The principal effect of TGF-β1 on mesenchymal cells is its stimulation of ECM synthesis. Previous reports indicated the significance of the autocrine TGF-β loop in the pathogenesis of scleroderma. In this study, we focused on Smad7 and Smurfs, principal molecules in the negative regulation of TGF-β signaling, to further understand the autocrine TGF-β loop in scleroderma. Scleroderma fibroblasts exhibited increased Smad7 levels compared with normal fibroblasts in vivo and in vitro. Smad7 constitutively formed a complex with the TGF-β receptors, and the inhibitory effect of Smad7 on the promoter activity of human α2(I) collagen and 3TP-lux was completely impaired in scleroderma fibroblasts. Furthermore, the protein stability of TGF-β receptor type I was significantly increased in scleroderma fibroblasts compared with normal fibroblasts. There was no significant difference in Smurf1 and Smurf2 levels between normal and scleroderma fibroblasts, and the transiently overexpressed Smurf1 and/or Smurf2 did not affect TGF-β receptor type I protein levels in scleroderma fibroblasts. These results indicate that the impaired Smad7-Smurf–mediated inhibitory effect on TGF-β signaling might contribute to maintaining the autocrine TGF-β loop in scleroderma fibroblasts. To our knowledge, this is the first report of a disturbed negative regulation of TGF-β signaling in fibrotic disorders.
Yoshihide Asano, Hironobu Ihn, Kenichi Yamane, Masahide Kubo, Kunihiko Tamaki
Relapsing polychondritis is a multisystem autoimmune disease involving cartilage destruction but no known causative antigen. HLA-DQ8 has been associated with various autoimmune diseases in humans. To study the role of DQ8 in autoimmune diseases, we have generated transgenic mice expressing DQ8 (DQA1*0301, DQB1*0302) in a NOD background lacking endogenous class II molecules (Aβo). Upon immunization with type II collagen (CII), 85% of NOD.DQ8 mice develop severe experimental polychondritis, auricular chondritis, and polyarthritis, with clinical and histological similarities to relapsing polychondritis (RP) in humans. CII-immunized mice mount a T cell response and produce Ab’s to type IX collagen (CIX) and self-CII. Transgene-negative littermates do not develop any serological and clinical manifestations following immunization. B10.DQ8 transgenic mice develop polyarthritis and Ab’s to CII only. The susceptibility to auricular chondritis in NOD.DQ8 mice can be attributed to response to CIX. A higher number of activated cells, CD4+CD44hiCD62Llo, and lower regulatory cells CD4+CD152+CD25+ were observed in NOD.DQ8 mice compared with B10.DQ8 mice. The NOD.DQ8 mice provide a model of RP with a high disease incidence and multiple organ involvement to investigate putative autoantigen and regulatory cells involved in disease pathogenesis. An experimental model restricted by the human class II molecule will be valuable when studying the role of various collagens in immunologic and pathologic responses in human RP.
Veena Taneja, Marie Griffiths, Marshall Behrens, Harvinder S. Luthra, Chella S. David
To determine the role of CD154-CD40 interactions in the B cell overactivity exhibited by patients with active systemic lupus erythematosus (SLE), CD19+ peripheral B cells were examined before and after treatment with humanized anti-CD154 mAb (BG9588, 5c8). Before treatment, SLE patients manifested activated B cells that expressed CD154, CD69, CD38, CD5, and CD27. Cells expressing CD38, CD5, or CD27 disappeared from the periphery during treatment with anti-CD154 mAb, and cells expressing CD69 and CD154 disappeared from the periphery during the post-treatment period. Before treatment, active-SLE patients had circulating CD38bright Ig-secreting cells that were not found in normal individuals. Disappearance of this plasma cell subset during treatment was associated with decreases in anti–double-stranded DNA (anti-dsDNA) Ab levels, proteinuria, and SLE disease activity index. Consistent with this finding, peripheral B cells cultured in vitro spontaneously proliferated and secreted Ig in a manner that was inhibited by anti-CD154 mAb. Finally, the CD38+/++IgD+, CD38+++, and CD38+IgD– B cell subsets present in the peripheral blood also disappeared following treatment with humanized anti-CD154. Together, these results indicate that patients with active lupus nephritis exhibit abnormalities in the peripheral B cell compartment that are consistent with intensive germinal center activity, are driven via CD154-CD40 interactions, and may reflect or contribute to the propensity of these patients to produce autoantibodies.
Amrie C. Grammer, Rebecca Slota, Randy Fischer, Hanan Gur, Hermann Girschick, Cheryl Yarboro, Gabor G. Illei, Peter E. Lipsky
Psoriasis is a chronic inflammatory disease of the skin characterized by epidermal hyperplasia, dermal angiogenesis, infiltration of activated T cells, and increased cytokine levels. One of these cytokines, IL-15, triggers inflammatory cell recruitment, angiogenesis, and production of other inflammatory cytokines, including IFN-γ, TNF-α, and IL-17, which are all upregulated in psoriatic lesions. To investigate the role of IL-15 in psoriasis, we generated mAb’s using human immunoglobulin-transgenic mice. One of the IL-15–specific antibodies we generated, 146B7, did not compete with IL-15 for binding to its receptor but potently interfered with the assembly of the IL-15 receptor α, β, γ complex. This antibody effectively blocked IL-15–induced T cell proliferation and monocyte TNF-α release in vitro. In a human psoriasis xenograft model, antibody 146B7 reduced the severity of psoriasis, as measured by epidermal thickness, grade of parakeratosis, and numbers of inflammatory cells and cycling keratinocytes. These results obtained with this IL-15–specific mAb support an important role for IL-15 in the pathogenesis of psoriasis.
Louise S. Villadsen, Janine Schuurman, Frank Beurskens, Tomas N. Dam, Frederik Dagnæs-Hansen, Lone Skov, Jørgen Rygaard, Marleen M. Voorhorst-Ogink, Arnout F. Gerritsen, Marc A. van Dijk, Paul W.H.I. Parren, Ole Baadsgaard, Jan G.J. van de Winkel
Roza I. Nurieva, Piper Treuting, Julie Duong, Richard A. Flavell, Chen Dong
In vivo treatment of mice with the natural killer T (NKT) cell ligand, α-galactosylceramide (αGalCer), ameliorates autoimmune diabetes and experimental autoimmune encephalomyelitis (EAE) by shifting pathogenic Th1-type immune responses to nonpathogenic Th2-type responses. In the current study, in vivo activation of NKT cells in adult NZB/W mice by multiple injections of αGalCer induced an abnormal Th1-type immune response as compared with the Th2-type response observed in nonautoimmune C57BL/6 mice. This resulted in decreased serum levels of IgE, increased levels of IgG2a and IgG2a anti–double-stranded DNA (anti-dsDNA) Ab’s, and exacerbated lupus. Conversely, treatment of NZB/W mice with blocking anti-CD1d mAb augmented Th2-type responses, increased serum levels of IgE, decreased levels of IgG2a and IgG2a anti-dsDNA Ab’s, and ameliorated lupus. While total CD4+ T cells markedly augmented in vitro IgM anti-dsDNA Ab secretion by splenic B cells, the non–CD1d-reactive (CD1d-αGalCer tetramer-negative) CD4+ T cells (accounting for 95% of all CD4+ T cells) failed to augment Ab secretion. The CD1d-reactive tetramer-positive CD4+ T cells augmented anti-dsDNA Ab secretion about tenfold. In conclusion, activation of NKT cells augments Th1-type immune responses and autoantibody secretion that contribute to lupus development in adult NZB/W mice, and anti-CD1d mAb might be useful for treating lupus.
Defu Zeng, Yinping Liu, Stephane Sidobre, Mitchell Kronenberg, Samuel Strober
CD8+ T cell depletion renders CD28-deficient mice susceptible to experimental autoimmune encephalomyelitis (EAE). In addition, CD8–/–CD28–/– double-knockout mice are susceptible to EAE. These findings suggest a role for CD8+ T cells in the resistance of CD28-deficient mice to disease. Adoptive transfer of CD8+CD28– T cells into CD8–/– mice results in significant suppression of disease, while CD8+CD28+ T cells demonstrate no similar effect on the clinical course of EAE in the same recipients. In vitro, CD8+CD28– but not CD8+CD28+ T cells suppress IFN-γ production of myelin oligodendrocyte glycoprotein–specific CD4+ T cells. This suppression requires cell-to-cell contact and is dependent on the presence of APCs. APCs cocultured with CD8+CD28– T cells become less efficient in inducing a T cell–dependent immune response. Such interaction prevents upregulation of costimulatory molecules by APCs, hence decreasing the delivery of these signals to CD4+ T cells. These are the first data establishing that regulatory CD8+CD28– T cells occur in normal mice and play a critical role in disease resistance in CD28–/– animals.
Nader Najafian, Tanuja Chitnis, Alan D. Salama, Bing Zhu, Christina Benou, Xueli Yuan, Michael R. Clarkson, Mohamed H. Sayegh, Samia J. Khoury
To detect and characterize autoreactive T cells in diabetes-prone NOD mice, we have developed a multimeric MHC reagent with high affinity for the BDC-2.5 T cell receptor, which is reactive against a pancreatic autoantigen. A distinct population of T cells is detected in NOD mice that recognizes the same MHC/peptide target. These T cells are positively selected in the thymus at a surprisingly high frequency and exported to the periphery. They are activated specifically in the pancreatic LNs, demonstrating an autoimmune specificity that recapitulates that of the BDC-2.5 cell. These phenomena are also observed in mouse lines that share with NOD the H-2g7 MHC haplotype but carry diabetes-resistance background genes. Thus, a susceptible haplotype at the MHC seems to be the only element required for the selection and emergence of autoreactive T cells, without requiring other diabetogenic loci from the NOD genome.
Thomas Stratmann, Natalia Martin-Orozco, Valérie Mallet-Designe, Laurent Poirot, Dorian McGavern, Grigoriy Losyev, Cathleen M. Dobbs, Michael B.A. Oldstone, Kenji Yoshida, Hitoshi Kikutani, Diane Mathis, Christophe Benoist, Kathryn Haskins, Luc Teyton
In studies using genetically deficient mice, a role for the lymphotoxin (LT) system in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) has remained controversial. Here, we have reassessed this conclusion by using a fusion protein decoy that blocks the LT pathway in vivo without evoking the developmental defects inherent in LT-deficient mice. We have found that inhibition of the LT pathway prevented disease in two models of EAE that do not rely on the administration of pertussis toxin. Surprisingly, disease attenuation was due to specific blockade of LTαβ binding rather than the binding of LIGHT to its receptors. In a third system that requires pertussis toxin, LT inhibition did not affect disease, as was observed when the same model was used with LT-deficient mice. Disease prevention in pertussis toxin–free models was associated with defects in T cell responses and migration. When the DO11.10 T cell transgenic system was used, inhibition of the LT pathway was shown to uncouple T cell priming from T cell recall responses. Therefore, it is hypothesized that the LT pathway and its ability to maintain lymphoid microenvironments is critical for sustaining late-phase T cell responses in multiple sclerosis.
Jennifer L. Gommerman, Keith Giza, Stuart Perper, Irene Sizing, Apinya Ngam-ek, Cheryl Nickerson-Nutter, Jeffrey L. Browning
Stepwise degradation of the invariant chain (Ii) is required for the binding of antigenic peptides to MHC class II molecules. Cathepsin (Cat) L in the murine thymus and Cat S in peripheral APCs have both been implicated in the last step of Ii degradation that gives rise to the class II–associated invariant chain peptides (CLIP). Cat V has been recently described as highly homologous to Cat L and exclusively expressed in human thymus and testis, but with no mouse orthologue. We report that Cat V is the dominant cysteine protease in cortical human thymic epithelial cells, while Cat L and Cat S seem to be restricted to dendritic and macrophage-like cells. Active Cat V in thymic lysosomal preparations was demonstrated by active-site labeling. Recombinant Cat V was capable of converting Ii into CLIP efficiently, suggesting that Cat V is the protease that controls the generation of αβ-CLIP complexes in the human thymus, in analogy to Cat L in mouse. Comparison of Cat V expression between thymi from patients with myasthenia gravis and healthy controls revealed a significantly higher expression level in the pathological samples, suggesting a potential involvement of this protease in the immunopathogenesis of myasthenia gravis, an autoimmune disease almost invariably associated with thymic pathology.
Eva Tolosa, Weijie Li, Yoshiyuki Yasuda, Wolfgang Wienhold, Lisa K. Denzin, Alfred Lautwein, Christoph Driessen, Petra Schnorrer, Ekkehard Weber, Stefan Stevanovic, Raffael Kurek, Arthur Melms, Dieter Brömme
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