Project description:Inducible co-stimulator (ICOS) interaction with its ligand (ICOSL) is involved in several T cell effector functions. While blockade of ICOS:ICOSL interaction in chronic graft versus host disease (GVHD) seems benefi cial, results for acute GVHD remain controversial. To further elucidate its role in acute GVHD, C57BL / 6 mice were lethally irradiated and reconstituted with allogeneic spleen cells in the absence or presence of ICOSL-blocking mAb. Mice reconstituted with allogeneic spleen cells experienced severe GVHD and died untreated within 6 M-bM-^@M-^S 9 days after transplantation. Mice treated with an anti-ICOSL mAb starting from day 3 after transplantation gained weight again and survived for at least additional 12 days, although the treatment was already stopped at day 11 after transplantation. In contrast, the anti-ICOSL treatment starting from day 0 did not prevent GVHD. The diff erence between therapeutic (day 3) and prophylactic (day 0) anti-ICOSL treatment was independent of CD25 + CD4 + regulatory T cells since their depletion did not abrogate the therapeutic eff ect of ICOSL blockade. Microarray analysis revealed IFN- M-NM-3 and chemokine up-regulation in spleen cells of prophylactically treated mice, emphasizing kinetic dependence of acute GVHD modulation via blockade of ICOS:ICOSL interaction. B6 recipients were irradiated with 10.0 Gray, administered from a 137 Cs source. Splenocytes from C3H mice were prepared as single cell suspensions in PBS, depleted of red blood cells and counted. 2 M-bM-^@M-^S 3 M-CM-^W 10^7 C3H splenocytes in a volume of 200 M-NM-<l were transplanted into B6 recipients via tail vein injection (4 mice per group per experiment) 4 M-bM-^@M-^S 6 h after irradiation. Mice in the treatment group with anti-ICOSL mAb and their respective controls, received 500 M-NM-<g mAb i. p starting at day 0 or day 3, followed by subsequent injections of 200 M-NM-<g of mAb every other day. At day 4 after transplantation RNA of spleen cells was prepared and subjected to microarray analysis. Combined RNA from allogeneic transplanted mice was hybridized onto 2 independent arrays.

Project description:Tuberculosis results from an interaction between a chronically persistent pathogen counteracted by IFN-g-mediated immune responses. Modulation of IFN-g signaling could therefore constitute a major immune evasion mechanism for M. tuberculosis. SOCS1 plays a major role in the inhibition of IFN-g-mediated responses. We found that M. tuberculosis infection stimulates SOCS1 expression in mouse and human myeloid cells. Significantly higher levels of SOCS1 were induced after in vitro or in vivo infection with virulent M. tuberculosis-than with attenuated M. bovis BCG. Different innate and adaptive immune mechanisms participated in infection-induced SOCS1 expression. SOCS1 hampered M. tuberculosis clearance both in macrophages and during murine infection in vivo. On the other hand, SOCS1 protected the host from an infection-induced inflammation. Despite SOCS1 expression, mycobacteria-infected macrophages were not tolerant to IFN-g. Instead, an impaired IFN-g secretion by macrophages, associated to lower responses to IL-12, accounted for the increased mycobacterial intracellular growth in presence of SOCS1. SOCS1 attenuated the expression of the majority of genes modulated by infection of macrophages (6,1% of the transcriptome), indicating the relevance of the molecule in the outcome of infection with M. tuberculosis. We suggest that SOCS1 is expressed during M. tuberculosis infection to establish a successful chronic infection, and dampen inflammatory damage. Difference in genotype and TB infection comparison Relative gene expressions were determined by normalized intensity values. GeneSpring analysis was performed using the Treg transcriptome data with following comparisons: no GvHD d90 versus no GvHD d150, no GvHD d90 versus acute GvHD, no GvHD d150 versus chronic GvHD, acute GvHD versus chronic GvHD, acute GvHD versus GvHD d90 and chronic GvHD versus GvHD d150 (Figure 2). Cut-off was a transcript fold change of +2 or -2 in at least one comparison. Student´s t-test was used to identify significant expression changes.

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Mus musculus

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