Characterization and role of intra-hepatic regulatory T cells in chronic hepatitis C pathogenesis.

BACKGROUND & AIMS: In chronic hepatitis C (CHC), HCV-specific T-cell responses are often dysfunctionnal. In vitro data point out that regulatory T cells (Treg) are able to suppress HCV-specific lymphocyte proliferation and cytokine secretion but their implication in this pathology is still debated. METHODS: Three complementary approaches were performed to investigate phenotype, frequency or localization of intra-hepatic Treg in treatment naïve CHC patients. Double immunohistochemical analysis was performed in 20 formalin-fixed biopsies with CD8/FoxP3 and CD4/FoxP3 antibodies. Cellular markers and cytokines were investigated by quantitative RT-PCR in 27 additional frozen biopsies. Eight other fresh liver biopsies were selected for complementary analysis of immunophenotyping and frequency of intra-hepatic Treg. RESULTS: Immunohistochemical analyses showed the presence of intra-hepatic CD4(+)FoxP3(+)T cells while CD8(+)FoxP3(+)T cells were very scarce. CD4(+)FoxP3(+)T cells were located in necro-inflammatory areas in contact with CD8(+)T cells, suggesting that Treg-mediated inhibition of CD8(+)T cell proliferation may occur by cell-cell contact. RT-PCR analyses showed strong correlations between CD8, FoxP3, and IL-10 with emergence of four distinct gene clusters, CD8-FoxP3, CD8-IL-10, TGF-beta-IL-10, and TNF-alpha-TGF-beta. No correlation was found between serum viral load and any immune markers. Interestingly, the FoxP3(+)/CD8(+) cells ratio significantly decreased in severe fibrosis (F>3) due to the dramatic decline of FoxP3 cells. CONCLUSIONS: This study provides new insights into the histological localization of Treg within HCV-infected liver, with a special accumulation of CD4(+)FoxP3(+)Treg cells in necro-inflammatory areas, in contact with CD8(+)T cells. Our results suggest a link between Treg, CD8, and IL-10 which altogether could balance immune responses against the virus to avoid immunopathogenesis.

Fine characterization of intrahepatic NK cells expressing natural killer receptors in chronic hepatitis B and C.

BACKGROUND/AIMS: The fate of intrahepatic NK cell subsets in the course of HCV and HBV infections is not clearly understood. METHODS: Blood and intrahepatic CD56(+) NK cell subsets (expressing NKG2A, CD158a,h or CD158b,j receptors) from HCV or HBV patients were quantified by flow cytometry and localized by immunohistochemistry in liver biopsies. RESULTS: A significant reduction in NK cell frequency and a quantitative imbalance between CD56(bright) and CD56(dim) subsets were observed in chronic HCV patients as compared to HBV patients, underlining that the inflammatory environment is not the only cause of these phenomena. The proportions of intrahepatic NK cells expressing either NKG2A, and/or CD158a,h, CD158b,j differed significantly between HCV and HBV patients. A higher frequency of perforin among intrahepatic CD56(+)CD3(-) cells was observed in HCV compared to HBV patients. Double immunohistochemical staining showed that CD56(+)CD3(-) cells were localized within necrotic areas. Immune monitoring of circulating CD56 subsets revealed that CD3(-)CD56(bright)NKG2A(+) and CD3(-)CD56(dim)NKG2A(+) cells were positively correlated with the necroinflammatory score and inversely correlated with viral load, respectively, in HCV patients. CONCLUSIONS: HCV and HBV affect NK cell subsets according to the status of the diseases, especially CD3(-)CD56(dim)NKG2A(+) and CD3(-)CD56(bright)NKG2A(+) cells, may be of interest for disease monitoring.

Control of experimental autoimmune encephalomyelitis by CD4+ suppressor T cells: peripheral versus in situ immunoregulation.

The pathogenesis of experimental autoimmune encephalomyelitis (EAE) can be efficiently kept under control by specialized subsets of CD4+ T lymphocytes able to negatively regulate the function of T cells with encephalitogenic potential. A number of observations support a role for such suppressor T cells in controlling early phases of disease development at the level of peripheral lymphoid organs but there is also evidence suggesting immunoregulation within the central nervous system (CNS) microenvironment itself. This review evaluates the sites of regulation based on available data from distinct experimental models. We then discuss these aspects with reference to suppressor CD4+ T cells induced through the epicutaneous application of pure CNS antigens that confer long term protection against EAE. Finally, we give an overview of genes recently discovered to be important in regulation of the immune system that may also prove to be key players in the modulation of EAE and MS.

Features and distribution of CD8 T cells with human leukocyte antigen class I-specific receptor expression in chronic hepatitis C.

UNLABELLED: CD8(+) T cells represent a sizable component of the liver inflammatory infiltrate in chronic hepatitis C and are thought to contribute to immune-mediated tissue injury. Because chronic stimulation may promote the expression by CD8(+) T cells of distinct human leukocyte antigen class I-specific natural killer cell receptors (NKRs) susceptible to both inhibiting effector functions and promoting cell survival, we examined the distribution and characteristics of CD8(+) T cells with such receptors in chronic hepatitis C patients. NKR CD8(+) T cells were detectable in liver and peripheral blood from hepatitis C virus (HCV)-infected patients but were not major subsets. However, the frequency of NKG2A(+) CD8(+) in the liver and in a lesser extent in the peripheral blood was positively correlated to histological activity in HCV-infected patients. No such correlation was found with KIR(+) T cells in liver in HCV-infected patients and with the both NKR CD8(+) T cells in hepatitis B virus (HBV) infected patients. Circulating CD8(+) T cells expressing KIRs exhibited phenotypic features of memory T cells with exacerbated expression of the senescence marker CD57 in patients. NKG2A(+)CD8(+) T cells were committed T cells that appeared less differentiated than KIR(+)CD8(+) T cells. In HCV-infected patients, their content in perforin was low and similar to that observed in NKG2A(-)CD8(+) T cells; this scenario was not observed in healthy subjects and HBV-infected patients. Both NKG2A and KIRs could inhibit the response of HCV-specific CD8(+) T cells ex vivo. CONCLUSION: These results support the concept that an accumulation in the liver parenchyma of NKR(+)CD8(+) T cells that have functional alterations could be responsible for liver lesions. They provide novel insights into the complexity of liver-infiltrating CD8(+) T cells in chronic hepatitis C and reveal that distinct subsets of antigen-experienced CD8(+) T cells are differentially sensitive to the pervasive influence of HCV.

Nitric oxide modulation of the immune response against cholera toxin-adjuvated ovalbumin administered by the intranasal route.

Here, we studied the effect of aminoguanidine (AG) treatment, a nitric oxide synthase (NOS)-2 inhibitor, during the immune response against intranasal administration of ovalbumin (OVA) mixed with cholera toxin (CT) in BALB/c mice. NOS-2 mRNA was detected by reverse transcription-PCR (RT-PCR) in samples of lungs and turbinates early post-inoculation of the antigen. Animals intranasally treated with AG, showed an increase in the levels of seric specific IgG and IgM. A higher IgG1/IgG2a ratio against OVA was also observed in sera of same animals. Moreover, high levels of specific IgA were detected in samples of pulmonar washings obtained from treated animals. On the contrary, treated animals showed a lower DTH response while splenocytes obtained from the same animals showed a reduced proliferative capability against OVA compared to controls. Finally, RT-PCR analysis showed increased expression of TGF-beta in turbinates, lungs and cells from pulmonar washings obtained from AG treated mice. Taken together, these data suggest a role of nitric oxide (NO) in modulating the primary immune response against intranasal antigens.