Experimental allergic encephalomyelitis: neutralizing antibody to TGF beta 1 enhances the clinical severity of the disease

Therapeutic role of interferon-γ in experimental autoimmune encephalomyelitis is mediated through a tolerogenic subset of splenic CD11b+ myeloid cells

Cumulative evidence has established that Interferon (IFN)-γ has both pathogenic and protective roles in Multiple Sclerosis and the animal model, Experimental Autoimmune Encephalomyelitis (EAE). However, the underlying mechanisms to the beneficial effects of IFN-γ are not well understood. In this study, we found that IFN-γ exerts therapeutic effects on chronic, relapsing-remitting, and chronic progressive EAE models. The frequency of regulatory T (Treg) cells in spinal cords from chronic EAE mice treated with IFN-γ was significantly increased with no effect on Th1 and Th17 cells. Consistently, depletion of FOXP3-expressing cells blocked the protective effects of IFN-γ, indicating that the therapeutic effect of IFN-γ depends on the presence of Treg cells. However, IFN-γ did not trigger direct in vitro differentiation of Treg cells. In vivo administration of blocking antibodies against either interleukin (IL)-10, transforming growth factor (TGF)-β or program death (PD)-1, revealed that the protective effects of IFN-γ in EAE were also dependent on TGF-β and PD-1, but not on IL-10, suggesting that IFN-γ might have an indirect role on Treg cells acting through antigen-presenting cells. Indeed, IFN-γ treatment increased the frequency of a subset of splenic CD11b+ myeloid cells expressing TGF-β-Latency Associated Peptide (LAP) and program death ligand 1 (PD-L1) in a signal transducer and activator of transcription (STAT)-1-dependent manner. Furthermore, splenic CD11b+ cells from EAE mice preconditioned in vitro with IFN-γ and myelin oligodendrocyte glycoprotein (MOG) peptide exhibited a tolerogenic phenotype with the capability to induce conversion of naïve CD4+ T cells mediated by secretion of TGF-β. Remarkably, adoptive transfer of splenic CD11b+ cells from IFN-γ-treated EAE mice into untreated recipient mice ameliorated clinical symptoms of EAE and limited central nervous system infiltration of mononuclear cells and effector helper T cells. These results reveal a novel cellular and molecular mechanism whereby IFN-γ promotes beneficial effects in EAE by endowing splenic CD11b+ myeloid cells with tolerogenic and therapeutic activities.

Regulation of Lymphatic GM-CSF Expression by the E3 Ubiquitin Ligase Cbl-b

Genome-wide association studies as well as lymphatic expression analyses have linked both Cbl-b and GM-CSF to human multiple sclerosis as well as other autoimmune diseases. Both Cbl-b and GM-CSF have been shown to play a prominent role in the development of murine encephalomyelitis; however, no functional connection between the two has yet been established. In this study, we show that Cblb knockout mice demonstrated significantly exacerbated severity of experimental autoimmune encephalomyelitis (EAE), augmented T cell infiltration into the central nervous system (CNS) and strongly increased production of GM-CSF in T cells in vitro and in vivo.GM-CSF neutralization demonstrated that the increased susceptibility of Cblb^−/− mice to EAE was dependent on GM-CSF. Mechanistically, p50 binding to the GM-CSF promoter and the IL-3/GM-CSF enhancer element “CNSa” was strongly increased in nuclear extracts from Cbl-b-deficient T cells. This study suggests that Cbl-b limits autoimmunity by preventing the pathogenic effects of GM-CSF overproduction in T cells.

Pioglitazone is superior to quetiapine, clozapine and tamoxifen at alleviating experimental autoimmune encephalomyelitis in mice

Recent evidence suggests that clozapine and quetiapine (atypical antipsychotics), tamoxifen (selective-estrogen receptor modulator) and pioglitazone (PPARγ agonist) may improve functional recovery in multiple sclerosis (MS). We have compared the effectiveness of oral administration of these drugs, beginning at peak disease, at reducing ascending paralysis, motor deficits and demyelination in mice subjected to experimental autoimmune encephalomyelitis (EAE). Mice were immunized with an immunogenic peptide corresponding to amino acids 35-55 of the myelin oligodendrocyte glycoprotein (MOG_35-55) in complete Freund's adjuvant and injected with pertussis toxin to induce EAE. Unlike clozapine, quetiapine and tamoxifen, administration of pioglitazone beginning at peak disease decreased both clinical scores and lumbar white matter loss in EAE mice. Using kinematic gait analysis, we found that pioglitazone also maintained normal movement of the hip, knee and ankle joints for at least 44 days after MOG_35-55 immunization. This long-lasting preservation of hindleg joint movements was accompanied by reduced white matter loss, microglial and macrophage activation and the expression of pro-inflammatory genes in the lumbar spinal cords of EAE mice. These results support clinical findings that suggest pioglitazone may reduce the progressive loss of motor function in MS by decreasing inflammation and myelin damage.

Activation of human B cells negatively regulates TGF-β1 production

BACKGROUND

Accumulating evidence indicate that B cells can exhibit pro- or anti-inflammatory activities. Similar to interleukin (IL)-10-competent B cells, we recently showed that transforming growth factor (TGF)-β1-producing regulatory B cells limit the induction of autoimmune neuroinflammation in mice, making them potentially important in maintaining peripheral immune tolerance in central nervous system inflammatory demyelinating disorders such as multiple sclerosis.

METHODS

In this study, we compared B cell production of TGF-β1 and IL-10, the two most studied regulatory cytokines, and the pro-inflammatory B cell-derived IL-6 and tumor necrosis factor cytokines under basal conditions and following polyclonal stimulation with dual B cell receptor (BCR) cross-linking and Toll-like receptor (TLR)9 engagement.

RESULTS

We showed that resting TGF-β1-producing B cells fall within both the naïve (CD27^-) and memory (CD27⁺) B cell compartments. We found no spontaneous B cell-derived IL-10, IL-6 or tumor necrosis factor (TNF) production. Human B cell activation with anti-Ig antibodies plus CPG-B leads to only modest IL-10 production by memory CD19⁺CD27⁺ B cells while expression levels of IL-6 and TNF by both naive and memory B cells were strongly induced. Remarkably, stimulated B cells showed significantly reduced capacity to produce TGF-β1.

CONCLUSIONS

These findings indicate that B cell activation may facilitate the development of excessive immune responses and autoimmunity by restricting B cell-derived TGF-β1 production by resting B cells and favoring in turns the proinflammatory actions of activated cytokine-producing B cells.

Possible role of transforming growth factor β in tuberculous meningitis

BACKGROUND

Transforming growth factor β (TGF-β) is an anti-inflammatory cytokine and its role in hydrocephalus and stoke has been suggested. Tuberculous meningitis (TBM) is associated with exudates, stroke, hydrocephalus and tuberculoma, but the role of TGF-β has not been evaluated in relation to these changes.

AIM

To evaluate the cerebrospinal fluid (CSF) TGF-β level in the patients with TBM, and correlate these with clinical findings, MRI changes, paradoxical response and outcome at 6months.

METHODS

TBM patients diagnosed on the basis of clinical, CSF and MRI criteria were prospectively included. The clinical details including duration of illness, seizures, focal motor deficit, Glasgow Coma Scale (GCS) score and stage of TBM were noted. Presence of exudate, hydrocephalus, tuberculoma and infarction in MRI was also noted. MRI was repeated at 3months and presence of paradoxical response was noted. Cerebrospinal fluid TGF-β was measured using ELISA on admission and repeated at 3months and these were compared with 20 controls.

RESULTS

TGF-β level was significantly higher in TBM compared to the controls (385.76±249.98Vs 177.85±29.03pg/ml, P<0.0001). TGF-β correlated with motor deficit, infarction and tuberculoma on admission but did not correlate with CSF abnormalities, drug induced hepatitis, paradoxical response and outcome. TGF-β level at 3months was significantly lower than the baseline but remained higher than the controls.

CONCLUSION

CSF TGF-β levels are elevated in TBM and correlate with infarction and tuberculoma.

TGFβ regulates persistent neuroinflammation by controlling Th1 polarization and ROS production via monocyte-derived dendritic cells

Intracerebral levels of Transforming Growth Factor beta (TGFβ) rise rapidly during the onset of experimental autoimmune encephalomyelitis (EAE), a mouse model of Multiple Sclerosis (MS). We addressed the role of TGFβ responsiveness in EAE by targeting the TGFβ receptor in myeloid cells, determining that Tgfbr2 was specifically targeted in monocyte‐derived dendritic cells (moDCs) but not in CNS resident microglia by using bone‐marrow chimeric mice. TGFβ responsiveness in moDCs was necessary for the remission phase since LysM^CreTgfbr2^fl/fl mice developed a chronic form of EAE characterized by severe demyelination and extensive infiltration of activated moDCs in the CNS. Tgfbr2 deficiency resulted in increased moDC IL‐12 secretion that skewed T cells to produce IFN‐γ, which in turn enhanced the production of moDC‐derived reactive oxygen species that promote oxidative damage and demyelination. We identified SNPs in the human NOX2 (CYBB) gene that associated with the severity of MS, and significantly increased CYBB expression was recorded in PBMCs from both MS patients and from MS severity risk allele rs72619425‐A carrying individuals. We thus identify a novel myeloid cell‐T cell activation loop active in the CNS during chronic disease that could be therapeutically targeted. GLIA 2016;64:1925–1937

Analysis of TGF-β1 and TGF-β3 as regulators of encephalitogenic Th17 cells: Implications for multiple sclerosis

The phenotype of the CD4(+) T cells that mediate the CNS pathology in multiple sclerosis is still unclear, and yet a vital question for developing therapies. One of the conundrums is the role of TGF-β in the development of encephalitogenic Th17 cells. In the present study, TGF-β1 and TGF-β3 were directly compared in their capacity to promote the differentiation of myelin-specific Th17 cells that could induce experimental autoimmune encephalomyelitis (EAE). Myelin-specific CD4(+) T cell receptor transgenic cells differentiated with antigen in the presence of IL-6+TGF-β1 or IL-6+TGF-β3 generated T cells that produced robust amounts of IL-17, but were incapable of inducing EAE when transferred into mice. Further analysis of these non-encephalitogenic Th17 cells found that they expressed lower amounts of GM-CSF or IL-23R, both molecules necessary for encephalitogenicity. Thus, TGF-β, irrespective of isoform, negatively regulates the differentiation of encephalitogenic Th17 cells.

Glial metabotropic glutamate receptor-4 increases maturation and survival of oligodendrocytes

Group III metabotropic glutamate (mGlu) receptors mediate important neuroprotective and anti-inflammatory effects. Stimulation of mGlu4 receptor reduces neuroinflammation in a mouse model of experimental autoimmune encephalomyelitis (EAE) whereas mGlu4 knockout mice display exacerbated EAE clinical scores. We now show that mGlu4 receptors are expressed in oligodendrocytes, astrocytes and microglia in culture. Oligodendrocytes express mGlu4 receptors only at early stages of maturation (O4 positive), but not when more differentiated (myelin basic protein, MBP positive). Treatment of immature oligodendrocytes with the mGlu4 receptor agonist L-2-Amino-4-phosphonobutyrate (L-AP4; 50 μM for 48 h) accelerates differentiation with enhanced branching and earlier appearance of MBP staining. Oligodendrocyte death induced by exposure to 1 mM kainic acid for 24 h is significantly reduced by a 30-min pretreatment with L-AP4 (50 μM), an effect observed only in the presence of astrocytes, mimicked by the specific mGlu4 receptor positive allosteric modulator N-Phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) (30 μM) and prevented by pretreatment with the mGlu4 receptor antagonist, cyclopropyl-4-phosphonophenylglycine (CPPG) (100 μM). In astrocytes, mGlu4 receptor is the most expressed among group III mGlu receptors, as by Quantitative real time PCR (QRT-PCR), and its silencing prevents protective effects. Protection is also observed when conditioned medium (CM) from L-AP4-pretreated astrocytes is transferred to oligodendrocytes challenged with kainic acid. Transforming growth factor β (TGF-β) mediates the increased oligodendrocyte survival as the effect of L-AP4 is mimicked by addition of 10 ng/ml TGF-β and prevented by incubation with a neutralizing anti-TGF-β antibody. In contrast, despite the expression of mGlu4 receptor in resting and activated microglia, CM from L-AP4-stimulated microglia does not modify kainate-induced oligodendrocyte toxicity. Our results suggest that mGlu4 receptors expressed in astrocytes mediate enhanced survival of oligodendrocytes under conditions of excitotoxicity.

TGF-β signaling initiated in dendritic cells instructs suppressive effects on Th17 differentiation at the site of neuroinflammation

While the role of Transforming Growth Factor β (TGF-β) as an intrinsic pathway has been well established in driving de novo differentiation of Th17 cells, no study has directly assessed the capacity of TGF-β signaling initiated within dendritic cells (DCs) to regulate Th17 differentiation. The central finding of this study is the demonstration that Th17 cell fate during autoimmune inflammation is shaped by TGF-β extrinsic pathway via DCs. First, we provide evidence that TGF-β limits at the site of inflammation the differentiation of highly mature DCs as a means of restricting Th17 cell differentiation and controlling autoimmunity. Second, we demonstrate that TGF-β controls DC differentiation in the inflammatory site but not in the priming site. Third, we show that TGF-β controls DC numbers at a precursor level but not at a mature stage. While it is undisputable that TGF-β intrinsic pathway drives Th17 differentiation, our data provide the first evidence that TGF-β can restrict Th17 differentiation via DC suppression but such a control occurs in the site of inflammation, not at the site of priming. Such a demarcation of the role of TGF-β in DC lineage is unprecedented and holds serious implications vis-à-vis future DC-based therapeutic targets.

TGFβ signaling regulates the timing of CNS myelination by modulating oligodendrocyte progenitor cell cycle exit through SMAD3/4/FoxO1/Sp1

Research on myelination has focused on identifying molecules capable of inducing oligodendrocyte (OL) differentiation in an effort to develop strategies that promote functional myelin regeneration in demyelinating disorders. Here, we show that transforming growth factor β (TGFβ) signaling is crucial for allowing oligodendrocyte progenitor (OP) cell cycle withdrawal, and therefore, for oligodendrogenesis and postnatal CNS myelination. Enhanced oligodendrogenesis and subcortical white matter (SCWM) myelination was detected after TGFβ gain of function, while TGFβ receptor II (TGFβ-RII) deletion in OPs prevents their development into mature myelinating OLs, leading to SCWM hypomyelination in mice. TGFβ signaling modulates OP cell cycle withdrawal and differentiation through the transcriptional modulation of c-myc and p21 gene expression, mediated by the interaction of SMAD3/4 with Sp1 and FoxO1 transcription factors. Our study is the first to demonstrate an autonomous and crucial role of TGFβ signaling in OL development and CNS myelination, and may provide new avenues in the treatment of demyelinating diseases.

Erythropoietin ameliorates rat experimental autoimmune neuritis by inducing transforming growth factor-β in macrophages

Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. In addition, in various preclinical models EPO exhibited protective activity against tissue injury. There is an urgent need for potent treatments of autoimmune driven disorders of the peripheral nervous system (PNS), such as the Guillain-Barré syndrome (GBS), a disabling autoimmune disease associated with relevant morbidity and mortality. To test the therapeutic potential of EPO in experimental autoimmune neuritis (EAN) - an animal model of human GBS--immunological and clinical effects were investigated in a preventive and a therapeutic paradigm. Treatment with EPO reduced clinical disease severity and if given therapeutically also shortened the recovery phase of EAN. Clinical findings were mirrored by decreased inflammation within the peripheral nerve, and myelin was well maintained in treated animals. In contrast, EPO increased the number of macrophages especially in later stages of the experimental disease phase. Furthermore, the anti-inflammatory cytokine transforming growth factor (TGF)-beta was upregulated in the treated cohorts. In vitro experiments revealed less proliferation of T cells in the presence of EPO and TGF-beta was moderately induced, while the secretion of other cytokines was almost not altered by EPO. Our data suggest that EPO revealed its beneficial properties by the induction of beneficial macrophages and the modulation of the immune system towards anti-inflammatory responses in the PNS. Further studies are warranted to elaborate the clinical usefulness of EPO for treating immune-mediated neuropathies in affected patients.

Transforming growth factor-beta: recent advances on its role in immune tolerance

Transforming growth factor (TGF-β1) is a pleiotropic cytokine, secreted by immune and nonhematopoietic cells. TGF-β is involved in many different critical processes, such as embryonal development, cellular maturation and differentiation, wound healing, and immune regulation. It maintains immune homeostasis by acting as a potent immune suppressor through inhibition of proliferation, differentiation, activation, and effector function of immune cells. Paradoxically, depending on the context, it displays proinflammatory properties by being a potent chemoattractant for neutrophils and promoting inflammation. In addition, it does not only induce differentiation into the anti-inflammatory Treg cells, but also into the proinflammatory Th17 and Th9 cells and inhibits Th22 differentiation. TGF-β has been demonstrated to be involved in multiple pathologies. In infections, it protects against collateral damages caused by the immune system, but it also promotes immune evasion and chronic infections. In autoimmune diseases, a TGF-β dysfunction leads to the loss of tolerance to self-antigens. In cancer, TGF-β is a potent inhibitor of cell proliferation and acts as a tumor suppressor at the beginning of tumorogenesis. However, once the cells become resistant to TGF-β, it mainly supports tumor growth and metastasis by promoting immune evasion and angiogenesis. In asthma, it is assumed to promote allergen tolerance, but plays a detrimental role in irreversible remodeling of the airways. Despite the high numbers of TGF-β-targeted pathways, it is a promising drug target for treatment of autoimmunity, cancer, fibrosis, if cell specificity can be achieved.This review summarizes the progresses that have been accomplished on the understanding of TGF-β's signaling in the immune homeostasis and its role in pathogenesis.

Role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination of the CNS

As the resident innate immune cells of the central nervous system (CNS), microglia fulfil a critical role in maintaining tissue homeostasis and in directing and eliciting molecular responses to CNS damage. The human disease Multiple Sclerosis and animal models of inflammatory demyelination are characterized by a complex interplay between degenerative and regenerative processes, many of which are regulated and mediated by microglia. Cellular communication between microglia and other neural and immune cells is controlled to a large extent by the activity of cytokines. Here we review the role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination, highlighting their importance in potentiating cell damage, promoting neuroprotection and enhancing cellular repair in a context-dependent manner.

Activin-A induces regulatory T cells that suppress T helper cell immune responses and protect from allergic airway disease

Activin-A is a pleiotropic cytokine that participates in developmental, inflammatory, and tissue repair processes. Still, its effects on T helper (Th) cell–mediated immunity, critical for allergic and autoimmune diseases, are elusive. We provide evidence that endogenously produced activin-A suppresses antigen-specific Th2 responses and protects against airway hyperresponsiveness and allergic airway disease in mice. Importantly, we reveal that activin-A exerts suppressive function through induction of antigen-specific regulatory T cells that suppress Th2 responses in vitro and upon transfer in vivo. In fact, activin-A also suppresses Th1-driven responses, pointing to a broader immunoregulatory function. Blockade of interleukin 10 and transforming growth factor β1 reverses activin-A–induced suppression. Remarkably, transfer of activin-A–induced antigen-specific regulatory T cells confers protection against allergic airway disease. This beneficial effect is associated with dramatically decreased maturation of draining lymph node dendritic cells. Therapeutic administration of recombinant activin-A during pulmonary allergen challenge suppresses Th2 responses and protects from allergic disease. Finally, we demonstrate that immune cells infiltrating the lungs from individuals with active allergic asthma, and thus nonregulated inflammatory response, exhibit significantly decreased expression of activin-A's responsive elements. Our results uncover activin-A as a novel suppressive factor for Th immunity and a critical controller of allergic airway disease.

TGF-beta signaling in dendritic cells is a prerequisite for the control of autoimmune encephalomyelitis

One unresolved issue in immune tolerance is what prevents self-reactive T cells from activation. In this study, we used a transgenic mouse model of targeted functional inactivation of TGF-betaR signaling in CD11c(+) cells (CD11c(dnR) mice) and showed a direct impact on the development of experimental autoimmune encephalomyelitis (EAE). We found that MOG(35-55) immunization of CD11c(dnR) mice results in strong inflammation of CNS, high frequency of T cells in CNS, increased levels of T helper 1 (T(H)1) and T(H)17 cytokines in the periphery, and lack of remission from EAE. Once crossed with mice prone to autoimmunity, double-transgenic CD11c(dnR)Mog(TCR) mice revealed a spontaneous EAE-like disease characterized by early infiltration of activated myelin-specific T cells into CNS, activation of microglial cells, inflammation of CNS, dysfunction of locomotion, and premature death. We constructed chimeric mice and demonstrated that inactivation of TGF-betaR signaling in dendritic cells (DCs) results in augmented EAE-associated T cell responses. Our data provide direct evidence that TGF-beta can control autoimmunity via actions on DCs.

Glia-dependent TGF-beta signaling, acting independently of the TH17 pathway, is critical for initiation of murine autoimmune encephalomyelitis

Autoimmune encephalomyelitis, a mouse model for multiple sclerosis, is characterized by the activation of immune cells, demyelination of axons in the CNS, and paralysis. We found that TGF-beta1 synthesis in glial cells and TGF-beta-induced signaling in the CNS were activated several days before the onset of paralysis in mice with autoimmune encephalomyelitis. While early production of TGF-beta1 was observed in glial cells TGF-beta signaling was activated in neurons and later in infiltrating T cells in inflammatory lesions. Systemic treatment with a pharmacological inhibitor of TGF-beta signaling ameliorated the paralytic disease and reduced the accumulation of pathogenic T cells and expression of IL-6 in the CNS. Priming of peripheral T cells was not altered, nor was the generation of TH17 cells, indicating that this effect was directed within the brain, yet affected the immune system. These results suggest that early production of TGF-beta1 in the CNS creates a permissive and dangerous environment for the initiation of autoimmune inflammation, providing a rare example of the brain modulating the immune system. Importantly, inhibition of TGF-beta signaling may have benefits in the treatment of the acute phase of autoimmune CNS inflammation.

Endogenous transforming growth factor beta 1 suppresses inflammation and promotes survival in adult CNS

Transforming growth factor beta1 (TGFbeta1) is a pleiotropic cytokine with potent neurotrophic and immunosuppressive properties that is upregulated after injury, but also expressed in the normal nervous system. In the current study, we examined the regulation of TGFbeta1 and the effects of TGFbeta1 deletion on cellular response in the uninjured adult brain and in the injured and regenerating facial motor nucleus. To avoid lethal autoimmune inflammation within 3 weeks after birth in TGFbeta1-deficient mice, this study was performed on a T- and B-cell-deficient RAG2-/- background. Compared with wild-type siblings, homozygous deletion of TGFbeta1 resulted in an extensive inflammatory response in otherwise uninjured brain parenchyma. Astrocytes increased in GFAP and CD44 immunoreactivity; microglia showed proliferative activity, expression of phagocytosis-associated markers [alphaXbeta2, B7.2, and MHC1 (major histocompatibility complex type 1)], and reduced branching. Ultrastructural analysis revealed focal blockade of axonal transport, perinodal damming of axonal organelles, focal demyelination, and myelin debris in granule-rich, phagocytic microglia. After facial axotomy, absence of TGFbeta1 led to a fourfold increase in neuronal cell death (52 vs 13%), decreased central axonal sprouting, and significant delay in functional recovery. It also interfered with the microglial response, resulting in a diminished expression of early activation markers [ICAM1 (intercellular adhesion molecule 1), alpha6beta1, and alphaMbeta2] and reduced proliferation. In line with axonal and glial findings in the otherwise uninjured CNS, absence of endogenous TGFbeta1 also caused an approximately 10% reduction in the number of normal motoneurons, pointing to an ongoing and potent trophic role of this anti-inflammatory cytokine in the normal as well as in the injured brain.

Transforming growth factor-beta regulation of immune responses

Transforming growth factor-beta (TGF-beta) is a potent regulatory cytokine with diverse effects on hemopoietic cells. The pivotal function of TGF-beta in the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-beta controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis, activation, and survival of lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. The regulatory activity of TGF-beta is modulated by the cell differentiation state and by the presence of inflammatory cytokines and costimulatory molecules. Collectively, TGF-beta inhibits the development of immunopathology to self or nonharmful antigens without compromising immune responses to pathogens. This review highlights the findings that have advanced our understanding of TGF-beta in the immune system and in disease.

Latent TGF-β1-transduced CD4+T cells suppress the progression of allergic encephalomyelitis

Systemic injection of small amounts of transforming growth factor-beta (TGF-beta), a cytokine produced by lymphoid and other cells, has a profound effect in protecting mice from the inflammatory demyelinating lesions of experimental allergic encephalomyelitis (EAE; an animal model for multiple sclerosis). However, TGF-beta has side-effects, which might be avoided if the cells producing TGF-beta can be delivered to the affected site in the nervous system to insure its local release in small amounts. Myelin basic protein (MBP)-specific, cloned CD4+ T cells were engineered by retroviral transduction to produce latent TGF-beta. Studies about the spontaneous form of EAE in T cell receptor (TCR)-transgenic recombination-activating gene (RAG)-1(-/-) mice showed that essentially all of the MBP-specific, TCR-transgenic RAG-1(-/-) (BALB/cxB10.PL)F1 mice develop spontaneous EAE by the age of 11 weeks. By 12 weeks, 25-50% of the mice have died from disease. A single injection of TGF-beta1-transduced T helper cell type 1 (Th1) cells significantly protected the mice from EAE, and untransduced Th1 cells did not protect. MBP-specific BALB/c Th2 clones, transduced with TGF-beta1-internal ribosome entry site-green fluorescent protein (GFP) significantly reduced EAE induction by untransduced Th1 cells in RAG-1(-/-) B10.PL mice. Furthermore, the GFP+ TGF-beta1-producing Th2 cells were detectable in the spinal cords of the injected mice.

Concentration-dependent bifunctional effect of TGF-beta 1 on immunoglobulin production: a role for Smad3 in IgA production in vitro

Injury to the liver results in rapid induction of transforming growth factor-beta1 (TGF-beta(1)) consistent with a role for TGF-beta(1) in repairing damaged tissue. In addition to its ubiquitous role in injury repair, TGF-beta(1) is also well established as a critical regulator of immune homeostasis; however, its mechanisms of action remain enigmatic. We have previously demonstrated that the hepatotoxic chlorinated hydrocarbon, carbon tetrachloride, suppresses helper T-lymphocyte function in a TGF-beta(1)-dependent manner. Here, we report that, in opposition to its immunosuppressive effects at picomolar concentrations, femtomolar concentrations of TGF-beta(1) augment T cell-dependent anti-sRBC IgM antibody forming cell (AFC) and T cell-independent DNP-Ficoll-induced AFC responses. These data support a concentration-dependent bifunctional effect by TGF-beta(1) on humoral immune responses in vitro. We further investigated a putative mechanistic role for Smad3, an intracellular mediator of TGF-beta(1) signaling, in propagating the inhibitory effects of TGF-beta(1) on humoral immune responses. Relative to wild type littermates, splenocytes from mice homologous for a null mutation in the gene encoding the TGF-beta receptor-activated Smad3 (Smad3(Exon8-/-)) were less sensitive to inhibition by TGF-beta(1) following anti-sRBC- and LPS-sensitization in vitro. In agreement, inhibition of IgM protein production by TGF-beta(1) was also dampened in LPS-sensitized Smad3(Exon8-/-) splenic B cells. Moreover, stimulation of IgA by TGF-beta(1) was abrogated in LPS-sensitized Smad3(Exon8-/-) splenocytes suggesting an additional role for Smad3 in regulating IgA production in vitro. Our results suggest that the effects of TGF-beta(1) on humoral immune responses fundamentally differ in a concentration-dependent manner and are mediated, in part, through Smad3 signaling.

Immunotherapeutic approaches in multiple sclerosis

The progress in understanding the mechanisms of T cell activation, inactivation and modulation has been translated into different immunotherapeutic strategies aiming at treating multiple sclerosis (MS). Key attack points for selective immunointervention in MS include modulation of antigen recognition, costimulation blockade, induction of regulatory cells, deviation to non-pathogenic or protective responses, neutralization of proinflammatory cytokines and administration of anti-inflammatory cytokines. In addition, several attempts have been made using less specific forms of immunointervention. The two resounding successes in the immunotherapy of MS, IFN-failed and glatiramer acetate, contrast with the many attempts, equally based on sound reasoning and promising animal data. Nevertheless, antigen-based immunointervention will continue to be tested clinically, and we will certainly witness the application of more articulate strategies able to selectively target cytokine production by Th1 or Th2 cells or to modify the Th1/Th2 balance. Perhaps, an effective manipulation of pathogenic and protective cells in MS may eventually rely on a combination of antigen- and cytokine-based approaches to selectively target autoreactive T cells and divert them from autoaggression. Most importantly, new avenues are opening, such as the use of chemokine receptor antagonists, and others look very promising, as targeting dendritic cells to favour their capacity to induce regulatory T cells.

Prevention of experimental autoimmune encephalomyelitis in DA rats by grafting primary skin fibroblasts engineered to express transforming growth factor-beta1

To determine whether primary fibroblasts producing latent transforming growth factor beta1 (TGF-beta1) are capable of down-regulating experimental autoimmune encephalomyelitis (EAE), a retroviral vector TGF-beta1-pBabe-neo (-5'UTR) was used for efficient gene transfer into primary skin fibroblasts of DA rats. After heat activation, conditioned medium from the transduced fibroblasts was found to inhibit significantly in vitro proliferation of lymphocytes from lymph nodes of DA rats with EAE. Intraperitoneal administration of TGF-beta1-transduced fibroblasts into DA rats during the priming phase of EAE resulted in a significant reduction in mortality and in the mean clinical and EAE scores versus the control immunized animals treated with non-transduced fibroblasts.

Cytokine shifts and tolerance in experimental autoimmune encephalomyelitis

Cytokines play an important role in the pathogenesis of both multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Effective treatments for both diseases have been shown to alter cytokines in the central nervous system and in activated mononuclear cells. EAE is an animal model that mimics many aspects of multiple sclerosis, and has been widely used to study the mechanisms of disease and therapeutic approaches to multiple sclerosis. Cytokines play an important role in regulation of disease expression in EAE, and in tolerance to disease induction. In this review, we will summarize the current findings on the role of cytokine shifts in the induction of tolerance in EAE. In addition, we will discuss modulation of EAE by altered expression of members of the cytokineregulated Jak/STAT intracellular signaling pathway.

Role of costimulatory pathways in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis is an immune-mediated disorder of the central nervous system. T lymphocytes are thought to play a central role in the initiation and potentially in the propagation of this disease. Two signals are required for T-cell activation. The first signal consists of the interaction of the T-cell receptor with antigen presented by the MHC molecule on antigen-presenting cells. The second signal requires engagement of costimulatory receptors on T cells with their ligands on antigen-presenting cells. Several costimulatory pathways have been shown to play an important role in T-lymphocyte activation. Here we will review the current literature on the contribution of the B7-1/2-CD28/CTLA-4, inducible costimulatory molecule-B7h, programmed death pathway 1-programmed death pathway ligand 1/ligand 2, CD40-CD154, OX40-OX40 ligand, and CD137-CD137 ligand pathways to the pathogenesis of multiple sclerosis and their potential roles as therapeutic targets.

Evidence for cytokine dysregulation in multiple sclerosis: peripheral blood mononuclear cell production of pro-inflammatory and anti-inflammatory cytokines during relapse and remission

We investigated circulating anti-inflammatory and pro-inflammatory cytokines, and their ex vivo PBMC production in the absence or presence of the neuroantigens myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) and T cell mitogen (PHA) in MS patients in relapse and remission, patients with other neurological disorders (OND) and normal healthy controls. MS patients in relapse exhibited significantly increased PBMC production of TNF-alpha spontaneously compared with MS remission and healthy controls and with MBP compared with MS remission. Patients in relapse had significantly increased spontaneous, PHA- and MBP-induced PBMC IL-1beta production compared with remission MS, and was increased compared (PHA only) with OND and healthy controls. In relapse there was also significantly increased PBMC IFN-gamma production (PHA only) compared with remission and a significantly lower production of biologically active TGF-beta1 (PHA only) compared with remission MS and OND. In contrast, MS patients in remission produced significantly less spontaneous and MBP-induced TNF-alpha, spontaneous, PHA- and MBP-induced IL-1beta and PHA-induced IFN-gamma together with increased production of biologically active TGF-beta1. MOG non-specifically increased PBMC TNF-alpha and IL-1beta production in all groups. Pro-inflammatory cytokines in corresponding plasma samples were undetectable whilst the concentration of biologically active TGF-beta1 was the reverse of ex vivo PBMC findings. The increase in biologically active TGF-beta1 production ex vivo in OND patients, despite active disease, compared with the low level in the MS relapse may indicate a regulatory defect in MS. We conclude that the balance between biologically active TGF-beta1 and the pro-inflammatory TNF-alpha, IL-1beta and IFN-gamma is dysregulated during MS relapse-remission and that normal counter-regulatory mechanisms during the relapse phase are defective.

The pathogenesis of oral lichen planus

Both antigen-specific and non-specific mechanisms may be involved in the pathogenesis of oral lichen planus (OLP). Antigen-specific mechanisms in OLP include antigen presentation by basal keratinocytes and antigen-specific keratinocyte killing by CD8(+) cytotoxic T-cells. Non-specific mechanisms include mast cell degranulation and matrix metalloproteinase (MMP) activation in OLP lesions. These mechanisms may combine to cause T-cell accumulation in the superficial lamina propria, basement membrane disruption, intra-epithelial T-cell migration, and keratinocyte apoptosis in OLP. OLP chronicity may be due, in part, to deficient antigen-specific TGF-beta1-mediated immunosuppression. The normal oral mucosa may be an immune privileged site (similar to the eye, testis, and placenta), and breakdown of immune privilege could result in OLP and possibly other autoimmune oral mucosal diseases. Recent findings in mucocutaneous graft-versus-host disease, a clinical and histological correlate of lichen planus, suggest the involvement of TNF-alpha, CD40, Fas, MMPs, and mast cell degranulation in disease pathogenesis. Potential roles for oral Langerhans cells and the regional lymphatics in OLP lesion formation and chronicity are discussed. Carcinogenesis in OLP may be regulated by the integrated signal from various tumor inhibitors (TGF-beta 1, TNF-alpha, IFN-gamma, IL-12) and promoters (MIF, MMP-9). We present our recent data implicating antigen-specific and non-specific mechanisms in the pathogenesis of OLP and propose a unifying hypothesis suggesting that both may be involved in lesion development. The initial event in OLP lesion formation and the factors that determine OLP susceptibility are unknown.

Role of TGFbeta in development of spontaneous autoimmune thyroiditis in NOD.H-2h4 mice

Nearly 100% of NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) and produce anti-mouse thyroglobulin autoantibodies when they receive 0.05% NaI in their drinking water beginning at 8 wk of age. Our previous studies showed that TGFbeta1 mRNA was constitutively expressed in thyroids and spleens of normal NOD.H-2h4 mice but not other strains of mice. To determine whether TGFbeta might have a role in SAT, mice were given anti-TGFbeta mAb at various times during development of SAT. Anti-TGFbeta markedly inhibited development of SAT and production of anti-mouse thyroglobulin IgG1 autoantibodies. Anti-TGFbeta was most effective in inhibiting SAT when given during the time thyroid lesions were developing, i.e., starting 4 wk after administration of NaI water. The active form of the TGFbeta1 protein was present in thyroids of mice with SAT but not in normal NOD.H-2h4 thyroids. However, thyrocytes of normal NOD.H-2h4 thyroids did express latent TGFbeta1. TGFbeta1 protein expression in the thyroid correlated with SAT severity scores, and administration of anti-TGFbeta inhibited TGFbeta1 protein expression in both the thyroid and spleen. TGFbeta1 was produced primarily by inflammatory cells and was primarily localized in areas of the thyroid containing clusters of CD4(+) T and B cells. Depletion of CD8(+) T cells had no effect on TGFbeta1 protein expression. Activation of splenic T cells was apparently not inhibited by anti-TGFbeta, because up-regulation of mRNA for cytokines and other T cell activation markers was similar for control and anti-TGFbeta-treated mice. TGFbeta1 may function by promoting migration to, or retention of, inflammatory cells in the thyroid.

Genetic variation in the transforming growth factor beta1 gene in multiple sclerosis

Transforming growth factor beta1 (TGFbeta1) is a Th2 cytokine encoded on chromosome 19q13, a region possibly linked to multiple sclerosis (MS). TGFbeta1 exerts favorable effects on experimental allergic encephalomyelitis. We performed a comprehensive search for genetic variants in this gene in 122 population-based sporadic cases of MS. We detected six variants, including three missense variants. We tested for association of the variants with susceptibility and course of MS and for linkage and transmission disequilibrium in a family series consisting of 395 samples in 59 pedigrees. Genetic variation in TGFB1 does not appear to contribute in a major way to susceptibility to MS.

Mycophenolate mofetil treatment accelerates recovery from experimental allergic encephalomyelitis

Mycophenolate mofetil (MM) acts through its metabolite mycophenolic acid to inhibit inosine monophosphate dehydrogenase (IMPDH), an enzyme essential for purine synthesis in lymphocytes. Oral treatment with MM from the day of immunization for 2 weeks significantly delayed both the development of active experimental allergic encephalomyelitis (EAE) in Lewis rats and reduced the antibody response to myelin basic protein (MBP). MM did not deplete T and B cells, nor did it prevent induction of Th1 or Th2 cytokine in the regional nodes. Treatment of EAE with MM at the onset of clinical symptoms resulted in more rapid recovery from EAE than in control or cyclosporin A (CsA)-treated. MM-treated rats had less infiltration of T cells, B cells, macrophages and dendritic cells into brainstems than either the control or CsA-treated. MM-treated brainstems also had lower level of mRNA for Thl (IL-2, IL-12Rbeta2, IFN-gamma), Th2 (IL-4, IL-10) cytokines and TNF-alpha and TGF-beta compared to that in CsA and controls groups. This study shows MM was superior to CsA in the treatment of EAE and acted by reducing the inflammatory infiltrate, not by suppression of Ig response or by promotion of regulatory cells such as Th2 or Th3.

Selective immunointervention in autoimmune diseases: lessons from multiple sclerosis

Activation of peripheral T cells by foreign and self antigens is under stringent control by different mechanisms, both thymic and peripheral. Control of T cell reactivity is accomplished by three major types of mechanisms: 1) deletion, the physical elimination of T cells specific for a given antigen, 2) anergy, the functional incapacity of T cells to respond to antigen, 3) suppression, the inhibition of T cell function by a regulatory (suppressor) cell. Their failure may lead to autoimmune diseases. The progress in understanding T cell activation, inactivation and modulation is being translated into strategies able to induce selective immunosuppression to treat different pathological situations, notably autoimmune diseases, allergies, and allograft rejection. The medical need for selective immunosuppression is very high, as the available immunosuppressive drugs are substantially inadequate because of limited efficacy, modest selectivity, and considerable toxicity. Key attack points for selective immunointervention have been identified: modulation of antigen recognition, co-stimulation blockade, induction of regulatory cells, deviation to non-pathogenic or protective responses, neutralization of proinflammatory cytokines, induction or administration of anti-inflammatory cytokines, and modulation of leukocyte trafficking. All these forms of immunointervention have been successfully used to prevent and sometimes treat experimental autoimmune diseases. Based on these results, expectations have been raised for exploiting the same strategies to inhibit the activation of human autoreactive T cells. In this overview, we will examine recent advances towards immunointervention in multiple sclerosis (MS) as a paradigm for successes and failures of current immunotherapeutic approaches in human autoimmune diseases.

Different therapeutic outcomes in experimental allergic encephalomyelitis dependent upon the mode of delivery of IL-10: a comparison of the effects of protein, adenoviral or retroviral IL-10 delivery into the central nervous system

Experimental allergic encephalomyelitis (EAE) is a CNS autoimmune disease mediated by the action of CD4(+) T cells, macrophages, and proinflammatory cytokines. IL-10 is a cytokine shown to have many anti-inflammatory properties. Studies have shown both inhibition and exacerbation of EAE after systemic IL-10 protein administration. We have compared the inhibitory effect in EAE of Il10 gene delivery in the CNS. Fibroblasts transduced with retroviral vectors expressing IL-10 could inhibit EAE. This was not associated with a prevention of cellular recruitment but an alteration in their phenotype, notably an increase in the numbers of CD8(+) T and B cells. In marked contrast, CNS delivery of adenovirus coding for mouse IL-10 or IL-10 protein performed over a wide dose range failed to inhibit disease, despite producing similar or greater amounts of IL-10 protein. Thus the action of IL-10 may differ depending on the local cytokine microenvironment produced by the gene-secreting cell types.

Targeting dipeptidyl peptidase IV (CD26) suppresses autoimmune encephalomyelitis and up-regulates TGF-beta 1 secretion in vivo

CD26 or dipeptidyl peptidase IV (DP IV) is expressed on various cell types, including T cells. Although T cells can receive activating signals via CD26, the physiological role of CD26/DP IV is largely unknown. We used the reversible DP IV inhibitor Lys[Z(NO(2))]-pyrrolidide (I40) to dissect the role of DP IV in experimental autoimmune encephalomyelitis (EAE) and to explore the therapeutic potential of DP IV inhibition for autoimmunity. I40 administration in vivo decreased and delayed clinical and neuropathological signs of adoptive transfer EAE. I40 blocked DP IV activity in vivo and increased the secretion of the immunosuppressive cytokine TGF-beta1 in spinal cord tissue and plasma during acute EAE. In vitro, while suppressing autoreactive T cell proliferation and TNF-alpha production, I40 consistently up-regulated TGF-beta1 secretion. A neutralizing anti-TGF-beta1 Ab blocked the inhibitory effect of I40 on T cell proliferation to myelin Ag. DP IV inhibition in vivo was not generally immunosuppressive, neither eliminating encephalitogenic T cells nor inhibiting T cell priming. These data suggest that DP IV inhibition represents a novel and specific therapeutic approach protecting from autoimmune disease by a mechanism that includes an active TGF-beta1-mediated antiinflammatory effect at the site of pathology.

Genetic models for CNS inflammation

The use of transgenic technology to over-express or prevent expression of genes encoding molecules related to inflammation has allowed direct examination of their role in experimental disease. This article reviews transgenic and knockout models of CNS demyelinating disease, focusing primarily on the autoimmune disease multiple sclerosis, as well as conditions in which an inflammatory response makes a secondary contribution to tissue injury or repair, such as neurodegeneration, ischemia and trauma.

IL-4, IL-10, IL-13, and TGF-beta from an altered peptide ligand-specific Th2 cell clone down-regulate adoptive transfer of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is induced in the SJL/J mouse by adoptive transfer of activated proteolipid protein peptide (PLP) 139-151-specific Th1 cells. T cells responding to altered peptide ligands (APL) of PLP, previously shown to induce Th2 differentiation and regulate disease in PLP-immunized mice, do not transfer EAE. However, the exact mechanism of disease regulation by APL-specific T cells has not been elucidated. In this report, we show that 1F1, a Th2 clone specific for an APL of PLP139-151 can prevent adoptive transfer of EAE when cocultured with PLP-encephalitogenic spleen cells (PLP-spleen). Cytokines from activated 1F1 cells were detected by hybridization of mRNA to oligonucleotide arrays (DNA chip) and by ELISA. The Th2 cytokines found to be present at the highest protein and mRNA levels were evaluated for their role in suppression of adoptive transfer of EAE from PLP-activated spleen cell cultures. Abs to individual cytokines in 1F1 PLP-spleen cocultures suggested that IL-4, IL-13, and TGF-beta played a significant role in suppressing EAE. Abs to the combination of IL-4, IL-10, IL-13, and TGF-beta completely neutralized the protective effect of 1F1. Addition of Th2 cytokines to PLP-spleen cultures showed that IL-13 and TGF-beta were each individually effective and low levels of IL-4 synergized with IL-13 to inhibit disease transfer. IL-5, IL-9, and IL-10 had little or no effect whereas GM-CSF slightly enhanced EAE. Our results demonstrate that Th2 cytokines derived from APL-specific Th2 cells can effectively down-regulate the encephalitogenic potential of PLP-spleen cells if present during their reactivation in culture.

The complexicity of cytokine treatment in ongoing EAE induced with MBP peptide 68-86 in Lewis rats

IL-10 and TGF-beta1 are important immunoregulatory cytokines associated with clinical remissions in multiple sclerosis and amelioration of experimental allergic encephalomyelitis (EAE). IL-10 and TGF-beta1 have previously been shown to prevent the development of EAE. Here, we study effects of IL-10 and TGF-beta1 in ongoing EAE. When IL-10 or TGF-beta1 was administered by the nasal route from day 0 to day 7 postimmunization (pi), both IL-10 and TGF-beta1 prevented the development of acute EAE in Lewis rats. When IL-10 or TGF-beta1 was administered by the nasal route from day 5 to day 12 pi, both IL-10 and TGF-beta1 failed to influence clinical EAE. The inhibition of clinical EAE severity in IL-10-prevented rats was associated with reduced proliferation, IFN-gamma mRNA expression, and IFN-gamma secretion, while proliferation as well as IFN-gamma mRNA expression and secretion were augmented in TGF-beta1-prevented rats. TGF-beta1-prevented rats exhibited high levels of NO production by DC, which may mediate apoptosis of CD4+ T cells and of the DC themselves. For prevention, both IL-10 and TGF-beta1 inhibited infiltration of CD4+ T cells within the CNS, but neither IL-10 nor TGF-beta1 induced immune deviation from Th1 to Th2. Expression of IL-4 mRNA was not altered in IL-10- and TGF-beta1-prevented rats. These results demonstrate that IL-10 and TGF-beta administration by the nasal route can prevent the development of acute EAE, but by different mechanisms. The findings in rats with ongoing EAE have implications for the clinical application of cytokine treatment in autoimmune diseases.

Adoptive transfer from interferon-alpha-fed mice is associated with inhibition of active experimental autoimmune encephalomyelitis by decreasing recipient tumor necrosis factor-alpha secretion

Ingested type I interferon (IFN) suppresses clinical relapse in murine chronic experimental autoimmune encephalomyelitis (EAE), inhibits clinical attacks more effectively than subcutaneous doses, and decreases the adoptive transfer of EAE. To determine whether splenocytes from IFN-fed donors were "suppressor-like" populations, donor SJL/J mice were immunized and fed with mock IFN-alpha or with IFN-alpha every other day for at least 4 weeks after initial clinical attack. Recipients of adoptively transferred CD8+ T cells from mock IFN-alpha-fed donors showed no clinical improvement of clinical disease compared with actively immunized controls. In contrast, recipients of adoptively transferred CD8+ T cells from IFN-alpha-fed donors showed decreased clinical disease compared with recipients of mock IFN-alpha-fed CD8+ T cells. To evaluate the mechanism of protection by donor CD8+ T cells and to determine if ingested IFN-alpha activates natural immunomodulatory cell populations, the authors used the acute EAE model and naïve-fed donor animals as sources of T cells and CD8+ T cells. Con A-activated spleen T cells from naïve nonimmunized mock IFN-alpha-fed donors inhibited actively induced disease and showed decreased recipient TNF-alpha secretion compared with recipients of T cells from mock IFN-fed mice. Donor activated spleen CD8+ T cells from naïve nonimmunized IFN-alpha-fed animals suppressed actively induced EAE in recipients and showed decreased IFN-gamma and TNF-alpha proinflammatory secretion. Decreased recipient TNF-alpha secretion correlates best with the disease protection from IFN-fed T and CD8+ T cells.

When engineered to produce latent TGF-beta1, antigen specific T cells down regulate Th1 cell-mediated autoimmune and Th2 cell-mediated allergic inflammatory processes

To determine whether T cells which produce large amounts of latent TGF-beta1 are capable of down-regulating autoimmune and allergic disease, myelin basic protein (MBP)-specific and ovalbumin (OVA)-specific BALB/c cloned Th1 cells were transduced with cDNA for murine TGF-beta1 by coculture with fibroblasts producing a genetically engineered retrovirus. The transduced MBP-specific Th1 cells were found to lose the capacity to provoke EAE in BALB/c mice, and to gain instead the ability to protect against EAE in (SJLxBALB/c) F1 mice immunized with proteolipid protein (PLP). This protective effect was not obtained with OVA-specific TGF-beta1 transduced Th1 cells. The transduced OVA-specific Th1 cells did protect against airway hyperreactivity induced by Th2-cell mediated responses to inhaled OVA. This effect was again antigen specific and it also could not be obtained with untransduced OVA-specific Th1 cells. In both cases these effects of antigen specific TGF-beta1 transduced T cells were nullified by administration of neutralizing anti-TGF-beta mAb. Thus, the antigen specificity of the cloned T cells allows the site-specific local delivery of therapeutic active TGF-beta1 to both Th1 and Th2 cell-mediated inflammatory infiltrates.

The inhibitory effects of transforming growth factor-beta-1 (TGF-beta1) in autoimmune diseases

The importance of transforming growth factor-beta-1 (TGF-beta1) in immunoregulation and tolerance has been increasingly recognized. It is now proposed that there are populations of regulatory T cells (T-reg), some designated T-helper type 3 (Th3), that exert their action primarily by secreting this cytokine. Here, we emphasize the following concepts: (1) TGF-beta1 has multiple suppressive actions on T cells, B cells, macrophages, and other cells, and increased TGF-beta1 production correlates with protection and/or recovery from autoimmune diseases; (2) TGF-beta1 and CTLA-4 are molecules that work together to terminate immune responses; (3) Th0, Th1 and Th2 clones can all secrete TGF-beta1 upon cross-linking of CTLA-4 (the functional significance of this in autoimmune diseases has not been reported, but TGF-beta1-producing regulatory T-cell clones can produce type 1 inflammatory cytokines); (4) TGF-beta1 may play a role in the passage from effector to memory T cells; (5) TGF-beta1 acts with some other inhibitory molecules to maintain a state of tolerance, which is most evident in immunologically privileged sites, but may also be important in other organs; (6) TGF-beta1 is produced by many cell types, is always present in the plasma (in its latent form) and permeates all organs, binding to matrix components and creating a reservoir of this immunosuppressive molecule; and (7) TGF-beta1 downregulates adhesion molecules and inhibits adhesion of leukocytes to endothelial cells. We propose that rather than being passive targets of autoimmunity, tissues and organs actively suppress autoreactive lymphocytes. We review the beneficial effects of administering TGF-beta1 in several autoimmune diseases, and show that it can be effectively administered by a somatic gene therapy approach, which results in depressed inflammatory cytokine production and increased endogenous regulatory cytokine production.

TGF-beta is elevated in the CSF of patients with severe traumatic brain injuries and parallels blood-brain barrier function

Traumatic brain injury (TBI) induces local and systemic immunologic changes, release of cytokines, and cell activation. Perpetuation of these cascades may contribute to secondary damage to the brain. Therefore, the ability of the antiinflammatory mediator transforming growth factor-beta (TGF-beta) to downregulate intrathecal immunoactivation may be of fundamental value for diminishing the incidence and extent of secondary insults. In this study, the release of TGF-beta into cerebrospinal fluid (CSF) and serum of 22 patients with severe TBI was analyzed with respect to the function of the blood-brain barrier (BBB) for 21 days. Levels of TGF-beta in CSF increased to their maximum on the first day (median, 1.26 ng/mL), thereafter decreasing gradually over time. Median TGF-beta values in serum always remained within the reference interval (6.5 to 71.5 ng/mL). Daily assessment of the CSF-serum albumin quotient (QA) and of the CSF-serum TGF-beta quotient (QTGF-beta) showed a strong correlation between maximal QTGF-beta and QA, indicating a passage of this cytokine from the periphery to the intrathecal compartment across the BBB. However, calculation of the TGF-beta index (QTGF-beta/Q(A)) suggested a cerebral production of TGF-beta in 9 of 22 patients. Levels of TGF-beta could not be correlated with extent of initial injury by computed tomography (CT), CD4/CD8 ratios, acute lung injury, or clinical outcome as rated by the Glasgow Outcome Scale (GOS). Although increased levels of TGF-beta in CSF seem to parallel BBB function, a partial intrathecal production is suggested, possibly modulated by elevation of interleukin-6 (IL-6). Thus, TGF-beta may function as a factor in the complex cytokine network following TBI, acting as an antiinflammatory and neuroprotective mediator.

Augmentation of natural immunity to a pro-inflammatory cytokine (TNF-alpha) by targeted DNA vaccine confers long-lasting resistance to experimental autoimmune encephalomyelitis

TNF-alpha is thought to be a key pro-inflammatory cytokine in T cell-mediated autoimmune diseases, particularly in rheumatoid arthritis (RA) and multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) serves as an animal model for MS. The current study observes a notable TNF-alpha-specific antibody titer generated during the course of EAE, apparently not sufficient to prevent the development of disease. Administration of TNF-alpha-naked DNA vaccine enhanced the production of TNF-alpha-specific antibody titer and conferred EAE resistance. These antibodies were found to be neutralizing in vitro and capable of inhibiting the development of disease when transferred to other EAE rats. Thus, modulation of EAE with TNF-alpha DNA vaccines enhances the regulation of natural immunity to a self pro-inflammatory cytokine and provides a tool by which the immune system is encouraged to elicit anti-self protective immunity to restrain its own harmful reactivity when such a response is needed.

Lack of association of transforming growth factor (TGF)-beta 1 and beta 2 gene polymorphisms with multiple sclerosis (MS) in Northern Ireland

OBJECTIVE

To examine the influence of TGF-beta genes on MS susceptibility.

BACKGROUND

TGF-beta, of which three homologous isoforms exist (1, 2 and 3), is a strongly immunosuppressive cytokine-inhibiting expression of pro-inflammatory cytokines and blocking cytokine induction of adhesion molecules. TGF-beta delays onset of EAE and TGF-beta 1 gene knockout mice develop fatal multifocal inflammatory disease. High TGF-beta levels exist during MS remission whilst E-selectin, whose expression is inhibited by TGF-beta, is found at higher levels in primary progressive disease (PPMS) and it is postulated that the unremitting course of PPMS may be due to low levels of TGF-beta.

METHODS

Gene association studies using separate polymorphic microsatellite markers for TGF-beta 1 and TGF-beta 2 were performed, incorporating 151 relapsing-remitting or secondary progressive MS (RR/SPMS) patients, 104 PPMS patients and 159 normal controls (Nor). Forward primers were 5' end-labelled with 6-Fam, PCR products were analysed on an Applied Biosystems 373A fluorescent fragment analyser and Genescan 672 software was used for allele sizing.

RESULTS

No significant differences existed in allele frequencies between either MS group and controls regarding the TGF-beta 1 marker: RR/SPMS vs Nor (P = 0.48, df = 8); PPMS vs Nor (P = 0.34, df = 8). Similarly there were no associations demonstrated with the TGF-beta 2 marker: RR/SPMS vs Nor (P = 0.24, df = 2); PPMS vs Nor (P = 0.53, df = 2).

CONCLUSION

These data indicate that TGF-beta 1 and beta 2 genes are not loci influencing MS susceptibility, either RR/SPMS or PPMS, in this population.

Anti-TGF-β Treatment Promotes Rapid Healing of Leishmania major Infection in Mice by Enhancing In Vivo Nitric Oxide Production

CB6F1 mice display intermediate susceptibility to Leishmania major infection compared with the highly susceptible BALB/c and resistant C57BL/6 parental strains. During early weeks of infection, these mice develop dominant Th2 type responses to L. major, although they eventually exhibit a Th2 to Th1 switch and spontaneously resolve their infections. In this study, we have examined the effects of either IL-12 or anti-TGF-β therapy on the immune response and course of disease in chronically infected CB6F1 mice. Local treatment with IL-12 inoculated into the parasitized lesion at 4 wk of infection induced a marked increase in IFN-γ production but did not result in a significant reduction in numbers of parasite or promote more rapid healing. However, local treatment with an Ab to TGF-β led to both a decrease in parasite numbers and more rapid healing, despite the fact that such treatment did not significantly alter the pattern of IL-4 and IFN-γ production. Immunohistochemical studies showed that anti-TGF-β treatment resulted in increased nitric oxide production within parasitized lesions. Our results suggest that TGF-β may play an important regulatory role during chronic stages of a L. major infection by suppressing macrophage production of nitric oxide and that, in the absence of TGF-β, even the relatively low levels of IFN-γ observed in mice with dominant Th2-type responses are sufficient to activate macrophages to destroy amastigotes within parasitized lesions.