Enhancement of experimental allergic encephalomyelitis in mice by antibodies against IFN-gamma

Acute experimental allergic encephalomyelitis (EAE) was induced in C57BL/6J and SJL/J mice by injection of isologous spinal cord homogenate given in conjunction with Bordetella pertussis and Freund's adjuvant. SJL/J mice showed a highly aggressive and 100% lethal form of the disease; C57BL/6J mice were much less susceptible as they had low morbidity rates (20 to 40%), low disease scores, and mostly no mortality. Treatment of these low susceptibility mice with neutralizing mAb against IFN-gamma caused an increase in morbidity rates as well as significant mortality (up to 80%). Similar antibody treatment did not affect the course of the disease in the high susceptibility SJL/J mice. However, treatment of these mice with IFN-gamma resulted in reduced morbidity and mortality. A similar but less pronounced inhibition of the disease in SJL/J mice could be obtained by administration of IFN-alpha/beta or by acute infection with lactate dehydrogenase virus. The results indicate that endogenous as well as exogenous IFN can exert a down-regulating effect on the development of EAE. They also indicate that endogenous IFN-gamma is produced during the development of EAE and plays a disease-limiting role.     

FcR interactions do not play a major role in inhibition of experimental autoimmune encephalomyelitis by anti-CD154 monoclonal antibodies

It has been demonstrated that anti-CD154 mAb treatment effectively inhibits the development of experimental autoimmune encephalomyelitis (EAE). However, although it appears to prevent the induction of Th1 cells and reactivation of encephalitogenic T cells within the CNS, little information is available regarding the involvement of alternative mechanisms, nor has the contribution of Fc effector mechanisms in this context been addressed. By contrast, efficacy of anti-CD154 mAbs in models of allotransplantation has been reported to involve long-term unresponsiveness, potentially via activation of T regulatory cells, and recently was reported to depend on Fc-dependent functions, such as activated T cell depletion through FcgammaR or complement. In this study we demonstrate that anti-CD154 mAb treatment inhibits EAE development in SJL mice without apparent long-term unresponsiveness or active suppression of disease. To address whether the mechanism of inhibition of EAE by anti-CD154 mAb depends on its Fc effector interactions, we compared an anti-CD154 mAb with its aglycosyl counterpart with severely impaired FcgammaR binding and reduced complement binding activity with regard to their ability to inhibit clinical signs of EAE and report that both forms of the Ab are similarly protective. This observation was largely confirmed by the extent of leukocyte infiltration of the CNS; however, mice treated with the aglycosyl form may display slightly more proteolipid protein 139-151-specific immune reactivity. It is concluded that FcR interactions do not play a major role in the protective effect of anti-CD154 mAb in the context of EAE, though they may contribute to the full abrogation of peripheral peptide-specific lymphocyte responses.     

Repetitive pertussis toxin promotes development of regulatory T cells and prevents central nervous system autoimmune disease

Bacterial and viral infections have long been implicated in pathogenesis and progression of multiple sclerosis (MS). Incidence and severity of its animal model experimental autoimmune encephalomyelitis (EAE) can be enhanced by concomitant administration of pertussis toxin (PTx), the major virulence factor of Bordetella pertussis. Its adjuvant effect at the time of immunization with myelin antigen is attributed to an unspecific activation and facilitated migration of immune cells across the blood brain barrier into the central nervous system (CNS). In order to evaluate whether recurring exposure to bacterial antigen may have a differential effect on development of CNS autoimmunity, we repetitively administered PTx prior to immunization. Mice weekly injected with PTx were largely protected from subsequent EAE induction which was reflected by a decreased proliferation and pro-inflammatory differentiation of myelin-reactive T cells. Splenocytes isolated from EAE-resistant mice predominantly produced IL-10 upon re-stimulation with PTx, while non-specific immune responses were unchanged. Longitudinal analyses revealed that repetitive exposure of mice to PTx gradually elevated serum levels for TGF-β and IL-10 which was associated with an expansion of peripheral CD4(+)CD25(+)FoxP3(+) regulatory T cells (Treg). Increased frequency of Treg persisted upon immunization and thereafter. Collectively, these data suggest a scenario in which repetitive PTx treatment protects mice from development of CNS autoimmune disease through upregulation of regulatory cytokines and expansion of CD4(+)CD25(+)FoxP3(+) Treg. Besides its therapeutic implication, this finding suggests that encounter of the immune system with microbial products may not only be part of CNS autoimmune disease pathogenesis but also of its regulation.     

Administration of agonistic anti-4-1BB monoclonal antibody leads to the amelioration of experimental autoimmune encephalomyelitis.

4-1BB, a member of the TNFR superfamily, is a costimulatory receptor primarily expressed on activated T cells. It has been shown that the administration of agonistic anti-4-1BB Abs enhances tumor immunity and allogenic immune responses. Paradoxically, we found that the administration of an agonistic anti-4-1BB mAb (2A) dramatically reduced the incidence and severity of experimental autoimmune encephalomyelitis (EAE). Adoptive transfer of T cells from such treated mice failed to induce EAE, whereas anti-4-1BB treatment following adoptive transfer of encephalitogenic T cells did not prevent EAE pathogenesis. These results suggest that anti-4-1BB treatment during the induction phase inhibits autoreactive T cell immune responses rather than preventing T cell trafficking into the CNS. This was substantiated by the observations that draining lymph node cells from anti-4-1BB-treated mice failed to respond to Ag stimulation in vitro. In addition, we found that such treatment initially promotes the activation and proliferation of Ag-specific CD4+ T cells but subsequently increases their probability of undergoing activation-induced cell death, thereby inhibiting effector T cell responses. More importantly, 2A treatment also inhibits the relapse of EAE in a clinically relevant murine model of multiple sclerosis. This study indicates that the agonistic Ab against 4-1BB can potentially be used as a novel immunotherapeutic agent for treating autoimmune diseases.     

Pertussis toxin prevents the induction of peripheral T cell anergy and enhances the T cell response to an encephalitogenic peptide of myelin basic protein.

In a murine model of T cell-mediated autoimmune disease, experimental autoimmune encephalitis (EAE), 80% of all encephalitogenic T cell clones in H-2u mice use the V beta 8.2 TCR element. To induce EAE in susceptible strains of mice either heat-killed Bordetella pertussis organisms or Bordetella pertussis toxin (PT) must be injected in addition to Ag in CFA. We investigated the mechanisms by which PT facilitates the induction of EAE. Our data show, that PT interferes with the induction of Ag-induced peripheral T cell anergy. Furthermore it has a specific adjuvanticity for the autoantigen pAc1-11 in vivo and acts as a selective mitogen in vitro. We also tested the hypothesis that PT is a bacterial superantigen that specifically expands the V beta 8.2+ subset of T cells, thereby expanding the encephalitogenic T cell clones that are contained in this subset, so that the number of autoreactive T cells is brought over a critical threshold, necessary to induce autoimmune disease. Our data show that PT is not a superantigen. Staphylococcal enterotoxin B, a V beta 8.2-specific superantigen, does not enhance the immune response to the encephalitogenic peptide.     

Cutting edge: paradigm revisited: antibody provides resistance to Listeria infection.

Listeriolysin O (LLO) is a secreted pore-forming toxin of the facultative intracellular bacterium Listeria monocytogenes. We assessed the ability of a murine anti-LLO mAb to affect the course of infection in mice challenged with Listeria. This mAb was previously shown to be capable of neutralizing LLO-mediated pore formation in vitro, and here we show that the passive administration of this Ab to mice before infection provides increased resistance. Mice treated with the mAb were protected from a lethal challenge with virulent Listeria and showed a significant reduction in Listeria burden during the first hours to days postinfection. These effects of the Ab were independent of host B or T cells, since treatment with the mAb provided enhanced resistance to SCID mice. The titer of anti-LLO Abs during the regular infection of mice with Listeria was found to be low to negative.     

Delta-like ligand 4 regulates central nervous system T cell accumulation during experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) T cell-mediated inflammatory demyelinating disease of the CNS that serves as a model for multiple sclerosis. Notch receptor signaling in T lymphocytes has been shown to regulate thymic selection and peripheral differentiation. In the current study, we hypothesized that Notch ligand-receptor interaction affects EAE development by regulating encephalitogenic T cell trafficking. We demonstrate that CNS-infiltrating myeloid dendritic cells, macrophages, and resident microglia expressed Delta-like ligand 4 (DLL4) after EAE induction. Treatment of mice with a DLL4-specific blocking Ab significantly inhibited the development of clinical disease induced by active priming. Furthermore, the treatment resulted in decreased CNS accumulation of mononuclear cells in the CNS. Anti-DLL4 treatment did not significantly alter development of effector cytokine expression by Ag-specific T cells. In contrast, anti-DLL4 treatment reduced T cell mRNA and functional cell surface expression of the chemokine receptors CCR2 and CCR6. Adoptive transfer of Ag-specific T cells to mice treated with anti-DLL4 resulted in decreased clinical severity and diminished Ag-specific CD4(+) T cell accumulation in the CNS. These results suggest a role for DLL4 regulation of EAE pathogenesis through modulation of T cell chemokine receptor expression and migration to the CNS.     

Critical roles of CXC chemokine ligand 16/scavenger receptor that binds phosphatidylserine and oxidized lipoprotein in the pathogenesis of both acute and adoptive transfer experimental autoimmune encephalomyelitis

The scavenger receptor that binds phosphatidylserine and oxidized lipoprotein (SR-PSOX)/CXCL16 is a chemokine expressed on macrophages and dendritic cells, while its receptor expresses on T and NK T cells. We investigated the role of SR-PSOX/CXCL16 on acute and adoptive experimental autoimmune encephalomyelitis (EAE), which is Th1-polarized T cell-mediated autoimmune disease of the CNS. Administration of mAb against SR-PSOX/CXCL16 around the primary immunization decreased disease incidence of acute EAE with associated reduced infiltration of mononuclear cells into the CNS. Its administration was also shown to inhibit elevation of serum IFN-gamma level at primary immune response, as well as subsequent generation of Ag-specific T cells. In adoptive transfer EAE, treatment of recipient mice with anti-SR-PSOX/CXCL16 mAb also induced not only decreased clinical disease incidence, but also diminished traffic of mononuclear cells into the CNS. In addition, histopathological analyses showed that clinical development of EAE correlates well with expression of SR-PSOX/CXCL16 in the CNS. All the results show that SR-PSOX/CXCL16 plays important roles in EAE by supporting generation of Ag-specific T cells, as well as recruitment of inflammatory mononuclear cells into the CNS.     

IL-10 plays an important role in the homeostatic regulation of the autoreactive repertoire in naive mice

We have previously shown that naive SJL (H-2(s)) mice, which are highly susceptible to myelin proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE), have a very high frequency (1/20,000 CD4 T cells) of PLP(139-151)-reactive T cells in the naive repertoire. In this study, we examine the function of this endogenous PLP(139-151)-reactive repertoire in vivo and find that this repertoire encompasses the precursors of pathogenic T cells. Because SJL mice do not develop spontaneous EAE, we have explored the mechanisms that keep this autopathogenic repertoire in check and prevent the development of spontaneous autoimmunity. We crossed IL-4 and IL-10 deficiency onto the SJL background and analyzed the roles of these two immunoregulatory cytokines in regulating the size and effector function of the endogenous PLP(139-151)-reactive repertoire and development of autoimmune disease. We find that IL-10 is important in the homeostatic regulation of the endogenous PLP(139-151)-reactive repertoire in that it both limits the size of the repertoire and prevents development of effector autoaggressive T cells. SJL IL-10(-/-) mice with high numbers of PLP(139-151)-specific precursors in the repertoire did not develop spontaneous EAE, but when they were injected with pertussis toxin, they showed atypical clinical signs of EAE with small numbers of typical mononuclear cell infiltrates predominantly in the meninges. EAE could be inhibited by prior tolerization of the mice with soluble PLP(139-151) peptide. These findings indicate that IL-10 may contribute to the regulation of the endogenous autoimmune repertoire.     

IL-4 suppression of in vivo T cell activation and antibody production

Injection of mice with a foreign anti-IgD Ab stimulates B and T cell activation that results in large cytokine and Ab responses. Because most anti-IgD-activated B cells die before they can be stimulated by activated T cells, and because IL-4 prolongs the survival of B cells cultured with anti-Ig, we hypothesized that treatment with IL-4 at the time of anti-IgD Ab injection would decrease B cell death and enhance anti-IgD-induced Ab responses. Instead, IL-4 treatment before or along with anti-IgD Ab suppressed IgE and IgG1 responses, whereas IL-4 injected after anti-IgD enhanced IgE responses. The suppressive effect of early IL-4 treatment on the Ab response to anti-IgD was associated with a rapid, short-lived increase in IFN-gamma gene expression but decreased CD4+ T cell activation and decreased or delayed T cell production of other cytokines. We examined the possibilities that IL-4 stimulation of IFN-gamma production, suppression of IL-1 or IL-2 production, or induction of TNF-alpha or Fas-mediated apoptosis could account for IL-4's suppressive effect. The suppressive effect of IL-4 was not reversed by IL-1, IL-2, or anti-TNF-alpha or anti-IFN-gamma mAb treatment, or mimicked by treatment with anti-IL-2Ralpha (CD25) and anti-IL-2Rbeta (CD122) mAbs. Early IL-4 treatment failed to inhibit anti-IgD-induced Ab production in Fas-defective lpr mice; however, the poor responsiveness of lpr mice to anti-IgD made this result difficult to interpret. These observations indicate that exposure to IL-4, while T cells are first being activated by Ag presentation, can inhibit T cells activation or promote deletion of responding CD4+ T cells.     

Amelioration of experimental autoimmune encephalomyelitis with anti-OX40 ligand monoclonal antibody: a critical role for OX40 ligand in migration, but not development, of pathogenic T cells

OX40 (CD134) and its ligand (OX40L) have been implicated in T cell activation and migration. In this study, we examined the contribution of these molecules to the pathogenesis of experimental autoimmune encephalomyelitis (EAE) by administering a neutralizing mAb against murine OX40L (RM134L) to proteolipid protein (139-151) peptide-induced EAE in SJL mice. Administration of RM134L effectively ameliorated the disease in both actively induced and adoptively transferred EAE models. Histological examination showed that the RM134L treatment greatly reduced mononuclear cell infiltration into the spinal cord. The RM134L treatment did not inhibit the development of pathogenic T cells, given that proliferative response and IFN-gamma production by draining lymph node cells were not reduced or rather enhanced upon restimulation with proteolipid protein (139-151) in vitro, and these cells effectively transferred EAE to naive SJL mice. Flow cytometric analyses showed that the RM134L treatment inhibited the accumulation of OX40-expressing CD4(+) T cells and the migration of adoptively transferred CD4(+) T cells in the spinal cord. Immunohistochemical staining showed that OX40L was most prominently expressed on endothelial cells in the inflamed spinal cord. These results suggest that the OX40/OX40L interaction plays a critical role for the migration of pathogenic T cells into the CNS in the pathogenesis of EAE.     

Experimental autoimmune encephalomyelitis (EAE) induced by antigen pulsed dendritic cells in the C57BL/6 mouse: influence of injection route.

Dendritic cells (DCs) are the most potent antigen-presenting cells (APC) of the immune system, and are critically involved in initiation of immune responses in autoimmune diseases. They can modulate the nature of immune responses to stimulatory or tolerogenic fashion. Previous studies have demonstrated that the administration route of DCs is an important variable in eliciting anti-tumor immunity. In this study we used experimental autoimmune encephalomyelitis (EAE) as an animal model of multiple sclerosis to compare different protocols of DC delivery in autoimmunity or tolerance induction. Dendritic cells were generated from bone marrow cells of C57BL/6 mice by culturing in the presence of GM-CSF and IL-4 for 7 days, followed by 2 days culture with TNF-alpha. The obtained DCs were pulsed in vitro with myelin oligodendrocyte glycoprotein (MOG) peptide and injected (5 x 10(5) cells/mouse) via the intravenous (i.v.), intraperitoneal (i.p.) or subcutaneous (s.c.) route into female C57BL/6 mice. In some instances pertussis toxin was also injected zero and 48 hours after DC injection. After follow up of the mice pretreated in this way for 4 weeks, in the i.v. group in which no clinical signs of EAE occurred, the mice were immunized with MOG peptide for EAE induction via the common method and the results were compared with mice that were not pre-immunized. Only after three s.c. DC injections with pertussis toxin, the mice showed mild clinical signs of EAE, whereas mice given i.v. or i.p. injections with or without pertussis toxin failed to develop EAE after 4 weeks. Induction of EAE via the common method after three injections of TNF-alpha treated DCs, in i.v. injected groups showed no protection from EAE. It seems that several factors influence the tolerance versus immunity induction by DCs. Our results showed that the administration route of DCs is one of the pivotal factors in DC-based induction of autoimmune diseases.     

Involvement of regulatory T cells in the experimental autoimmune encephalomyelitis-preventive effect of dendritic cells expressing myelin oligodendrocyte glycoprotein plus TRAIL

We previously reported the protection from myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) by the adoptive transfer of genetically modified embryonic stem cell-derived dendritic cells (ES-DC) presenting MOG peptide in the context of MHC class II molecules and simultaneously expressing TRAIL (ES-DC-TRAIL/MOG). In the present study, we found the severity of EAE induced by another myelin autoantigen, myelin basic protein, was also decreased after treatment with ES-DC-TRAIL/MOG. This preventive effect diminished, if the function of CD4(+)CD25(+) regulatory T cells (Treg) was abrogated by the injection of anti-CD25 mAb into mice before treatment with ES-DC-TRAIL/MOG. The adoptive transfer of CD4(+)CD25(+) T cells from ES-DC-TRAIL/MOG-treated mice protected the recipient mice from MOG- or myelin basic protein-induced EAE. The number of Foxp3(+) cells increased in the spinal cords of mice treated with ES-DC-TRAIL/MOG. In vitro experiments showed that TRAIL expressed in genetically modified ES-DC and also in LPS-stimulated splenic macrophages had a capacity to augment the proliferation of CD4(+)CD25(+) T cells. These results suggest that the prevention of EAE by treatment with ES-DC-TRAIL/MOG is mediated, at least in part, by MOG-reactive CD4(+)CD25(+) Treg propagated by ES-DC-TRAIL/MOG. For the treatment of organ-specific autoimmune diseases, induction of Treg reactive to the organ-specific autoantigens by the transfer of DC-presenting Ags and simultaneously overexpressing TRAIL therefore appears to be a promising strategy.     

Retrogenic modeling of experimental allergic encephalomyelitis associates T cell frequency but not TCR functional affinity with pathogenicity

The properties of a self-specific T cell's TCR that determine its pathogenicity are not well understood. We developed TCR retroviral transgenic, or retrogenic, models of myelin oligodendroglial glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) to compare the pathologic potential of five H-2 Ab/MOG35-55-specific TCRs. The TCRs were cloned and retrovirally transduced into either TCRalphabeta-deficient hybridoma cells or Rag1-/- bone marrow progenitor cells. Comparison of the hybridomas, identical except for TCR sequence, revealed distinct responsiveness, or functionally determined affinity, for cognate Ag. Retrogenic mice were produced by transfer of transduced progenitor cells into Rag1-/- recipients. T cells were detected within 4 wk. Engraftment levels varied considerably among the different TCRs and showed separate variability among individual mice. T cells were predominantly naive and virtually exclusively CD4+ and CD25-. Relative responses of the retrogenic T cells to Ag paralleled those of the hybridoma cells. Induction of EAE through active immunization led to rapid and severe disease in all mice expressing MOG-specific TCR. The mice additionally developed spontaneous disease, the incidence of which varied with the individual receptors. Interestingly, spontaneous disease frequency and intensity could not be correlated with the functional affinity of the respective TCR. Instead, it was associated with engraftment level, even when measured weeks before the onset of disease symptoms. Our results demonstrate the feasibility of using retrogenic modeling to compare TCRs in the EAE system. They further suggest that affinity is not a primary determinant in spontaneous EAE development in mice expressing monotypic TCRs and that autoreactive T cell frequency is of greater significance.     

TLR4 mediates vaccine-induced protective cellular immunity to Bordetella pertussis: role of IL-17-producing T cells

Whole cell pertussis vaccines (Pw) induce Th1 responses and protect against Bordetella pertussis infection, whereas pertussis acellular vaccines (Pa) induce Ab and Th2-biased responses and also protect against severe disease. In this study, we show that Pw failed to generate protective immunity in TLR4-defective C3H/HeJ mice. In contrast, protection induced with Pa was compromised, but not completely abrogated, in C3H/HeJ mice. Immunization with Pw, but not Pa, induced a population of IL-17-producing T cells (Th-17), as well as Th1 cells. Ag-specific IL-17 and IFN-gamma production was significantly lower in Pw-immunized TLR4-defective mice. Furthermore, treatment with neutralizing anti-IL-17 Ab immediately before and after B. pertussis challenge significantly reduced the protective efficacy of Pw. Stimulation of dendritic cells (DC) with Pw promoted IL-23, IL-12, IL-1beta, and TNF-alpha production, which was impaired in DC from TLR4-defective mice. B. pertussis LPS, which is present in high concentrations in Pw, induced IL-23 production by DC, which enhanced IL-17 secretion by T cells, but the induction of Th-17 cells was also dependent on IL-1. In addition, we identified a new effector function for IL-17, activating macrophage killing of B. pertussis, and this bactericidal activity was less efficient in macrophages from TLR4-defective mice. These data provide the first definitive evidence of a role for TLRs in protective immunity induced by a human vaccine. Our findings also demonstrate that activation of innate immune cells through TLR4 helps to direct the induction of Th1 and Th-17 cells, which mediate protective cellular immunity to B. pertussis.     

Critical requirement of CD11b (Mac-1) on T cells and accessory cells for development of experimental autoimmune encephalomyelitis

Mac-1 (CD18/CD11b) is a member of the beta2-integrin family of adhesion molecules and is implicated in the development of many inflammatory diseases. The role of Mac-1 in the development of CNS demyelinating diseases, including multiple sclerosis, is not understood, and Ab inhibition studies in experimental allergic encephalomyelitis (EAE), the animal model for multiple sclerosis, have produced conflicting findings. To clarify these results and to determine Mac-1-mediated mechanisms in EAE, we performed EAE using Mac-1-deficient mice. Mac-1 homozygous-deficient, but not Mac-1 heterozygous-deficient mice, had significantly delayed onset and attenuated EAE. Leukocyte infiltration was similar in both groups of mice in early disease but significantly reduced in spinal cords of receptor-deficient mice in late disease. Adoptive transfer of Ag-restimulated T cells from wild-type to Mac-1-deficient mice produced significantly attenuated EAE, whereas transfer of Mac-1-deficient Ag-restimulated T cells to control mice failed to induce EAE. T cells from myelin oligodendrocyte glycoprotein (MOG)35-55 peptide-primed Mac-1-deficient mice displayed an altered cytokine phenotype with elevated levels of TGF-beta and IL-10, but reduced levels of IL-2, IFN-gamma, TNF-alpha, IL-12, and IL-4 compared with control mice. Mac-1-deficient T cells from primed mice proliferated comparably to that of control T cells on MOG35-55 restimulation in vitro. However, the draining lymph nodes of MAC-1-deficient mice on day 10 after MOG35-55 immunization contained lower frequency of blast T cells than in control mice, suggesting poor priming. Our results indicate that Mac-1 expression is critical on both phagocytic cells and T cells for the development of demyelinating disease.     

Homeostatic expansion of CD4(+) T cells upregulates VLA-4 and exacerbates HSV-induced corneal immunopathology

Using a viral-induced immunopathology model, we showed that when CD4(+) T cells were allowed to undergo homeostatic expansion prior to ocular herpes simplex virus infection, mice developed more severe inflammatory lesions with the increased severity associated with enhanced effector function of ocular CD4(+) T cells, and blocking their functional activity reduced the lesion severity. Additionally, homeostatically expanded CD4(+) T cells upregulated VLA-4, and in vivo administration of anti-VLA-4 mAb significantly decreased the homeostatic proliferation. Furthermore, blocking of VLA-4 interaction also diminished the infiltration of CD4(+) T cells into the cornea and decreased lesion severity. Our results imply that homeostatic expansion of T cells, as could occur in a virus-induced lymphopenia, may generate cells with enhanced effector function that can contribute to tissue damage.     

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.     

Essential role of CD8+CD122+ regulatory T cells in the recovery from experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is one of the best-documented animal models of autoimmune disease. We examined the role of CD8+CD122+ regulatory T cells, which we previously identified as naturally occurring regulatory T cells that effectively regulate CD8+ T cells, in EAE. Depletion of CD8+CD122+ regulatory T cells by in vivo administration of anti-CD122 mAb resulted in persistent EAE symptoms. Transfer of CD8+CD122+ regulatory T cells into EAE mice at the peak EAE score clearly improved symptoms, indicating an important role of CD8+CD122+ regulatory T cells in the recovery phase of EAE. This was further confirmed by an increase and a decrease in the number of infiltrating T cells in the CNS and T cell cytokine production in mice that were depleted of or complemented with CD8+CD122+ cells. Furthermore, transfer of preactivated CD8+CD122+ regulatory T cells resulted in diminished EAE symptoms, especially in the recovery phase of EAE. These results elucidate the essential role of CD8+CD122+ regulatory T cells in the recovery phase of EAE and suggest the preventive effect of preactivated CD8+CD122+ regulatory T cells for EAE.     

Rapid depletion of peripheral antigen-specific T cells in TCR-transgenic mice after oral administration of myelin basic protein

In myelin basic protein (MBP)-specific TCR-transgenic (Tg) mice, peripheral T cells express the Valpha2.3/Vbeta8.2-Tg TCR, demonstrate vigorous proliferative responses to MBP in vitro, and can exhibit experimental autoimmune encephalomyelitis (EAE) within 5 days of pertussis toxin injection. We explored the effects of oral administration of MBP on the cellular trafficking of the MBP-specific TCR-Tg cells and the ability of oral MBP to protect Tg mice from EAE. Tg mice were fed MBP, OVA or vehicle and sacrificed at various times after feeding. An immediate and dramatic decrease in Valpha2.3/Vbeta8.2(+)-Tg cells was observed in the periphery within 1 h after feeding. By 3 days after feeding, the percentage of Tg cells increased to near control levels, but decreased again by 10 days. When MBP or vehicle-fed Tg mice were challenged for EAE at this point, disease was severe in the vehicle-fed mice and reduced in the MBP-fed mice over the 40-day observation period. In vitro studies revealed a biphasic pattern of MBP proliferative unresponsiveness and an induction of Th1 cytokines. Immunohistochemical staining showed that the number of Tg cells found in the intestinal lamina propria increased dramatically as the number of Tg cells in the periphery decreased. There was no apparent proliferation of Tg cells in the lamina propria, indicating that Tg cells trafficked there from the periphery. Taken together, these results suggest that T cell trafficking into the site of Ag deposition acts to protect the TCR-Tg mouse from EAE.