Deregulated Mucosal Immune Surveillance through Gut-Associated Regulatory T Cells and PD-1+ T Cells in Human Colorectal Cancer.

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8+ T cells (CTLs) isolated from the adenocarcinoma. Adenocarcinoma-associated Tregs directly inhibit the function of normal human CTLs in vitro. With histopathological analysis, Foxp3+ Tregs were preferentially located in stroma. Concurrent transcriptome analysis of epithelial cells, stromal cells, and T cell subsets obtained from carcinomatous and normal intestinal samples from patients revealed a distinct gene expression signature in colorectal adenocarcinoma-associated Tregs, with overexpression of CCR1, CCR8, and TNFRSF9, whereas their ligands CCL4 and TNFSF9 were found upregulated in cancerous epithelium. Overexpression of WNT2 and CADM1, associated with carcinogenesis and metastasis, in cancer-associated stromal cells suggests that both cancer cells and stromal cells play important roles in the development and progression of colorectal cancer through the formation of a tumor microenvironment. The identification of CTL anergy by Tregs and the unique gene expression signature of human Tregs and stromal cells in colorectal cancer patients may facilitate the development of new therapeutics against malignancies.

Vitamin A-dependent transcriptional activation of the nuclear factor of activated T cells c1 (NFATc1) is critical for the development and survival of B1 cells.

B1 cells represent a distinct subset of B cells that produce most of the natural serum IgM and much of the gut IgA and function as an important component of early immune responses to pathogens. The development of B1 cells depends on the nuclear factor of activated T cells c1 (NFATc1), a transcription factor abundantly expressed by B1 cells but not by conventional B2 cells. However, the factors that regulate the expression of NFATc1 in B1 cells remain unknown. Here we show that a vitamin A-deficient diet results in reduction of NFATc1 expression in B1 cells and almost complete loss of the B1 cell compartment. As a consequence, vitamin A-deficient mice have reduced serum IgM and are unable to mount T cell-independent antibody responses against bacterial antigens. We demonstrate that injection of all-trans retinoic acid induces the expression of NFATc1, particularly from the constitutive P2 promoter, and leads to the increase of the B1 cells. Thus, the retinoic acid-dependent pathway is critical for regulating NFATc1 expression and for maintenance of the natural memory B cell compartment.

Functional differences of two distinct catalases in Mesorhizobium loti MAFF303099 under free-living and symbiotic conditions.

Protection against reactive oxygen species (ROS) is important for legume-nodulating rhizobia during the establishment and maintenance of symbiosis, as well as under free-living conditions, because legume hosts might assail incoming microbes with ROS and because nitrogenase is extremely sensitive to ROS. We generated mutants of two potential catalase genes in Mesorhizobium loti MAFF303099 to investigate their physiological significance. Biochemical results indicated that genes with the locus tags mlr2101 and mlr6940 encoded a monofunctional catalase and a bifunctional catalase-peroxidase, respectively, that were named katE and katG. Under free-living conditions, the katG mutant demonstrated an extended generation time and elevated sensitivity to exogenous H(2)O(2), whereas the katE mutant exhibited no generation time extension and only a slight increase in sensitivity to exogenous H(2)O(2). However, the katE mutant showed a marked decrease in its survival rate during the stationary phase. With regard to symbiotic capacities with Lotus japonicus, the katG mutant was indistinguishable from the wild type; nevertheless, the mutants with disrupted katE formed nodules with decreased nitrogen fixation capacities (about 50 to 60%) compared to those formed by the wild type. These mutant phenotypes agreed with the expression profiles showing that transcription of katG, but not katE, was high during the exponential growth phase and that transcription levels of katE versus sigA were elevated during stationary phase and were approximately fourfold higher in bacteroids than mid-exponential-phase cells. Our results revealed functional separation of the two catalases, as well as the importance of KatE under conditions of strong growth limitation.

Exhaustive exercise and type-1/type-2 cytokine balance with special focus on interleukin-12 p40/p70.

It is known that interleukin (IL)-12 p70 promotes the differentiation of type-1 helper T (Th1) cells, which produce type-1 cytokines such as IL-2 and interferon (IFN), thereby supporting cellular immunity, whereas IL-12 p40 acts as an antagonist of IL-12 p70. In contrast, IL-4 and IL-6 promote the differentiation of Th2 cells, which produce type-2 cytokines IL-4, IL-6 and IL-10, induce humoral immunity and are involved in allergic reactions. Exhaustive exercise causes the suppression of T lymphocyte activity while asthmatic and allergic diseases are subclinically more prevalent in athletes. One of the mechanisms behind these observations might be a lower type-1 and higher type-2 cytokine balance, which we previously demonstrated to occur after exhaustive exercise. In the present study, we investigated the type-1/type-2 cytokine balance by measuring plasma concentrations of IL-2, IL-4, IL-5, IL-10, tumor necrosis factor (TNF)-alpha and IFN-gamma with microparticle-based flow cytometric technology. IL-5, IL-6 and IL-13 were measured by enzyme-linked immunosorbent assay (ELISA). IL-12 p40 and p70 were measured separately, also by ELISA. Plasma IL-12 p40 concentration rose significantly after maximal exercise and to an even greater extent after a marathon race. Conversely, plasma IL-12 p70 could not be detected even using two different assays. The marathon race caused a marked increase in the plasma concentrations of IL-6 and IL-10. Their responses were correlated (r = 0.78, p < 0.01), indicating that IL-6 is an inducer of IL-10, and may partly induce the type-1 < type-2 cytokine balance. With the exception of one study involving maximal exercise, other studies have failed to show any change in circulating IL-12 concentration with exercise. The present study demonstrated that IL-12 p40 was present in excess of p70 especially after exercise. This may be one of the mechanisms behind several phenomena including cellular immunosuppression, an increase in the relative proportion of type-2 cytokines following exhaustive exercise, and the higher incidence of infections and allergic disorders in regularly exercising endurance athletes.