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ObjectiveTissue-resident memory T cells (TRM) are vital immune sentinels that provide protective immunity. While hepatic CD8+TRMhave been well described, little is known about the location, phenotype and function of CD4+TRM.DesignWe used multiparametric flow cytometry, histological assessment and novel human tissue coculture systems to interrogate the ex vivo phenotype, function and generation of the intrahepatic CD4+T-cell compartment. We also used leukocytes isolated from human leukocyte antigen (HLA)-disparate liver allografts to assess long-term retention.ResultsHepatic CD4+T cells were delineated into three distinct populations based on CD69 expression: CD69−, CD69INTand CD69HI. CD69HICD4+cells were identified as tissue-resident CD4+T cells on the basis of their exclusion from the circulation, phenotypical profile (CXCR6+CD49a+S1PR1−PD-1+) and long-term persistence within the pool of donor-derived leukcoocytes in HLA-disparate liver allografts. CD69HICD4+T cells produced robust type 1 polyfunctional cytokine responses on stimulation. Conversely, CD69INTCD4+T cells represented a more heterogenous population containing cells with a more activated phenotype, a distinct chemokine receptor profile (CX3CR1+CXCR3+CXCR1+) and a bias towards interleukin-4 production. While CD69INTCD4+T cells could be found in the circulation and lymph nodes, these cells also formed part of the long-term resident pool, persisting in HLA-mismatched allografts. Notably, frequencies of CD69INTCD4+T cells correlated with necroinflammatory scores in chronic hepatitis B infection. Finally, we demonstrated that interaction with hepatic epithelia was sufficient to generate CD69INTCD4+T cells, while additional signals from the liver microenvironment were required to generate liver-resident CD69HICD4+T cells.ConclusionsHigh and intermediate CD69 expressions mark human hepatic CD4+TRMand a novel functionally distinct recirculating population, respectively, both shaped by the liver microenvironment to achieve diverse immunosurveillance.

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Obesity is increasingly prevalent, strongly associated with nonalcoholic liver disease, and a risk factor for numerous cancers. Here, we describe the liver-related consequences of long-term diet-induced obesity. Mice were exposed to an extended obesity model comprising a diet high in trans-fats and fructose corn syrup concurrent with a sedentary lifestyle. Livers were assessed histologically using the nonalcoholic fatty liver disease (NAFLD) activity score (Kleiner system). Mice in the American Lifestyle-Induced Obesity Syndrome (ALIOS) model developed features of early nonalcoholic steatohepatitis at 6 months (mean NAFLD activity score = 2.4) and features of more advanced nonalcoholic steatohepatitis at 12 months, including liver inflammation and bridging fibrosis (mean NAFLD activity score = 5.0). Hepatic expression of lipid metabolism and insulin signaling genes were increased in ALIOS mice compared with normal chow-fed mice. Progressive activation of the mouse hepatic stem cell niche in response to ALIOS correlated with steatosis, fibrosis, and inflammation. Hepatocellular neoplasms were observed in 6 of 10 ALIOS mice after 12 months. Tumors displayed cytological atypia, absence of biliary epithelia, loss of reticulin, alteration of normal perivenular glutamine synthetase staining (absent or diffuse), and variable α-fetoprotein expression. Notably, perivascular tumor cells expressed hepatic stem cell markers. These studies indicate an adipogenic lifestyle alone is sufficient for the development of nonalcoholic steatohepatitis, hepatic stem cell activation, and hepatocarcinogenesis in wild-type mice.

Changes in glucose metabolism in the liver during transplantation have been recently described using microdialysis. Here, these findings are correlated with histopathologic, immunohistochemical, and ultrastructural changes in liver.

In ∼50% of patients with Hodgkin's lymphoma (HL), the Epstein-Barr virus (EBV), an oncogenic herpesvirus, is present in tumor cells. After microarray profiling of both HL tumors and cell lines, we found that EBV infection increased the expression of the chemokine CCL20 in both primary Hodgkin and Reed-Sternberg cells and Hodgkin and Reed-Sternberg cell-derived cell lines. Additionally, this up-regulation could be mediated by the EBV nuclear antigen 1 protein. The higher levels of CCL20 in the supernatants of EBV-infected HL cell lines increased the migration of CD4+lymphocytes that expressed FOXP3, a marker of regulatory T cells (Tregs), which are specialized CD4+T cells that inhibit effector CD4+and CD8+T cells. In HL, an increased number of Tregs is associated with the loss of EBV-specific immunity. Our results identify a mechanism by which EBV can recruit Tregs to the microenvironment of HL by inducing the expression of CCL20 and, by doing so, prevent immune responses against the virus-infected tumor population. Further investigation of how EBV recruits and modifies Tregs will contribute not only to our understanding of the pathogenesis of virus-associated tumors but also to the development of therapeutic strategies designed to manipulate Treg activity.

The Epstein-Barr virus (EBV) contributes to the growth and survival of Hodgkin lymphoma (HL) cells. Here we report that down-regulation of the transforming growth factor-beta (TGF-beta) target gene, protein tyrosine phosphatase receptor kappa (PTPRK), followed EBV infection of HL cells and was also more frequently observed in the Hodgkin and Reed-Sternberg (HRS) cells of EBV-positive compared with EBV-negative primary HL. The viability and proliferation of EBV-positive HL cells was decreased by overexpression of PTPRK, but increased following the knockdown of PTPRK expression in EBV-negative HL cells, demonstrating that PTPRK is a functional tumor suppressor in HL. EBV suppressed the TGF-beta–mediated activation of PTPRK expression, suggesting disruption of TGF-beta signaling upstream of PTPRK. This was confirmed when we showed that the Epstein-Barr nuclear antigen-1 (EBNA1) decreased Smad2 protein levels and that this was responsible for PTPRK down-regulation. EBNA1 decreased the half-life of Smad2 but did not interact with Smad2. By down-regulating Smad2 protein expression, EBNA1 apparently disables TGF-beta signaling, which subsequently decreases transcription of the PTPRK tumor suppressor. We speculate that loss of the phosphatase function of PTPRK may activate as-yet-unidentified growth-promoting protein tyrosine kinases, which in turn contribute to the pathogenesis of EBV-positive HL.

A proportion of patients with Hodgkin lymphoma carry Epstein-Barr virus (EBV), an oncogenic herpesvirus, in their tumor cells. Although it is generally assumed that EBV contributes to the malignant phenotype of Hodgkin lymphoma cells, direct evidence in support of this is lacking. Here we show that EBV infection of Hodgkin lymphoma cells results in the induction of autotaxin, a secreted tumor-associated factor with lysophospholipase-D activity. Up-regulation of autotaxin increased the generation of lysophosphatidic acid (LPA) and led to the enhanced growth and survival of Hodgkin lymphoma cells, whereas specific down-regulation of autotaxin decreased LPA levels and reduced cell growth and viability. In lymphoma tissues, autotaxin expression was mainly restricted to CD30+ anaplastic large-cell lymphomas and Hodgkin lymphoma; in the latter, high levels of autotaxin were strongly associated with EBV positivity (P = .006). Our results identify the induction of autotaxin and the subsequent generation of LPA as key molecular events that mediate the EBV-induced growth and survival of Hodgkin lymphoma cells and suggest that this pathway may provide opportunities for novel therapeutic intervention. (Blood. 2005;106:2138-2146)

The ataxia telangiectasia mutated (ATM) protein plays a central role in the cellular response to DNA double-strand breaks (DSBs). Developmentally programmed DSBs are restricted to cellular subsets within lymphoid tissues and we asked whether ATM expression is differentially regulated during lymphoid differentiation. We showed that immature B cells in bone marrow and immature T cells of the thymic cortex were negative or weakly ATM-positive. T cells of thymic medulla and peripheral tissues strongly expressed ATM. High levels of ATM were present in the B lymphocytes of the mantle zone and in plasma cells, while the majority of germinal center B cells were negative or weakly labeled. Therefore, ATM expression appears to be down-regulated at those stages of lymphoid development where physiological DNA DSBs occur. In B-chronic lymphocytic leukemia and mantle cell lymphoma we observed two categories: ATM-negative tumors, most likely reflecting the presence of ATM mutation, and tumors with abundant ATM expression. Most follicular center-cell lymphomas and diffuse large B-cell lymphomas, which rarely show inactivation of the ATM gene, were negative or weakly ATM-positive. Tumor cells from most cases of Hodgkin's disease were ATM-negative. Therefore, unless ATM inactivation occurs, ATM expression in lymphoid tumors is likely to reflect their cellular origin. As a result, immunostaining to identify lymphoid neoplasias with ATM inactivation might only be feasible for tumors derived from the stages where ATM is constitutively highly expressed.

The Drosophila tumour suppressor discs large (Dlg) is a cell-junction localized protein that is required for the maintenance of epithelial cyto-architecture and the negative control of cell proliferation. The mammalian homologue is likely to have a similar mode of action, and therefore functional perturbation of this protein may be linked to the development of epithelial-derived cancers. The finding that several unrelated viral oncoproteins, including the E6 protein of oncogenic human papillomaviruses, bind to the human homologue of Dlg (hDlg) supports this proposition. Employing immunohistochemistry, we show that in uterine cervical squamous epithelia, prominent localization of hDlg at sites of intercellular contact occurs in cells that have left the proliferating basal cell layers and begun maturation. The presence of hDlg at sites of cell:cell contact diminishes, whilst intracellular cytoplasmic levels increase significantly in high-grade, but not low-grade, cervical neoplasias. In invasive squamous cell carcinomas, total cellular hDlg levels are greatly reduced. Our data suggest that loss of hDlg at sites of intercellular contact may be an important step in the development of epithelial cancers.

Nasopharyngeal carcinoma (NPC) is an aggressive tumour of multifactorial aetiology that, although rare in most parts of the world, poses a significant mortality problem in its high incidence area of Southern China. Improved therapies are an urgent requirement and, towards this end, immunotherapeutic methods are being developed in several centres. Such strategies are dependent on the immune competence of the target tumour, in particular its expression of HLA class-I. We examined HLA class-I and -II expression in 27 primary NPC biopsies and found that 15% were extensively down-regulated for class-I expression with the majority of tumour cells appearing negative. Whilst HLA class-II was expressed at high levels in the majority of tumours, 37% showed substantial down-regulation. NPC is associated with Epstein-Barr virus (EBV). Expression of the virus-encoded EBER RNAs is accepted as a marker of EBV latency and is regarded as a valuable diagnostic criterion. EBER RNAs were expressed in all samples, but in some the level was remarkably heterogeneous, being barely detectable in many tumour cells. Our study reinforces the concept of extensive phenotypic variation in NPC. There are morphological differences between tumour cells. Some tumours express HLA class-I and/or –II, whilst others are down-regulated or negative. Individual tumours may or may not express the EBV-encoded LMP-1 protein, and individual tumour cells may express high levels of EBER, yet adjacent tumour cells express very little or none. Int. J. Cancer 88:949–955, 2000. © 2000 Wiley-Liss, Inc.

CD4+T cells play critical roles in directing immunity, both as T helper and as regulatory T (Treg) cells. Here, we demonstrate that hepatocytes can modulate T cell populations through engulfment of live CD4+lymphocytes. We term this phenomenon enclysis to reflect the specific enclosure of CD4+T cells in hepatocytes. Enclysis is selective for CD4+but not CD8+cells, independent of antigen-specific activation, and occurs in human hepatocytes in vitro, ex vivo, and in vivo. Intercellular adhesion molecule 1 (ICAM-1) facilitates T cell early adhesion and internalization, whereas hepatocytes form membrane lamellipodia or blebs to mediate engulfment. T cell internalization is unaffected by wortmannin and Rho kinase inhibition. Hepatocytes engulf Treg cells more efficiently than non-Treg cells, but Treg cell-containing vesicles preferentially acidify overnight. Thus, enclysis is a biological process with potential effects on immunomodulation and opens a new field for research to fully understand CD4+T cell dynamics in liver inflammation.