Autoimmunity is a complex trait disease where the environment influences susceptibility to disease by unclear mechanisms. T cell receptor clustering and signaling at the immune synapse, T cell proliferation, CTLA-4 endocytosis, T H 1 differentiation, and autoimmunity are negatively regulated by ␤1,6GlcNAc-branched N-glycans attached to cell surface glycoproteins. ␤1,6GlcNAc-branched N-glycan expression in T cells is dependent on metabolite supply to UDP-GlcNAc biosynthesis (hexosamine pathway) and in turn to Golgi N-acetylglucosaminyltransferases Mgat1, -2, -4, and -5. In Jurkat T cells, ␤1,6Glc-NAc-branching in N-glycans is stimulated by metabolites supplying the hexosamine pathway including glucose, GlcNAc, acetoacetate, glutamine, ammonia, or uridine but not by control metabolites mannosamine, galactose, mannose, succinate, or pyruvate. Hexosamine supplementation in vitro and in vivo also increases ␤1,6GlcNAc-branched N-glycans in naïve mouse T cells and suppresses T cell receptor signaling, T cell proliferation, CTLA-4 endocytosis, T H 1 differentiation, experimental autoimmune encephalomyelitis, and autoimmune diabetes in non-obese diabetic mice. Our results indicate that metabolite flux through the hexosamine and N-glycan pathways conditionally regulates autoimmunity by modulating multiple T cell functionalities downstream of ␤1,6GlcNAc-branched N-glycans. This suggests metabolic therapy as a potential treatment for autoimmune disease.Complex trait diseases such as autoimmunity are determined by poorly understood genetic and environmental interactions. The T cell-mediated autoimmune diseases multiple sclerosis (MS) 3 and type 1 diabetes exemplify this problem, where identical twins of Northern European descent are discordant ϳ60 -70% of the time despite displaying an ϳ150 -300 times higher risk than the general population prevalence of ϳ0.1 and ϳ0.4%, respectively (1, 2). Genetic-environmental interactions have been established between disease-associated major histocompatibility complex haplotypes and specific pathogen peptides that mimic disease self antigens (3, 4). The prevalence of MS and type 1 diabetes changes along north-south gradients, implicating ultraviolet light exposure and production of vitamin D3 in the skin (5-7), a hormone known to negatively regulate T cell function, the MS animal model experimental autoimmune encephalomyelitis (EAE), and spontaneous autoimmune diabetes in the non-obese diabetic (NOD) mouse (5, 8 -11). However, molecular mechanisms for genetic-environmental interactions are poorly understood.Salvage of glucosamine by the hexosamine pathway to UDPGlcNAc is reported to suppress T cell function and EAE in mice by an unknown mechanism (12, 13). De novo biosynthesis of UDP-GlcNAc by the hexosamine pathway utilizes glucose, acetyl-CoA, glutamine, and UTP (see Fig. 1), key allosteric regulators of basic metabolism, suggesting regulation of UDP-GlcNAc supply is integrated with down-stream pathways requiring this sugar-nucleotide. In this regard, the Golgi pathway to ␤1,6Glc-NAc-b...

The differentiation of naive CD4+ T cells into either proinflammatory Th1 or proallergic Th2 cells strongly influences autoimmunity, allergy, and tumor immune surveillance. We previously demonstrated that β1,6GlcNAc-branched complex-type (N-acetylglucosaminyltransferase V (Mgat5)) N-glycans on TCR are bound to galectins, an interaction that reduces TCR signaling by opposing agonist-induced TCR clustering at the immune synapse. Mgat5−/− mice display late-onset spontaneous autoimmune disease and enhanced resistance to tumor progression and metastasis. In this study we examined the role of β1,6GlcNAc N-glycan expression in Th1/Th2 cytokine production and differentiation. β1,6GlcNAc N-glycan expression is enhanced by TCR stimulation independent of cell division and declines at the end of the stimulation cycle. Anti-CD3-activated splenocytes and naive T cells from Mgat5−/− mice produce more IFN-γ and less IL-4 compared with wild-type cells, the latter resulting in the loss of IL-4-dependent down-regulation of IL-4Rα. Swainsonine, an inhibitor of Golgi α-mannosidase II, blocked β1,6GlcNAc N-glycan expression and caused a similar increase in IFN-γ production by T cells from humans and mice, but no additional enhancement in Mgat5−/− T cells. Mgat5 deficiency did not alter IFN-γ/IL-4 production by polarized Th1 cells, but caused an ∼10-fold increase in IFN-γ production by polarized Th2 cells. These data indicate that negative regulation of TCR signaling by β1,6GlcNAc N-glycans promotes development of Th2 over Th1 responses, enhances polarization of Th2 cells, and suggests a mechanism for the increased autoimmune disease susceptibility observed in Mgat5−/− mice.

Multiple sclerosis (MS) is characterized by inflammatory demyelination of axons and neurodegeneration, the latter inadequately modeled in experimental autoimmune encephalomyelitis (EAE). Susceptibility of inbred mouse strains to EAE is in part determined by major histocompatibility complex haplotype; however, other molecular mechanisms remain elusive. Galectins bind GlcNAc-branched N-glycans attached to surface glycoproteins, forming a molecular lattice that restricts lateral movement and endocytosis of glycoproteins. GlcNAc branching negatively regulates T cell activity and autoimmunity, and when absent in neurons, induces apoptosis in vivo in young adult mice. We find that EAE susceptible mouse strains PL/J, SJL, and NOD have reduced GlcNAc branching. PL/J mice display the lowest levels, partial deficiencies in N-acetylglucosaminyltransferase I, II, and V (i.e. Mgat1, -2, and -5), T cell hyperactivity and spontaneous late onset inflammatory demyelination and neurodegeneration; phenotypes markedly enhanced by Mgat5 ؉/؊ and Mgat5 ؊/؊ backgrounds in a gene dose-dependent manner. Spontaneous disease is transferable and characterized by progressive paralysis, tremor, dystonia, neuronophagia, and axonal damage in both demyelinated lesions and normal white matter, phenocopying progressive MS. Our data identify hypomorphic Golgi processing as an inherited trait that determines susceptibility to EAE, provides a unique spontaneous model of MS, and suggests GlcNAc-branching deficiency may promote T cell-mediated demyelination and neurodegeneration in MS.Relapsing remitting multiple sclerosis is characterized by inflammatory destruction of the myelin sheath surrounding axons in the central nervous system (CNS), 3 producing relapsing and remitting attacks of neurological dysfunction (1). This is commonly followed by a secondary progressive neurodegenerative phase distinguished by axonal damage and neuronal loss (1). Primary progressive MS is similar to secondary progressive disease but lacks the initial relapsing-remitting phase. However, recent investigations have demonstrated that gray matter involvement and axonal damage in otherwise normal appearing white matter are present at the onset of relapsing remitting multiple sclerosis (2, 3). This indicates neurodegeneration is an early and prominent feature of disease and questions the interpretation that MS is only a T cell-mediated demyelinating disease. Experimental autoimmune encephalomyelitis (EAE) is a useful model of T cell-dependent inflammatory demyelination, but fails to properly address the neurodegenerative phenotype of MS. MS is characterized by adult onset and partially familial relationships, indicating complex interactions between environmental and genetic factors in disease pathogenesis (4). Whole genome screens have identified a number of candidate loci associated with MS (5) and EAE (6, 7), but non-MHC genes that strongly promote disease have yet to be described. This is despite long standing observations that T cell dysfunction is critical to development ...

Many studies have shown that stress is associated with gut microbiota. Environmental enrichment (EE) could reduce stress in farm animals; however, limited information is available on the microbial community composition in rabbits raised with or without EE. This study aimed to identify EE influences on the behavior, serum hormonal levels, and cecal microbiota of rabbits. Two hundred Rex rabbits were segregated randomly within four cohorts (n = 50); reared for 76 d within standardized enclosures (non-enriched) or within cages containing a willow-stick (WS), rubber-duck (RD), or a can of beans (CB). The rabbits’ ingestive, rest, locomotion, exploratory, grooming, and abnormal behavior were observed. The serum hormone levels for rabbits were measured, and cecal specimens were sequencedfrom the V3–V4 region using 16S rRNA amplicons. Environmental enrichment increased feeding and drinking time, promoted exploratory behavior, and reduced abnormal behavior in rabbits. Insulin-like growth factor 1(IGF-1) levels of the enriched cohorts were elevated in comparison to the control cohort. Serum cortisol level for CB cohort was markedly reduced in comparison to the control cohort (p < 0.05), while dopamine levels for CB cohort peaked. Further, we found that EE mainly affected the dominant microbiota. Several families, such as Erysipelotrichaceae, Tannerellaceae, Enterobacteriaceae, Burkholderiaceae, and Prevotellaceae were markedly reduced within the CB cohort. Bacteria such as Alloprevotella, Bifidobacterium, Enterobacteriaceae, Parabacteroides, and Erysipelatoclostridium were identified as having negative associations with the presence of serum cortisol. EE influenced rabbit behavior and serum hormonal levels, and CB enrichment was the most suitable for rabbits. Further, cecal microbiota composition and diversity were affected by CB enrichment. These findings suggested that CB could be considered for use in rabbit husbandry.