Duchenne muscular dystrophy (DMD) is an X-linked, degenerative muscle disease that is exacerbated by secondary inflammation. Here, we characterized the immunological milieu of dystrophic muscle in mdx mice, a model of DMD, to identify potential therapeutic targets. We identified a specific subpopulation of cells expressing the Vβ8.1/8.2 TCR that is predominant among TCR-β + T cells. These cells expressed high levels of osteopontin (OPN), a cytokine that promotes immune cell migration and survival. Elevated OPN levels correlated with the dystrophic process, since OPN was substantially elevated in the serum of mdx mice and muscle biopsies after disease onset. Muscle biopsies from individuals with DMD also had elevated OPN levels. To test the role of OPN in mdx muscle, mice lacking both OPN and dystrophin were generated and termed doublemutant mice (DMM mice). Reduced infiltration of NKT-like cells and neutrophils was observed in the muscle of DMM mice, supporting an immunomodulatory role for OPN in mdx muscle. Concomitantly, an increase in CD4 + and FoxP3 + Tregs was also observed in DMM muscle, which also showed reduced levels of TGF-β, a known fibrosis mediator. These inflammatory changes correlated with increased strength and reduced diaphragm and cardiac fibrosis. These studies suggest that OPN may be a promising therapeutic target for reducing inflammation and fibrosis in individuals with DMD.

Galectin-1 has been implicated in regulating T-cell survival, function, and Th1/Th2 balance in several mouse models, though the molecular and cellular basis of its immunomodulatory activity has not been completely elucidated. Therefore, we examined galectin-1 expression and activity within differentiated murine Th1 and Th2 subsets. While recombinant galectin-1 specifically bound to both T-cell subsets, Th1 and Th2 T cells expressed distinct combinations of galectin-1-reactive epitopes and were differentially responsive to galectin-1 exposure. Indeed, Th1 cells were more susceptible to galectin-1-induced death than Th2 cells. Th2 protection from apoptosis was correlated with expression of anti-apoptotic galectin-3. Further, galectin-1 promoted TCR-induced type 2 cytokine production by Th2 cells. Differentiated Th2 cells constitutively expressed high levels of galectin-1 and can be induced to produce even higher levels of galectin-1 with restimulation, whereas comparable levels of galectin-1 in Th1 cells were only observed after restimulation. Co-culturing experiments using galectin-1 À/À and galectin-1 1/1 Th1 and Th2 T cells demonstrated that Th2-derived galectin-1 induced Th1 apoptosis, whereas Th1-derived galectin-1 promoted Th2 cytokine production. These studies identify galectin-1 as a cross-regulatory cytokine that selectively antagonizes Th1 survival, while promoting TCR-induced Th2 cytokine production.

TCR engagement triggers the polarized recruitment of membrane, actin, and transducer assemblies within the T cell–APC contact that amplify and specify signaling cascades and Teffector activity. We report that caveolin-1, a scaffold that regulates polarity and signaling in nonlymphoid cells, is required for optimal TCR-induced actin polymerization, synaptic membrane raft polarity, and function in CD8, but not CD4, T cells. In CD8+ T cells, caveolin-1 ablation selectively impaired TCR-induced NFAT-dependent NFATc1 and cytokine gene expression, whereas caveolin-1 re-expression promoted NFATc1 gene expression. Alternatively, caveolin-1 ablation did not affect TCR-induced NF-κB–dependent Iκbα expression. Cav-1−/− mice did not efficiently promote CD8 immunity to lymphocytic choriomeningitis virus, nor did cav-1−/− OT-1+ CD8+ T cells efficiently respond to Listeria mono-cytogenes-OVA after transfer into wild-type hosts. Therefore, caveolin-1 is a T cell-intrinsic orchestrator of TCR-mediated membrane polarity and signal specificity selectively employed by CD8 T cells to customize TCR responsiveness.

CDK8 is a dissociable kinase module of the Mediator complex and has been shown to play an important role in transcriptional regulation in organisms as diverse as yeast and humans. Recent studies suggest that CDK8 functions as an oncoprotein in melanoma and colon cancer. Importantly, these studies were conducted using in vitro cell line models and the role of CDK8 in tumourigenesis in vivo has not been explored. We have generated a mouse with a Cdk8 conditional knockout allele and examined the consequences of Cdk8 loss on normal tissue homeostasis and tumour development in vivo. Cdk8 deletion in the young adult mouse did not induce any gross or histopathological abnormalities, implying that Cdk8 is largely dispensable for somatic cellular homeostasis. In contrast, Cdk8 deletion in the Apc(Min) intestinal tumour model shortened the animals' survival and increased tumour burden. Although Cdk8 deletion did not affect tumour initiation, intestinal tumour size and growth rate were significantly increased in Cdk8-null animals. Transcriptome analysis performed on Cdk8-null intestinal cells revealed up-regulation of genes that are governed by the Polycomb group (PcG) complex. In support of these findings, Cdk8-null intestinal cells and tumours displayed a reduction in histone H3K27 trimethylation, both globally and at the promoters of a number of PcG-regulated genes involved in oncogenic signalling. Together, our findings uncover a tumour suppressor function for CDK8 in vivo and suggest that the role of CDK8 activity in driving oncogenesis is context-specific. Sequencing data were deposited at GEO (Accession No. GSE71385).

During thymocyte development, the Tcell receptor (TCR) can discriminate major histocompatibility complex (MHC)/ peptide ligands over a narrow range of affinities and translate subtle differences into functional fate decisions. How small differences in TCR input are translated into absolute differences in functional output is unclear. We examined the effects of galectin-1 ablation in the context of class-I-restricted thymocyte development. Galectin-1 expression opposed TCR partial agonist-driven positive selection, but promoted TCR agonist-driven negative selection of conventional CD8 ؉ T cells. Galectin-1 expression also promoted TCR agonist-driven CD8␣␣ intestinal intraepithelial lymphocytes ( IntroductionDuring T-cell development in the thymus, thymocytes are subjected to selection processes designed to ensure the generation of a diverse repertoire of functional T cells (positive selection), the removal of self-reactive thymocytes with auto-aggressive potential (negative selection), and the development of regulatory T populations that function in maintaining self-tolerance. 1 Selection is cued through T-cell receptor (TCR) interactions with specific self-peptide/major histocompatibility complexes (MHCs) expressed by thymic antigen-presenting cells. Very weak TCR-peptide-MHC interactions are insufficient to elicit signals required for thymocyte survival, whereas exceptionally strong TCRagonist peptide-MHC interactions direct thymocyte apoptosis during negative selection or promote the generation of regulatory CD8␣␣ intestinal intraepithelial lymphocytes (IEL) or T-regulatory cells. [2][3][4] Thymocytes bearing TCRs with intermediate affinity for self-peptide/ MHC complexes (partial agonists) are cued to survive and initiate programs for development into mature T-helper or cytotoxic T lymphocyte (CTL) lineages during positive selection. 4 How the TCR discriminates subtle differences in ligand binding and translates them into distinct signals and functional fates remains unresolved. Recent findings indicate that developing thymocytes convert small differences in TCR binding affinity into discrete functional outcomes by controlling the compartmentalization, duration, and intensity of mitogen-activated protein (MAP) kinase signaling cascades. 5,6 However, it remains unclear how TCR engagement differentially couples to MAP kinase activation pathways under these circumstances.Immunologists have long recognized that developing thymocytes express characteristic patterns of cell surface glycosylation. 7,8 Plant lectins were first used to define thymocyte subsets expressing particular oligosaccharide ligands. 7,8 For instance, peanut agglutinin (PNA) binds developing CD4 ϩ CD8 ϩ double-positive (DP) thymocytes, but not mature CD4 ϩ or CD8 ϩ single-positive (SP) thymocytes due to its specificity for the O-linked disaccharide Gal␤1,3GalNAc, which becomes masked on mature SP thymocytes due to sialic acid addition. 8 In contrast, Sambucus nigra lectin (SNA), a lectin that recognizes ␣-2, 6-linked sialic acid on N-glycans, b...