Blockade of costimulation through B7/CD28 inhibits experimental autoimmune uveoretinitis, but does not induce long-term tolerance

It has been reported that costimulation blockade can result in T cell anergy. We investigated the effects of blocking costimulatory molecules in vivo on the development of experimental autoimmune uveoretinitis (EAU), a model for autoimmune uveitis in humans that is induced in mice by immunization with the retinal Ag interphotoreceptor retinoid binding protein. B10.A mice immunized with a uveitogenic regimen of interphotoreceptor retinoid-binding protein were treated with Abs to B7.1 and B7.2 for 2 wk. Evaluation of EAU and immunological responses 1 wk later showed that disease had been abrogated, and cellular responses were suppressed. To determine whether the costimulation blockade resulted in tolerance, adult-thymectomized mice immunized for uveitis and treated with anti-B7 or anti-CD28 were rechallenged for uveitis induction 5 wk after the initial immunization. Although confirmed to be disease free after the initial immunization, both anti-B7- and anti-CD28-treated mice developed severe EAU and elevated cellular responses after the rechallenge, equivalent to those of control mice. We conclude that in this model costimulatory blockade in vivo prevents the development of autoimmune disease, but does not result in long-term tolerance. The data are compatible with the interpretation that B7/CD28 blockade prevents generation of effector, but not of memory, T cells.     

Novel function of IFN-gamma: negative regulation of dendritic cell migration and T cell priming

IFN-gamma is considered to be a Th1 cytokine with immunomodulatory effects on a variety of immune cells. In this study, we determined whether dendritic cell (DC) function was aberrant in IFN-gamma knockout (GKO) mice. The results demonstrated that IFN-gamma deficiency did not interfere with bone marrow-derived DC development and maturation in vitro. However, functional analysis showed that bone marrow-derived DC from GKO mice had altered cytokine secretion, allostimulatory and Ag presentation capacity, chemokine receptor expression, and in vitro chemotaxis. LPS induced the recruitment of DC from different organs into the spleen; epicutaneously sensitized DC with hapten (FITC) accumulated in the draining lymph nodes and CD11c(+) DC levels in the draining lymph nodes from autoantigen (interphotoreceptor retinoid-binding protein) immunized mice were enhanced in GKO mice as compared with wild-type mice. After treatment of GKO mice with i.p. IFN-gamma injection restored IFN-gamma levels in vivo, DC migration decreased in response to LPS or FITC. IFN-gamma altered the adaptive immune responses in vivo, since T cell priming and IL-2 production were increased in interphotoreceptor retinoid-binding protein-immunized GKO mice. Furthermore, in IFN-gamma-treated GKO mice, experimental autoimmune uveitis score enhancement and T cell activation were eliminated. Taken together, IFN-gamma appears to play a negative regulatory role on in vivo DC function, resulting in suppression of Ag-specific T cell priming.     

Galectin-1 suppresses autoimmune retinal disease by promoting concomitant Th2- and T regulatory-mediated anti-inflammatory responses

Intraocular inflammatory diseases are a common cause of severe visual impairment and blindness. In this study, we investigated the immunoregulatory role of galectin-1 (Gal-1), an endogenous lectin found at sites of T cell activation and immune privilege, in experimental autoimmune uveitis (EAU), a Th1-mediated model of retinal disease. Treatment with rGal-1 either early or late during the course of interphotoreceptor retinoid-binding protein-induced EAU was sufficient to suppress ocular pathology, inhibit leukocyte infiltration, and counteract pathogenic Th1 cells. Administration of rGal-1 at the early or late phases of EAU ameliorated disease by skewing the uveitogenic response toward nonpathogenic Th2 or T regulatory-mediated anti-inflammatory responses. Consistently, adoptive transfer of CD4(+) regulatory T cells obtained from rGal-1-treated mice prevented the development of active EAU in syngeneic recipients. In addition, increased levels of apoptosis were detected in lymph nodes from mice treated with rGal-1 during the efferent phase of the disease. Our results underscore the ability of Gal-1 to counteract Th1-mediated responses through different, but potentially overlapping anti-inflammatory mechanisms and suggest a possible therapeutic use of this protein for the treatment of human uveitic diseases of autoimmune etiology.     

Osteopontin aggravates experimental autoimmune uveoretinitis in mice

Human endogenous uveitis is a common sight-threatening intraocular inflammatory disease and has been studied extensively using a murine model of experimental autoimmune uveoretinitis (EAU). It is possibly mediated by Th1 immune responses. In the present study, we investigated the role of osteopontin (OPN), a protein with pleiotropic functions that contributes to the development of Th1 cell-mediated immunity. Accompanying EAU progression, OPN was elevated in wild-type (WT) mice that had been immunized with human interphotoreceptor retinoid-binding protein (hIRBP) peptide 1-20. OPN-deficient (OPN-/-) mice showed milder EAU progression in clinical and histopathological scores compared with those of WT mice. The T cells from hIRBP-immunized OPN-/- mice exhibited reduced Ag-specific proliferation and proinflammatory cytokine (TNF-alpha and IFN-gamma) production compared with those of WT T cells. When hIRBP-immunized WT mice were administered M5 Ab reacting to SLAYGLR sequence, a cryptic binding site to integrins within OPN, EAU development was significantly ameliorated. T cells from hIRBP-immunized WT mice showed significantly reduced proliferative responses and proinflammatory cytokine production upon stimulation with hIRBP peptide in the presence of M5 Ab in the culture. Our present results demonstrate that OPN may represent a novel therapeutic target to control uveoretinitis.     

Retinal expression of a neo-self antigen, beta-galactosidase, is not tolerogenic and creates a target for autoimmune uveoretinitis.

Recent studies revealing active mechanisms of immune privilege in neural tissues have diminished the putative role of passive tolerance. To examine the significance of Ag localization in the retina on immune privilege, the immune responses of transgenic mice expressing high and low levels of beta-galactosidase (beta-gal) in the photoreceptor cells of the retina were compared with those of normal mice and those of mice expressing moderate levels of beta-gal systemically. Immunization with beta-gal induced experimental autoimmune uveoretinitis indistinguishable from that induced by known photoreceptor cell autoantigens, including destruction of photoreceptor cells, in transgenic mice with high level retinal expression. Retinal expression had no apparent effect on the immune responses to beta-gal, showing that tolerance was not elicited by levels of retinal beta-gal sufficient to serve as a target for autoimmune disease. Mice with systemic expression exhibited reduced lymphoproliferative responses following immunization with beta-gal and did not develop autoimmune disease. T cells prepared from normal mice immunized with beta-gal transferred experimental autoimmune uveoretinitis to the transgenic mice with high level retinal beta-gal expression, but no disease was found in mice with systemic transgene expression under these conditions. The results of our experiments are most consistent with sequestration being the primary mechanism of retinal immune privilege. The results also show that beta-gal can serve as an immunopathogenic neural autoantigen, and that T cells raised by immunization of normal mice with a foreign Ag can be immunopathogenic in certain transgenic recipients.     

Disruption of CD40/CD40-ligand interactions in a retinal autoimmunity model results in protection without tolerance

We examined the role of CD40/CD40L interactions on the development of experimental autoimmune uveoretinitis (EAU), a cell-mediated, Th1-driven autoimmune disease that serves as a model for autoimmune uveitis in humans. EAU-susceptible B10.RIII mice immunized with the retinal autoantigen interphotoreceptor retinoid binding protein in CFA and treated with anti-CD40L Ab (MR1) had reduced incidence and severity of disease. Real-time PCR analysis revealed that the innate and adaptive responses of protected mice were reduced, without an obvious shift toward a Th2 cytokine profile. In contrast to some other reports, no evidence was found for regulatory cells in adoptive transfer experiments. To determine whether CD40L blockade resulted in long-term tolerance, mice protected by treatment with MR1 Ab were rechallenged for uveitis after circulating MR1 Ab levels dropped below the detection limit of ELISA. MR1-treated mice developed severe EAU and strong cellular responses to interphotoreceptor retinoid binding protein, comparable to those of control mice. These responses were higher than in mice that had not received the primary immunization concurrently with anti-CD40L treatment. We conclude that 1) CD40/CD40L interaction is required for EAU and its disruption prevents disease development; 2) CD40L blockade inhibits the innate response to immunization and reduces priming, but does not result in immune deviation; and 3) protection is dependent on persistence of anti-CD40L Abs, and long-term tolerance is not induced. Furthermore, immunological memory develops under cover of CD40L blockade causing enhanced responses upon rechallenge. Taken together, our data suggest that ongoing CD40/CD40L blockade might be required to maintain a therapeutic effect against uveitis.     

Uveitogenic potential of lymphocytes sensitized to interphotoreceptor retinoid-binding protein

In our previous study rats immunized with bovine retinal interphotoreceptor retinoid-binding protein (IRBP) were found to develop inflammation in the eye and the pineal gland. This inflammatory disease was distinct in several aspects from experimental autoimmune uveoretinitis (EAU) induced by the retinal S-antigen (S-Ag). The current study examined the adoptive transfer of IRBP-induced EAU. We established that lymphocytes from IRBP immunized donor rats were capable of transferring EAU after in vitro stimulation with either IRBP (lymph node or spleen cells) or concanavalin A (spleen cells only). Recipients of these cells developed uveoretinitis and pinealitis identical to the actively induced disease. As compared with the S-Ag system, recipients of IRBP sensitized cells developed disease earlier, and smaller numbers of cells were needed to transfer EAU. Development of inflammation was directly related to a cellular response to the specific retinal antigen used for sensitization. Moreover, the unique nature of ocular inflammation was reestablished in the IRBP system: high proportions of polymorphonuclear leukocytes were found in the inflamed tissue of certain recipients despite a lack of a humoral response to the specific antigen. In contrast to the eye, only mononuclear leukocytes comprised the inflammation in the pineal gland.     

S-antigen-specific rat T cell lines recognize peptide fragments of S-antigen and mediate experimental autoimmune uveoretinitis and pinealitis

Two S-antigen-specific rat T cell lines expressing the T helper cell surface phenotype (W 3/25+, OX 8-) have been isolated from the spleen and lymph node cells of retinal S-antigen-immunized Lewis rats, one of which displayed neither clinical nor histopathologic signs of experimental autoimmune uveoretinitis. The other rat had recovered from severe experimental autoimmune uveoretinitis for 2 mo before isolation of the cell line. Both lines are specific for S-antigen presented by histocompatible antigen-presenting cells, and also respond in vitro to several of the peptides produced by cyanogen bromide cleavage of bovine retinal S-antigen. The lesions induced by the i.v. transfer of from 1 to 10 X 10(6) viable line cells involve the retina and pineal gland, as is found when Lewis rats are immunized with immunopathogenic doses of S-antigen. Histologic examination of the eyes and pineal glands revealed pathologic lesions typical of experimental autoimmune uveoretinitis, and consisted of marked infiltration of the retina and surrounding tissues and the pineal gland by lymphocytes and inflammatory cells. T cells capable of mediating autoimmune disease are clearly present and readily isolated from both asymptomatic and convalescent animals. No significant differences in specificity for the cyanogen bromide peptides of S-antigen or cell surface phenotype were found in the T cell lines isolated from these two rats, nor was any difference found in the specificity or titer of serum antibodies taken from the original rats for the cyanogen bromide peptides of S-antigen.     

Selective immunosuppression of activated T cells with the chimeric toxin IL-2-PE40. Inhibition of experimental autoimmune uveoretinitis

A characteristic of activated T lymphocytes is the expression of high affinity IL-2R. We studied a new method of selective immunosuppression directed against activated T cells by using a chimeric recombinant protein (IL-2-PE40) composed of IL-2 fused to a modified Pseudomonas exotoxin lacking its cell recognition domain. As a model of T cell-mediated disease, we used experimental autoimmune uveoretinitis (EAU) produced in Lewis rats by active immunization with the retinal S-Ag. The treatment protocol consisted of i.p. injection of IL-2-PE40 at 0.25 micrograms/g every 12 h. Controls were PBS, PE40, or IL-2-PE40asp553 a mutant form of the molecule with reduced activity. Treatment with IL-2-PE40 resulted in a significant reduction of the incidence and severity of EAU over controls. The analysis of the effect of i.p. injection of IL-2-PE40 on the popliteal draining lymph nodes of immunized animals showed a marked reduction in the lymphocytes content. Transfer experiments demonstrated that IL-2-PE40 prevented the development of EAU effector T cells. Interestingly, although activated B cells were reported to express IL-2R, there was no significant reduction of antibody production against the immunizing Ag under IL-2-PE40 treatment, suggesting sparing of the B cells.     

Activation of CD8 T cells by mycobacterial vaccination protects against pulmonary tuberculosis in the absence of CD4 T cells

We have investigated whether both primary CD8 T cell activation and CD8 T cell-mediated protection from Mycobacterium tuberculosis challenge could occur in mycobacterial-vaccinated CD4 T cell-deficient (CD4KO) mice. Different from wild-type C57BL/6 mice, s.c. vaccination with bacillus Calmette-Guérin (BCG) in CD4KO mice failed to provide protection from secondary M. tuberculosis challenge at 3 wk postvaccination. However, similar to C57BL/6 mice, CD4KO mice were well protected from M. tuberculosis at weeks 6 and 12 postvaccination. This protection was mediated by CD8 T cells. The maintenance of protective effector/memory CD8 T cells in CD4KO mice did not require the continuous presence of live BCG vaccine. As in C57BL/6 mice, similar levels of primary activation of CD8 T cells in CD4KO mice occurred in the draining lymph nodes at 3 wk after BCG vaccination, but different from C57BL/6 mice, the distribution of these cells to the spleen and lungs of CD4KO mice was delayed, which coincided with delayed acquisition of protection in CD4KO mice. Our results suggest that both the primary and secondary activation of CD8 T cells is CD4 T cell independent and that the maintenance of these CD8 T cells is also independent of CD4 T cells and no longer requires the presence of live mycobacteria. However, the lack of CD4 T cells may result in delayed distribution of activated CD8 T cells from draining lymph nodes to distant organs and consequently a delayed acquisition of immune protection. Our findings hold implications in rational design of tuberculosis vaccination strategies for humans with impaired CD4 T cell function.     

Administration of PLP139-151 primes T cells distinct from those spontaneously responsive in vitro to this antigen

We examined the TCR repertoire used by naive SJL mice in their in vitro spontaneous response to proteolipid protein (PLP) 139-151 by Vbeta-Jbeta spectratyping and compared it to that used after immunization with the peptide. T cells from immunized mice use the public rearrangement Vbeta10-Jbeta1.1, but naive mice do not; in contrast, TCR CDR3-beta rearrangements of Vbeta18-Jbeta1.2 and Vbeta19-Jbeta1.2 consistently are associated with the spontaneous response. T cells involved in spontaneous and induced responses can each recognize PLP(139-151) presented in vivo, but its s.c. administration has different consequences for the two repertoires. Four days after immunization, T cells associated with spontaneous responsiveness appear in the draining lymph nodes but disappear by day 10 and never appear elsewhere. Simultaneously, Vbeta10-Jbeta1.1 T cells are likewise activated in the lymph nodes by day 4 and spread to the spleen by day 10. Eight- to 10-wk-old naive mice use a narrower repertoire of TCRs than do immunized age-matched mice. Induced Vbeta10-Jbeta1.1 T cells home to the CNS during experimental autoimmune encephalomyelitis, whereas we failed to detect Vbeta18-Jbeta1.2 and Vbeta19-Jbeta1.2 TCR rearrangements in the CNS. Thus, we observe that administration of PLP(139-151) primes a T cell repertoire distinct from the one responsible for spontaneous responsiveness. This "immunized" repertoire substitutes for the naive one and becomes dominant at the time of disease onset.     

Mice deficient in CD38 develop an attenuated form of collagen type II-induced arthritis

CD38, a type II transmembrane glycoprotein expressed in many cells of the immune system, is involved in cell signaling, migration and differentiation. Studies in CD38 deficient mice (CD38 KO mice) indicate that this molecule controls inflammatory immune responses, although its involvement in these responses depends on the disease model analyzed. Here, we explored the role of CD38 in the control of autoimmune responses using chicken collagen type II (col II) immunized C57BL/6-CD38 KO mice as a model of collagen-induced arthritis (CIA). We demonstrate that CD38 KO mice develop an attenuated CIA that is accompanied by a limited joint induction of IL-1β and IL-6 expression, by the lack of induction of IFNγ expression in the joints and by a reduction in the percentages of invariant NKT (iNKT) cells in the spleen. Immunized CD38 KO mice produce high levels of circulating IgG1 and low of IgG2a anti-col II antibodies in association with reduced percentages of Th1 cells in the draining lymph nodes. Altogether, our results show that CD38 participates in the pathogenesis of CIA controlling the number of iNKT cells and promoting Th1 inflammatory responses.     

IFN-inducible protein 10/CXC chemokine ligand 10-independent induction of experimental autoimmune encephalomyelitis

In multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), autoaggressive T cells traffic into the CNS and induce disease. Infiltration of these pathogenic T cells into the CNS has been correlated with the expression of the chemokine IFN-inducible protein (IP)10/CXC chemokine ligand (CXCL)10, a chemoattractant for activated T cells, and its receptor CXCR3, in the CNS of both MS patients and mice with EAE. In the present study, we report that targeted deletion of IP-10 did not diminish the expression, severity, or histopathology of EAE induced by active immunization with 100 micro g of myelin oligodendrocyte glycoprotein peptide (MOG)p35-55. However, we found that IP-10-deficient mice had a lower threshold for expression of disease compared with wild-type littermates. EAE induced by immunization with 5 micro g of MOGp35-55 resulted in more severe disease characterized by a greater number of CNS lesions and infiltrating mononuclear cells in IP-10-deficient mice compared with wild-type controls. IP-10-deficient mice immunized with MOGp35-55 demonstrated increased levels of IFN-inducible T cell alpha-chemokine/CXCL11 mRNA in the CNS and decreased levels of monokine induced by IFN-gamma/CXCL9 mRNA in draining lymph nodes, suggesting differential compensation for loss of IP-10 in lymphoid vs parenchymal tissue compartments. EAE in IP-10-deficient mice induced by low-dose immunization was associated with enhanced Ag-specific Th1 responses in the draining lymph node, which corresponded with diminished lymph node TGF-beta1 expression. Our data demonstrated that IP-10 was not required for the trafficking of pathogenic T cells into the CNS in EAE but played an unexpected role in determining the threshold of disease susceptibility in the periphery.     

Pertussis toxin enhances Th1 responses by stimulation of dendritic cells

Pertussis toxin (PTX) has been widely used as an adjuvant to induce Th1-mediated organ-specific autoimmune diseases in animal models. However, the cellular and molecular mechanisms remain to be defined. In this study, we showed that dendritic cells (DC) stimulated with PTX (PTX-DC) were able to substitute for PTX to promote experimental autoimmune uveitis (EAU). EAU induced by PTX-DC revealed a typical Th1 response, characterized by high uveitogenic retinal Ag interphotoreceptor retinoid-binding protein (IRBP)-specific IFN-gamma and IL-12 production in the draining lymph nodes, as well as increased levels of anti-IRBP IgG2a and decreased levels of anti-IRBP IgG1 in the serum of IRBP-immunized mice. Furthermore, PTX-DC preferentially induced T cells to produce the Th1 cytokine, IFN-gamma. After being stimulated with PTX, DC exhibited up-regulation of MHC class II, CD80, CD86, CD40, and DEC205. PTX-DC had also increased allostimulatory capacity and IL-12 and TNF-alpha production. Serum IL-12 was increased in naive mice that received PTX-DC i.p. In addition, PTX activated extracellular signal-regulated kinase in DC. Following the inhibition of extracellular signal-regulated kinase signaling, the maturation of PTX-DC was reduced. Subsequently, the ability of PTX-DC to promote IFN-gamma production by T cells in vitro and to induce EAU in vivo was blocked. The results suggest that PTX might exert an adjuvant effect on DC to promote their maturation and the production of proinflammatory cytokines, thereby eliciting a Th1 response.     

Therapeutic effect of the potent IL-12/IL-23 inhibitor STA-5326 on experimental autoimmune uveoretinitis

Introduction

The purpose of this study was to determine if oral administration of the interleukin (IL) 12/IL-23 inhibitor, STA-5326, is effective in experimental autoimmune uveoretinitis (EAU).

Methods

C57BL/6J mice were immunised with human interphotoreceptor retinoid binding protein peptide (IRBP_1–20). STA-5326 at a dose of either 5 mg/kg or 20 mg/kg, or vehicle alone, was orally administered once a day for six days a week from day 0 to day 14. Fundus examination was performed on day 14 and day 18 after immunisation. Mice were euthanased on day 18 and the eyes were enucleated for histopathological examination. In vivo-primed draining lymph node cells were stimulated with IRBP_1–20 and culture supernatant was harvested for assay of interferon (IFN)-γ and IL-17 by ELISA. Intracellular expression of IFN-γ and IL-17 in CD4⁺ T cells of cultured draining lymph node cells was assessed by flow cytometry. The level of IL-12 p40 in serum was examined in STA-5326-treated or vehicle-treated mice receiving immunisation.

Results

The level of IL-12 p40 in serum was decreased in mice treated with STA-5326. Oral administration of either 5 mg/kg or 20 mg/kg STA-5326 reduced the severity of EAU on day 14 and 18. In addition, mice treated with 20 mg/kg STA-5326 showed significantly decreased severity of EAU by histopathological analysis. Although IFN-γ production of draining lymph node cells was increased in STA-5326-treated mice by ELISA analysis, the proportion of IFN-γ-producing cells was not significantly altered. However, IL-17 production and the proportion of IL-17-producing cells were significantly reduced in STA-5326-treated mice. Furthermore, oral administration of STA-5326 during the effector phase reduced the severity of EAU.

Conclusions

These results indicate that oral administration of the IL-12/IL-23 inhibitor STA-5326 is effective in suppressing inflammation in the EAU model, and reduces the expansion of IL-17-producing cells. STA-5326 may represent a new therapeutic modality for human refractory uveitis.     

Lipopolysaccharide-activated IL-10-secreting dendritic cells suppress experimental autoimmune uveoretinitis by MHCII-dependent activation of CD62L-expressing regulatory T cells

Dendritic cells (DC) are key regulators of immune responses. Mature DC are traditionally considered to be immunogenic, although there is accumulating evidence that they can also be tolerogenic and induce Ag-specific regulatory T cells (Tregs). However, the mechanism of this Treg induction and the site of Treg action in vivo are yet to be defined. In this study, using the experimental model of interphotoreceptor retinoid-binding protein peptide (1-20)-induced experimental autoimmune uveoretinitis, we show that s.c. inoculation of IRBP-peptide-pulsed IL-10-producing LPS-activated mature DC (IL-10-DC) at one site (the cervical region) suppresses autoimmunity induced at a separate site (the inguinal region). Our data show that s.c. IL-10-DC correlates with an increase in the number of CD4(+)CD25(+)Foxp3(+) Tregs at the DC-draining lymph nodes (DC-dLN). However, although MHCII(-/-) IL-10-DC also induces Treg expansion at this DC-dLN, they failed to suppress experimental autoimmune uveoretinitis. Furthermore, unlike wild-type IL-10-DC, MHCII(-/-) IL-10-DC did not correlate with an increase in the percentage of Tregs expressing CD62L at the DC-dLN, nor did they associate with an increase in Treg number at a distal site. Similar effects were also observed after s.c. hen egg lysozyme-pulsed IL-10-DC, which produced a strong reduction in the number and activation of proliferating Ag-specific CD4(+) 3A9 T effector cells. We therefore propose that IL-10-DC require MHCII-dependent Ag presentation, and hence TCR ligation, to promote CD62L-mediated trafficking of Tregs to the site of T effector cell priming, where they suppress autoimmunity.     

Loss of STAT3 in CD4+ T cells prevents development of experimental autoimmune diseases

Th17 cells are implicated in CNS autoimmune diseases. We show that mice with targeted-deletion of Stat3 in CD4(+) T cells (CD4(Stat3)(-/-)) do not develop experimental autoimmune uveoretinitis (EAU) or experimental autoimmune encephalomyelitis. Defective Th17 differentiation noted in CD4(Stat3)(-/-) mice is compensated by exaggerated increases in Foxp3-, IL-10-, IL-4-, and IFN-gamma-expressing T cells, suggesting critical roles of STAT3 in shaping Ag-specific CD4(+) T cell repertoire. In mice with EAU, a high percentage of IL-17-expressing T cells in their peripheral lymphoid organs also secrete IFN-gamma while these double-expressors are absent in CD4(Stat3)(-/-) and wild-type mice without EAU, raising the intriguing possibility that uveitis maybe mediated by Th17 and IL-17-expressing Th1 cells. Resistance of Stat3-deficient mice to EAU derives in part from an inability of uveitogenic Th17 and Th1 cells to enter eyes or brain of the CD4(Stat3)(-/-) mouse because of the reduction in the expression of activated alpha4/beta1 integrins on CD4(Stat3)(-/-) T cells. Adoptive transfer of activated interphotoreceptor retinoid-binding protein-specific uveitogenic T cells induced in CD4(Stat3)(-/-) mice a severe EAU characterized by development of retinal folds, infiltration of inflammatory cells into the retina, and destruction of retinal architecture, underscoring our contention that the loss of STAT3 in CD4(+) T cells results in an intrinsic developmental defect that renders CD4(Stat3)(-/-) resistant to CNS inflammatory diseases. STAT3 requirement for IL-17 production by Th17, generation of double positive T cells expressing IL-17 and IFN-gamma, and for T cell trafficking into CNS tissues suggests that STAT3 may be a therapeutic target for modulating uveitis, sceritis, or multiple sclerosis.     

OGR1/GPR68 Modulates the Severity of Experimental Autoimmune Encephalomyelitis and Regulates Nitric Oxide Production by Macrophages

Ovarian cancer G protein-coupled receptor 1 (OGR1) is a proton-sensing molecule that can detect decreases in extracellular pH that occur during inflammation. Although OGR1 has been shown to have pro-inflammatory functions in various diseases, its role in autoimmunity has not been examined. We therefore sought to determine whether OGR1 has a role in the development of T cell autoimmunity by contrasting the development of experimental autoimmune encephalomyelitis between wild type and OGR1-knockout mice. OGR1-knockout mice showed a drastically attenuated clinical course of disease that was associated with a profound reduction in the expansion of myelin oligodendrocyte glycoprotein 35-55-reactive T helper 1 (Th1) and Th17 cells in the periphery and a reduced accumulation of Th1 and Th17 effectors in the central nervous system. We determined that these impaired T cell responses in OGR1-knockout mice associated with a reduced frequency and number of dendritic cells in draining lymph nodes during EAE and a higher production of nitric oxide by macrophages. Our studies suggest that OGR1 plays a key role in regulating T cell responses during autoimmunity.