Podoplanin negatively regulates CD4+ effector T cell responses

Podoplanin (PDPN, also known as Gp38) is highly expressed on the surface of lymphatic endothelial cells, where it regulates development of lymphatic vessels. We have recently observed that PDPN is also expressed on effector T cells that infiltrate target tissues during autoimmune inflammation; however, the function of PDPN in T cells is largely unclear. Here, we demonstrated that global deletion of Pdpn results in exaggerated T cell responses and spontaneous experimental autoimmune encephalomyelitis (EAE) in mice with a susceptible genetic background. In contrast, T cell–specific overexpression of PDPN resulted in profound defects in IL-7–mediated T cell expansion and survival. Consequently, these animals exhibited a more rapid resolution of CNS inflammation, characterized by a reduced effector CD4(+) T cell population in the CNS. Mice harboring a T cell–specific deletion of Pdpn developed exacerbated EAE, with increased accumulation of effector CD4(+) T cells in the CNS. Transcriptional profiling of naturally occurring PDPN(+) effector T cells in the CNS revealed increased expression of other inhibitory receptors, such as Pd1 and Tim3, and decreased expression of prosurvival factors, including Il7ra. Together, our data suggest that PDPN functions as an inhibitory molecule on T cells, thereby promoting tissue tolerance by limiting long-term survival and maintenance of CD4(+) effector T cells in target organs

Non-Hematopoietic Cells in Lymph Nodes Drive Memory CD8 T Cell Inflation during Murine Cytomegalovirus Infection

During human and murine cytomegalovirus (MCMV) infection an exceptionally large virus-specific CD8 T cell pool is maintained in the periphery lifelong. This anomalous response is only seen for specific subsets of MCMV-specific CD8 T cells which are referred to as 'inflationary T cells'. How memory CD8 T cell inflation is induced and maintained is unclear, though their activated phenotype strongly suggests an involvement of persistent antigen encounter during MCMV latency. To dissect the cellular and molecular requirements for memory CD8 T cell inflation, we have generated a transgenic mouse expressing an MHC class I-restricted T cell receptor specific for an immunodominant inflationary epitope of MCMV. Through a series of adoptive transfer experiments we found that memory inflation was completely dependent on antigen presentation by non-hematopoietic cells, which are also the predominant site of MCMV latency. In particular, non-hematopoietic cells selectively induced robust proliferation of inflationary CD8 T cells in lymph nodes, where a majority of the inflationary CD8 T cells exhibit a central-memory phenotype, but not in peripheral tissues, where terminally differentiated inflationary T cells accumulate. These results indicate that continuous restimulation of central memory CD8 T cells in the lymph nodes by infected non-hematopoietic cells ensures the maintenance of a functional effector CD8 T pool in the periphery, providing protection against viral reactivation events

The IL-33/ST2 pathway contributes to intestinal tumorigenesis in humans and mice.

Colorectal cancer (CRC) develops through a multistep process and is modulated by inflammation. However, the inflammatory pathways that support intestinal tumors at different stages remain incompletely understood. Interleukin (IL)-33 signaling plays a role in intestinal inflammation, yet its contribution to the pathogenesis of CRC is unknown. Using immunohistochemistry on 713 resected human CRC specimens, we show here that IL-33 and its receptor ST2 are expressed in low-grade and early-stage human CRCs, and to a lesser extent in higher-grade and more advanced-stage tumors. In a mouse model of CRC, ST2-deficiency protects from tumor development. Moreover, bone marrow (BM) chimera studies indicate that engagement of the IL-33/ST2 pathway on both the radio-resistant and radio-sensitive compartment is essential for CRC development. Mechanistically, activation of IL-33/ST2 signaling compromises the integrity of the intestinal barrier and triggers the production of pro-tumorigenic IL-6 by immune cells. Together, this data reveals a tumor-promoting role of IL-33/ST2 signaling in CRC

Hepatitis E, Helicobacter pylori, and gastrointestinal symptoms in workers exposed to waste water

BACKGROUND: Workers exposed to sewage may have an increased risk of infection by Helicobacter pylori and hepatitis E virus (HEV). AIMS: To assess the prevalence of clinical hepatitis E (HE) and peptic ulcer disease as well as the seroprevalence of antibodies to H pylori and HEV in workers with and without sewage exposure and to look for symptoms due to exposure to endotoxin. METHODS: In the first year of a prospective cohort study 349 sewage exposed workers and 429 municipal manual workers (participation: 61%) underwent a complete medical examination. Travelling to endemic areas, socioeconomic level, age, country in which childhood was spent, and number of siblings were considered as the main confounding factors. RESULTS: Peptic ulcer disease and clinical HE did not occur more often in workers exposed to sewage. Prevalence of antibodies to HEV was 3.3% and overall prevalence of IgG antibodies to H pylori was 42% with large differences between subgroups. Logistic regression did not show an increased risk of seropositivity or antibodies to parietal cells in sewage exposed workers, but disentangling the effect of exposure from that of confounders was extremely difficult. No increase of symptoms due to exposure to endotoxin was found in sewage workers, with the exception of diarrhoea. CONCLUSIONS: No clear increased risk of infection by H pylori or by HEV in workers exposed to sewage was found in this cross-sectional study, but these results need to be confirmed by follow up