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Activation of a naive T cell is a highly energetic event,which requires a substantial increase in nutrient metabolism. Upon stimulation,T cells increase in size,rapidly proliferate,and differentiate,all of which lead to a high demand for energetic and biosynthetic precursors. Although amino acids are the basic building blocks of protein biosynthesis and contribute to many other metabolic processes,the role of amino acid metabolism in T cell activation has not been well characterized. We have found that glutamine in particular is required for T cell function. Depletion of glutamine blocks proliferation and cytokine production,and this cannot be rescued by supplying biosynthetic precursors of glutamine. Correlating with the absolute requirement for glutamine,T cell activation induces a large increase in glutamine import,but not glutamate import,and this increase is CD28-dependent. Activation coordinately enhances expression of glutamine transporters and activities of enzymes required to allow the use of glutamine as a Krebs cycle substrate in T cells. The induction of glutamine uptake and metabolism requires ERK function,providing a link to TCR signaling. Together,these data indicate that regulation of glutamine use is an important component of T cell activation. Thus,a better understanding of glutamine sensing and use in T cells may reveal novel targets for immunomodulation. View Publication

Retinoic acid (RA) produced by intestinal dendritic cells (DCs) imprints gut-homing specificity on lymphocytes and enhances Foxp3(+) regulatory T-cell differentiation. The expression of aldehyde dehydrogenase (ALDH) 1A in these DCs is essential for the RA production. However,it remains unclear how the steady-state ALDH1A expression is induced under specific pathogen-free (SPF) conditions. Here,we found that bone marrow-derived dendritic cells (BM-DCs) generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) expressed Aldh1a2,an isoform of Aldh1a,but that fms-related tyrosine kinase 3 ligand-generated BM-DCs did not. DCs from mesenteric lymph nodes (MLN) and Peyer's patches (PP) of normal SPF mice expressed ALDH1A2,but not the other known RA-producing enzymes. Employing a flow cytometric method,we detected ALDH activities in 10-30% of PP-DCs and MLN-DCs. They were CD11c(high)CD4(-/low)CD8alpha(intermediate)CD11b(-/low) F4/80(low/intermediate)CD45RB(low)CD86(high)MHC class II(high)B220(-)CD103(+). Equivalent levels of aldehyde dehydrogenase activity (ALDHact) and ALDH1A2 expression were induced synergistically by GM-CSF and IL-4 in splenic DCs in vitro. In BM-DCs,however,additional signals via Toll-like receptors or RA receptors were required for inducing the equivalent levels. The generated ALDH1A2(+) DCs triggered T cells to express gut-homing receptors or Foxp3. GM-CSF receptor-deficient or vitamin A-deficient mice exhibited marked reductions in the ALDHact in intestinal DCs and the T cell number in the intestinal lamina propria,whereas IL-4 receptor-mediated signals were dispensable. GM-CSF(+)CD11c(-)F4/80(+) cells existed constitutively in the intestinal tissues. The results suggest that GM-CSF and RA itself are pivotal among multiple microenvironment factors that enable intestinal DCs to produce RA. View Publication

To define novel human NK cell markers,we generated two mAbs specific for G-protein-coupled receptor 56 (GPR56),a surface glycoprotein that appears to be involved in cell-to-cell and cell-to-matrix interactions. GPR56 has been described in selected normal tissues,and in certain tumors,while,as yet,its expression on leukocytes is unknown. In this study,we show that anti-GPR56 mAbs,among leukocytes,prevalently recognize NK cells. In particular,these mAbs brightly stain CD56(dull) CD16(+) NK cells while react poorly with CD56(bright) CD16(+/-) NK cells. Consistently,we found that GPR56 was expressed on NK cells populating inflamed peripheral tissues while it was absent in lymph node-derived NK cells. We also show that activating stimuli,such as cytokines or exposure to monocyte-derived dendritic cell,down-regulate NK cell expression of GPR56 both at the protein and at the transcriptional level. Interestingly,IL-18,known to induce de novo expression of CCR7 on CD56(dull) CD16(+) NK cells,displayed the highest capability of modulating GPR56. Thus,together with the identification of GPR56 as a novel marker capable of discriminating different NK cells subsets,our data suggest that GPR56 may take part to the mechanisms regulating NK cell migration through the blood stream,peripheral tissues and lymph nodes. View Publication

Neutrophil apoptosis is essential for the resolution of inflammation but is delayed by several inflammatory mediators. In such terminally differentiated cells it has been uncertain whether these agents can inhibit apoptosis through transcriptional regulation of anti-death (Bcl-X(L),Mcl-1,Bcl2A1) or BH3-only (Bim,Bid,Puma) Bcl2-family proteins. We report that granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-α prevent the normal time-dependent loss of Mcl-1 and Bcl2A1 in neutrophils,and we demonstrate that they cause an NF-κB-dependent increase in Bcl-X(L) transcription/translation. We show that GM-CSF and TNF-α increase and/or maintain mRNA levels for the pro-apoptotic BH3-only protein Bid and that GM-CSF has a similar NF-κB-dependent effect on Bim transcription and BimEL expression. The in-vivo relevance of these findings was indicated by demonstrating that GM-CSF is the dominant neutrophil survival factor in lung lavage from patients with ventilator-associated pneumonia,confirming an increase in lung neutrophil Bim mRNA. Finally GM-CSF caused mitochondrial location of Bim and a switch in phenotype to a cell that displays accelerated caspase-9-dependent apoptosis. This study demonstrates the capacity of neutrophil survival agents to induce a paradoxical increase in the pro-apoptotic proteins Bid and Bim and suggests that this may function to facilitate rapid apoptosis at the termination of the inflammatory cycle. View Publication

There is emerging evidence that the commensal microbiota has a role in the pathogenesis of multiple sclerosis (MS),a putative autoimmune disease of the CNS. Here,we compared the gut microbial composition of 34 monozygotic twin pairs discordant for MS. While there were no major differences in the overall microbial profiles,we found a significant increase in some taxa such as Akkermansia in untreated MS twins. Furthermore,most notably,when transplanted to a transgenic mouse model of spontaneous brain autoimmunity,MS twin-derived microbiota induced a significantly higher incidence of autoimmunity than the healthy twin-derived microbiota. The microbial profiles of the colonized mice showed a high intraindividual and remarkable temporal stability with several differences,including Sutterella,an organism shown to induce a protective immunoregulatory profile in vitro. Immune cells from mouse recipients of MS-twin samples produced less IL-10 than immune cells from mice colonized with healthy-twin samples. IL-10 may have a regulatory role in spontaneous CNS autoimmunity,as neutralization of the cytokine in mice colonized with healthy-twin fecal samples increased disease incidence. These findings provide evidence that MS-derived microbiota contain factors that precipitate an MS-like autoimmune disease in a transgenic mouse model. They hence encourage the detailed search for protective and pathogenic microbial components in human MS. View Publication

Halofuginone,a low molecular weight plant alkaloid,inhibits collagen alpha1 (I) gene expression in several animal models and in patients with fibrotic disease,including scleroderma and graft-versus-host disease. In addition,halofuginone has been shown to inhibit angiogenesis and tumor progression. It was demonstrated recently that halofuginone inhibits transforming growth factor-beta (TGF-beta),an important immunomodulator. The present study was undertaken to explore the effects of halofuginone on activated T cells. Peripheral blood T cells were activated by anti-CD3 monoclonal antibodies in the absence and presence of halofuginone and assessed for nuclear factor (NF)-kappaB activity,production of tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma),T cell apoptosis,chemotaxis,and phosphorylation of p38 mitogen-activated protein kinase (MAPK). A delayed-type hypersensitivity (DTH) model was applied to investigate the effect of halofuginone on T cells in vivo. Preincubation of activated peripheral blood T cells with 10-40 ng/ml halofuginone resulted in a significant dose-dependent decrease in NF-kappaB activity (80% inhibition following incubation with 40 ng halofuginone,P = 0.002). In addition,40 ng/ml halofuginone inhibited secretion of TNF-alpha,IFN-gamma,interleukin (IL)-4,IL-13,and TGF-beta (P textless 0.005). Similarly,halofuginone inhibited the phosphorylation of p38 MAPK and apoptosis in activated T cells (P = 0.0001 and 0.005,respectively). In contrast,T cell chemotaxis was not affected. Halofuginone inhibited DTH response in mice,indicating suppression of T cell-mediated inflammation in vivo. Halofuginone inhibits activated peripheral blood T cell functions and proinflammatory cytokine production through inhibition of NF-kappaB activation and p38 MAPK phosphorylation. It also inhibited DTH response in vivo,making it an attractive immunomodulator and anti-inflammatory agent. View Publication

Costimulation by the chemokine,stromal cell-derived factor-1 (SDF-1)/CXCL12,has been shown to increase the amount of IL-10 secreted by TCR-stimulated human T cells; however,the molecular mechanisms of this response are unknown. Knowledge of this signaling pathway may be useful because extensive evidence indicates that deficient IL-10 secretion promotes autoimmunity. The human IL-10 locus is highly polymorphic. We report in this study that SDF-1 costimulates IL-10 secretion from T cells containing all three of the most common human IL-10 promoter haplotypes that are identified by single-nucleotide polymorphisms at -1082,-819,and -592 bp (numbering is relative to the transcription start site). We further show that SDF-1 primarily costimulates IL-10 secretion by a diverse population of CD45RA(-) (memory") phenotype T cells that includes cells expressing the presumed regulatory T cell marker� View Publication

HCMV is a highly sophisticated virus that has developed various mechanisms for immune evasion and viral dissemination throughout the body (partially mediated by neutrophils). NK cells play an important role in elimination of HCMV-infected cells. Both neutrophils and NK cells utilize similar sets of chemokine receptors to traffic,to and from,various organs. However,the mechanisms by which HCMV attracts neutrophils and not NK cells are largely unknown. Here,we show a unique viral protein,vCXCL1,which targets three chemokine receptors: CXCR1 and CXCR2 expressed on neutrophils and CXCR1 and CX3CR1 expressed on NK cells. Although vCXCL1 attracted both cell types,neutrophils migrated faster and more efficiently than NK cells through the binding of CXCR2. Therefore,we propose that HCMV has developed vCXCL1 to orchestrate its rapid systemic dissemination through preferential attraction of neutrophils and uses alternative mechanisms to counteract the later attraction of NK cells. View Publication

The lectin galectin-9 may help establish and maintain chronic hepatitis C virus infection. Galectin-9 is elevated in the liver and sera of hepatitis C virus patients,induces apoptosis of hepatitis C virus-specific T cells,and increases inhibitory regulatory T cells. Kupffer cells stain strongly for galectin-9 protein in hepatitis C virus patients. In the current study,we determined stimuli that induce galectin-9 production by monocytes and macrophages in hepatitis C virus infection. With the use of real-time PCR and flow cytometry,we analyzed galectin-9 mRNA and protein from human monocytes cocultured with hepatitis C virus-infected cells or noninfectious hepatitis C virus subgenomic replicon cells. We focused on finding the stimuli for galectin-9 production. Additionally,we measured galectin-9 during monocyte-to-macrophage maturation. Finally,we examined galectin-9 in peripheral monocytes from hepatitis C virus patients using flow cytometry. Galectin-9 mRNA increased 8-fold when primary monocytes were exposed to hepatitis C virus--infected cells. Maximum induction required proximity or contact and did not require IFN-γ or hepatitis C virus virions. Coculture of monocytes with subgenomic replicon cells increased galectin-9 5-fold,and purified exosomes from infected cells stimulated galectin-9 production. Stimulation of monocyte TLR3,-7,and -8 increased galectin-9 production. Differentiation of monocytes to macrophages increased galectin-9,and nonclassic monocytes from hepatitis C virus patients had the highest levels of galectin-9. Hepatitis C virus-infected cells stimulated monocytes to produce galectin-9 in close proximity,possibly,in part,as a result of exosomes and endosomal TLRs. Differentiation of monocytes to macrophages increased galectin-9. Nonclassic monocytes from hepatitis C virus patients express the highest galectin-9 levels,suggesting they may contribute to elevated galectin-9 and adaptive immune inhibition in hepatitis C virus infection. View Publication

CD4+CD25+ Tregs regulate immunity,but little is known about their own regulation. We now report that the human 60-kDa heat shock protein (HSP60) acts as a costimulator of human Tregs,both CD4+CD25int and CD4+CD25hi. Treatment of Tregs with HSP60,or its peptide p277,before anti-CD3 activation significantly enhanced the ability of relatively low concentrations of the Tregs to downregulate CD4+CD25- or CD8+ target T cells,detected as inhibition of target T cell proliferation and IFN-gamma and TNF-alpha secretion. The enhancing effects of HSP60 costimulation on Tregs involved innate signaling via TLR2,led to activation of PKC,PI3K,and p38,and were further enhanced by inhibition of ERK. HSP60-treated Tregs suppressed target T cells both by cell-to-cell contact and by secretion of TGF-beta and IL-10. In addition,the expression of ERK,NF-kappaB,and T-bet by downregulated target T cells was inhibited. Thus,HSP60,a self-molecule,can downregulate adaptive immune responses by upregulating Tregs innately through TLR2 signaling. View Publication

Helminthic infections modulate host immunity and may protect their hosts from developing immunological diseases like inflammatory bowel disease. Induction of regulatory T cells (Tregs) may be an important part of this protective process. Heligmosomoides polygyrus bakeri infection also promotes the production of the regulatory cytokines TGF-beta and IL-10 in the gut. In the intestines,TGF-beta helps induce regulatory T cells. This study used Foxp3/IL-10 double reporter mice to investigate the effect of TGF-beta on the differentiation of colon and mesenteric lymph node-derived murine Foxp3- IL-10- CD4+ T cells into their regulatory phenotypes. Foxp3- IL-10- CD4+ T cells from H. polygyrus bakeri-infected mice,as opposed to T cells from uninfected animals,cultured in vitro with TGF-beta and anti-CD3/CD28 mAb differentiated into Foxp3+ and/or IL-10+ T cells. The IL-10-producing T cells nearly all displayed CD25. Smad7 is a natural inhibitor of TGF-beta signaling. In contrast to gut T cells from uninfected mice,Foxp3- IL10- CD4+ T cells from H. polygyrus bakeri-infected mice displayed reduced Smad7 expression and responded to TGF-beta with Smad2/3 phosphorylation. The TGF-beta-induced Tregs that express IL-10 blocked colitis when transferred into the Rag/CD25- CD4+ T cell transfer model of inflammatory bowel disease. TGF-beta had a greatly diminished capacity to induce Tregs in H. polygyrus bakeri-infected transgenic mice with constitutively high T cell-specific Smad7 expression. Thus,infection with H. polygyrus bakeri causes down-modulation in Smad7 expression in intestinal CD4+ T cells,which allows the TGF-beta produced in response to the infection to induce the Tregs that prevent colitis. View Publication

Transplantation-associated stress can compromise the hematopoietic potential of hematopoietic stem cells (HSCs). As a consequence,HSCs may undergo exhaustion" in serial transplant recipients� View Publication