Gammadelta T cells enhance the expression of experimental autoimmune encephalomyelitis by promoting antigen presentation and IL-12 production

Using an adoptive transfer model of experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein (MBP)-reactive lymph node cells (LNC), we have shown that depletion of gammadelta T cells from LNC resulted in diminished severity of EAE in recipient mice, both clinically and histopathologically. The reduced potency of gammadelta T cell-depleted LNC to induce EAE correlated with decreased cell proliferation in response to MBP. The gammadelta T cell effect upon the threshold of MBP-induced LNC proliferation and EAE transfer was restored by reconstitution of gammadelta T cells derived from either MBP-immunized or naive mice, indicating that this effect was not Ag specific. The enhancing effect of gammadelta T cells on MBP-induced proliferation and EAE transfer required direct cell-to-cell contact with LNC. The gammadelta T cell effect upon the LNC response to MBP did not involve a change in expression of the costimulatory molecules CD28, CD40L, and CTLA-4 on TCRalphabeta(+) cells, and CD40, CD80, and CD86 on CD19(+) and CD11b(+) cells. However, depletion of gammadelta T cells resulted in significant reduction in IL-12 production by LNC. That gammadelta T cells enhanced the MBP response and severity of adoptive EAE by stimulating IL-12 production was supported by experiments showing that reconstitution of the gammadelta T cell population restored IL-12 production, and that gammadelta T cell depletion-induced effects were reversed by the addition of IL-12. These results suggest a role for gammadelta T cells in the early effector phase of the immune response in EAE.     

The role of IL-12 in the induction of intravenous tolerance in experimental autoimmune encephalomyelitis

Intravenous administration of autoantigen is an effective method to induce Ag-specific tolerance against experimental autoimmune encephalomyelitis (EAE). IL-12 is a potent Th1 stimulator and an essential cytokine in the induction of EAE. The role of IL-12 in the induction of i.v. tolerance is not clear. In this study, we induced tolerance by i.v. administering myelin basic protein (MBP) peptide Ac1-11 (MBP1-11) in EAE. We observed significant suppression of IL-12 production by the lymph node cells of MBP1-11-injected mice. To see whether the low level of IL-12 is the cause or effect of tolerance, we administered IL-12 to the EAE mice at the time of i.v. MBP1-11 injection. Exogenous IL-12 abrogated the suppression of clinical and pathological EAE by i.v. tolerance. IL-12 blocked the suppressive effect of i.v. tolerance on the proliferative response to MBP1-11 and MBP1-11-induced production of IL-12 and IFN-gamma. Furthermore, IL-12 completely blocked the i.v. tolerance-induced type 1 T regulatory cell response. These data suggest that i.v. administration of autoantigen results in the suppression of endogenous IL-12 and the consequent switching of the immune response from an immunogenic to a tolerogenic form.     

Peripheral tolerance induction using ethylenecarbodiimide-fixed APCs uses both direct and indirect mechanisms of antigen presentation for prevention of experimental autoimmune encephalomyelitis

MHC class II (MHC II)-restricted T cell responses are a common driving force of autoimmune disease. Accordingly, numerous therapeutic strategies target CD4(+) T cells with the hope of attenuating autoimmune responses and restoring self-tolerance. We have previously reported that i.v. treatment with Ag-pulsed, ethylenecarbodiimide (ECDI)-fixed splenocytes (Ag-SPs) is an efficient protocol to induce Ag-specific tolerance for prevention and treatment of experimental autoimmune encephalomyelitis (EAE). Ag-SPs coupled with peptide can directly present peptide:MHC II complexes to target CD4(+) T cells in the absence of costimulation to induce anergy. However, Ag-SPs coupled with whole protein also efficiently attenuates Ag-specific T cell responses suggesting the potential contribution of alternative indirect mechanisms/interactions between the Ag-SPs and target CD4(+) T cells. Thus, we investigated whether MHC II compatibility was essential to the underlying mechanisms by which Ag-SP induces tolerance during autoimmune disease. Using MHC-deficient, allogeneic, and/or syngeneic donor Ag-SPs, we show that MHC compatibility between the Ag-SP donor and the host is not required for tolerance induction. Interestingly, we found that ECDI treatment induces apoptosis of the donor cell population which promotes uptake and reprocessing of donor cell peptides by host APCs resulting in the apparent MHC II-independent induction of tolerance. However, syngeneic donor cells are more efficient at inducing tolerance, suggesting that Ag-SPs induce functional Ag-SP tolerance via both direct and indirect (cross-tolerance) mechanisms leading to prevention and effective treatment of autoimmune disease.     

Identification of differentially expressed proteins in experimental autoimmune encephalomyelitis (EAE) by proteomic analysis of the spinal cord

The present study used isobaric tags for relative and absolute quantitation (iTRAQ) to identify novel targets in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. The expression of 41 proteins was significantly altered in the inflamed spinal cord. Twenty of these are implicated in EAE for the first time and many have previously been shown to play a role in antigen processing, inflammation, neuroprotection, or neurodegeneration.     

Detection of autoimmune cells proliferating to myelin basic protein and selection of T cell lines that mediate experimental autoimmune encephalomyelitis (EAE) in mice

A procedure is described for the detection of an in vitro proliferative response to the autologous mouse myelin basic protein in mice injected with mouse spinal cord homogenate (MSCH) or with myelin basic proteins (BP) of mouse (MBP) or rat (RBP) origin. The administration of MSCH, but not of MBP or RBP, in a suitable adjuvant could produce a reproducible clinical disease. Nevertheless, a proliferative response to the autologous MBP could not be detected after either inoculation. Only the removal of the adherent cell fraction from the immunized cell population and its replacement with fresh naive accessory cells could reveal a proliferative response to the autologous MBP and to the heterologous RBP. A heteroclitic cross-reactivity between MBP and RBP is demonstrated. The possibility of detecting an in vitro proliferative response to BP allowed the selection and propagation in vitro of cells specific to BP. T cell lines were established that specifically proliferated in response to BP and mediated EAE in normal mice. Intravenous inoculation of as few as 10(6) line cells was capable of producing clinical signs of EAE in normal recipients within 5 to 6 days. Thus, although an inoculation of MSCH was required for active induction of the disease, T cells specifically reactive against BP are sufficient for mediation of EAE in mice.     

Overcoming unresponsiveness in experimental autoimmune encephalomyelitis (EAE) resistant mouse strains by adoptive transfer and antigenic challenge

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system (CNS) and has been used as an animal model for study of the human demyelinating disease, multiple sclerosis (MS). EAE is characterized by pathologic infiltration of mononuclear cells into the CNS and by clinical manifestation of paralytic disease. Similar to MS, EAE is also under genetic control in that certain mouse strains are susceptible to disease induction while others are resistant. Typically, C57BL/6 (H-2(b)) mice immunized with myelin basic protein (MBP) fail to develop paralytic signs. This unresponsiveness is certainly not due to defects in antigen processing or antigen presentation of MBP, as an experimental protocol described here had been used to induce severe EAE in C57BL/6 mice as well as other reputed resistant mouse strains. In addition, encephalitogenic T cell clones from C57BL/6 and Balb/c mice reactive to MBP had been successfully isolated and propagated. The experimental protocol involves using a cellular adoptive transfer system in which MBP-primed (200 μg/mouse) C57BL/6 donor lymph node cells are isolated and cultured for five days with the antigen to expand the pool of MBP-specific T cells. At the end of the culture period, 50 million viable cells are transferred into naive syngeneic recipients through the tail vein. Recipient mice so treated normally do not develop EAE, thus reaffirming their resistant status, and they can remain normal indefinitely. Ten days post cell transfer, recipient mice are challenged with complete Freund adjuvant (CFA)-emulsified MBP in four sites in the flanks. Severe EAE starts to develop in these mice ten to fourteen days after challenge. Results showed that the induction of disease was antigenic specific as challenge with irrelevant antigens did not induce clinical signs of disease. Significantly, a titration of the antigen dose used to challenge the recipient mice showed that it could be as low as 5 μg/mouse. In addition, a kinetic study of the timing of antigenic challenge showed that challenge to induce disease was effective as early as 5 days post antigenic challenge and as long as over 445 days post antigenic challenge. These data strongly point toward the involvement of a "long-lived" T cell population in maintaining unresponsiveness. The involvement of regulatory T cells (Tregs) in this system is not defined.     

A fusion protein consisting of IL-16 and the encephalitogenic peptide of myelin basic protein constitutes an antigen-specific tolerogenic vaccine that inhibits experimental autoimmune encephalomyelitis

To test a novel concept for the generation of tolerogenic vaccines, fusion proteins were constructed encompassing a tolerogenic or biasing cytokine and the major encephalitogenic peptide of guinea pig myelin basic protein (GPMBP; i.e., neuroantigen or NAg). The cytokine domain was predicted to condition APC while simultaneously targeting the covalently linked encephalitogenic peptide to the MHC class II Ag processing pathway of those conditioned APC. Rats were given three s.c. injections of cytokine-NAg in saline 1-2 wk apart and then at least 1 wk later were challenged with NAg in CFA. The rank order of tolerogenic activity in the Lewis rat model of EAE was NAgIL16 > IL2NAg > IL1RA-NAg, IL13NAg >or= IL10NAg, GPMBP, GP69-88, and saline. NAgIL16 was also an effective inhibitor of experimental autoimmune encephalomyelitis when administered after an encephalitogenic challenge during the onset of clinical signs. Covalent linkage of the NAg and IL-16 was required for inhibition of experimental autoimmune encephalomyelitis. These data identify IL-16 as an optimal cytokine partner for the generation of tolerogenic vaccines and indicate that such vaccines may serve as Ag-specific tolerogens for the treatment of autoimmune disease.     

IL-23 is critical in the induction but not in the effector phase of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a T cell-mediated inflammatory disease of the CNS, is a rodent model of human multiple sclerosis. IL-23 is one of the critical cytokines in EAE development and is currently believed to be involved in the maintenance of encephalitogenic responses during the tissue damage effector phase of the disease. In this study, we show that encephalitogenic T cells from myelin oligodendrocyte glycopeptide (MOG)-immunized wild-type (WT) mice caused indistinguishable disease when adoptively transferred to WT or IL-23-deficient (p19 knockout (KO)) recipient mice, demonstrating that once encephalitogenic cells have been generated, EAE can develop in the complete absence of IL-23. Furthermore, IL-12/23 double-deficient (p35/p19 double KO) recipient mice developed EAE that was indistinguishable from WT recipients, indicating that IL-12 did not compensate for IL-23 deficiency during the effector phase of EAE. In contrast, MOG-specific T cells from p19KO mice induced EAE with delayed onset and much lower severity when transferred to WT recipient mice as compared with the EAE that was induced by cells from WT controls. MOG-specific T cells from p19KO mice were highly deficient in the production of IFN-gamma, IL-17A, and TNF, indicating that IL-23 plays a critical role in development of encephalitogenic T cells and facilitates the development of T cells toward both Th1 and Th17 pathways.     

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 IL-1R/TLR signalling in experimental autoimmune encephalomyelitis and multiple sclerosis

Multiple sclerosis is a complex disease characterised by chronic inflammation, demyelination and axonal pathology resulting in progressive neurological disabilities. Multiple sclerosis is generally considered to be an autoimmune disease, even though the primary cause of the underlying autoimmune response is unknown. Epidemiological evidence suggests that both genetic and environmental factors play a key role in susceptibility to multiple sclerosis; however, the relative contributions of these factors in triggering the onset of the disease remain unclear. Several studies indicate that receptors belonging to the Interleukin-1 and Toll-like receptor families are crucially involved in the mechanisms underlying the development of experimental autoimmune encephalomyelitis, an animal model that mimics multiple sclerosis. Moreover, recent evidence highlights the importance of downstream signalling proteins in the Interleukin-1 and Toll-like receptor signalling pathways, namely, myeloid differentiation primary response protein 88 and Interleukin-1-receptor-associated kinase. This review summarises the current knowledge concerning the involvement of Interleukin-1/Toll-like receptor signalling in the development of experimental autoimmune encephalomyelitis and multiple sclerosis. A deeper understanding of the role of these important pathways in the pathogenesis of experimental autoimmune encephalomyelitis may eventually yield clinical benefits in the treatment of central nervous system-based inflammatory disorders.     

Cutting edge: a critical role for IL-10 in induction of nasal tolerance in experimental autoimmune myocarditis

Appropriate treatment of autoimmune myocarditis following virus infection remains a major clinical problem. Induction of nasal tolerance may provide a new approach to treatment. However, the exact mechanism of nasal tolerance is unknown. To assess the mechanism of nasal tolerance, we examined the role of IL-10 in the induction and suppression of autoimmune myocarditis. First we showed that blocking IL-10 concurrent with nasal administration of Ag abolished the disease-suppressing effect of nasal tolerization. It also led to increased cardiac myosin-specific IL-1 and TNF-alpha production. Then we demonstrated that blocking IL-10 during the effector phase increased not only the incidence and severity of disease but also Ag-specific IL-2, IL-4, and TNF-alpha production as well as cardiac myosin-specific IgG1 and IgG2b production, whereas blocking IL-10 during the induction phase had no effect. This study implicates IL-10 in the induction of nasal tolerance and in limiting inflammation later during the disease process.     

B lymphocytes treated in vitro with antigen coupled to cholera toxin B subunit induce antigen-specific Foxp3(+) regulatory T cells and protect against experimental autoimmune encephalomyelitis

The ability of activated B cells to protect against various experimental autoimmune or allergic diseases makes them attractive for use in cell-based therapies. We describe an efficient way to generate B cells with strong suppressive functions by incubating naive B cells with a relevant Ag conjugated to cholera toxin B subunit (CTB). This allows most B cells, irrespective of BCR, to take up and present Ag and induces their expression of latency-associated polypeptide (LAP)/TGF-β and after adoptive transfer also their production of IL-10. With OVA as model Ag, when naive T cells were cocultured in vitro with B cells pretreated with OVA conjugated to CTB (OVA/CTB) Ag-specific CD4(+) Foxp3 regulatory T (Treg) cells increased >50-fold. These cells effectively suppressed CD25(-)CD4(+) effector T (Teff) cells in secondary cultures. Adoptive transfer of OVA/CTB-treated B cells to mice subsequently immunized with OVA in CFA induced increase in Foxp3 Treg cells together with suppression and depletion of Teff cells. Likewise, adoptive transfer of B cells pulsed with myelin oligodendrocyte glycoprotein peptide(35-55) (MOGp) conjugated to CTB increased the number of Treg cells, suppressed MOGp-specific T cell proliferation and IL-17 and IFN-γ production, and prevented the development of experimental autoimmune encephalomyelitis. Similar effects were seen when B cells were given "therapeutically" to mice with early-stage experimental autoimmune encephalomyelitis. Our results suggest that B cells pulsed in vitro with relevant Ag/CTB conjugates may be used in cell therapy to induce Ag-specific suppression of autoimmune disease.     

Genetic analysis of disease subtypes and sexual dimorphisms in mouse experimental allergic encephalomyelitis (EAE): relapsing/remitting and monophasic remitting/nonrelapsing EAE are immunogenetically distinct

Experimental allergic encephalomyelitis (EAE) is the principal animal model of multiple sclerosis (MS), the major inflammatory disease of the central nervous system. Murine EAE is generally either an acute monophasic or relapsing disease. Because the clinical spectrum of MS is more diverse, the limited range of disease subtypes observed in EAE has raised concern regarding its relevance as a model for MS. During the generation of a large F2 mapping population between the EAE-susceptible SJL/J and EAE-resistant B10.S/DvTe inbred lines, we identified four distinct subtypes of murine EAE resembling clinical subtypes seen in MS. We observed acute progressive, chronic/nonremitting, remitting/relapsing, and monophasic remitting/nonrelapsing EAE. An additional subtype, benign EAE, was identified after histologic examination revealed that some mice had inflammatory infiltrates of the central nervous system, but did not show clinical signs of EAE. Genome exclusion mapping was performed to identify the loci controlling susceptibility to each disease subtype. We report three novel EAE-modifying loci on chromosomes 16, 7, and 13 (eae11-13, respectively). Additionally, unique loci with gender-specific effects govern susceptibility to remitting/relapsing (eae12) and monophasic remitting/nonrelapsing (eae7 and 13) EAE.     

Tissue concentration changes of amino acids and biogenic amines in the central nervous system of mice with experimental autoimmune encephalomyelitis (EAE)

We have characterized the changes in tissue concentrations of amino acids and biogenic amines in the central nervous system (CNS) of mice with MOG_35-55-induced experimental autoimmune encephalomyelitis (EAE), an animal model commonly used to study multiple sclerosis (MS). High performance liquid chromatography was used to analyse tissue samples from five regions of the CNS at the onset, peak and chronic phase of MOG_35-55 EAE. Our analysis includes the evaluation of several newly examined amino acids including d-serine, and the inter-relations between the intraspinal concentration changes of different amino acids and biogenic amines during EAE. Our results confirm many of the findings from similar studies using different variants of the EAE model as well as those examining changes in amino acid and biogenic amine levels in the cerebrospinal fluid (CSF) of MS patients. However, several notable differences were observed between mice with MOG_35-55-induced EAE with findings from human studies and other EAE models. In addition, our analysis has identified strong correlations between different amino acids and biogenic amines that appear to change in two distinct groups during EAE. Group I analyte concentrations are increased at EAE onset and peak but then decrease in the chronic phase with a large degree of variability. Group II is composed of amino acids and biogenic amines that change in a progressive manner during EAE. The altered levels of these amino acids and biogenic amines in the disease may represent a critical pathway leading to neurodegenerative processes that are now recognized to occur in EAE and MS.     

Transforming growth factor-beta enhances the in vivo effector function and memory phenotype of antigen-specific T helper cells in experimental autoimmune encephalomyelitis.

Transforming growth factor-beta (TGF-beta) had a profound effect on the in vitro phenotypic development of Ag-activated Th cells and enhanced the in vivo effector function of these cells upon adoptive transfer. Previous studies have shown that there are two types of Th cell populations found in unimmunized animals, naive helper cells, which are short-lived and express low levels of CD44 and high levels of CD45R and Mel-14, and memory helper cells, which have a long life span and express high levels of CD44 and low levels of CD45R and Mel-14. Culturing of Ag-specific murine Th cell lines and clones in the presence of TGF-beta greatly enhanced both the memory phenotype of the cultured cells and the effector function upon adoptive transfer in experimental autoimmune encephalomyelitis. Histologic evaluation of spinal cords from recipients receiving passively transferred murine T cell lines cultured with TGF-beta revealed large demyelinated plaques (multiple sclerosis-like) that were not present in animals receiving cells cultured with Ag alone. TGF-beta also enhanced the capability of myelin basic protein-specific Lewis rat T cell lines to transfer experimental autoimmune encephalomyelitis and potentiated a purified protein derivative-specific rat helper cell line to transfer delayed type hypersensitivity. Thus, the effects of TGF-beta did not appear to be limited by species specificity, Ag specificity, or in vivo T cell function. This is the first study showing that TGF-beta can potentiate the development and maintenance of the Th cell memory phenotype in vitro and enhance their in vivo effector function in an animal disease model.     

IL-12p35-deficient mice are susceptible to experimental autoimmune encephalomyelitis: evidence for redundancy in the IL-12 system in the induction of central nervous system autoimmune demyelination

Experimental autoimmune encephalomyelitis (EAE) serves as a model for multiple sclerosis and is considered a CD4(+), Th1 cell-mediated autoimmune disease. IL-12 is a heterodimeric cytokine, composed of a p40 and a p35 subunit, which is thought to play an important role in the development of Th1 cells and can exacerbate EAE. We induced EAE with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 (MOG(35-55)) in C57BL/6 mice and found that while IL-12p40-deficient (-/-) mice are resistant to EAE, IL-12p35(-/-) mice are susceptible. Typical spinal cord mononuclear cell infiltration and demyelination were observed in wild-type and IL-12p35(-/-) mice, whereas IL-12p40(-/-) mice had normal spinal cords. A Th1-type response to MOG(35-55) was observed in the draining lymph node and the spleen of wild-type mice. A weaker MOG(35-55)-specific Th1 response was observed in IL-12p35(-/-) mice, with lower production of IFN-gamma. By contrast, a Th2-type response to MOG(35-55) correlated with disease resistance in IL-12p40(-/-) mice. Production of TNF-alpha by microglia, CNS-infiltrating macrophages, and CD4(+) T cells was detected in wild-type and IL-12p35(-/-), but not in IL-12p40(-/-), mice. In addition, NO production was higher in IL-12p35(-/-) and wild-type mice than in IL-12p40(-/-) mice. These data demonstrate a redundancy of the IL-12 system in the induction of EAE and suggest that p40-related heterodimers, such as the recently cloned IL-23 (p40p19), may play an important role in disease pathogenesis.     

Role of IL-12 receptor beta 1 in regulation of T cell response by APC in experimental autoimmune encephalomyelitis

IL-12 was thought to be involved in the development of experimental autoimmune encephalomyelitis (EAE), a Th1 cell-mediated autoimmune disorder of the CNS. However, we have recently found that IL-12 responsiveness, via IL-12Rbeta2, is not required in the induction of EAE. To determine the role of IL-12Rbeta1, a key subunit for the responsiveness to both IL-12 and IL-23, in the development of autoimmune diseases, we studied EAE in mice deficient in this subunit of IL-12R. IL-12Rbeta1(-/-) mice are completely resistant to myelin oligodendrocyte glycoprotein (MOG)-induced EAE, with an autoantigen-specific Th2 response. To study the mechanism underlying this Th2 bias, we cocultured purified CD4(+) T cells and APCs of MOG-immunized mice. We demonstrate that IL-12Rbeta1(-/-) APCs drive CD4(+) T cells of both wild-type and IL-12Rbeta1(-/-) mice to an Ag-induced Th2 phenotype, whereas wild-type APCs drive these CD4(+) T cells toward a Th1 type. IL-12Rbeta1(-/-) CD4(+) T cells, in turn, appear to exert an immunoregulatory effect on the capacity of wild-type APCs to produce IFN-gamma and TNF-alpha. Furthermore, decreased levels of IL-12p40, p35, and IL-23p19 mRNA expression were found in IL-12Rbeta1(-/-) APCs, indicating an autocrine pathway of IL-12/IL-23 via IL-12Rbeta1. IL-18 production and IL-18Ralpha expression are also significantly decreased in IL-12Rbeta1(-/-) mice immunized with MOG. We conclude that in the absence of IL-12Rbeta1, APCs play a prominent regulatory role in the induction of autoantigen-specific Th2 cells.     

Cellular FLIP (long isoform) overexpression in T cells drives Th2 effector responses and promotes immunoregulation in experimental autoimmune encephalomyelitis

Cellular FLIP (c-FLIP) is an endogenous inhibitor of death receptor-induced apoptosis through the caspase 8 pathway. It is an NF-kappaB-inducible protein thought to promote the survival of T cells upon activation, and its down-regulation has been implicated in activation-induced cell death. We have generated transgenic mice overexpressing human c-FLIP long form (c-FLIP(L)) specifically in T cells using the CD2 promoter (TgFLIP(L)). TgFLIP(L) mice exhibit increased IgG1 production upon stimulation by a T cell-dependent Ag and a markedly enhanced contact hypersensitivity response to allergen. In addition to showing augmented Th2-type responses, TgFLIP(L) mice are resistant to the development of myelin oligodendrocyte glycoprotein 35-55 peptide-induced experimental autoimmune encephalomyelitis, a Th1-driven autoimmune disease. In vitro analyses revealed that T cells of TgFLIP(L) mice proliferate normally, but produce higher levels of IL-2 and show preferential maturation of Th2 cytokine-producing cells in response to antigenic stimulation. After adoptive transfer, these (Th2) cells protected wild-type recipient mice from experimental autoimmune encephalomyelitis induction. Our results show that the constitutive overexpression of c-FLIP(L) in T cells is sufficient to drive Th2 polarization of effector T cell responses and indicate that it might function as a key regulator of Th cell differentiation.