP1 impairs natural killer cell cytotoxicity
J Virol
Cited by (131)
Innate immunity related pathogen recognition receptors and chronic hepatitis B infection
2017, Molecular ImmunologyThe Role of Inflammation in Cholestatic Liver Injury
2023, Journal of Inflammation ResearchProspects for NK-based immunotherapy of chronic HBV infection
2022, Frontiers in Immunology
- ☆
The authors who have taken part in this study declared that they do not have anything to disclose regarding funding from industry or conflict of interest with respect to this manuscript.
- #
These authors contributed equally to this work.