Research ArticleAbundant numbers of regulatory T cells localize to the liver of chronic hepatitis C infected patients and limit the extent of fibrosis☆
Introduction
Following infection with the hepatitis C virus (HCV), immunity fails to successfully eradicate the virus in the majority of individuals [1], [2], [3]. As a consequence, an estimated 120–170 million individuals are currently chronically infected worldwide [4]. Due to ongoing immunopathology, these patients are at increased risk of developing cirrhosis, and subsequent liver decompensation and/or hepatocellular carcinoma. However, without accelerating factors, such as co-infections and co-morbidities, disease progression is slow and it typically takes over a decade before serious health problems occur.
Patients chronically infected with HCV generally show a weak peripheral blood T cell response against HCV, which is insufficient to eradicate the virus [5], [6], [7], [8]. It has been convincingly shown that peripheral blood regulatory T cells (Treg) from HCV-infected patients suppress both HCV-specific T cell proliferation and IFN-gamma production [9], [10], [11], [12], [13]. Thus, these cells may hamper the immune response against HCV during chronic infection, although other mechanisms have been proposed as well (reviewed in [1], [2], [3], [14], [15]). The role of intrahepatic Treg may be especially important to understand the chronic nature of the disease, since HCV predominantly infects hepatocytes. Although Treg have been detected before in livers of chronic HCV patients by performing immunohistochemical stainings [16], [17], [18], [19], data on the phenotype of Treg at the primary site of infection is still lacking and their role in immunopathology remains unclear.
Regulation of the magnitude of the effector response may result in failure to eliminate the pathogen, and thus in the case of HCV infection, may lead to the establishment of a persistent infection. It has been demonstrated in many experimental infections that Treg act by dampening excessive inflammatory responses, and consequently help to limit tissue damage associated with the inflammatory reaction (reviewed in [20]). In chronic HCV infections, a higher suppressive capacity of peripheral blood Treg was observed in patients showing a relatively low level of hepatocyte death, as reflected by alanine transaminase (ALT) levels [10]. However, Treg have not yet been implicated in controlling the outcome of immunopathology, i.e. liver fibrosis.
In this study, we characterized intrahepatic Treg in chronic HCV patients and their impact on disease progression. An extensive lymphocyte infiltration containing abundant numbers of CD4+FoxP3+ Treg was present in HCV-infected livers, while absent from the healthy liver. Moreover, these intrahepatic CD4+FoxP3+ Treg of patients at diverse stages of liver disease showed a fully differentiated and highly activated phenotype, and were more numerous in HCV-infected livers with mild fibrosis, suggesting an important role for intrahepatic Treg during chronic HCV infection.
Section snippets
Patients and healthy controls
Intrahepatic cells were obtained from 43 chronic HCV-infected patients (Table 1 for clinical characteristics) by fine needle aspiration biopsy (FNAB; n = 28) or percutaneous core needle biopsy (n = 15). Paired venous blood samples were collected from all patients. All patients had detectable HCV RNA levels in serum. Patients co-infected with human immunodeficiency virus or hepatitis B virus were excluded from the study. Diagnostic core biopsy specimens from all 43 patients, obtained within 3 months
Extensive inflammation of the liver is observed in patients with chronic HCV infections
To determine the degree and nature of inflammation in the liver of patients with chronic HCV infections, flow cytometric analyses were performed. As expected, vast numbers of CD45-expressing inflammatory cells were detected in the liver of patients with chronic HCV infections (Fig. 1). The degree of inflammation, defined as the fraction of CD45-positive leukocytes out of the total number of liver cells [22], was on average 15% for HCV-infected livers whereas in control livers, only an average
Discussion
In patients chronically infected with HCV, the virus replicates at high levels within the liver for decades. In order to maintain this viral persistence, regulatory mechanisms are in place that balance an ineffective protective HCV-specific immunity and mild immune-mediated liver damage. The present study shows that high numbers of CD4+FoxP3+ Treg accumulate in the HCV-infected liver. These CD4+FoxP3+ Treg display a highly activated and differentiated effector/memory phenotype and may be
Acknowledgements
The authors who have taken part in this study state that they do not have anything to declare regarding funding from industry or conflict of interest with respect to this manuscript. This work was supported by ZonMW (VIDI-Grant 917.56.329) for H.J. The authors thank Janneke Samsom and Jaap Kwekkeboom for helpful discussions and Duygu Turgut for excellent technical assistance.
References (37)
- et al.
Global epidemiology of hepatitis C virus infection
Lancet Infect Dis
(2005) - et al.
Differential CD4(+) and CD8(+) T-cell responsiveness in hepatitis C virus infection
Hepatology
(2001) - et al.
Detection of functionally altered hepatitis C virus-specific CD4 T cells in acute and chronic hepatitis C
Hepatology
(2003) - et al.
Foxp3+CD4+CD25+ T cells control virus-specific memory T cells in chimpanzees that recovered from hepatitis C
Blood
(2006) - et al.
Immune responses during acute and chronic infection with hepatitis C virus
Clin Immunol
(2008) - et al.
Quantification and localisation of FOXP3+ T lymphocytes and relation to hepatic inflammation during chronic HCV infection
J Hepatol
(2007) - et al.
Intrahepatic regulatory T cells are phenotypically distinct from their peripheral counterparts in chronic HBV patients
Clin Immunol
(2008) - et al.
Differential expression of CCR7 defines two distinct subsets of human memory CD4+CD25+ Tregs
Clin Immunol
(2008) - et al.
Regulatory T cell lineage specification by the forkhead transcription factor foxp3
Immunity
(2005) - et al.
Expression of interleukin-10 by in vitro and in vivo activated hepatic stellate cells
J Biol Chem
(1998)
TGF-beta: a master of all T cell trades
Cell
Flying under the radar: the immunobiology of hepatitis C
Annu Rev Immunol
Immunology of hepatitis B virus and hepatitis C virus infection
Nat Rev Immunol
Cell-mediated immunity and the outcome of hepatitis C virus infection
Annu Rev Microbiol
Preferential loss of IL-2-secreting CD4+ T helper cells in chronic HCV infection
Hepatology
Cellular immune responses persist and humoral responses decrease two decades after recovery from a single-source outbreak of hepatitis C
Nat Med
T cells with a CD4+CD25+ regulatory phenotype suppress in vitro proliferation of virus-specific CD8+ T cells during chronic hepatitis C virus infection
J Virol
Increased hepatitis C virus (HCV)-specific CD4+CD25+ regulatory T lymphocytes and reduced HCV-specific CD4+ T cell response in HCV-infected patients with normal versus abnormal alanine aminotransferase levels
Clin Exp Immunol
Cited by (131)
2,3,5,4′- tetrahydroxystilbene-2-O-β-D- glucopyranoside (TSG)-Driven immune response in the hepatotoxicity of Polygonum multiflorum
2024, Journal of EthnopharmacologyKnockout of Sema4D alleviates liver fibrosis by suppressing AOX1 expression
2023, Pharmacological ResearchStructure, Function and Responses to Injury
2023, MacSween's Pathology of the Liver, Eighth EditionRegulatory T cells (Tregs) in liver fibrosis
2023, Cell Death Discovery
- ☆
This work was supported by ZonMW (VIDI-Grant 917.56.329) for H.J.