T cell repertoire diversity is required for relapses in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis

Comparison of TCRalphabeta repertoires of myelin oligodendrocyte glycoprotein (MOG)-specific T lymphocytes in C57BL/6 and TdT-deficient littermates (TdT(-/-)) generated during experimental autoimmune encephalomyelitis (EAE) highlights a link between a diversified TCRalphabeta repertoire and EAE relapses. At the onset of the disease, the EAE-severity is identical in TdT(+/-) and TdT(-/-) mice and the neuropathologic public MOG-specific T cell repertoires express closely similar public Valpha-Jalpha and Vbeta-Jbeta rearrangements in both strains. However, whereas TdT(+/+) and TdT(+/-) mice undergo successive EAE relapses, TdT(-/-) mice recover definitively and the lack of relapses does not stem from dominant regulatory mechanisms. During the first relapse of the disease in TdT(+/-) mice, new public Valpha-Jalpha and Vbeta-Jbeta rearrangements emerge that are distinct from those detected at the onset of the disease. Most of these rearrangements contain N additions and are found in CNS-infiltrating T lymphocytes. Furthermore, CD4(+) T splenocytes bearing these rearrangements proliferate to the immunodominant epitope of MOG and not to other immunodominant epitopes of proteolipid protein and myelin basic protein autoantigens, excluding epitope spreading to these myelin proteins. Thus, in addition to epitope spreading, a novel mechanism involving TCRalphabeta repertoire diversification contributes to autoimmune progression.     

Intercellular adhesion molecule-1 expression is required on multiple cell types for the development of experimental autoimmune encephalomyelitis

Many members of the Ig superfamily of adhesion molecules, such as ICAM-1 and VCAM-1, have been implicated in the pathogenesis of multiple sclerosis. Although it is well-established that VCAM-1/VLA-4 interactions can play important roles in mediating CNS inflammatory events in multiple sclerosis patients and during the development of experimental allergic encephalomyelitis (EAE), the contributions of ICAM-1 are poorly understood. This is due in large part to conflicting results from Ab inhibition studies and the observation of exacerbated EAE in ICAM-1 mutant mice that express a restricted set of ICAM-1 isoforms. To determine ICAM-1-mediated mechanisms in EAE, we analyzed ICAM-1 null mutant mice (ICAM-1(null)), which express no ICAM-1 isoforms. ICAM-1(null) mice had significantly attenuated EAE characterized by markedly reduced spinal cord T cell infiltration and IFN-gamma production by these cells. Adoptive transfer of Ag-restimulated T cells from wild-type to ICAM-1(null) mice or transfer of ICAM-1(null) Ag-restimulated T cells to control mice failed to induce EAE. ICAM-1(null) T cells also showed reduced proliferative capacity and substantially reduced levels of IFN-gamma, TNF-alpha, IL-4, IL-10, and IL-12 compared with that of control T cells following myelin oligodendrocyte glycoprotein 35-55 restimulation in vitro. Our results indicate that ICAM-1 expression is critical on T cells and other cell types for the development of demyelinating disease and suggest that expression of VCAM-1 and other adhesion molecules cannot fully compensate for the loss of ICAM-1 during EAE development.     

Differential regulation of CD4+ T helper cell responses by curcumin in experimental autoimmune encephalomyelitis

Nutraceuticals and phytochemicals are important regulators of human health and diseases. Curcumin is a polyphenolic phytochemical isolated from the rhizome of the plant Curcuma longa (turmeric) that has been traditionally used for the treatment of inflammation and wound healing for centuries. Systematic analyses have shown that curcumin exerts its beneficial effects through antioxidant, antiproliferative and anti-inflammatory properties. We and others have shown earlier that curcumin ameliorates experimental autoimmune encephalomyelitis (EAE) model for multiple sclerosis. In this study, we show that C57BL/6 mice induced to develop EAE express elevated levels of interferon (IFN) γ and interleukin (IL)-17 in the central nervous system (CNS) and lymphoid organs that decreased significantly following in vivo treatment with curcumin. The EAE mice also showed elevated expression of IL-12 and IL-23 that decreased after treatment with curcumin. Ex vivo and in vitro treatment with curcumin resulted in a dose-dependent decrease in the secretion of IFNγ, IL-17, IL-12 and IL-23 in culture. The inhibition of EAE by curcumin was also associated with an up-regulation of IL-10, peroxisome proliferator activated receptor γ and CD4⁺CD25⁺Foxp3⁺ Treg cells in the CNS and lymphoid organs. These findings highlight that curcumin differentially regulates CD4⁺ T helper cell responses in EAE.     

Epitope spreading is not required for relapses in experimental autoimmune encephalomyelitis

The sequential emergence of specific T lymphocyte-mediated immune reactivity directed against multiple distinct myelin epitopes (epitope spreading) has been associated with clinical relapses in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Based on this association, an appealing and plausible model for immune-mediated progression of the advancing clinical course in MS and EAE has been proposed in which epitope spreading is the cause of clinical relapses in T cell-mediated CNS inflammatory diseases. However, the observed association between epitope spreading and disease progression is not universal, and absolute requirements for epitope spreading in progressive EAE have not been tested in the absence of multiple T cell specificities, because most prior studies have been conducted in immunocompetent mouse strains that possessed broad TCR repertoires. Consequently, the precise nature of a causal relationship between epitope spreading and disease progression remains uncertain. To determine whether relapsing or progressive EAE can occur in the absence of epitope spreading, we evaluated the course of disease in mice which possessed only a single myelin-specific TCR. These mice (transgenic/SCID +/+) exhibited a progressive and sometimes remitting/relapsing disease course in the absence of immune reactivity to multiple, spreading myelin epitopes. The results provide direct experimental evidence relevant to discussions on the mechanisms of disease progression in MS and EAE.     

Special AT‐rich sequence binding protein 1 is required for maintenance of T cell receptor responsiveness and development of experimental autoimmune encephalomyelitis

The genome organizer special AT‐rich sequence binding protein 1 (SATB1) regulates specific functions through chromatin remodeling in T helper cells. It was recently reported by our team that T cells from SATB1 conditional knockout (SATB1cKO) mice, in which the Satb1 gene is deleted from hematopoietic cells, impair phosphorylation of signaling molecules in response to T cell receptor (TCR) crosslinking. However, in vivo T cell responses upon antigen presentation in the absence of SATB1 remain unclear. In the current study, it was shown that SATB1 modulates T cell antigen responses during the induction and effector phases. Expression of SATB1 was upregulated in response to TCR stimulation, suggesting that SATB1 is important for this antigen response. The role of SATB1 in TCR responses and induced experimental autoimmune encephalomyelitis (EAE) was therefore examined using the myelin oligodendrocyte glycoprotein peptide 35‐55 (MOG35‐55) and pertussis toxin. SATB1cKO mice were found to be resistant to EAE and had defects in IL‐17‐ and IFN‐γ‐producing pathogenic T cells. Thus, SATB1 expression appears necessary for T cell function in the induction phase. To examine SATB1 function during the effector phase, a tamoxifen‐inducible SATB1 deletion system, SATB1cKO‐ER‐Cre mice, was used. Encephalitogenic T cells from MOG35‐55‐immunized SATB1cKO‐ER‐Cre mice were transferred into healthy mice. Mice that received tamoxifen before the onset of paralysis were resistant to EAE. Furthermore, no disease progression occurred in recipient mice treated with tamoxifen after the onset of EAE. Thus, SATB1 is essential for maintaining TCR responsiveness during the induction and effector phases and may provide a novel therapeutic target for T cell‐mediated autoimmune diseases.     

Cutting edge: the silent chemokine receptor D6 is required for generating T cell responses that mediate experimental autoimmune encephalomyelitis

D6, a promiscuous nonsignaling chemokine binding molecule expressed on the lymphatic endothelium, internalizes and degrades CC chemokines, and D6(-/-) mice demonstrated increased cutaneous inflammation following topical phorbol ester or CFA injection. We report that D6(-/-) mice were unexpectedly resistant to the induction of experimental autoimmune encephalomyelitis due to impaired encephalitogenic responses. Following induction with myelin oligodendroglial glycoprotein (MOG) peptide 35-55 in CFA, D6(-/-) mice showed reduced spinal cord inflammation and demyelination with lower incidence and severity of experimental autoimmune encephalomyelitis attacks as compared with D6(+/+) littermates. In adoptive transfer studies, MOG-primed D6(+/-) T cells equally mediated disease in D6(+/+) or D6(-/-) mice, whereas cells from D6(-/-) mice transferred disease poorly to D6(+/-) recipients. Lymph node cells from MOG-primed D6(-/-) mice showed weak proliferative responses and made reduced IFN-gamma but normal IL-5. CD11c(+) dendritic cells accumulated abnormally in cutaneous immunization sites of D6(-/-) mice. Surprisingly, D6, a "silent" chemokine receptor, supports immune response generation.     

Neuronal antigens modulate the immune response associated with experimental autoimmune encephalomyelitis

Rats primed with bovine myelin (BM) in complete Freunds adjuvant, develop acute experimental autoimmune encephalomyelitis (EAE). We have previously described that intraperitoneal administration prior to the active induction of the disease of a bovine synaptosomal fraction (BSF) and BM were effective ways of suppressing EAE. We found that both treatments diminish the incidence of the disease and reduced biochemical and histological alterations of the central nervous system (CNS). To characterize this suppression process, in this study we examined the antigen-specific immune response in animals protected from EAE. Lymph node mononuclear cells derived from sick EAE rats, as well as from those protected by BM and BSF, showed strong myelin basic protein (MBP) proliferation. Analysis of the humoral response against MBP showed a significant diminution of IgG2b anti-MBP titres in protected BM and BSF rats in contrast to sick EAE rats whose condition could be related to a diminished anti-MBP Th1 response. Finally, cells from rats protected by BSF and BM reduced the incidence of EAE when they were adoptively transferred into animals prior to active induction of the disease. These results suggest that a mechanism based on the generation of regulatory cells and immune deviation could account for the EAE suppression mediated by myelin as well as synaptosomal antigens.     

Coincident parasite and CD8 T cell sequestration is required for development of experimental cerebral malaria

Cerebral malaria (CM) is a fatal complication of Plasmodium falciparum infection. Using a well defined murine model, we observed the effect on disease outcome of temporarily reducing parasite burden by anti-malarial drug treatment. The anti-malarial treatment regime chosen decreased parasitaemia but did not cure the mice, allowing recrudescence of parasites. These mice were protected against CM, despite their parasitaemia having increased, following treatment cessation, to levels surpassing that associated with CM in mice not treated with the drug. The protection was associated with reduced levels of cytokines, chemokines, CD8⁺ T cells and parasites in the brain. The results suggest that the development of the immunopathological response that causes CM depends on a continuous stimulus provided by parasitised red blood cells, either circulating or sequestered in small vessels.     

Coronin 1-mediated naive T cell survival is essential for the development of autoimmune encephalomyelitis

Autoimmune encephalomyelitis is a disease of the CNS that can develop when an initial peripheral inflammatory stimulus is followed by infiltration and reactivation of T lymphocytes in the CNS. We report a crucial role for coronin 1, which is essential for maintenance of the naive T cell pool, for the development of murine experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. In the absence of coronin 1, immunization with myelin oligoglycoprotein (MOG(35-55)) peptide largely failed to induce EAE symptoms, despite normal mobilization of leukocyte subsets in the blood, as well as effector cytokine expression comparable with wild-type T cells on polyclonal stimulation. Susceptibility of coronin 1-deficient mice to EAE induction was restored by transfer of wild-type CD4(+) T cells, suggesting that the observed resistance of coronin 1-deficient mice to EAE development is T cell intrinsic. Importantly, although coronin 1-deficient regulatory T cells (Tregs) showed a suppressor activity comparable with wild-type Tregs, Treg depletion failed to restore EAE development in coronin 1-deficient animals. These results suggest a hitherto unrecognized role of naive T cells in the development of autoimmune encephalomyelitis and reveal coronin 1 as a crucial modulator of EAE induction.     

CD47 expression on T cell is a self-control negative regulator of type 1 immune response

The cytokine milieu and dendritic cells (DCs) direct Th1 development. Yet, the control of Th1 polarization by T cell surface molecules remains ill-defined. We here report that CD47 expression on T cells serves as a self-control mechanism to negatively regulate type 1 cellular and humoral immune responses in vivo. Th2-prone BALB/c mice that lack CD47 (CD47(-/-)) displayed a Th1-biased Ab profile at steady state and after immunization with soluble Ag. CD47(-/-) mice mounted a T cell-mediated exacerbated and sustained contact hypersensitivity (CHS) response. After their adoptive transfer to naive CD47-deficient hosts 1 day before immunization with soluble Ag, CD47(-/-) as compared with CD47(+/+)CD4(+) transgenic (Tg) T cells promoted the deviation of Ag-specific T cell responses toward Th1 that were characterized by a high IFN-gamma:IL-4 cytokine ratio. Although selective CD47 deficiency on DCs led to increased IL-12p70 production, CD47(-/-)Tg T cells produced more IFN-gamma and displayed higher T-bet expression than CD47(+/+) Tg T cells in response to OVA-loaded CD47(-/-) DCs. CD47 as part of the host environment has no major contribution to the Th1 polarization responses. We thus identify the CD47 molecule as a T cell-negative regulator of type 1 responses that may limit unwanted collateral damage to maximize protection and minimize host injury.     

CD28 costimulation is crucial for the development of spontaneous autoimmune encephalomyelitis

Multiple sclerosis (MS) is a severe central nervous system disease. Experimental autoimmune encephalomyelitis (EAE) mimics MS in mice. We report that spontaneous development of EAE in RAG-1-deficient mice transgenic for a myelin basic protein (MBP)-specific TCR (TgMBP+/RAG-1-/-) requires expression of the T cell costimulatory molecule CD28. Surprisingly, T cells from CD28-/-TgMBP+/RAG-1-/- mice proliferate and produce IL-2 in response to MBP1-17 peptide in vitro, excluding clonal anergy as the mechanism of CD28-regulated pathogenesis. Proliferation of autoaggressive T cells was dependent on the concentration of the MBP peptide, as was the development of MBP-induced EAE in CD28-deficient PL/J mice. These results provide the first genetic evidence that CD28 costimulation is crucial for MBP-specific T cell activation in vivo and the initiation of spontaneous EAE.     

CD18 is required for intestinal T cell responses at multiple immune checkpoints

The intestinal immune response to oral Ags involves a complex multistep process. The requirements for optimal intestinal T cell responses in this process are unclear. LFA-1 plays a critical role in peripheral T cell trafficking and activation, however, its role in intestinal immune responses has not been precisely defined. To dissect the role of LFA-1 in intestinal immune responses, we used a system that allows for segregation of T cell migration and activation through the adoptive transfer of LFA-1-deficient (CD18(-/-)) CD4(+) T cells from DO11.10 TCR transgenic mice into wild-type BALB/c mice. We find that wild-type mice adoptively transferred with CD18(-/-) DO11.10 CD4(+) T cells demonstrate decreases in the numbers of Ag-specific T cells in the intestinal lamina propria after oral Ag administration. We also find that in addition to its role in trafficking to intestinal secondary lymphoid organs, LFA-1 is required for optimal CD4(+) T cell proliferation in vivo upon oral Ag immunization. Furthermore, CD18(-/-) DO11.10 CD4(+) T cells primed in the intestinal secondary lymphoid organs demonstrate defects in up-regulation of the intestinal-specific trafficking molecules, alpha(4)beta(7) and CCR9. Interestingly, the defect in trafficking of CD18(-/-) DO11.10 CD4(+) T cells to the intestinal lamina propria persists even under conditions of equivalent activation and intestinal-tropic differentiation, implicating a role for CD18 in the trafficking of activated T cells into intestinal tissues independent of the earlier defects in the intestinal immune response. This argues for a complex role for CD18 in the early priming checkpoints and ultimately in the trafficking of T cells to the intestinal tissues during an intestinal immune response.     

Functional heterogeneity among CD4+ encephalitogenic T cells in recruitment of CD8+ T cells in experimental autoimmune encephalomyelitis

Inoculation of Lewis rats with live or attenuated (irradiated or paraformaldehyde-fixed) CD4+ encephalitogenic T cells (S1 line) protects the recipients from transferred experimental autoimmune encephalomyelitis (tEAE) induced by S1 cells. A CD8+ T lymphocyte population specifically activated against the EAE-inducing S1 cells can be readily isolated from the lymphoid organs of pretreated animals. We show, in the present study, that encephalitogenic T cell lines derived from Lewis rats differ in their ability to induce resistance against tEAE in vivo and to stimulate CD8+ cell proliferation in vitro. We also demonstrate that the S19 line of encephalitogenic T cells, in combination with myelin basic protein (MBP), can stimulate CD8+ cell proliferation in vitro. The CD8+ cells generated in this way strongly suppress MBP-specific T cell proliferation in vitro. This combined effect of T cells and MBP was also evident in vivo. Neither S19 cells nor MBP alone induced resistance against S19-mediated tEAE, rather coinjection of these cells and MBP was required. Our results suggest that resistance to EAE is mediated by distinct populations of encephalitogenic T cells that activate Ts cells through different mechanisms. In some instances, both autoreactive T cells and their relevant autoantigen(s) may be needed to activate Ts cells in vivo.