Yutaka Komiyama

IL-17 Plays an Important Role in the Development of Experimental Autoimmune Encephalomyelitis

IL-17 is a proinflammatory cytokine that activates T cells and other immune cells to produce a variety of cytokines, chemokines, and cell adhesion molecules. This cytokine is augmented in the sera and/or tissues of patients with contact dermatitis, asthma, and rheumatoid arthritis. We previously demonstrated that IL-17 is involved in the development of autoimmune arthritis and contact, delayed, and airway hypersensitivity in mice. As the expression of IL-17 is also augmented in multiple sclerosis, we examined the involvement of this cytokine in these diseases using IL-17−/− murine disease models. We found that the development of experimental autoimmune encephalomyelitis (EAE), the rodent model of multiple sclerosis, was significantly suppressed in IL-17−/− mice; these animals exhibited delayed onset, reduced maximum severity scores, ameliorated histological changes, and early recovery. T cell sensitization against myelin oligodendrocyte glycoprotein was reduced in IL-17−/− mice upon sensitization. The major producer of IL-17 upon treatment with myelin digodendrocyte glycopritein was CD4+ T cells rather than CD8+ T cells, and adoptive transfer of IL-17−/− CD4+ T cells inefficiently induced EAE in recipient mice. Notably, IL-17-producing T cells were increased in IFN-γ−/− cells, while IFN-γ-producing cells were increased in IL-17−/− cells, suggesting that IL-17 and IFN-γ mutually regulate IFN-γ and IL-17 production. These observations indicate that IL-17 rather than IFN-γ plays a crucial role in the development of EAE.

Antigen-Specific T Cell Sensitization Is Impaired in IL-17-Deficient Mice, Causing Suppression of Allergic Cellular and Humoral Responses

Interleukin-17 (IL-17) is a proinflammatory cytokine produced by T cells. The involvement of IL-17 in human diseases has been suspected because of its detection in sera from asthmatic patients and synovial fluids from arthritic patients. In this study, we generated IL-17-deficient mice and investigated the role of IL-17 in various disease models. We found that contact, delayed-type, and airway hypersensitivity responses, as well as T-dependent antibody production, were significantly reduced in the mutant mice, while IL-17 deficiency of donor T cells did not affect acute graft-versus-host reaction. The results suggest that impaired responses were caused by the defects of allergen-specific T cell activation. Our findings indicate that IL-17 plays an important role in activating T cells in allergen-specific T cell-mediated immune responses.

Differential Roles of Interleukin-17A and -17F in Host Defense against Mucoepithelial Bacterial Infection and Allergic Responses

Interleukin-17A (IL-17A) is a cytokine produced by T helper 17 (Th17) cells and plays important roles in the development of inflammatory diseases. Although IL-17F is highly homologous to IL-17A and binds the same receptor, the functional roles of this molecule remain largely unknown. Here, we demonstrated with Il17a(-/-), Il17f(-/-), and Il17a(-/-)Il17f(-/-) mice that IL-17F played only marginal roles, if at all, in the development of delayed-type and contact hypersensitivities, autoimmune encephalomyelitis, collagen-induced arthritis, and arthritis in Il1rn(-/-) mice. In contrast, both IL-17F and IL-17A were involved in host defense against mucoepithelial infection by Staphylococcus aureus and Citrobacter rodentium. IL-17A was produced mainly in T cells, whereas IL-17F was produced in T cells, innate immune cells, and epithelial cells. Although only IL-17A efficiently induced cytokines in macrophages, both cytokines activated epithelial innate immune responses. These observations indicate that IL-17A and IL-17F have overlapping yet distinct roles in host immune and defense mechanisms.

A comparison of the Galaxy populations in the coma and distant clusters: The evolution of k + a galaxies and the role of the intracluster medium

The spectroscopic properties of galaxies in the Coma Cluster are compared with those of galaxies in rich clusters at z ~ 0.5, to investigate the evolution of the star formation history in clusters. Luminous galaxies with MV ≤ -20 and poststarburst/post-star-forming (k+a) spectra that constitute a significant fraction of galaxies in distant cluster samples are absent in Coma, where spectacular cases of k+a spectra are found instead at MV > -18.5 and represent a significant proportion of the cluster dwarf galaxy population. A simple inspection of their positions on the sky indicates that this type of galaxy does not show a preferential location within the cluster, but the bluest and strongest lined group of k+a galaxies lie in projection toward the central 1.4 Mpc of Coma and have radial velocities significantly higher than the cluster mean. We find a striking correlation between the positions of these young and strong poststarburst galaxies and substructure in the hot intracluster medium (ICM) identified from XMM-Newton data, with these galaxies lying close to the edges of two infalling substructures. This result strongly suggests that the interaction with the dense ICM could be responsible for the quenching of the star formation (thus creating the k+a spectrum) and, possibly, for any previous starburst. The evolution with redshift of the luminosity distribution of k+a galaxies can be explained by a downsizing effect, with the maximum luminosity/mass of actively star-forming galaxies infalling onto clusters decreasing at lower redshift. We discuss the possible physical origin of this downsizing effect and the implications of our results for current scenarios of environmental effects on the star formation in galaxies.

THE HST/ACS COMA CLUSTER SURVEY. II. DATA DESCRIPTION AND SOURCE CATALOGS ∗

The Coma cluster, Abell 1656, was the target of an HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially completed survey still covers ~50% of the core high-density region in Coma. Observations were performed for 25 fields that extend over a wide range of cluster-centric radii (~1.75 Mpc or 1°) with a total coverage area of 274 arcmin2. The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the southwest region of the cluster. In this paper, we present reprocessed images and SEXTRACTOR source catalogs for our survey fields, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SEXTRACTOR Kron magnitudes based only on the measured source flux and its half-light radius. We have performed photometry for ~73,000 unique objects; approximately one-half of our detections are brighter than the 10σ point-source detection limit at F814W = 25.8 mag (AB). The slight majority of objects (60%) are unresolved or only marginally resolved by ACS. We estimate that Coma members are 5%-10% of all source detections, which consist of a large population of unresolved compact sources (primarily globular clusters but also ultra-compact dwarf galaxies) and a wide variety of extended galaxies from a cD galaxy to dwarf low surface brightness galaxies. The red sequence of Coma member galaxies has a color-magnitude relation with a constant slope and dispersion over 9 mag (–21 < M F814W < –13). The initial data release for the HST-ACS Coma Treasury program was made available to the public in 2008 August. The images and catalogs described in this study relate to our second data release.

Characterization and mosaicking of CCDs and the applications to the Subaru wide-field camera (Suprime-Cam)

We are building an 8192 X 10240 CCD mosaic camera for 8 m Japanese Telescope (Subaru). The mosaic will consist of 2 X 5 arrays of 3-edge buttable 4096 X 2048 15 micrometer pixel imagers. Although several vendors have just started supplying the type of large format CCD, it is still in the development phase. Therefore, careful characterization and optimizations of individual CCD are critical. We describe the system used to evaluate several kinds of the CCDs. In addition to the CCD characterization, we also present the mechanical design of the mosaic focal plane which is an another issue to realize the large mosaic.

The Morphology Dependence of Luminosity Segregation in the Coma Cluster

We carry out CCD photometry of galaxies in the 5.25 square region centered on Coma cluster down to

The Role of TNFα and IL-17 in the Development of Excess IL-1 Signaling-Induced Inflammatory Diseases in IL-1 Receptor Antagonist-Deficient Mice

M_R=-16.0

Narrowband filter system at the Subaru prime focus

, beyond the limit of conventional morphological classification. We use the angular two-point correlation function as well as radial profiles in order to characterize the luminosity segregation. We find strong luminosity segregation for our total sample over the magnitude range of

The Role of IL-1 in the Immune System

-20 leq M_R leq -16