Liver-resident Natural Killer Research Articles

Galectin-3-ITGB1 Signaling Mediates Interleukin 10 Production of Hepatic Conventional Natural Killer Cells in Hepatitis B Virus Transgenic Mice and Correlates with Hepatocellular Carcinoma Progression in Patients.

The outcomes of HBV infections are related to complex immune imbalances; however, the precise mechanisms by which HBV induces immune dysfunction are not well understood. HBV transgenic (HBs-Tg) mice were used to investigate intrahepatic NK cells in two distinct subsets: conventional NK (cNK) and liver-resident NK (LrNK) cells during a chronic HBV infection. The cNK cells, but not the LrNK cells, were primarily responsible for the increase in the number of bulk NK cells in the livers of ageing HBs-Tg mice. The hepatic cNK cells showed a stronger ability to produce IL-10, coupled with a higher expression of CD69, TIGIT and PD-L1, and lower NKG2D expression in ageing HBs-Tg mice. A lower mitochondrial mass and membrane potential, and less polarized localization were observed in the hepatic cNK cells compared with the splenic cNK cells in the HBs-Tg mice. The enhanced galectin-3 (Gal-3) secreted from HBsAg+ hepatocytes accounted for the IL-10 production of hepatic cNK cells via ITGB1 signaling. For humans, LGALS3 and ITGB1 expression is positively correlated with IL-10 expression, and negatively correlated with the poor clinical progression of HCC. Gal-3-ITGB1 signaling shapes hepatic cNK cells but not LrNK cells during a chronic HBV infection, which may correlate with HCC progression.

Single-cell landscape of functionally cured chronic hepatitis B patients reveals activation of innate and altered CD4-CTL-driven adaptive immunity

Hepatitis B surface antigen (HBsAg) loss or functional cure (FC) is considered the optimal therapeutic outcome for patients with chronic hepatitis B (CHB). However, the immune-pathological biomarkers and underlying mechanisms of FC remain unclear. In this study we comprehensively interrogate disease-associated cell states identified within intrahepatic tissue and matched PBMCs (peripheral blood mononuclear cells) from patients with CHB or after FC, at the resolution of single cells, to provide novel insights into putative mechanisms underlying FC. We combined single-cell transcriptomics (single-cell RNA sequencing) with multiparametric flow cytometry-based immune phenotyping, and multiplexed immunofluorescence to elucidate the immunopathological cell states associated with CHB vs. FC. We found that the intrahepatic environment in CHB and FC displays specific cell identities and molecular signatures that are distinct from those found in matched PBMCs. FC is associated with the emergence of an altered adaptive immune response marked by CD4 cytotoxic T lymphocytes, and an activated innate response represented by liver-resident natural killer cells, specific Kupffer cell subtypes and marginated neutrophils. Surprisingly, we found MHC class II-expressing hepatocytes in patients achieving FC, as well as low but persistent levels of covalently closed circular DNA and pregenomic RNA, which may play an important role in FC. Our study provides conceptually novel insights into the immuno-pathological control of HBV cure, and opens exciting new avenues for clinical management, biomarker discovery and therapeutic development. We believe that the discoveries from this study, as it relates to the activation of an innate and altered immune response that may facilitate sustained, low-grade inflammation, may have broader implications in the resolution of chronic viral hepatitis. This study dissects the immuno-pathological cell states associated with functionally cured chronic hepatitis B (defined by the loss of HBV surface antigen or HBsAg). We identified the sustained presence of very low viral load, accessory antigen-presenting hepatocytes, adaptive-memory-like natural killer cells, and the emergence of helper CD4 T cells with cytotoxic or effector-like signatures associated with functional cure, suggesting previously unsuspected alterations in the adaptive immune response, as well as a key role for the innate immune response in achieving or maintaining functional cure. Overall, the insights generated from this study may provide new avenues for the development of alternative therapies as well as patient surveillance for better clinical management of chronic hepatitis B.

The aryl hydrocarbon receptor maintains antitumor activity of liver resident natural killer cells after partial hepatectomy in C57BL/6J mice.

Liver-resident natural killer (lr-NK) cells are distinct from conventional NK cells and exhibit higher cytotoxicity against hepatoma via tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). However, the mechanism by which partial hepatectomy (PH) significantly suppresses TRAIL expression in lr-NK cells remains unclear. This study aimed to investigate the PH influence on the function and characteristics of liver-resident NK (lr-NK) cells using a PH mouse model. Here, we report that PH alters the differentiation pattern of NK cells in the liver, and an aryl hydrocarbon receptor (AhR) molecule is involved in these changes. Treatment with the AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ) inhibited the maturation of NK cells. FICZ increased the immature subtype proportion of NK cells with high TRAIL activity and decreased the mature subtype of NK cells with low TRAIL activity. Consequently, FICZ increased the expression of TRAIL and cytotoxic activity of NK cells in the liver, and this effect was confirmed even after hepatectomy. The participation of AhR promoted FoxO1 expression in the mTOR signaling pathway involved in the maturation of NK cells, resulting in TRAIL expression. Our findings provide direct in-vivo evidence that partial hepatectomy affects lrNK cell activity through NK cell differentiation in the liver. Perioperative therapies using an AhR agonist to improve NK cell function may reduce the recurrence of hepatocellular carcinoma after hepatectomy.

Early life gut microbiota sustains liver-resident natural killer cells maturation via the butyrate-IL-18 axis

Liver-resident natural killer cells, a unique lymphocyte subset in liver, develop locally and play multifaceted immunological roles. However, the mechanisms for the maintenance of liver-resident natural killer cell homeostasis remain unclear. Here we show that early-life antibiotic treatment blunt functional maturation of liver-resident natural killer cells even at adulthood, which is dependent on the durative microbiota dysbiosis. Mechanistically, early-life antibiotic treatment significantly decreases butyrate level in liver, and subsequently led to defective liver-resident natural killer cell maturation in a cell-extrinsic manner. Specifically, loss of butyrate impairs IL-18 production in Kupffer cells and hepatocytes through acting on the receptor GPR109A. Disrupted IL-18/IL-18R signaling in turn suppresses the mitochondrial activity and the functional maturation of liver-resident natural killer cells. Strikingly, dietary supplementation of experimentally or clinically used Clostridium butyricum restores the impaired liver-resident natural killer cell maturation and function induced by early-life antibiotic treatment. Our findings collectively unmask a regulatory network of gut-liver axis, highlighting the importance of the early-life microbiota in the development of tissue-resident immune cells.

Control of human cytomegalovirus replication by liver resident natural killer cells

Natural killer cells are considered to be important for control of human cytomegalovirus– a major pathogen in immune suppressed transplant patients. Viral infection promotes the development of an adaptive phenotype in circulating natural killer cells that changes their anti-viral function. In contrast, less is understood how natural killer cells that reside in tissue respond to viral infection. Here we show natural killer cells resident in the liver have an altered phenotype in cytomegalovirus infected individuals and display increased anti-viral activity against multiple viruses in vitro and identify and characterise a subset of natural killer cells responsible for control. Crucially, livers containing natural killer cells with better capacity to control cytomegalovirus replication in vitro are less likely to experience viraemia post-transplant. Taken together, these data suggest that virally induced expansion of tissue resident natural killer cells in the donor organ can reduce the chance of viraemia post-transplant.

Innate lymphocytes: Role in alcohol-induced immune dysfunction.

Alcohol use is known to alter the function of both innate and adaptive immune cells, such as neutrophils, macrophages, B cells, and T cells. Immune dysfunction has been associated with alcohol-induced end-organ damage. The role of innate lymphocytes in alcohol-associated pathogenesis has become a focus of research, as liver-resident natural killer (NK) cells were found to play an important role in alcohol-associated liver damage pathogenesis. Innate lymphocytes play a critical role in immunity and homeostasis; they are necessary for an optimal host response against insults including infections and cancer. However, the role of innate lymphocytes, including NK cells, natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, gamma delta T cells, and innate lymphoid cells (ILCs) type 1–3, remains ill-defined in the context of alcohol-induced end-organ damage. Innate-like B lymphocytes including marginal zone B cells and B-1 cells have also been identified; however, this review will address the effects of alcohol misuse on innate T lymphocytes, as well as the consequences of innate T-lymphocyte dysfunction on alcohol-induced tissue damage.

Requirement of RORα for maintenance and antitumor immunity of liver-resident natural killer cells/ILC1s.

Liver type 1 innate lymphoid cells (ILC1s), also known as liver-resident natural killer (LrNK) cells, comprise a high proportion of total hepatic ILCs. However, factors regulating their maintenance and function remain unclear. In this study, we found high expression of retinoid-related orphan nuclear receptor alpha (RORα) in LrNK cells/ILC1s. Mice with conditional ablation of retinoid-related orphan nuclear receptor alpha (Rorα) in LrNK cells/ILC1s and conventional natural killer (cNK) cells had decreased LrNK cells/ILC1s but normal numbers of cNK cells. RORα-deficient LrNK cells/ILC1s displayed increased apoptosis and significantly altered transcriptional profile. Using a murine model of colorectal cancer liver metastasis, we found that RORα conditional deficiency resulted in more aggressive liver tumor progression and impaired effector molecule expression in LrNK cells/ILC1s. Consequently, treatment with the RORα agonist efficiently limited liver metastases and promoted effector molecule expression of LrNK cells/ILC1s. This study reveals a role of RORα in LrNK cell/ILC1 maintenance and function, providing insights into the harnessing of LrNK cell/ILC1 activity in the treatment of liver cancer.

A subset of liver resident natural killer cells is expanded in hepatitis C-infected patients with better liver function

Viral hepatitis leads to immune-mediated liver injury. The rate of disease progression varies between individuals. We aimed to phenotype immune cells associated with preservation of normal liver function during hepatitis C virus (HCV) infection. Clinical data and specimens were obtained from 19 HCV-infected patients undergoing liver transplantation. Liver and peripheral blood mononuclear cells were isolated and eight subsets of innate immune cells were delineated by multiparameter flow cytometry. Cytokine assays and microarrays were performed. Intrahepatic CD56Bright/CD16- natural killer (NK) cells comprised the only subset correlating with better liver function, i.e., lower bilirubin (p = 0.0002) and lower model for end stage of liver disease scores (p = 0.03). The signature of liver NK cells from HCV-infected patients included genes expressed by NK cells in normal liver and by decidual NK cells. Portal vein blood had a higher concentration of interleukin (IL)-10 than peripheral blood (p = 0.03). LMCs were less responsive to toll-like receptor (TLR) stimulation than PBMCs, with fewer pro-inflammatory gene-expression pathways up-regulated after in vitro exposure to lipopolysaccharide and a TLR-7/8 agonist. Hepatic CD56Bright/CD16- NK cells may be critical for maintaining liver homeostasis. Portal vein IL-10 may prime inhibitory pathways, attenuating TLR signaling and reducing responsiveness to pro-inflammatory stimuli.

Tim-3 Hampers Tumor Surveillance of Liver-Resident and Conventional NK Cells by Disrupting PI3K Signaling.

Natural killer (NK) cells are enriched within the liver. Apart from conventional NK (cNK) cells, recent studies identified a liver-resident NK (LrNK) subset, which constitutes about half of hepatic NK cells and exhibits distinct developmental, phenotypic, and functional features. However, it remains unclear whether and how LrNK cells, as well as cNK cells, participate in the development of hepatocellular carcinoma (HCC) individually. Here, we report that both LrNK and cNK cells are significantly decreased in HCC. The T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) was significantly upregulated in both tumor-infiltrating LrNK and cNK cells and suppressed their cytokine secretion and cytotoxic activity. Mechanistically, phosphatidylserine (PtdSer) engagement promoted phosphorylation of Tim-3, which then competed with PI3K p110 to bind p85, inhibiting downstream Akt/mTORC1 signaling and resulting in malfunctioning of both NK-cell subsets. Tim-3 blockade retarded HCC growth in a NK-cell-dependent manner. These studies for the first time report the presence and dysfunction of LrNK cells in HCC and show that Tim-3-mediated PI3K/mTORC1 interference is responsible for the dysfunction of both tumor-infiltrating cNK and LrNK cells, providing a new strategy for immune checkpoint-based targeting. SIGNIFICANCE: Tim-3 enhances hepatocellular carcinoma growth by blocking natural killer cell function.

Everolimus enhances TRAIL-mediated anti-tumor activity of liver resident natural killer cells in mice.

In transplantation, innate immunity plays a pivotal role in immunosurveillance and host defence against microbes and neoplastic cells. Liver-resident NK cells express TNF-related apoptosis-inducing ligand (TRAIL), which distinguishes them from conventional NK cells. In this study, we investigated the impact of mTOR inhibition on liver-resident NK cells in comparison with that on splenic NK cells in a mouse model. In mice that received everolimus (EVR) for 7days (range: 0.0125-0.25mg/kg/day), the proportion of splenic NK cells was unchanged, whereas the number of liver NK cells including TRAIL+ NK subpopulation increased for all doses of EVR. Consistently, liver-resident NK cells from the EVR-treated mice displayed enhanced cytotoxicity against TRAIL-sensitive neoplastic cells. EVR treatment inhibited the transition of the immature subset of liver NK cells to a mature state. The negative regulator of NK cells FoxO1 was activated as a consequence of impaired mTORC2-dependent AKT phosphorylation. Activated FoxO1 both reduced T-bet expression and induced TRAIL expression, thereby inhibiting NK cell maturation and promoting the antitumour activity of the immature subset of liver NK cells in response to EVR treatment. These findings indicate that EVR treatment enhances the antitumour activity of immature liver-resident NK cells through TRAIL upregulation.

Accumulation of Tumor-Infiltrating CD49a+ NK Cells Correlates with Poor Prognosis for Human Hepatocellular Carcinoma

The discovery of CD49a+ liver-resident natural killer (NK) cells in mice alters our view of NK cells and provides another opportunity to study NK cells. Although evidence has suggested roles for NK cells in liver diseases, whether and how CD49a+ NK cells contribute to liver diseases remain unclear. In this study, we observed that accumulation of CD49a+ tissue-resident NK cells in human hepatocellular carcinoma (HCC) was higher than in peritumoral tissues. We studied the exhausted and regulatory phenotypes of CD49a+ tissue-resident NK cells by analysis of protein and mRNA. The proportion of CD49a+ NK cells was positively correlated to the proportion of NK cells expressing inhibitory receptors. In addition, CD49a+ NK cells expressed more of checkpoint molecules PD-1, CD96, and TIGIT. Transcriptomic analysis implicated CD49a+ tissue-resident NK cells in the negative regulation of immune responses. Comparison of murine and human CD49a+ NK cells revealed their distinct characteristics and functions. Finally, accumulation of tissue-resident CD49a+ NK cells in liver tumor was correlated to deteriorating disease condition and poor prognosis. Our findings show that CD49a+ NK cells accumulate in liver tumor and suggest a role for CD49a+ NK cells in the negative regulation of immune responses and the development of HCC.

CD8+ T Cells Promote Maturation of Liver-Resident NK Cells Through the CD70-CD27 axis.

Liver-resident natural killer (LrNK) cells are a unique subset of NK cells that are distinct from conventional NK cells. However, little is known about the mechanisms by which LrNK cells mature. In this study, we discovered that LrNK cells exhibit a relatively immature phenotype and impaired cytotoxic capacity in the absence of CD8+ T cells. The provision of CD8+ T cells to Cd8-/- or Rag1-/- mice led to the restoration of LrNK cell maturation. Furthermore, co-culture with CD8+ T cells induced immature CD27+ LrNK cells to convert into mature CD27- LrNK cells, whereas blocking the interaction of CD70 and CD27 abrogated the ability of CD8+ T cells to promote the maturation of LrNK cells. Conclusion: Our findings indicate that CD8+ T cells promote the maturation of LrNK cells through the CD70-CD27 axis, and therefore highlight a previously unknown mechanism responsible for the mediation of LrNK cell maturation.

γδT Cells Suppress Liver Fibrosis via Strong Cytolysis and Enhanced NK Cell-Mediated Cytotoxicity Against Hepatic Stellate Cells.

Liver fibrosis is the excessive accumulation of extracellular matrix proteins, resulting from maladaptive wound healing responses to chronic liver injury. γδT cells are important in chronic liver injury pathogenesis and subsequent liver fibrosis; however, their role and underlying mechanisms are not fully understood. The present study aims to assess whether γδT cells contribute to liver fibrosis regression. Using a carbon tetrachloride (CCl4)-induced murine model of liver fibrosis in wild-type (WT) and γδT cell deficient (TCRδ−/−) mice, we demonstrated that γδT cells protected against liver fibrosis and exhibited strong cytotoxicity against activated hepatic stellate cells (HSCs). Further study show that chronic liver inflammation promoted hepatic γδT cells to express NKp46, which contribute to the direct killing of activated HSCs by γδT cells. Moreover, we identified that an IFNγ-producing γδT cell subset (γδT1) cells exhibited stronger cytotoxicity against activated HSCs than the IL-17-producing subset (γδT17) cells upon chronic liver injury. In addition, γδT cells promoted the anti-fibrotic ability of conventional natural killer (cNK) cells and liver-resident NK (lrNK) cells by enhancing their cytotoxicity against activated HSCs. The cell crosstalk between γδT and NK cells was shown to depend partly on co-stimulatory receptor 4-1BB (CD137) engagement. In conclusion, our data confirmed the protective effects of γδT cells, especially the γδT1 subset, by directly killing activated HSCs and increasing NK cell-mediated cytotoxicity against activated HSCs in CCl4-induced liver fibrosis, which suggest valuable therapeutic targets to treat liver fibrosis.

Lactate-Mediated Acidification of Tumor Microenvironment Induces Apoptosis of Liver-Resident NK Cells in Colorectal Liver Metastasis.

Colorectal cancer is the third most common malignancy worldwide, with 1.3 million new cases annually. Metastasis to the liver is a leading cause of mortality in these patients. In human liver, metastatic cancer cells must evade populations of liver-resident natural killer (NK) cells with potent cytotoxic capabilities. Here, we investigated how these tumors evade liver NK-cell surveillance. Tissue biopsies were obtained from patients undergoing resection of colorectal liver metastasis (CRLM, n = 18), from the tumor, adjacent tissue, and distal resection margin. The number and phenotype of liver-resident NK cells, at each site, were analyzed by flow cytometry. Tumor-conditioned media (TCM) was generated for cytokine and metabolite quantification and used to treat healthy liver-resident NK cells, isolated from donor liver perfusate during transplantation. Liver-resident NK cells were significantly depleted from CRLM tumors. Healthy liver-resident NK cells exposed to TCM underwent apoptosis in vitro, associated with elevated lactate. Tumor-infiltrating liver-resident NK cells showed signs of mitochondrial stress, which was recapitulated in vitro by treating liver-resident NK cells with lactic acid. Lactic acid induced apoptosis by decreasing the intracellular pH of NK cells, resulting in mitochondrial dysfunction that could be prevented by blocking mitochondrial ROS accumulation. CRLM tumors produced lactate, thus decreasing the pH of the tumor microenvironment. Liver-resident NK cells migrating toward the tumor were unable to regulate intracellular pH resulting in mitochondrial stress and apoptosis. Targeting CRLM metabolism provides a promising therapeutic approach to restoring local NK-cell activity and preventing tumor growth.

Liver-Resident NK Cells Control Antiviral Activity of Hepatic T Cells via the PD-1-PD-L1 Axis

The tolerogenic microenvironment of the liver is associated with impaired hepatic Tcell function. Here, weexamined the contribution of liver-resident naturalkiller (LrNK) cells, a prominent hepatic NK cell compartment, to Tcell antiviral responses in the liver. The number of virus-specific Tcells increased in LrNK-cell-deficient mice during both acute and chronic lymphocytic choriomeningitis virus infection. Upon infection with adenovirus, hepatic Tcells from these mice produced more cytokines, which was accompanied by reduced viral loads. Transfer of LrNK cells into LrNK-cell-deficient or wild-type mice inhibited hepatic Tcell function, resulting in impaired viral clearance, whereas transfer of conventional NK cells promoted Tcell antiviral responses. LrNK-cell-mediated inhibition of Tcell function was dependent on the PD-1-PD-L1 axis. Our findings reveal a role forLrNK cells in the regulation of Tcell immunity and provide insight into the mechanisms of immune tolerance in the liver.

Hepatectomy leads to loss of TRAIL-expressing liver NK cells via downregulation of the CXCL9-CXCR3 axis in mice.

Liver-resident natural killer (NK) cells express TNF-related apoptosis-inducing ligand (TRAIL), a critical molecule for NK cell-mediated tumor cell killing. We previously reported that TRAIL expression in liver NK cells decreases markedly after hepatectomy; however, the mechanism underlying this drastic alteration remains unknown. In this study, we assessed the role of chemokine signaling in liver-resident NK cells during the perioperative period of hepatectomy. The expression levels of various chemokine receptors on liver-resident NK cells and their associations with TRAIL expression were analyzed by flow cytometry. The expression of various intrahepatic chemokines/cytokines was analyzed after 70% hepatectomy in mice by quantitative RT-PCR and flow cytometry. We further investigated whether polyinosinic—polycytidylic acid (poly I:C)-induced NK cell activation could ameliorate TRAIL expression in the liver after 70% hepatectomy in CXCR3-/- and wild-type mice. TRAIL+ NK cells strongly and exclusively expressed CXCR3, and the expression of its ligand CXCL9 was significantly decreased in the liver after hepatectomy. The kinetics of hepatic CXCL9 expression resembled the changes in hepatic TRAIL+ NK cells after hepatectomy. Among liver-resident mononuclear cells, CXCL9 was predominantly secreted by macrophages in response to interferon-γ stimulation. Although the administration of poly I:C, an inducer of interferon-γ, increased hepatic CXCL9 levels in both CXCR3-/- and wild-type mice even after hepatectomy, only wild-type mice exhibited the recovery of TRAIL expression on NK cells. Partial hepatectomy remarkably reduced the proportion of TRAIL-expressing NK cells in the liver via the downregulation of the CXCL9–CXCR3 axis in mice. These findings extend our knowledge of the factors contributing to hepatocellular carcinoma recurrence after hepatectomy.

Tumorous niche drives NK exhaustion by disordering metabolic program

Abstract Natural killer (NK) cells are important effectors of the immune system that can lyse malignancy-transformed cells. In the human liver, NK cells can account up to 50% of the total lymphocyte population. How NK cells lose immune surveillance occurs in hepatocellular carcinoma progression. In this study, 75 cases from hepatocellular carcinoma (HCC) patients were analyzed by RNA sequence, pathology, flow cytometry and cell culture in vitro. We found a significant enrichment of infiltrating T cells within the tumor tissues of HCC patients but not NK cells, as compared to the adjacent peritumoral tissues. It is interesting that the infiltrating NK cells enrich CD56brightCD49a+ NK subset, like liver-resident NK. Nearly 50% of the entire healthy liver NK cell population is composed of functionally relevant CD56bright CD49a-NK cells, and almost all of the subset was lose. The infiltrating CD56brightCD49a+ NK cells present exhausted phenotype and downregulated expression of efficacy molecules of CD11b, CD226 and IFN-γ. We also found a few of CD56dimCD16+ NK cells were infiltrating, which were similar to their peripheral circulating counterparts in transcription and phenotype, but the lower effect function and viability of infiltrating NK cells compared with normal liver or peripheral circulating counterparts. Dynamic reprogramming of metabolism is essential for immune cell stable liveness and effector function. Gene Ontology profiling and metabolism analysis revealed the infiltrating NK cells bioenergetic insufficiencies and enrichment of metabolic oxygen specis leading to its subset variations and immune surveillance insensitivity.

The aryl hydrocarbon receptor is required for the maintenance of liver-resident natural killer cells

A tissue-resident population of natural killer cells (NK cells) in the liver has recently been described to have the unique capacity to confer immunological memory in the form of hapten-specific contact hypersensitivity independent of T and B cells. Factors regulating the development and maintenance of these liver-resident NK cells are poorly understood. The aryl hydrocarbon receptor (AhR) is a transcription factor modulated by exogenous and endogenous ligands that is important in the homeostasis of immune cells at barrier sites, such as the skin and gut. In this study, we show that liver-resident NK (NK1.1+CD3-) cells, defined as CD49a+TRAIL+CXCR6+DX5- cells in the mouse liver, constitutively express AhR. In AhR-/- mice, there is a significant reduction in the proportion and absolute number of these cells, which results from a cell-intrinsic dependence on AhR. This deficiency in liver-resident NK cells appears to be the result of higher turnover and increased susceptibility to cytokine-induced cell death. Finally, we show that this deficiency has functional implications in vivo. Upon hapten exposure, AhR-/- mice are not able to mount an NK cell memory response to hapten rechallenge. Together, these data demonstrate the requirement of AhR for the maintenance of CD49a+TRAIL+CXCR6+DX5- liver-resident NK cells and their hapten memory function.

WITHDRAWN: Natural Killer Cell Activating Receptor NKG2D Is Involved in the Immunosuppressant Effect of Mycophenolate Mofetil and Infection of Hepatitis B Virus

In this study we investigated whether mycophenolate mofetil (MMF), a new immunosuppressant, and its metabolite mycophenolic acid (MPA) influence the activity of liver resident natural killer (NK) cells, resulting in increased susceptibility to hepatitis B virus (HBV) infection. We isolated the hepatic NK cells of C57BL/6 and C57BL/6JTgN (A1b1HBV) 44Bri) transgenic mice administered MMF in the presence or absence of interleukin (IL)-15, or incubated isolated hepatic NK cells in the presence or absence of MPA and used RT-PCR, immunolabeling to assess the expression of NK receptors Ly49A, NKG2A and NKG2D, and cytokine ELISA and [(3)H]-TdR-release assay to assess the activation and cytotoxic capacity of NK cells. After treatment of MMF in the presence or absence of IL-15, HBsAg titer was also measured in C57BL/6JTgN (A1b1HBV) 44Bri) transgenic mice. After both MPA and MMF treatments, NK cytotoxicity was reduced, NKG2D and Ly49A expression was down-regulated, but NKG2A was up-regulated. Down-regulation of NKG2D could be ameliorated by IL-15, and in HBV-transgenic mice, MMF treatment impaired NK cell activity, but did not influence virus replication, whereas IL-15 treatment depressed HBsAg titer. MPA and MMF mediate down-regulation of NKG2D in vitro and vivo, restricting the cytotoxic capacity of NK cells. Regulation of NKG2D may be important in the effect of immunosuppressant on NK cell activity and involved in HBV infection.

Natural Killer Cell Activating Receptor NKG2D Is Involved in the Immunosuppressive Effects of Mycophenolate Mofetil and Hepatitis B Virus Infection

The purpose of this study is to investigate whether mycophenolate mofetil (MMF), a new immunosuppressant, and its metabolite mycophenolic acid (MPA) affect the activity of liver resident natural killer (NK) cells, resulting in increased susceptibility to hepatitis B virus (HBv) infection. Hepatic NK cells were isolated from C57BL/6 and C57BL/ 6JTgN (A1b1HBV) 44Bri transgenic mice treated with MMF in the presence or absence of IL-15. After incubation of isolated hepatic NK cells in the presence or absence of MPA, reverse transcription polymerase chain reaction and immunolabeling were used to assess the expression of NK receptors Ly49A, NKG2A and NKG2D. In addition, cytokine enzyme-linked immunosorbent assay and [3H]-TdR-release assay were carried out to assess NK cell activation and cytotoxic capacity. After treatment with MMF in the presence or absence of IL-15, HBsAg titers were measured in C57BL/6JTgN (A1b1HBV) 44Bri transgenic mice. Treatment with either MPA or MMF resulted in reduced NK cell cytotoxicity, downregulated NKG2D and Ly49A expression and upregulated NKG2A. Interestingly, NKG2D downregulation was ameliorated by IL-15. In HBV-transgenic mice, MMF treatment impaired NK cell activity but did not affect virus replication, whereas IL-15 treatment reduced HBsAg titers. MPA and MMF mediate NKG2D downregulation both in vitro and in vivo, reducing the cytotoxic capacity of NK cells. These findings indicate that NKG2D regulation may be important in the immunosuppressive effect NK cells and involved in HBV infection.