[Show abstract][Hide abstract] ABSTRACT: Immunotherapy by using multimerized self-peptides has demonstrated a clear protective effect on experimental models of autoimmune diseases. However, the mechanisms involved remain ill-defined. Here we have evaluated the therapeutic efficacy of multimerized self-peptides at the effector phase of autoimmune diabetes and examined their mechanisms of action. Diabetes was induced in rat insulin promoter-hemagglutinin (HA) mice expressing HA in pancreatic beta-cells by adoptive transfer of HA(110-119)-specific T helper 1 cells. Complete protection was provided by low doses of the HA 4-mer consisting of four covalently linked linear HA(107-119) peptides. In vivo, the 4-mer appeared to act directly on the pathogenic HA-specific T helper 1 cells and indirectly by activation/recruitment of lymphocytes with regulatory properties so that mice became resistant to a second transfer of diabetogenic T cells. This effect was associated with a recruitment of Foxp3(+) CD4 T cells around islets. Moreover, we show that dominant protection from autoimmunity was transferable by spleen cells, and that development of this regulatory population was crucially dependent on the lymphocytes from treated rat insulin promoter-HA mice. Thus, immunotherapy using multimerized epitopes emerges as a promising strategy in view of the current identification of self-epitopes that are major targets of the pathogenic CD4 T cell response in autoimmune diseases.
Full-text · Article · Jun 2007 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The influence of enteric glia on the regulation of intestinal functions is unknown. Our aim was to determine the phenotype of enteric neurones in a model of glia alterations and the putative changes in intestinal motility and permeability.
Transgenic mice expressing haemagglutinin (HA) in glia were used. Glia disruption was induced by injection of activated HA specific CD8+ T cells. Control mice consisted of non-transgenic littermates injected with activated HA specific CD8+ T cells. Immunohistochemical staining for choline acetyltransferase (ChAT), substance P (SP), vasoactive intestinal peptide (VIP), and nitric oxide synthase (NOS) was performed on jejunal submucosal plexus (SMP) and myenteric plexus (MP). Neurally induced jejunal muscle activity was characterised in vitro. Gastrointestinal transit and paracellular permeability were measured using fluorescein isothiocyanate-dextran markers.
CD3 positive T cells infiltrates were observed in the MP of transgenic mice. In the SMP, the proportions of VIP and SP positive neurones decreased in transgenic mice compared with control mice. ChAT remained unchanged. In the MP, the proportions of ChAT and NOS positive neurones increased and decreased, respectively, in transgenic mice. In contrast, VIP and SP remained unchanged. Neurally mediated jejunal relaxation was lower in transgenic mice than in controls. This relaxation was reduced by NG-nitro-L-arginine methyl ester in control mice but not in transgenic mice. Gastrointestinal transit was delayed and intestinal permeability increased in transgenic mice compared with control mice.
Glia disruption induces changes in the neurochemical coding of enteric neurones, which may partly be responsible for dysfunctions in intestinal motility and permeability.
[Show abstract][Hide abstract] ABSTRACT: Thymus-derived regulatory T cells (Tregs) expressing CD4, CD25, and the transcription factor Foxp3 play major roles in preventing autoimmunity. The Treg population is enriched in T cells expressing high-avidity self-reactive T cell receptors, and thymic epithelial cells expressing self-antigens (Ag) have been implicated in their induction and/or selection. However, the thymic selection events leading to Treg lineage commitment remain unclear. We followed the thymic development of self-Ag-specific Tregs in double-transgenic mice coexpressing a neo-self-Ag, hemagglutinin (HA) under the control of a neural tissue-specific promoter, and a transgenic class II-restricted T cell antigen receptor specific for HA111-119. Our data show that the promiscuous expression of the HA transgene in thymic epithelial cells is involved in the selective induction and/or expansion of HA-specific Foxp3(+) Treg thymic precursors as early as the double-positive stage.
Full-text · Article · Jun 2006 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The fate of autoreactive CD4+T cells was investigated in HNT-TCR x GFAP-HA double transgenic mice, in which the majority of CD4+T cells is specific for a neo-selfantigen expressed under a glial cell-specific promoter. These mice do not develop any clinical or histological signs of central or enteric nervous system autoimmunity. Although HA is transcribed in the thymus of GFAP-HA mice, similar numbers of CD4+ CD8- thymocytes, expressing comparable levels of the transgenic TCR, developed in HNT-TCR x GFAP-HA double transgenic and HNT-TCR single transgenic mice, indicating that HA-specific thymocytes are not negatively selected. In the periphery, the HA-specific T cells remained similarly unaffected as they displayed a naïve phenotype and were neither deleted nor anergized. Finally, immunization of HNT-TCR x GFAP-HA mice with the HNT peptide in CFA and/or in vivo depletion of CD25+ cells did not reverse this state of immune ignorance as judged by the lack of clinical manifestations of intestinal and neurological disease in these mice. Taken together these data demonstrate a profound state of immune ignorance towards a self-antigen expressed in the enteric and central nervous system.
No preview · Article · Jun 2004 · Journal of Autoimmunity
[Show abstract][Hide abstract] ABSTRACT: Cytotoxic CD8(+) T cells are abundantly present in human virus-induced or putative autoimmune diseases of the central nervous system (CNS). Their direct role in the induction of inflammatory brain damage is, however, poorly understood. We have studied CD8(+) T cell-mediated brain inflammation by transferring MHC class I-restricted hemagglutinin (HA)-reactive T cells from a TCR transgenic mouse line into transgenic mice, which express HA in astrocytes. We show that activated CD8(+) T cells alone can induce monophasic brain inflammation in immunocompetent recipient animals. Similar to previous studies, involving transfer of CD4(+) cells, brain inflammation peaks after 5-7 days and then declines. The pathology of brain inflammation, however, differs fundamentally from that induced by CD4(+) cells. The inflammatory reaction is dominated by T cells and activated microglia in the virtual absence of hematogenous macrophages. This is associated with exquisitely specific destruction of antigen-containing astrocytes in the absence of any bystander damage of myelin, oligodendrocytes or neurons. Furthermore, in contrast to CD4(+) T cells, some CD8(+) cells accumulate in the brain and activate microglia in recipient animals, even in the absence of the specific antigen in the CNS. These data indicate that CD8(+) T cells are prime candidates for immune surveillance of the CNS.
Full-text · Article · May 2003 · European Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Enteric glial cells (EGCs) represent an extensive but relatively poorly described cell population within the gastrointestinal tract. Accumulating data suggest that EGCs represent the morphological and functional equivalent of CNS astrocytes within the enteric nervous system (ENS). The EGC network has trophic and protective functions toward enteric neurons and is fully implicated in the integration and the modulation of neuronal activities. Moreover, EGCs seem to be active elements of the ENS during intestinal inflammatory and immune responses, sharing with astrocytes the ability to act as antigen-presenting cells and interacting with the mucosal immune system via the expression of cytokines and cytokine receptors. Transgenic mouse systems have demonstrated that specific ablation of EGC by chemical ablation or autoimmune T-cell targeting induces an intestinal pathology that shows similarities to the early intestinal immunopathology of Crohn's disease. EGCs may also share with astrocytes the ability to regulate tissue integrity, thereby postulating that similar interactions to those observed for the blood-brain barrier may also be partly responsible for regulating mucosal and vascular permeability in the gastrointestinal tract. Disruption of the EGC network in Crohn's disease patients may represent one possible cause for the enhanced mucosal permeability state and vascular dysfunction that are thought to favor mucosal inflammation.
[Show abstract][Hide abstract] ABSTRACT: Early pathological manifestations of Crohn's disease (CD) include vascular disruption, T cell infiltration of nerve plexi, neuronal degeneration, and induction of T helper 1 cytokine responses. This study demonstrates that disruption of the enteric glial cell network in CD patients represents another early pathological feature that may be modeled after CD8(+) T cell-mediated autoimmune targeting of enteric glia in double transgenic mice. Mice expressing a viral neoself antigen in astrocytes and enteric glia were crossed with specific T cell receptor transgenic mice, resulting in apoptotic depletion of enteric glia to levels comparable in CD patients. Intestinal and mesenteric T cell infiltration, vasculitis, T helper 1 cytokine production, and fulminant bowel inflammation were characteristic hallmarks of disease progression. Immune-mediated damage to enteric glia therefore may participate in the initiation and/or the progression of human inflammatory bowel disease.
Preview · Article · Dec 2001 · Proceedings of the National Academy of Sciences