Activating immunity in the liver. II. IFN-beta attenuates NK cell-dependent liver injury triggered by liver NKT cell activation

Cross Talk Between Natural Killer T and Dendritic Cells and Its Impact on T Cell Responses in Infections

Both innate and adaptive immunity is vital for host defense against infections. Dendritic cells (DCs) are critical for initiating and modulating adaptive immunity, especially for T-cell responses. Natural killer T (NKT) cells are a small population of innate-like T cells distributed in multiple organs. Many studies have suggested that the cross-talk between these two immune cells is critical for immunobiology and host defense mechanisms. Not only can DCs influence the activation/function of NKT cells, but NKT cells can feedback on DCs also, thus modulating the phenotype and function of DCs and DC subsets. This functional feedback of NKT cells on DCs, especially the preferential promoting effect on CD8α+ and CD103+ DC subsets in lymphoid and non-lymphoid tissues, significantly impacts the systemic and local adaptive CD4 and CD8 T cell responses in infections. This review focuses on the two-way interaction between NKT cells and DCs, emphasizing the importance of NKT cell feedback on DCs in bridging innate and adaptive immune responses for host defense purposes.

Soluble and Exosome-Bound α-Galactosylceramide Mediate Preferential Proliferation of Educated NK Cells with Increased Anti-Tumor Capacity

Natural killer (NK) cells can kill target cells via the recognition of stress molecules and down-regulation of major histocompatibility complex class I (MHC-I). Some NK cells are educated to recognize and kill cells that have lost their MHC-I expression, e.g., tumor or virus-infected cells. A desired property of cancer immunotherapy is, therefore, to activate educated NK cells during anti-tumor responses in vivo. We here analyze NK cell responses to α-galactosylceramide (αGC), a potent activator of invariant NKT (iNKT) cells, or to exosomes loaded with αGC. In mouse strains which express different MHC-I alleles using an extended NK cell flow cytometry panel, we show that αGC induces a biased NK cell proliferation of educated NK cells. Importantly, iNKT cell-induced activation of NK cells selectively increased in vivo missing self-responses, leading to more effective rejection of tumor cells. Exosomes from antigen-presenting cells are attractive anti-cancer therapy tools as they may induce both innate and adaptive immune responses, thereby addressing the hurdle of tumor heterogeneity. Adding αGC to antigen-loaded dendritic-cell-derived exosomes also led to an increase in missing self-responses in addition to boosted T and B cell responses. This study manifests αGC as an attractive adjuvant in cancer immunotherapy, as it increases the functional capacity of educated NK cells and enhances the innate, missing self-based antitumor response.

Natural Killer Cell-Derived Interferon-Gamma Promotes Hepatocellular Carcinoma Through the Epithelial Cell Adhesion Molecule-Epithelial-to-Mesenchymal Transition Axis in Hepatitis B Virus Transgenic Mice

Hepatitis B virus (HBV) is a major risk factor for development of hepatocellular carcinoma (HCC), at least partially due to dysfunctional anti-HBV adaptive immunity; however, the role of innate immune response to HBV in this process is not well understood. In this study, low-dose polyinosinic:polycytidylic acid (poly [I:C]), a natural killer (NK) cell activator (3 μg/g body weight, twice/week for 8 weeks), induced HCC in HBV transgenic (HBs-Tg) mice, with an incidence of 100% after 6 months, while HBs-Tg mice without treatment only had HCC with an incidence of 16.7%. In HBs-Tg mice, poly (I:C) induced liver inflammation with markedly increased infiltrating lymphocytes, along with the concurrently increased apoptosis and proliferation of hepatocytes, leading to the accelerated epithelial-to-mesenchymal transition (EMT) of hepatocytes shown by increased expression of the typical transcriptional factors (Slug, Twist, and mothers against decapentaplegic-interacting protein 1) and phenotypic proteins (vimentin and chemokine [C-X-C motif] receptor 4). The EMT and tumorigenesis in this model depended on the presence of NK cells because depletion of these cells significantly reduced the HCC rate to 28.6%. Further, intrahepatic NK cells highly expressed interferon-gamma (IFN-γ), anti-IFN-γ neutralizing monoclonal antibody might obviously alleviate the hepatitis, and hepatocyte-specific IFN-γ overexpression promoted HCC. Moreover, IFN-γ deficiency in HBs-Tg mice prevented HCC occurring, though hepatic NK cells existed and could be activated, suggesting the critical role of IFN-γ in NK cell-mediated tumorigenesis. In an in vitro experiment, IFN-γ up-regulated epithelial cell adhesion molecule (EpCAM) expression through phosphorylated signal transducer and activator of transcription (p-STAT1) pathway, which was followed by EMT, and p-STAT1 inhibitor might absolutely abolish the expression of EpCAM and EMT in HBV surface antigen-positive hepatocytes. Conclusion: This work demonstrates that NK cell-derived IFN-γ promotes HCC through the EpCAM-EMT axis in HBs-Tg mice, revealing the importance of innate immunity in pathogenesis of HBV-associated HCC.

The Role of Invariant NKT in Autoimmune Liver Disease: Can Vitamin D Act as an Immunomodulator?

Natural killer T (NKT) cells are a distinct lineage of T cells which express both the T cell receptor (TCR) and natural killer (NK) cell markers. Invariant NKT (iNKT) cells bear an invariant TCR and recognize a small variety of glycolipid antigens presented by CD1d (nonclassical MHC-I). CD1d-restricted iNKT cells are regulators of immune responses and produce cytokines that may be proinflammatory (such as interferon-gamma (IFN-γ)) or anti-inflammatory (such as IL-4). iNKT cells also appear to play a role in B cell regulation and antibody production. Alpha-galactosylceramide (α-GalCer), a derivative of the marine sponge, is a potent stimulator of iNKT cells and has been proposed as a therapeutic iNKT cell activator. Invariant NKT cells have been implicated in the development and perpetuation of several autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus (SLE). Animal models of SLE have shown abnormalities in iNKT cells numbers and function, and an inverse correlation between the frequency of NKT cells and IgG levels has also been observed. The role of iNKT cells in autoimmune liver disease (AiLD) has not been extensively studied. This review discusses the current data with regard to iNKT cells function in AiLD, in addition to providing an overview of iNKT cells function in other autoimmune conditions and animal models. We also discuss data regarding the immunomodulatory effects of vitamin D on iNKT cells, which may serve as a potential therapeutic target, given that deficiencies in vitamin D have been reported in various autoimmune disorders.

Current concepts on immunopathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) infection is a leading cause of liver damage and hepatic inflammation. Upon infection, effective antiviral responses by CD8+ T cells, CD4+ T cells, Natural killer (NK) cells, and monocytes can lead to partial or complete eradication of the viral infection. To date, many studies have shown that the production of inhibitory cytokines such as Interleukin 10 (IL-10), Transforming growth factor beta (TGF-β), along with dysfunction of the dendritic cells (DCs), and the absence of efficient innate immune responses could lead to T cell exhaustion, development of persistent infection, and inability to eradicate the viral infection from liver. Understanding the immunopathogenesis of the virus could be useful in providing further insights toward novel strategies in the eradication of HBV infection.

The role of natural killer T cells in a mouse model with spontaneous bile duct inflammation

Natural killer T (NKT) cells are activated by lipid antigens presented by CD1d molecules and represent a major lymphocyte subset of the liver. NODc3c4 mice spontaneously develop biliary inflammation in extra- and intrahepatic bile ducts. We demonstrated by flow cytometry that invariant NKT (iNKT) cells were more abundant in the thymus, spleen, and liver of NODc3c4 mice compared to NOD mice. iNKT cells in NODc3c4 mice displayed an activated phenotype. Further, NOD and NODCd1d^-/- mice were irradiated and injected with NODc3c4 bone marrow, and injection of NODc3c4 bone marrow resulted in biliary infiltrates independently of CD1d expression in recipient mice. Activation or blocking of NKT cells with α-galactosylceramide or anti-CD1d antibody injections did not affect the biliary phenotype of NODc3c4 mice. NODc3c4.Cd1d^-/- mice were generated by crossing NODCd1d^-/- mice onto a NODc3c4 background. NODc3c4.Cd1d^-/- and NODc3c4 mice developed the same extent of biliary disease. This study demonstrates that iNKT cells are more abundant and activated in the NODc3c4 model. The portal inflammation of NODc3c4 mice can be transferred to irradiated recipients, which suggests an immune-driven disease. Our findings imply that NKT cells can potentially participate in the biliary inflammation, but are not the primary drivers of disease in NODc3c4 mice.

γδ T cells are indispensable for interleukin-23-mediated protection against Concanavalin A-induced hepatitis in hepatitis B virus transgenic mice

Hepatitis B virus surface antigen (HBsAg) carriers are highly susceptible to liver injury triggered by environmental biochemical stimulation. Previously, we have reported an inverse correlation between γδ T cells and liver damage in patients with hepatitis B virus (HBV). However, whether γδ T cells play a role in regulating the hypersensitivity of HBsAg carriers to biochemical stimulation-induced hepatitis is unknown. In this study, using HBV transgenic (HBs-Tg) and HBs-Tg T-cell receptor-δ-deficient (TCR-δ^-/- ) mice, we found that mice genetically deficient in γδ T cells exhibited more severe liver damage upon Concanavalin A (Con A) treatment, as indicated by substantially higher serum alanine aminotransferase levels, further elevated interferon-γ (IFN-γ) levels and more extensive necrosis. γδ T-cell deficiency resulted in elevated IFN-γ in CD4⁺ T cells but not in natural killer or natural killer T cells. The depletion of CD4⁺ T cells and neutralization of IFN-γ reduced liver damage in HBs-Tg and HBs-Tg-TCR-δ^-/- mice to a similar extent. Further investigation revealed that HBs-Tg mice showed an enhanced interleukin-17 (IL-17) signature. The administration of exogenous IL-23 enhanced IL-17A production from Vγ4 γδ T cells and ameliorated liver damage in HBs-Tg mice, but not in HBs-Tg-TCR-δ^-/- mice. In summary, our results demonstrated that γδ T cells played a protective role in restraining Con A-induced hepatitis by inhibiting IFN-γ production from CD4⁺ T cells and are indispensable for IL-23-mediated protection against Con A-induced hepatitis in HBs-Tg mice. These results provided a potential therapeutic approach for treating the hypersensitivity of HBV carriers to biochemical stimulation-induced liver damage.

CD205-TLR9-IL-12 axis contributes to CpG-induced oversensitive liver injury in HBsAg transgenic mice by promoting the interaction of NKT cells with Kupffer cells

Gut-derived bacterial products contribute to liver inflammation and injury during chronic hepatitis B virus infection; however, the underlying mechanisms remain obscure. In this study, hepatitis B surface antigen transgenic (HBs-Tg) mice and their wild-type (WT) control C57BL/6 mice were injected with CpG-oligodeoxynucleotides (ODNs) to mimic the translocation of gut microbial products into the systemic circulation. We found that, compared with the WT mice, the HBs-Tg mice were oversensitive to CpG-ODN-induced liver injury, which was dependent on natural killer T (NKT) cells. CpG-ODN injection enhanced the expression of Fas ligand (FasL) on NKT cells. In addition, hepatocytes from the HBs-Tg mice expressed higher levels of Fas than did those from the WT mice, which was further augmented by CpG-ODN. Interaction of Fas and FasL was involved in the cytotoxicity of NKT cells against hepatocytes in the HBs-Tg mice. Moreover, Kupffer cells in the HBs-Tg mice expressed higher levels of CD205 and produced greater amounts of interleukin (IL)-12 than did those in the WT mice. Finally, the depletion of Kupffer cells, neutralization of IL-12 or specific silencing of CD205 on Kupffer cells significantly inhibited CpG-ODN-induced liver injury and NKT activation in the HBs-Tg mice. Our data suggest that CD205-expressing Kupffer cells respond to CpG-ODNs and subsequently release IL-12 to promote NKT cell activation. Activated NKT cells induce liver damage through the Fas signaling pathway in HBs-Tg mice.

Preoperative hepatitis B virus DNA level is a risk factor for postoperative liver failure in patients who underwent partial hepatectomy for hepatitis B-related hepatocellular carcinoma

OBJECTIVE

Our objective was to explore the short-term effects of preoperative serum hepatitis B virus DNA level (HBV DNA) on postoperative hepatic function in patients who underwent partial hepatectomy for hepatitis B-related hepatocellular carcinoma (HCC).

METHODS

The clinical data of 1,602 patients with hepatitis B-related HCC who underwent partial hepatectomy in our department were retrospectively studied. The patients were divided into three groups according to their preoperative HBV DNA levels: group A <200 IU/mL, group B 200-20,000 IU/mL, and group C >20,000 IU/mL. The rates of postoperative complications, especially the rate of postoperative liver failure, were compared.

RESULTS

There were significant differences among the three groups in the rates of postoperative liver failure. On multivariate logistic regression analysis, a high preoperative HBV DNA level was an independent risk factor for postoperative liver failure.

CONCLUSIONS

Preoperative HBV DNA level was a significant risk factor for postoperative hepatic dysfunction.

Long-term effect on natural killer cells by interferon-α therapy on the outcomes of HCV infection

Natural killer (NK) cells act as innate immune cells against hepatitis C virus (HCV) infection. Interferon-α (IFN-α) and ribavirin are the standard treatments for patients with HCV infection. This study is aimed at investigating the dynamic changes in the frequency of different subsets of NK cells following treatment in xx chronic hepatitis C (CHC) patients. CHC patients were treated with peg-IFN or IFN-α, and followed up for 72 weeks. The frequency of different subsets of NK in CHC patients was determined longitudinally by flow cytometry. Treatment with the standard therapy increased the percentages of NKp30(+), NKp46(+), and CD107a(+) NK cells, which were positively correlated with the declining of serum HCV-RNA, but not IFN-γ(+) NK cells. NKG2A(+) and KIR2DL3(+) NK cells were associated with an early virological response in CHC patients. Treatment with IFN-α adjusts the balance of activated receptors and inhibitory receptors and enhances the cytotoxic activity of NK cells. Therefore, measuring NK subsets may be valuable for therapeutic responses in CHC patients.

Innate immune responses in hepatitis B virus (HBV) infection

Hepatitis B virus (HBV) infection has a low rate of chronicity compared to HCV infection, but chronic liver inflammation can evolve to life threatening complications. Experimental data from HBV infected chimpanzees and HBV transgenic mice have indicated that cytotoxic T cells are the main cell type responsible for inhibition of viral replication, but also for hepatocyte lysis during chronic HBV infection. Their lower activation and impaired function in later stages of infection was suggested as a possible mechanism that allowed for low levels of viral replication. The lack of an interferon response in these models also indicated the importance of adaptive immunity in clearing the infection. Increased knowledge of the signalling pathways and pathogen associated molecular patterns that govern activation of innate immunity in the early stages of viral infections in general has led to a re-evaluation of the innate immune system in HBV infection. Numerous studies have shown that HBV employs active strategies to evade innate immune responses and induce immunosuppression. Some of the immune components targeted by HBV include dendritic cells, natural killer cells, T regulatory cells and signalling pathways of the interferon response. This review will present the current understanding of innate immunity in HBV infection and of the challenges associated with clearing of the HBV infection.

Pretreatment with TCDD exacerbates liver injury from Concanavalin A: critical role for NK cells

For many liver diseases, including viral and autoimmune hepatitis, immune cells play an important role in the development and progression of liver injury. Concanavalin A (Con A) administration to rodents has been used as a model of immune-mediated liver injury resembling human autoimmune hepatitis. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been demonstrated to alter the development of immune-mediated diseases. Mice pretreated with TCDD developed exacerbated liver injury in response to administration of a mild dose (6 mg/kg) of Con A. In the present study, we tested the hypothesis that TCDD pretreatment exacerbates Con A-induced liver injury by enhancing the activation and recruitment of accessory cell types including neutrophils, macrophages, and natural killer (NK) cells. Mice were treated with 0, 0.3, 3, or 30 μg/kg TCDD and 4 days later with Con A or saline. TCDD pretreatment with doses of 3 and 30 μg/kg significantly increased liver injury from Con A administration. The plasma concentrations of neutrophil chemokines were significantly increased in TCDD-pretreated mice after Con A administration. NKT cell-deficient (CD1d KO) mice were used to examine whether NKT cells were required for TCDD/Con A-induced liver injury. CD1d KO mice were completely protected from liver injury induced by treatment with Con A alone, whereas the injury from TCDD/Con A treatment was reduced but not eliminated. However, T-cell deficient (RAG1 KO) mice were protected from liver injury induced by Con A irrespective of pretreatment with TCDD. TCDD/Con A treatment increased the percentage of NK cells expressing the activation marker CD69. Depletion of NK cells prior to treatment resulted in significant reductions in plasma interferon-γ and liver injury from TCDD/Con A treatment. In summary, exposure to TCDD exacerbated the immune-mediated liver injury induced by Con A, and our findings suggest that NK cells play a critical role in this response.

Inactivated ORF virus shows antifibrotic activity and inhibits human hepatitis B virus (HBV) and hepatitis C virus (HCV) replication in preclinical models

Inactivated orf virus (iORFV), strain D1701, is a potent immune modulator in various animal species. We recently demonstrated that iORFV induces strong antiviral activity in animal models of acute and chronic viral infections. In addition, we found D1701-mediated antifibrotic effects in different rat models of liver fibrosis. In the present study, we compare iORFV derived from two different strains of ORFV, D1701 and NZ2, respectively, with respect to their antifibrotic potential as well as their potential to induce an antiviral response controlling infections with the hepatotropic pathogens hepatitis C virus (HCV) and hepatitis B virus (HBV). Both strains of ORFV showed anti-viral activity against HCV in vitro and against HBV in a transgenic mouse model without signs of necro-inflammation in vivo. Our experiments suggest that the absence of liver damage is potentially mediated by iORFV-induced downregulation of antigen cross-presentation in liver sinus endothelial cells. Furthermore, both strains showed significant anti-fibrotic activity in rat models of liver fibrosis. iORFV strain NZ2 appeared more potent compared to strain D1701 with respect to both its antiviral and antifibrotic activity on the basis of dosages estimated by titration of active virus. These results show a potential therapeutic approach against two important human liver pathogens HBV and HCV that independently addresses concomitant liver fibrosis. Further studies are required to characterize the details of the mechanisms involved in this novel therapeutic principle.

The combination therapy of α-galactosylceramide and 5-fluorouracil showed antitumor effect synergistically against liver tumor in mice

α-Galactosylceramide (α-GalCer) has been reported to be therapeutic against metastatic liver tumors in mice. However, little is known regarding the efficacy of combined chemo-immunotherapy using α-GalCer and anticancer drugs. In this study, we evaluated the antitumor effect of the combination therapy of α-GalCer and 5-fluorouracil (5-FU) against liver tumors of MC38 colon cancer cells. The liver weights of tumor-bearing mice treated with the combination were significantly lower than those of nontreated mice and of mice treated with 5-FU or α-GalCer alone. No toxic effects on the liver and renal functions were observed in any of the treatment groups. α-GalCer treatment induced significant activation of liver NK cells in vivo, but 5-FU treatment did not. 5-FU treatment resulted in a significant upregulation of NKG2D activating molecules (Rae-1 and H60) and DNAM-1 ligands (CD112 and CD155) on MC38 cells, but α-GalCer did not. The cytolytic activity of α-GalCer-activated liver mononuclear cells against 5-FU-treated MC38 cells was significantly higher than that against nontreated cells. The increase of the cytolytic activity induced by 5-FU partially depended on NKG2D-Rae-1 or H60 signals. Depletion of NK cells significantly inhibited the antitumor efficacy of 5-FU against MC38 liver tumors, which suggested that the antitumor effect of 5-FU partially depended on the cytolytic activity of NK cells. These results demonstrated that the combination therapy of α-GalCer and 5-FU produced synergistic antitumor effects against liver tumors by increasing the expression of NK activating molecules on cancer cells. This study suggests a promising new chemo-immunotherapy against metastatic liver cancer.

Increased peripheral RORα and RORγt mRNA expression is associated with acute-on-chronic hepatitis B liver failure

T helper cells17 (Th17) have accurate but inconclusive roles in the pathogenesis of acute-on-chronic hepatitis B liver failure (ACHBLF). Retinoic acid-related orphan receptor γ t(RORγt) and RORα are two lineage-specific nuclear receptors directly mediating Th17 differentiation. This study was aimed to evaluate the gene expression of RORα and RORγt and their potential role in ACHBLF. Forty patients with liver failure, 30 with chronic hepatitis B (CHB) and 20 healthy controls were studied. The mRNA levels of RORα and RORγt in peripheral mononuclear cells were determined by quantitative real-time polymerase chain reaction. The frequency of peripheral Th17 cells was determined using flow cytometry. The serum levels of interleukin-6(IL-6), transforming growth factor -β (TGF-β), interleukin-17(IL-17), interleukin-23(IL-23) and interferon-γ (IFN-γ) were measured by enzyme-linked immunosorbent assay. The frequency of peripheral Th17 cells in patients with liver failure was significantly increased compared to patients with CHB and controls. The peripheral mRNA levels of RORα and RORγt in hepatitis B-associated acute-on-chronic liver failure were significantly higher than in patients with CHB and controls as were the serum levels of IL-6 and TGF-β. The serum level of IFN-γ in patients with acute-on-chronic liver failure from HBV was significantly higher than patients with CHB but lower than controls. In patients with acute-on-chronic liver failure associated with HBV, RORγt, IL-6 and IL-23 were positively correlated with the frequency of Th17 cells, while RORα, TGF-β and IFN-γ had no correlation with the latter. The mRNA level of RORγt was positively correlated with model of end-stage liver disease (MELD) score, but there was no correlation of RORα and MELD score. RORγt plays an important role in the pathogenesis of acute-on-chronic HBV-associated liver failure and might be considered to be a candidate factor consistent with the severity of disease.

The role of innate immunity in HBV infection

Hepatitis B virus (HBV) infection is one of the main causes of chronic liver diseases. Whether HBV infection is cleared or persists is determined by both viral factors and host immune responses. It becomes clear that innate immunity is of importance in protecting the host from HBV infection and persistence. However, HBV develops strategies to suppress the antiviral immune responses. A combined therapeutic strategy with both viral suppression and enhancement of antiviral immune responses is needed for effective long-term clearance and cure for chronic HBV infection. We and others confirmed that bifunctional siRNAs with both gene silencing and innate immune activation properties are beneficial for inhibition of HBV and represent a potential approach for treatment of viral infection. Understanding the nature of liver innate immunity and their roles in chronic HBV progression and HBV clearance may aid in the design of novel therapeutic strategies for chronic HBV infection.

Hepatitis C virus soluble E2 in combination with QuilA and CpG ODN induces neutralizing antibodies in mice

Several studies have emphasized the importance of an early, highly neutralizing antibody response in the clearance of Hepatitis C virus (HCV) infection. The envelope glycoprotein E2 is a major target for HCV neutralizing antibodies. Here, we compared antibody responses in mice immunized with native soluble E2 (sE2) from the H77 1a isolate coupled with different adjuvants or combinations of adjuvants. Adjuvanting sE2 with Freund's, monophosphoryl lipid A (MPL), cytosine phosphorothioate guanine oligodeoxynucleotide (CpG ODN), or alpha-galactosylceramide (αGalCer) derivatives elicited only moderate antibody responses. In contrast, immunizations with sE2 and QuilA elicited exceptionally high anti-E2 antibody titers. Sera from these mice effectively neutralized HCV pseudoparticles (HCVpp) 1a entry. Moreover, the combination of QuilA and CpG ODN further enhanced neutralizing antibody titers wherein cross-neutralization of HCVpp 4 was observed. We conclude that the combination of QuilA and CpG ODN is a promising adjuvant combination that should be further explored for the development of an HCV subunit vaccine. Our work also emphasizes that the ideal combination of adjuvant and immunogen has to be determined empirically.

Isolation of murine intrahepatic immune cells employing a modified procedure for mechanical disruption and functional characterization of the B, T and natural killer T cells obtained

Intrahepatic immune cells (IHIC) are known to play central roles in immunological responses mediated by the liver, and isolation and phenotypic characterization of these cells is therefore of considerable importance. In the present investigation, we developed a simple procedure for the mechanical disruption of mouse liver that allows efficient isolation and phenotypic characterization of IHIC. These cells are compared with the corresponding cells purified from the liver after enzymatic digestion with different concentrations of collagenase and DNase. The mechanical disruption yielded viable IHIC in considerably greater numbers than those obtained following enzymatic digestion. The IHIC isolated employing the mechanical disruption were heterogeneous in composition, consisting of both innate and adaptive immune cells, of which B, T, natural killer (NK), NK T cells, granulocytes and macrophages were the major populations (constituting 37.5%, 16.5%, 12.1%, 7.9%, 7.9% and 7.5% of the total number of cells recovered respectively). The IHIC obtained following enzymatic digestion contained markedly lower numbers of NK T cells (1.8%). The B, T and NK T cells among IHIC isolated employing mechanical disruption were found to be immunocompetent, i.e. they proliferated in vitro in response to their specific stimuli (lipopolysaccharide, concanavalin A and alpha-galactosylceramide respectively) and produced immunoglobulin M and interferon-gamma. Thus, the simple procedure for the mechanical disruption of mouse liver described here results in more efficient isolation of functionally competent IHIC for various types of investigation.

Characterization of the role of TCR gammadelta in NK cell accumulation during viral liver inflammation

Polyinosinic-polyctidylic acid (Poly I:C) is a viral RNA mimic that can induce immune responses similar to that seen during viral infection. Although poly I:C administration into mice is associated increased NK cell infiltrates in the liver, the mechanisms underlying increased hepatic NK cell accumulation in response to poly I:C administration are incompletely defined. In the current study, we have identified a novel and important role for gammadelta T cells in driving the accumulation and activation of NK cells in the liver during poly I:C-mediated viral liver infection. Specifically, NK cell accumulation but not activation in gammadelta T cell deficient mice following poly I:C administration was significantly attenuated in comparison to that seen in poly I:C-treated wildtype mice. The ability of gammadelta T cells to promote NK cell accumulation and activation in the liver may be virus-specific since NK cell accumulation in the liver was not altered by TCR gammadelta deficiency following adenovirus administration.

Hepatitis B virus DNA is more powerful than HBeAg in predicting peripheral T-lymphocyte subpopulations in chronic HBV-infected individuals with normal liver function tests

AIM: To investigate the peripheral T-lymphocyte subpopulation profile, and its correlations with hepatitis B virus (HBV) replication level in chronic HBV-infected (CHI) individuals with normal liver function tests (LFTs).

METHODS: Frequencies of T-lymphocyte subpopu-lations in peripheral blood were measured by flow cytometry in 216 CHI individuals. HBV markers were detected with ELISA. Serum HBV DNA load was assessed with quantitative real-time PCR. Information of age at HBV infection, and maternal HBV infection status was collected. ANOVA linear trend test and linear regression were used in statistical analysis.

RESULTS: CHI individuals had significantly decreased relative frequencies of CD3⁺, CD4⁺ subpopulations and CD4⁺/CD8⁺ ratio, and increased CD8⁺ subset percentage compared with uninfected individuals (all P < 0.001). There was a significant linear relationship between the load of HBV DNA and the parameters of T-lymphocyte subpopulations (ANOVA linear trend test P < 0.01). The parameters were also significantly worse among individuals whose mothers were known to be HBV carriers, and those having gained infection before the age of 8 years. In multiple regressions, after adjustment for age at HBV infection and status of maternal HBV infection, log copies of HBV DNA maintained its highly significant predictive coefficient on T-lymphocyte subpopulations, whereas the effect of HBeAg was not significant.

CONCLUSION: HBV DNA correlates with modification in the relative T-lymphocyte subpopulation frequencies. High viral load is more powerful than HBeAg in predicting the impaired balance of T-cell subsets.

Effect of viral load on T-lymphocyte failure in patients with chronic hepatitis B

AIM

To investigate peripheral T-lymphocyte sub-population profile and its correlation with hepatitis B virus (HBV) replication in patients with chronic hepatitis B (CHB).

METHODS

Distribution of T-lymphocyte subpopulations in peripheral blood was measured by flow cytometry in 206 CHB patients. HBV markers were detected with ELISA. Serum HBV DNA load was assessed with quantitative real-time polymerase chain reaction (PCR). The relationship between HBV replication and variation in peripheral T-cell subsets was analyzed.

RESULTS

CHB patients had significantly decreased CD3+ and CD4+ cells and CD4+/CD8+ ratio, and increased CD8+ cells compared with uninfected controls (55.44 +/- 12.39 vs 71.07 +/- 4.76, 30.92 +/- 7.48 vs 38.94 +/- 3.39, 1.01 +/- 0.49 vs 1.67 +/- 0.33, and 34.39 +/- 9.22 vs 24.02 +/- 4.35; P < 0.001, respectively). Univariate analysis showed a similar pattern of these parameters was significantly associated with high viral load, presence of serum hepatitis B e antigen (HBeAg) expression, liver disease severity, history of maternal HBV infection, and young age at HBV infection, all with P < 0.01. There was a significant linear relationship between viral load and these parameters of T-lymphocyte subpopulations (linear trend test P < 0.001). There was a negative correlation between the levels of CD3+ and CD4+ cells and CD4+/CD8+ ratio and serum level of viral load in CHB patients (r = -0.68, -0.65 and -0.75, all P < 0.0001), and a positive correlation between CD8+ cells and viral load (r = 0.70, P < 0.0001). There was a significant decreasing trend in CD3+ and CD4+ cells and CD4+/CD8+ ratio with increasing severity of hepatocyte damage and decreasing age at HBV infection (linear trend test P < 0.01). In multiple regression (after adjustment for age at HBV infection, maternal HBV infection status and hepatocyte damage severity) log copies of HBV DNA maintained a highly significant predictive coefficient on T-lymphocyte subpopulations, and was the strongest predictor of variation in CD3+, CD4+, CD8+ cells and CD4+/CD8+ ratio. However, the effect of HBeAg was not significant.

CONCLUSION

T-lymphocyte failure was significantly associated with viral replication level. The substantial linear dose-response relationship and strong independent predictive effect of viral load on T-lymphocyte subpopulations suggests the possibility of a causal relationship between them, and indicates the importance of viral load in the pathogenesis of T cell hyporesponsiveness in these patients.

Human invariant Valpha24+ natural killer T cells acquire regulatory functions by interacting with IL-10-treated dendritic cells

Glycolipid-reactive Valpha24(+) invariant natural killer T (iNKT) cells have been implicated in regulating a variety of immune responses and in the induction of immunologic tolerance. Activation of iNKT cells requires interaction with professional antigen-presenting cells, such as dendritic cells (DCs). We have investigated the capacity of distinct DC subsets to modulate iNKT cell functions. We demonstrate that tolerogenic DCs (tolDCs), generated by treatment of monocyte-derived DC with interleukin (IL)-10, induced regulatory functions in human iNKT cells. tolDCs, compared with immunogenic DCs, had reduced capacity to induce iNKT-cell proliferation, but these cells produced large amounts of IL-10 and acquired an anergic phenotype. These anergic Valpha24(+) iNKT cells were able to potently inhibit allogeneic CD4(+) T-cell proliferation in vitro. Furthermore, the anergic Valpha24(+) iNKT cells could suppress DC maturation in vitro. We conclude that the interaction of iNKT cells with tolDCs plays an important role in the immune regulatory network, which might be exploited for therapeutic purposes.

Activation of invariant NKT cells by toll-like receptor 9-stimulated dendritic cells requires type I interferon and charged glycosphingolipids

Invariant natural killer T (iNKT) cells are a subset of innate lymphocytes that recognize lipid antigens in the context of CD1d and mediate potent immune regulatory functions via the rapid production of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4). We investigated whether diverse Toll-like receptor (TLR) signals in myeloid dendritic cells (DCs) could differentially stimulate iNKT cells. Together with the lipopolysaccharide-detecting receptor TLR4, activation of the nucleic acid sensors TLR7 and TLR9 in DCs were particularly potent in stimulating iNKT cells to produce IFN-gamma, but not IL-4. iNKT cell activation in response to TLR9 stimulation required combined synthesis of type I interferon and de novo production of charged beta-linked glycosphingolipid(s) by DCs. In addition, DCs stimulated via TLR9 activated both iNKT cells and NK cells in vivo and protected mice against B16F10-induced melanoma metastases. These data underline the role of TLR9 in iNKT cell activation and might have relevance to infectious diseases and cancer.

Role of NKT cells in the digestive system. I. Invariant NKT cells and liver diseases: is there strength in numbers?

Information regarding the functional role of the innate immune T cell, invariant natural killer T (iNKT) cells, in the pathophysiology of liver diseases continues to emerge. Results from animal studies suggest that iNKT cells can have divergent roles by specifically promoting the development of proinflammatory or anti-inflammatory responses in liver diseases. In this themes article, I discuss the critical evidence from animal models that demonstrate a vital role for iNKT cells in the pathophysiology of liver diseases with emphasis on viral, autoimmune, and toxin-induced liver diseases. Furthermore, I discuss the controversial issues (including iNKT cell apoptosis) that typify some of these studies. Finally, I highlight areas that require additional investigation.

Increased susceptibility to liver injury in hepatitis B virus transgenic mice involves NKG2D-ligand interaction and natural killer cells

The innate immunopathogenesis responsible for the susceptibility to hepatocyte injury in chronic hepatitis B surface antigen carriers is not well defined. In this study, hepatitis B virus (HBV) transgenic mice (named HBs-Tg) were oversensitive to liver injury after immunologic [polyinosinic:polycytidylic acid or concanavalin A (ConA)] or chemical (CCl4) triggering. It was then found that the nonhepatotoxic low dose of ConA for wild-type mice induced severe liver injury in HBs-Tg mice, which was dependent on the accumulated intraheptic natural killer (NK) cells. Expressions of NKG2D ligands (Rae-1 and Mult-1) in hepatocytes were markedly enhanced upon ConA stimulation in HBs-Tg mice, which greatly activated hepatic NK cells via NKG2D/Rae-1 or Mult-1 recognition. Interestingly, the presence of NK T cells was necessary for NK cell activation and worked as positive helper cell possibly by producing interferon-gamma and interleukin-4 in this process.

CONCLUSION

Our findings for the first time suggested the critical role of NKG2D recognition of hepatocytes by NK cells in oversensitive liver injury during chronic HBV infection.

Liver-specific HBsAg transgenic mice are over-sensitive to Poly(I:C)-induced liver injury in NK cell- and IFN-gamma-dependent manner

BACKGROUND/AIMS

The role of natural killer (NK) cells in the development of hepatitis B virus (HBV)-associated liver injury remains obscure. In this study, we elucidated the role of NK cells in liver injury of HBsAg transgenic mice (HBs-B6), a mimic of human healthy chronic HBsAg carriers, triggered by polyinosinic:polycytidylic acid [Poly(I:C)].

METHODS

HBs-B6 or wild B6 mice were intraperitoneally injected with Poly(I:C) at different doses. Liver injury was evaluated by serum transaminase activity and histopathologic changes.

RESULTS

HBs-B6 mice were over-sensitive to Poly(I:C)-induced liver injury, which was absolutely dependent on the presence of NK cells and IFN-gamma produced by intrahepatic NK cells. Much stronger IFN-gamma receptor expression was observed on hepatocytes of HBs-B6 mice, which was significantly enhanced by Poly(I:C) injection. Treatment with IFN-gammain vitro triggered much higher activation of downstream signals (pSTAT1-IRF-1) in hepatocytes of HBs-B6 mice. Depletion of Kupffer cells and neutralization of endogenous IL-12 did not affect Poly(I:C)-induced over-sensitive liver injury in HBs-B6 mice.

CONCLUSIONS

NK cells played a critical role in an IFN-gamma dependent, Kupffer cell- and IL-12-independent manner in over-sensitive liver injury triggered by Poly(I:C) in murine chronic HBsAg carriers.

Lymphocyte function during hepatic ischemia/reperfusion injury

The liver is the primary organ affected by ischemia/reperfusion (I/R) injury after shock, surgical resection, or transplantation. The actions of myeloid leukocytes have been well studied and are thought to be the primary cells responsible for propagating the injury response. However, there is an emerging view that T lymphocytes can also regulate liver I/R-induced inflammation. Resident lymphocytes found within the liver include conventional alphabeta TCR cells as well as unconventional NK and gammadelta T cells. These lymphocytes can alter inflammation through the secretion of soluble mediators such as cytokines and chemokines or through cognate interactions in an antigen-dependent manner. Expression of these mediators will then result in the recruitment of more lymphocytes and neutrophils. There is evidence to suggest that T cell activation in the liver during I/R can be driven by antigenic or nonantigenic mechanisms. Finally, immune cells are exposed to different oxygen tensions, including hypoxia, as they migrate and function within tissues. The hypoxic environment during liver ischemia likely modulates T cell function, at least in part through the actions of hypoxia-inducible factor-1alpha. Further, this hypoxic environment leads to the increased concentration of extracellular adenosine, which is generally known to suppress T cell proinflammatory function. Altogether, the elucidation of T lymphocyte actions during liver I/R will likely allow for novel targets for therapeutic intervention.

Type I IFN-producing CD4 Valpha14i NKT cells facilitate priming of IL-10-producing CD8 T cells by hepatocytes

Upon entering the liver CD8 T cells encounter large numbers of NKT cells patrolling the hepatocyte (HC) surface facing the perisinusoidal space. We asked whether hepatic NKT cells modulate the priming of CD8 T cells by HC. Hepatic (alpha-galactosyl-ceramide-loaded CD1d dimer binding) NKT cells produce predominantly IL-4 when stimulated with glycolipid-presenting HC but predominantly IFN-gamma when stimulated with glycolipid-presenting dendritic cells. These NKT cells prime naive CD8 T cells to a (K(b)-presented) peptide ligand if they simultaneously recognize a CD1d-binding glycolipid presented to them on the surface of the responding CD8 T cells that they prime. No IL-10-producing CD8 T cells are detected if these T cells are primed by either HC or NKT cells. In contrast, IL-10 is produced by HC-primed CD8 T cells if IFN-beta-producing NKT cells are coactivated by the same HC presenting a glycolipid (in the context of CD1d) and an antigenic peptide (in the context of K(b)). Hence, IL-10-producing CD8 T cells are generated in a type I IFN-dependent manner if the three cell types (CD8 T cells, NKT cells, and ligand-presenting HC) specifically and closely interact. IL-10-producing CD8 T cells generated under these conditions down-modulate IL-2 (and proliferative) responses of naive CD4 or CD8 T cells primed by DC. If in close proximity, NKT cells can thus locally modulate the phenotype of CD8 T cells during their priming by HC thereby limiting the local activation of proinflammatory immune effector cells and protecting the liver against immune injury.

Dynamic changes of HBV DNA in serum and peripheral blood mononuclear cells of chronic hepatitis patients after lamivudine treatment

AIM: To study the dynamic changes of hepatits B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMCs) of patients after lamivudine therapy.

METHODS: A total of 72 patients with chronic HBV infection were included in this study. All patients were confirmed to have the following conditions: above 16 years of age, elevated serum alanine amonotransferase (ALT), positive hepatitis B e antigen (HBeAg), positive HBV DNA in serum and PBMCs, negative antibodies against HAV, HCV, HDV, HEV. Other possible causes of chronic liver damages, such as drugs, alcohol and autoimmune diseases were excluded. Seventy-two cases were randomly divided into lamivudine treatment group (n = 42) and control group (n = 30). HBV DNA was detected both in serum and in PBMCs by fluorescence quantitative polymerase chain reaction (PCR), during and after lamivudine treatment.

RESULTS: In the treatment group, HBV DNA became negative both in serum and in PBMC, of 38 and 25 out of 42 cases respectively during the 48 wk of lamivudine treatment, the negative rate was 90.5% and 59.5% respectively. In the control group, the negative rate was 23.3% and 16.7% respectively. It was statistically significant at 12, 24 and 48 wk as compared with the control group (P < 0.005). The average conversion period of HBV DNA was 6 wk (2-8 wk) in serum and 16 wk (8-24 wk) in PBMC.

CONCLUSION: Lamivudine has remarkable inhibitory effects on HBV replication both in serum and in PBMCs. The inhibitory effect on HBV DNA in PBMCs is weaker than that in serum.

Impaired NK cell cytotoxicity by high level of interferon-gamma in concanavalin A-induced hepatitis

Unlike T cells, the role of natural killer (NK) cells is not well documented in the concanavalin (ConA)- induced hepatitis model. This study aimed to investigate the regulatory effect of high levels of interferon-gamma (IFN-gamma) on NK cells in ConA-induced hepatitis. The cytotoxicities of NK cells from ConA-injected mice or NK cell lines (NK92 and NKL) were detected by the 4-h 51Cr release assay. Depletion of NK cells with AsGM1 antibody was used to assess the NK cell role in ConA-induced hepatitis. Expression of NK cell receptors and cytotoxic molecules was measured by reverse transcription-polymerase chain reaction. Twelve hours after ConA injection, serum IFN-gamma was significantly increased in wild mice, but not in severe combined immunodeficiency mice, and hepatic NK cells exerted impaired cytotoxicity against YAC-l cells in wild mice. Eight hours after NK cells were incubated in serum from ConA-treated mice, NK cell cytotoxicity was down-modulated and the effect was abolished by pretreatment with neutralizing serum IFN-gamma with specific antibody in vitro. A high concentration of IFN-gamma (> 1000 U/mL) inhibited the cytotoxicities of 2 NK cell lines in vitro, accompanied with down-regulation of NKG2D transcripts and up-regulation of NKG2A/B and KIR2DL transcripts. The inhibitive role of IFN-gamma was not seen in NKG2D ligand negative cells. These results suggest that NK cell cytotoxicity was inhibited by high levels of IFN-gamma in ConA-induced hepatitis, which may relate to the dispensable role of NK cells.

Impaired function of hepatic natural killer cells from murine chronic HBsAg carriers

In the present study, we demonstrated hepatic NK cells in murine chronic HBsAg carriers for the first time. It was found that the number of hepatic NK cells was decreased; natural activation of hepatic NK cells was declined; and cytotoxicity of hepatic NK cells was attenuated, which might relate to the down-regulated expression of TRAIL on hepatic NK cells. Additionally, the response of hepatic NK cells to the specific stimulation of Poly (I:C) in murine chronic HBsAg carriers was changed. The increase in anti-tumor cytotoxic activity of intrahepatic activated NK cells was markedly impaired in the transgenic mice. The transgenic mice used here had high incidence of hepatocellular carcinoma, which might result from the relative weak reactivity and impaired anti-tumor activity of NK cells in the liver. Furthermore, remarkable liver injury was observed after stimulation of Poly (I:C), demonstrating the hypersensitivity to Poly (I:C) of murine chronic HBsAg carriers which might be related to the accumulated NK cells in the liver. Why the murine chronic HBsAg carriers are characterized with impaired hepatic NK cells and the implication of the impaired hepatic NK cells in pathogenesis of HBV-related diseases, such as hepatocellular carcinoma and recrudescent hepatitis, is worth of further investigating. These results of the functions of hepatic NK cells in murine chronic HBsAg carriers would contribute to interpreting the immune responses of NK cells in the liver and the immunological mechanisms of liver diseases in human chronic HBsAg carriers.

Natural Killer-Cell Cytotoxicity in HIV-Positive and HIV-Negative Patients with and Without Severe Course of Hepatitis B Virus Infection

Natural killer (NK) cells represent the first line of defence against viral infections but, in the case of hepatitis B virus (HBV), may also be involved in liver injury. We here compared NK-cell activity of 11 patients with acute HBV infection, either HIV-positive or HIV-negative, with that of 11 healthy subjects. One of the HIV-positive patients, characterized by a severe immunodeficiency, died 3 weeks after hospitalization for HBV-related fulminant hepatitis (FH). He displayed a remarkable NK-cell cytotoxicity against both cell lines and autologous dendritic cells, whereas the NK-cell activity of the remaining patients was significantly reduced as compared with healthy individuals. Our findings suggest that NK-cell-mediated cytotoxicity could contribute to the development of HBV-related acute liver failure in HIV-positive patients with severe immunodeficiency. An immunopathological model of FH in immunocompromised patients was proposed.

Negative regulation of liver regeneration by innate immunity (natural killer cells/interferon-gamma)

BACKGROUND AND AIMS

Hepatic lymphocytes are composed mainly of natural killer (NK) cells and NKT cells, which play key roles in innate immune responses against pathogens and tumors in the liver. This report analyzes the effects of activation of innate immunity by viral infection or the toll-like receptor 3 (TLR3) ligand on liver regeneration.

METHODS

The partial hepatectomy (PHx) method was used as a model of liver regeneration. Murine cytomegalovirus (MCMV) infection and the TLR3 ligand polyinosinic-polycytidylic acid [poly(I:C)] were used to activate innate immunity.

RESULTS

NK cells are activated after PHx, as evidenced by producing interferon (IFN)-gamma. Infection with MCMV or injection of poly(I:C) further activates NK cells to produce IFN-gamma and attenuates liver regeneration in the PHx model. Depletion of NK cells or disruption of either the IFN-gamma gene or the IFN-gamma receptor gene enhances liver regeneration and partially abolishes the negative effects of MCMV and polyI:C on liver regeneration, whereas NKT cells may only play a minor role in suppression of liver regeneration. Adoptive transfer of IFN-gamma +/+ NK cells, but not IFN-gamma -/- NK cells, restores the ability of polyI:C to attenuate liver regeneration in NK-depleted mice. Finally, administration of polyI:C or IFN-gamma enhances expression of several antiproliferative proteins, including STAT1, IRF-1, and p21cip1/waf1 in the livers of partially hepatectomized mice.

CONCLUSIONS

Our findings suggest that viral infection and the TLR3 ligand negatively regulate liver regeneration via activation of innate immunity (NK/IFN-gamma), which may play an important role in the pathogenesis of viral hepatitis.

Pivotal role of nuclear factor kappaB signaling in anti-CD40-induced liver injury in mice

Nuclear factor kappaB (NF-kappaB) has a central role in coordinating the expression of a wide variety of genes that control immune responses and is also recognized as an antiapoptotic transcription factor. Here, we focused on the role of the NF-kappaB signaling pathway in the interaction between inflammatory cells and hepatocytes in liver inflammation. We found that pretreatment of mice with adenoviruses expressing a mutant form of the inhibitor kappaB superrepressor (Ad5IkappaB), a NF-kappaB inhibitor, reduced the migration of inflammatory cells and cytokine and chemokine expression in the liver 12 hours after a single intravenous injection of an anti-CD40 antibody (alphaCD40) compared with mice infected with control adenoviruses (Ad5LacZ). We also confirmed reductions in cytokine production by macrophages, T cells, and natural killer (NK) cells in the liver of Ad5IkappaB-treated mice by FACS analysis. However, alphaCD40 treatment in Ad5IkappaB-infected mice induced elevation of serum alanine aminotransferase at 24 hours, and the liver injury was associated with massive hepatocyte apoptosis. Furthermore, interferon gamma (IFN-gamma) production by NK cells and T cells was increased and stimulated tumor necrosis factor alpha (TNF-alpha) production by macrophages in the Ad5IkappaB-infected liver. Moreover, the liver injury was completely suppressed by the administration of anti-IFN-gamma and anti-TNF-alpha. These results suggest that inhibition of NF-kappaB activity suppressed alphaCD40-induced liver inflammation at an early phase, resulting in a reduction in cytokine and chemokine production, whereas it sensitized hepatocytes to TNF-alpha-induced apoptosis and exacerbated liver injury at the late phase. In conclusion, NF-kappaB exerts pivotal activities at inflammatory sites, and caution should be exercised in NF-kappaB-targeted therapy of liver disease.

Tumor-infiltrating effector cells of alpha-galactosylceramide-induced antitumor immunity in metastatic liver tumor

Background

α-Galactosylceramide (α-GalCer) can be presented by CD1d molecules of antigen-presenting cells, and is known to induce a potent NKT cell-dependent cytotoxic response against tumor cells. However, the main effector cells in α-GalCer-induced antitumor immunity are still controversial.

Methods

In order to elucidate the cell phenotype that plays the most important role in α-GalCer-induced antitumor immunity, we purified and analyzed tumor-infiltrating leukocytes (TILs) from liver metastatic nodules of a colon cancer cell line (Colon26), comparing α-GalCer- and control vehicle-treated mice. Flow cytometry was performed to analyze cell phenotype in TILs and IFN-γ ELISA was performed to detect antigen-specific immune response.

Results

Flow cytometry analysis showed a significantly higher infiltration of NK cells (DX5+, T cell receptor αβ (TCR)-) into tumors in α-GalCer-treated mice compared to vehicle-treated mice. The DX5+TCR+ cell population was not significantly different between these two groups, indicating that these cells were not the main effector cells. Interestingly, the CD8+ T cell population was increased in TILs of α-GalCer-treated mice, and the activation level of these cells based on CD69 expression was higher than that in vehicle-treated mice. Moreover, the number of tumor-infiltrating dendritic cells (DCs) was increased in α-GalCer-treated mice. IFN-γ ELISA showed stronger antigen-specific response in TILs from α-GalCer-treated mice compared to those from vehicle-treated mice, although the difference between these two groups was not significant.

Conclusions

In α-GalCer-induced antitumor immunity, NK cells seem to be some of the main effector cells and both CD8+ T cells and DCs, which are related to acquired immunity, might also play important roles in this antitumor immune response. These results suggest that α-GalCer has a multifunctional role in modulation of the immune response.

Isolation of murine hepatic lymphocytes using mechanical dissection for phenotypic and functional analysis of NK1.1+ cells

AIM

To choose an appropriate methods for the isolation of hepatic lymphocytes between the mechanical dissection and the enzymatic digestion and investigate the effects of two methods on phenotype and function of hepatic lymphocytes.

METHODS

Hepatic lymphocytes were isolated from untreated, poly (I:C)-stimulated or ConA-stimulated mice using the two methods, respectively. The cell yield per liver was evaluated by direct counting under microscope. Effects of digestive enzymes on the surface markers involved in hepatic lymphocytes were represented by relative change rate ((percentage of post-digestion -percentage of pre-digestion)/percentage of pre-digestion). Phenotypic analyses of the subpopulations of hepatic lymphocytes and intracellular cytokines were detected by flow cytometry. The cytotoxicity of NK cells from wild C57BL/6 or poly (I:C)-stimulated C57BL/6 mice was analyzed with a 4-h (51)Cr release assay.

RESULTS

NK1.1(+) cell markers, NK1.1 and DX5, were significantly down-expressed after enzymatic digestion and their relative change rates were about 28% and 32%, respectively. Compared with the enzymatic digestion, the cell yield isolated from unstimulated, poly (I:C)-treated or ConA-treated mice by mechanical dissection was not significantly decreased. Hepatic lymphocytes isolated by the mechanical dissection comprised more innate immune cells like NK, NKT and gammadelta cells in normal C57BL/6 mice. After poly (I:C) stimulation, hepatic NK cells rose to about 35%, while NKT cells simultaneously decreased. Following ConA injection, the number of hepatic NKT cells was remarkably reduced to 3.67%. Higher ratio of intracellular IFN-gamma(+) (68%) or TNF-alpha(+) (15%) NK1.1(+) cells from poly (I:C)-treated mice was obtained using mechanical dissection method than control mice. There was no difference in viability between the mechanical dissection and the enzymatic digestion, and hepatic lymphocytes obtained with the two methods had similar cytotoxicity against YAC-1 cells.

CONCLUSION

There is no difference in the cell yield and viability of the hepatic lymphocyte isolated with the two methods. The mechanical dissection, but not the enzymatic digestion, may be suitable for the phenotypic analysis of hepatic NK1.1(+) cell.

Murine hepatocyte cell lines promote expansion and differentiation of NK cells from stem cell precursors

While fetal liver is a major hematopoietic organ, normal adult liver provides a suitable microenvironment for a variety of immune cells and, in several pathological conditions, may become a site of extramedullary hematopoiesis. The direct influence of hepatocytes on hematopoietic cell differentiation is poorly understood. We have previously reported that the Met murine hepatocyte (MMH) untransformed hepatocytic lines retain several morphological and functional features of hepatocytes in vivo and are able to support the survival, self-renewal, and differentiation of hematopoietic precursors in a cell-cell contact system. Here we report the effects of soluble factors released by MMH lines on bone marrow-derived cells. Lymphohematopoietic cells were cultured in two different cell contact-free systems: transwell inserts on MMH feeder layers, and MMH conditioned medium (MMH-CM). Both culture systems were able to promote a substantial expansion of bone marrow-derived cells and their differentiation to natural killer (NK) cells that express the NK1.1 and U5A2-13 markers. Purified hematopoietic stem cells (Sca-1+Lin-), either plated as a bulk population or as single cells, were also able to differentiate into NK cells, when cultured in MMH-CM; thus, soluble factors secreted by MMH lines promote the expansion and differentiation of NK precursor cells. MMH-CM-derived NK cells are functionally active; stimulation by interleukin (IL)-12 together with IL-18 was required to induce interferon-gamma (IFNgamma) expression and to enhance their cytotoxic activity. In conclusion, our findings may imply a direct role of hepatocytes in NK cell development, and the system we have used may provide a tool for studying the molecular mechanisms of NK cell differentiation.

Activated natural killer T cells induce liver injury by Fas and tumor necrosis factor-alpha during alcohol consumption

BACKGROUND & AIMS

Chronic alcohol abuse induces liver injury and increases the severity of viral hepatitis, but the precise mechanisms responsible are not well understood. In particular, little is known about the role of natural killer T cells in alcohol-induced liver injury. Natural killer T cells are mediators of important regulator and effector functions making use of Fas and tumor necrosis factor (TNF)-alpha in apoptosis induction. This report analyzes the role of natural killer T cells, Fas, and TNF-alpha in a model of chronic alcohol consumption.

METHODS

Mice fed alcohol by intragastric tube were assayed for serum alanine aminotransferase values, liver histology, and liver mononuclear cells before and after activation of natural killer T cells by ligand alpha-galactosylceramide.

RESULTS

In alcohol-consuming animals, liver natural killer T cells increase, and further activation by alpha-galactosylceramide causes lethal liver injury. This is explained by alcohol-induced hepatocyte sensitization to cell-mediated lysis, which develops concomitant to increased cytolytic activity of natural killer T cells. Natural killer T cell-mediated apoptosis proceeds by the Fas pathway, and Fas is essential for alcohol-associated liver injury. TNF-alpha plays an additional role as a defect in TNF receptor-1 inhibits alcohol-associated liver injury. Alcohol-fed natural killer T cell-deficient Jalpha281(-/-) mice express a delay in alcohol-induced liver injury.

CONCLUSIONS

Alcohol consumption induces an increase of natural killer T cells in the liver and a high sensitivity of hepatocytes to cell-mediated lysis. Stimulation of natural killer T cells during alcohol consumption induces serious liver injury by a mechanism that involves concomitant signals by Fas and tumor necrosis factor receptor-1 on alcohol-stressed hepatocytes.

Recently primed CD8+ T cells entering the liver induce hepatocytes to interact with naïve CD8+ T cells in the mouse

Large number of T cells traffic through the liver. In order to examine the effects of such traffic on the phenotype of hepatocytes, we vaccinated mice using DNA vaccines encoding antigens with MHC class I-binding epitopes. Small numbers of activated CD8(+) T blasts (10(5)-10(6)/liver) changed the surface phenotype and cytokine expression profile of hepatocytes (HCs). HCs upregulate surface expression of major histocompatibility complex (MHC) class I molecules and CD1d but not MHC class II molecules Qa-1, CD80, CD86, CD54, or CD95; in addition, they expressed/secreted interleukin (IL)-10 and IL-4 but not IL-1, IL-6, IL-13, interferon (IFN)-gamma, tumor necrosis factor (TNF), IL-4, or IL-27 (i.e., they acquire the HC* phenotype). HCs* (but not HCs) induced specific activation, proliferation, and IFN-gamma, TNF, and IL-13 release of cocultured naïve CD8(+) T cells. In contrast to the specific activation of naïve CD8(+) T cells by dendritic cells (DCs), specific CD8(+) T cell activation by HC* was not down-modulated by IFN-alphabeta. Only recently activated CD8(+) T blasts (but not recently activated CD4(+) T blasts or activated cells of the innate immune system, including natural killer T [NKT] cells) induced the HC* phenotype that is prominent from day 10 to day 20 postvaccination (i.e., time points at which peak numbers of recently primed CD8(+) T blasts are found in the liver). In conclusion, recently activated CD8(+) T blasts that enter the liver postimmunization in small numbers can transiently modulate the phenotype of HC, allowing them to activate naïve CD8(+) T cells with unrelated specificities.

Localization of lymphocyte apoptosis in murine lymphoid tissues after stimulation of natural killer T cells with alpha-galactosylceramide

Alpha-galactosylceramide (alpha-GalCer) has been reported to induce activation-induced cell death (AICD) in natural killer T (NKT) cells. We undertook this study to demonstrate the distribution of AICD of NKT cells in the lymphoid tissues and differences in frequency between the central and peripheral lymphoid tissues, histologically and quantitatively analyzing the apoptotic figure in the murine spleen, lymph node, and thymus after alpha-GalCer treatment. Lymphocyte apoptosis was identified as a cluster of nuclei with chromatin condensation in hematoxylin-eosin-stained sections, and was confirmed by TUNEL staining, double staining for TUNEL and CD4, and electron microscopy. In the spleen, it appeared at 12 h after alpha-GalCer administration, increased in number, reaching a peak at 24 h, and then falling to a normal level at 72 h. It was preferentially found in the white pulp, especially in the periarterial lymphoid sheath, but was sparse in the red pulp. Alpha-GalCer-induced lymphocyte apoptosis was seen in tumor-necrosis factor (TNF)-deficient mice as well, but was not in lpr/lpr (Fas-deficient) or gld/gld (Fas ligand-deficient) mice. As for the tissue distribution, lymphocyte apoptosis was frequently seen in the paracortex of the lymph node, whereas it was rare in the thymus. These data indicate that alpha-GalCer-induced AICD of NKT cells takes place in the T-cell area of peripheral lymphoid tissues (i.e., the spleen and lymph node) through the Fas/Fas ligand, but not the TNF pathway.

Specific, functional effector/memory CD8+ T cells are found in the liver post-vaccination

BACKGROUND

The liver efficiently eliminates activated CD8+ T blasts. It is unknown if vaccine-primed CD8+ T blasts migrate to and establish functional CD8+ T cell immunity in the liver post-immunization.

AIMS

We tested, if functional CD8+ T cell populations can be detected in the liver post-vaccination.

METHODS

Murine CD8+ T cells with different epitope/restriction specificities were primed by intramuscular injection of protein- or DNA-based vaccines. The kinetics of appearance in the liver, as well as the surface phenotype and functional competence of intrahepatic, specific CD8+ T cell populations was tested.

RESULTS

High numbers of specific CD8+ T cells appear in the liver after vaccination that are activated (CD69+ CD44+), express effector functions (CD27lo/CD28lo phenotype, interferon gamma secretion, specific cytolytic reactivity), but show no evidence of apoptosis (annexin V-, B220lo, similar numbers/kinetics in primed, congenic lpr/lpr mice). Specific CD8+ T cells from the liver adoptively transferred into a naïve, syngeneic host successfully reconstitute specific CD8+ T cell immunity.

CONCLUSIONS

Specific, functionally competent CD8+ effector/memory T cell populations are established in the liver for months post-vaccination.

Detection of T lymphocyte subsets and mIL-2R on surface of PBMC in patients with hepatitis B

AIM: To study the levels of T lymphocyte subsets and membrane interleukin-2 receptor (mIL-2R) on surface of peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B and its role in the pathogenesis of hepatitis B.

METHODS: The levels of T lymphocyte subsets and mIL-2R in PBMC before and after being stimulated with PHA were detected by biotin-streptavidin (BSA) technique in 196 cases of hepatitis B.

RESULTS: In patients with hepatitis B, the levels of CD₃⁺, CD₄⁺ cells, and the ratio of CD₄⁺ cells/CD₈⁺ cells were lower, but the level of CD₈⁺ cells was higher than those in normal controls (42.20 ± 6.01 vs 65.96 ± 6.54, 38.17 ± 5.93 vs 41.73 ± 6.40, 0.91 ± 0.28 vs 1.44 ± 0.31, 39.86 ± 6.36 vs 30.02 ± 4.54, P < 0.01). The total expression level of mIL-2R in PBMC before and after being stimulated with PHA was also lower than those in normal controls (3.47 ± 1.55 vs 4.52 ± 1.49, 34.03 ± 2.94 vs 37.95 ± 3.00, P < 0.01). In all the patients with hepatitis B, the levels of T lymphocyte subsets and mIL-2R in PBMC with HBV-DNA (+) were lower than those with HBV-DNA (-), which were significantly different (39.57 ± 7.11 vs 44.36 ± 5.43, 34.36 ± 7.16 vs 40.75 ± 5.87, 37.82 ± 6.54 vs 41.72 ± 6.21, 0.88 ± 0.33 vs 0.99 ± 0.27, 2.82 ± 1.62 vs 3.85 ± 1.47, 31.56 ± 3.00 vs 35.84 ± 2.83, P < 0.01). In addition, the levels of CD₃⁺, CD₄⁺, CD₈⁺ cells, the ratio of CD₄⁺ cells/CD₈⁺ cells and mIL-2R among different courses of hepatitis B were all significantly different (F = 3723.18, P < 0.01. F = 130.43, P < 0.01. F = 54.01, P < 0.01. F = 2.99, P < 0.05. F = 7.16, P < 0.01).

CONCLUSION: Both cellular and humoral immune functions are obviously in disorder in patients with hepatitis B, which might be closely associated with the chronicity in patients.

NKT cells provide help for dendritic cell-dependent priming of MHC class I-restricted CD8+ T cells in vivo

Dendritic cells (DC) are potent APCs for naive T cells in vivo. This is evident by inducing T cell responses through adoptive DC transfer. Priming specific CTL responses in vivo often requires "help". We study alternative sources of help in DC-dependent priming of MHC class I-restricted CTL. Priming an anti-viral CTL response in naive B6 mice by adoptive transfer of antigenic peptide-pulsed DC required CD4(+) T cell help. CTL priming was facilitated by providing MHC class II-dependent specific help. Furthermore, transfers of MHC class II-deficient pulsed DC into naive, normal hosts, or DC transfers into naive, CD4(+) T cell-depleted hosts primed CTL inefficiently. Pretreatment of DC with immune-stimulating oligodeoxynucleotides rendered them more efficient for CD4(+) T cell-independent priming of CTL. DC copresenting a K(b)-binding antigenic peptide and the CD1d-binding glycolipid alpha-galactosyl-ceramide efficiently primed CTL in a class II-independent way. To obtain NKT cell-dependent help in CTL priming, the same DC had to present both the peptide and the glycolipid. CTL priming by adoptive DC transfer was largely NK cell-dependent. The requirement for NK cells was only partially overcome by recruiting NKT cell help into DC-dependent CTL priming. NKT cells thus are potent helper cells for DC-dependent CTL priming.