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

TGF-β/Smad signaling in kidney disease

Chronic progressive kidney diseases typically are characterized by active renal fibrosis and inflammation. Transforming growth factor-β1 (TGF-β1) is a key mediator in the development of renal fibrosis and inflammation. TGF-β1 exerts its biological effects by activating Smad2 and Smad3, which is regulated negatively by an inhibitory Smad7. In the context of fibrosis, although Smad3 is pathogenic, Smad2 and Smad7 are protective. Under disease conditions, Smads also interact with other signaling pathways, such as the mitogen-activated protein kinase and nuclear factor-κB pathways. In contrast to the pathogenic role of active TGF-β1, latent TGF-β1 plays a protective role in renal fibrosis and inflammation. Furthermore, recent studies have shown that TGF-β/Smad signaling plays a regulating role in microRNA-mediated renal injury. Thus, targeting TGF-β signaling by gene transfer of either Smad7 or microRNAs into diseased kidneys has been shown to retard progressive renal injury in a number of experimental models. In conclusion, TGF-β/Smad signaling plays a critical role in renal fibrosis and inflammation. Advances in understanding of the mechanisms of TGF-β/Smad signaling in renal fibrosis and inflammation during chronic kidney diseases should provide a better therapeutic strategy to combat kidney diseases.

Enhancement of Allergen-induced Airway Inflammation by NOX2 Deficiency

Background

NADPH oxidase (NOX) modulates cell proliferation, differentiation and immune response through generation of reactive oxygen species. Particularly, NOX2 is recently reported to be important for regulating Treg cell differentiation of CD4+ T cells.

Methods

We employed ovalbumin-induced airway inflammation in wild-type and NOX2-deficient mice and analyzed tissue histopathology and cytokine profiles.

Results

We investigated whether NOX2-deficiency affects T cell-mediated airway inflammation. Ovalbumin injection which activates T cell-mediated allergic response increased airway inflammation in wild-type mice, as evidenced by increased immune cell infiltration, allergic cytokine expression, and goblet cell hyperplasia in the lung. Interestingly, NOX2 knockout (KO) mice were more susceptible to allergen-induced lung inflammation compared to wild-type mice. Immune cells including neutrophils, lymphocytes, macrophages, and eosinophils were drastically infiltrated into the lung of NOX2 KO mice and mucus secretion was substantially increased in deficiency of NOX2. Furthermore, inflammatory allergic cytokines and eotaxin were significantly elevated in NOX2 KO mice, in accordance with enhanced generation of inflammatory cytokines interleukin-17 and interferon-γ by CD4+ T cells.

Conclusion

These results indicate that NOX2 deficiency favorably produces inflammatory cytokines by T cells and thus increases the susceptibility to severe airway inflammation.

Shedded neuronal ICAM-5 suppresses T-cell activation

Intercellular adhesion molecules (ICAMs) bind to leukocyte beta2 integrins, which, among other functions, provide costimulatory signals for T-cell activation. ICAM-5 (telencephalin) is expressed in the somadendritic region of neurons of the mammalian brain. The receptor for ICAM-5 is the integrin LFA-1, a major leukocyte integ-rin expressed in lymphocytes and microglia. In conditions of brain ischemia, epilepsy, and encephalitis, the soluble form of ICAM-5 (sICAM-5) has been detected in physiologic fluids. Here, we report that sICAM-5 attenuates the T-cell receptor-mediated activation of T cells as demonstrated by the decreased expression of the activation markers CD69, CD40L, and CD25 (IL-2R). This effect is most clearly seen in CD45ROLow (naive), and not in CD45ROHigh (memory) T cells, and is most effective early in priming, but not in the presence of strong costimulatory signals. Furthermore, sICAM-5 promotes the mRNA expression of the cytokines TGF-beta1 and IFN-gamma, but not TNF. The formation of sICAM-5 is promoted by activated T cells through the cleavage of ICAM-5 from neurons. This suggests that ICAM-5 is involved in immune privilege of the brain and acts as an anti-inflammatory agent.

Latent TGF-beta1 protects against crescentic glomerulonephritis

Despite the critical role that TGF-beta plays in renal fibrosis, transgenic mice that overexpress human latent TGF-beta1 in the skin exhibit normal renal histology and function even though circulating levels of latent TGF-beta1 are an order of magnitude higher than wild-type animals. In fact, latent TGF-beta1 seems to protect against renal inflammation in a model of ureteral obstruction. It is unknown, however, whether latent TGF-beta1 also has this effect in immunologically mediated forms of renal disease such as anti-GBM crescentic glomerulonephritis. We induced anti-GBM disease in wild-type and transgenic mice overexpressing latent TGF-beta1 in keratinocytes. After 14 days, wild-type mice developed progressive crescentic glomerulonephritis with severe renal inflammation and fibrosis. In transgenic mice, proteinuria was reduced by 50%, renal function was preserved, and the formation of glomerular crescents was suppressed by 70%. In addition, transgenic animals had reduced renal inflammation, evidenced by a 70% decrease in the accumulation of T cells and macrophages, and reduced expression of renal IL-1beta, TNFalpha, and MCP-1 by 70 to 80%. Progressive renal fibrosis was also prevented in the transgenic mice, and these protective effects were associated with elevated levels of latent, but not active, TGF-beta1 in plasma and renal tissue. Renal Smad7 was up-regulated and both NF-kappaB and TGF-beta/Smad2/3 activation were suppressed. In conclusion, mice overexpressing latent TGF-beta1 in the skin were protected against anti-GBM crescentic glomerulonephritis, possibly via Smad 7-mediated inhibition of NF-kappaB-dependent renal inflammation and TGF-beta/Smad2/3-dependent fibrosis.

Semliki Forest virus vectors expressing transforming growth factor beta inhibit experimental autoimmune encephalomyelitis in Balb/c mice

Cytokine immunomodulation of experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, has remained a formidable treatment option, but access into the CNS is hampered due to the impermeability of the blood-brain barrier. In this report, we describe the construction and characterization of CNS-homing gene delivery/therapy vectors based on avirulent Semliki Forest virus (SFV) expressing either native or mutant transforming growth factor beta 1 (TGF-beta1). Biological activity of the expressed inserts was demonstrated by PAI-1 promoter driven luciferase production in mink cells and TGF-beta1 mRNA was demonstrated in the CNS of virus treated mice by in situ hybridization and RT-PCR. Both vectors, when given intraperitoneally to EAE mice significantly reduced disease severity compared to untreated mice. Our results imply that immunomodulation by neurotropic viral vectors may offer a promising treatment strategy for autoimmune CNS disorders.

Association between parasite infection and immune responses in multiple sclerosis

OBJECTIVE

To assess whether parasite infection is correlated with a reduced number of exacerbations and altered immune reactivity in multiple sclerosis (MS).

METHODS

A prospective, double-cohort study was performed to assess the clinical course and radiological findings in 12 MS patients presenting associated eosinophilia. All patients presented parasitic infections with positive stool specimens. In all parasite-infected MS patients, the eosinophilia was not present during the 2 previous years. Eosinophil counts were monitored at 3- to 6-month intervals. When counts became elevated, patients were enrolled in the study. Interleukin (IL)-4, IL-10, IL-12, transforming growth factor (TGF)-beta, and interferon-gamma production by myelin basic protein-specific peripheral blood mononuclear cells were studied using enzyme-linked immunospot (ELISPOT). FoxP3 and Smad7 expression were studied by reverse-transcriptase polymerase chain reaction.

RESULTS

During a 4.6-year follow-up period, parasite-infected MS patients showed a significantly lower number of exacerbations, minimal variation in disability scores, as well as fewer magnetic resonance imaging changes when compared with uninfected MS patients. Furthermore, myelin basic protein-specific responses in peripheral blood showed a significant increase in IL-10 and TGF-beta and a decrease in IL-12 and interferon-gamma-secreting cells in infected MS patients compared with noninfected patients. Myelin basic protein-specific T cells cloned from infected subjects were characterized by the absence of IL-2 and IL-4 production, but high IL-10 and/or TGF-beta secretion, showing a cytokine profile similar to the T-cell subsets Tr1 and Th3. Moreover, cloning frequency of CD4+CD25+ FoxP3+ T cells was substantially increased in infected patients compared with uninfected MS subjects. Finally, Smad7 messenger RNA was not detected in T cells from infected MS patients secreting TGF-beta.

INTERPRETATION

Increased production of IL-10 and TGF-beta, together with induction of CD25+CD4+ FoxP3+ T cells, suggests that regulatory T cells induced during parasite infections can alter the course of MS.

The role of TGF-β in mice infected with Heligmosomoides polygyrus

Hyporesponsiveness induced by Heligmosomoides polygyrus was quantified and the relationship between TGF-beta and inflammation was identified in BALB/c mice. The immune response and pathological changes modified by neutralization of TGF-beta were characterized in vivo. Nine and twelve days following infection, BALB/c mice were injected intraperitoneally with anti-TGF-beta (1,2,3) antibodies, isotype control antibodies or isosmotic solution. We assessed both Th1 and Th2 related cytokines production ex vivo and in vitro, IgA, the number of CD4+ cells, and eosinophils in the lamina propria and the villus : crypt ratio in the small intestine 6 weeks after infection. The pattern of cytokine production differed in the intestine, peritoneal fluid and serum. In mice infected with H. polygyrus the concentrations of IL-5, IL-12, TNF-alpha and IL-10 were raised in the intestine, but in serum the level of cytokines was diminished below the value observed in uninfected mice. The neutralization of TGF-beta converted the pattern of immune response induced by H. polygyrus. The elevation of cytokines in serum coincided with the reduction of cytokine concentration in the intestine or peritoneum. Neutralization of TGF-beta restored infiltration of eosinophils into the lamina propria of the intestine despite the low level of IL-5. We conclude that H. polygyrus infection suppresses the immune response through pathways involving TGF-beta production or activity and that the Th2 related immune response was not affected by neutralization.

Clonal restriction of the expansion of antigen-specific CD8+ memory T cells by transforming growth factor-{beta}

Recent evidence showed that transforming growth factor-beta (TGF-beta) regulates the global expansion of CD8+ T cells, which are CD44hi, a marker for memory cells. However, it is not clear whether this regulatory mechanism also applies to the antigen-specific CD8+ memory cells. By using a murine mixed lymphocyte culture (MLC) model, we examined the effect of TGF-beta on antigen-specific CD8+ memory cells [cytotoxic T lymphocyte (CTL)]. We found that the secondary CTL response in CD8+ memory cells from untreated MLC was not affected by TGF-beta but augmented by interleukin (IL)-2, whereas the CD8+ memory cells from TGF-beta-pretreated MLC (MLC-TGF-beta) failed to mount a significant, secondary CTL response, even when IL-2 was added. In exploring this dichotomy, in combination with flow cytometry analysis, we found that prolonged exposure to TGF-beta reduces the CTL activity in CD8+ memory cells. The increase by IL-2 and the reduction by TGF-beta of the CTL responses were clonal-specific. TGF-beta did not affect the CTL response to a third-party antigen or polyclonal T cell activation. Experiments performed with transgenic 2C cells gave similar results. Cell-cycle study performed with adoptive transfer of the cell tracker-labeled MLC cells revealed that the in vivo expansion of CD8+ memory cells from MLC-TGF-beta was restricted severely, and the restriction was clonal-specific, thus offering direct evidence to show that TGF-beta induces clonal restriction of CD8+ memory cell expansion.

Signaling mechanism of TGF-beta1 in prevention of renal inflammation: role of Smad7

TGF-beta has been shown to play a critical role in anti-inflammation; however, the signaling mechanisms of TGF-beta in anti-inflammatory response remains largely unclear. This study reported that mice that overexpress latent TGF-beta1 on skin are protected against renal inflammation in a model of obstructive kidney disease and investigated the signaling mechanism of TGF-beta1 in inhibition of renal inflammation in vivo and in vitro. Seven days after urinary obstruction, wild-type mice developed severe renal inflammation, including massive T cell and macrophage infiltration and marked upregulation of IL-1beta, TNF-alpha, and intercellular adhesion molecule-1 (all P < 0.001). Surprising, renal inflammation was prevented in transgenic mice. This was associated with an increase in latent TGF-beta1 in circulation (a 10-fold increase) and renal tissues (a 2.5-fold increase). Further studies showed that inhibition of renal inflammation in TGF-beta1 transgenic mice was also associated with a marked upregulation of renal Smad7 and IkappaBalpha and a suppression of NF-kappaB activation in the diseased kidney (all P < 0.01). These in vivo findings suggested the importance of TGF-beta-NF-kappaB cross-talk signaling pathway in regulating renal inflammation. This was tested in vitro in a doxycycline-regulated Smad7-expressing renal tubular cell line. Overexpression of Smad7 was able to upregulate IkappaBalpha directly in a time- and dose-dependent manner, thereby inhibiting NF-kappaB activation and NF-kappaB-driven inflammatory response. In conclusion, latent TGF-beta may have protective roles in renal inflammation. Smad7-mediated inhibition of NF-kappaB activation via the induction of IkBalpha may be the central mechanism by which latent TGF-beta prevents renal inflammation.

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.

TGF-beta 1 regulates lymphocyte homeostasis by preventing activation and subsequent apoptosis of peripheral lymphocytes

TGF-beta1 plays an important role in the maintenance of immune homeostasis and self-tolerance. To determine the mechanism by which TGF-beta1 prevents autoimmunity we have analyzed T cell activation in splenic lymphocytes from TGF-beta1-deficient mice. Here we demonstrate that unlike wild-type splenic lymphocytes, those from Tgfb1(-/-) mice are hyporesponsive to receptor-mediated mitogenic stimulation, as evidenced by diminished proliferation and reduced IL-2 production. However, they have elevated levels of IFN-gamma and eventually undergo apoptosis. Receptor-independent stimulation of Tgfb1(-/-) T cells by PMA plus ionomycin induces IL-2 production and mitogenic response, and it rescues them from anergy. Tgfb1(-/-) T cells display decreased CD3 expression; increased expression of the activation markers LFA-1, CD69, and CD122; and increased cell size, all of which indicate prior activation. Consistently, mutant CD4(+) T cells have elevated intracellular Ca(2+) levels. However, upon subsequent stimulation in vitro, increases in Ca(2+) levels are less than those in wild-type cells. This is also consistent with the anergic phenotype. Together, these results demonstrate that the ex vivo proliferative hyporesponsiveness of Tgfb1(-/-) splenic lymphocytes is due to prior in vivo activation of T cells resulting from deregulated intracellular Ca(2+) levels.

TGF beta 1 inhibits Ca2+-calcineurin-mediated activation in thymocytes

TGFbeta1 is a polypeptide growth modulatory and differentiation factor involved in many biological processes including immune homeostasis and self-tolerance. Tgfb1 knockout mice die around weaning age due to severe inflammation in most major organ systems, but the mechanism underlying this disease is not understood. In this study we demonstrate that Tgfb1(-/-) CD4(+)CD8(+) and CD4(+)CD8(-) thymocytes are hyperresponsive to receptor-mediated and receptor-independent mitogenic stimulation. A suboptimal concentration of ionomycin in the presence of PMA fully activates Tgfb1(-/-) thymocytes, whereas the inhibitors of Ca(2+) influx and calcineurin, EGTA and FK506, eliminate the hyperresponsiveness. Hence, the hypersensitivity of Tgfb1(-/-) thymocytes is due to a lowered threshold for Ca(2+)-dependent activation. Further, we demonstrate that the hypersensitivity of thymocytes results from the absence of TGFbeta1 and not from the inflammatory environment because the thymocytes are hyperresponsive in preinflammatory-stage Tgfb1(-/-) mice. Our results suggest for the first time that TGFbeta1 functions to inhibit aberrant T cell expansion by maintaining intracellular calcium concentration levels low enough to prevent a mitogenic response by Ca(2+)-independent stimulatory pathways alone. Consequently, TGFbeta1 prevents autoimmune disease through a Ca(2+) regulatory pathway that maintains the activation threshold above that inducible by self-MHC-TCR interactions.

Oral feeding with ethinyl estradiol suppresses and treats experimental autoimmune encephalomyelitis in SJL mice and inhibits the recruitment of inflammatory cells into the central nervous system

There is much interest in the possible ameliorating effects of estrogen on various autoimmune diseases. We previously established the protective effects of 17 beta-estradiol (E2) on experimental autoimmune encephalomyelitis (EAE). In the current study we investigated the effectiveness of oral treatment with ethinyl estradiol (EE) on EAE and the mechanisms involved. Ethinyl estradiol is a semisynthetic estrogen compound found in birth control pills, and its chemical structure allows this compound to retain activity when given orally. We found that oral EE, like E2, drastically suppressed EAE induced by proteolipid protein 139-151 peptide when given at initiation of EAE. However, unlike E2, EE reduced clinical severity when given after the onset of clinical signs. Treatment with EE significantly decreased the secretion of proinflammatory cytokines (IFN-gamma, TNF-alpha, and IL-6) by activated T cells as well as the expression of a key matrix metalloproteinase, disease-mediating chemokines/receptors, and IgG2a levels, but increased the expression of TGF-beta 3 in the CNS. The absence of infiltrating lymphocytes together with the suppression of cytokines, matrix metalloproteinase, and chemokines/receptors suggests that EE, like E2, protects mice from EAE by inhibiting the recruitment of T cells and macrophages into the CNS. These results suggest that oral ethinyl estradiol might be a successful candidate as therapy for multiple sclerosis.

Cytokines in Lyme borreliosis: lack of early tumour necrosis factor-alpha and transforming growth factor-beta1 responses are associated with chronic neuroborreliosis

The clinical outcome of the tick born infection Lyme borreliosis seems to be influenced by the type of immune response mounted during the disease, as suggested by various animal models. Here we report the serum and cerebrospinal fluid levels of tumour necrosis factor-alpha (TNF-alpha), transforming growth factor beta1 (TGF-beta1) and interleukin-6 (IL-6) in samples drawn at different disease intervals during the course of non-chronic neuroborreliosis (n=10), chronic neuroborreliosis (n=15), erythema migrans (n=8, serum only) and controls (n=7). When comparing early neuroborreliosis cerebrospinal fluid samples, significantly higher levels of TNF-alpha were found in non-chronic patients than in chronic patients (P<0.05). Moreover, TGF-beta1 was increased in the early serum samples of non-chronic patients, as compared to chronic patients (P<0.01). Elevated serum levels of TGF-beta1 were also found in erythema migrans as compared to neuroborreliosis and controls (P<0.05). The high TNF-alpha levels noted in early cerebrospinal fluid samples of non-chronic patients only, possibly reflects an ongoing pro-inflammatory immune response in the central nervous system, which could be beneficial in eliminating disease. High serum levels of TGF-beta1 probably mirror an anti-inflammatory response, which might play a role in controlling the systemic immune response.

TGF-beta-mediated control of allergen-specific T-cell responses

Control of allergen-specific response by suppressive cytokines involves several layers of regulation, including secretion of the cytokine, deviation of cytokine expression by altered T-cell differentiation, immediate (de-) phosphorylation events upon binding of suppressive cytokines, and laterations in susceptibility of suppression.

Th1 and Th2 responses in pathogenesis and regulation of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) in animals can be induced by immunization with retinal antigens or their fragments and represents human uveitis of putative autoimmune origin. The pathogenesis of EAU, and likely also of human uveitis, involves cell-mediated destruction of retinal tissues that is dependent on retinal antigen-specific T cells. Because in most cases a Th1-type response has been implicated in pathogenesis, the prevailing consensus has been that immunoregulatory manipulations designed to enhance the Th2 response at the expense of the Th1 response will be beneficial in clinical treatment of uveitis. This assumption may not always be correct. The present review will summarize the evidence that, despite a central role for Th1 response in uveitis, an unopposed Th2-like response can be equally or more destructive to the retinal tissues. Furthermore, the Th1 response itself triggers regulatory circuits that feed back and dampen further recruitment of antigen-specific T cells into the Th1 effector pool. Thus, although the Th1 effector response can and does result in retinal pathology, immunoregulatory strategies must take into account that immune deviation therapies designed to replace the Th1 with a Th2 response might result in exchanging one type of pathology for another rather than in achieving the desired therapeutic effect.

The Cytokine Odyssey 2001, a joint meeting of the Society of Leukocyte Biology and the International Cytokine Society. 8-11 November 2001, Maui, Hawaii, USA

The Cytokine Odyssey 2001 was held at the Outrigger Wailea Resort in Maui, Hawaii, USA. The meeting, jointly sponsored by the International Cytokine Society (ICS, 9th Annual Meeting) and the Society of Leukocyte Biology (SLB, 35th Annual Meeting), was organised by Carl Ware (Chair) from the La Jolla Institute for Allergy and Immunology (La Jolla, USA) and Thomas Hamilton (Co-Chair) from the Cleveland Clinic Foundation (Cleveland, USA). This international conference was designed to bring together leading investigators in molecular and cellular biology, physiology and genetics, interested in cytokines and cells of the immune system. This forum was aimed to assess the impact of this expanding science on new approaches to disease intervention [1].

Atopic disorders: a vaccine around the corner?

The incidence and severity of atopic disorders, in particular asthma, is steadily increasing at an alarming rate. Furthermore, no primary prevention measure exists to date. However, recent results obtained from numerous animal studies suggest that primary prevention in humans might be possible in the near future. The most promising approaches include the induction of systemic or local allergen-dependent or -independent T helper 1 (Th1) immune responses, through the use of killed bacteria (or components derived from them), CpG oligodeoxynucleotides or plasmid DNA, and the induction of allergen-specific T-cell tolerance. Here, we review the data showing that animals can be protected from developing allergic Th2 responses by vaccination. Possible future use in humans and potential side-effects of the described vaccination strategies are discussed also.

Vaccination with autologous dendritic cells: from experimental autoimmune encephalomyelitis to multiple sclerosis

Autoimmune diseases such as multiple sclerosis (MS) are characterized by the loss of tolerance to self-determinants, activation of autoreactive lymphocytes and subsequent damage to single or multiple organs. The mechanisms by which autoimmune responses are triggered, and how activation of autoreactive lymphocytes is initiated and maintained, are not fully understood. Therapeutic approaches in autoimmune diseases have so far concentrated on antigens and T cells. Given the exceptional capacity of dendritic cells (DCs) to induce immunity in vivo, recent reports of the first successful clinical trials based on vaccination of tumor patients with autologous blood DCs pulsed in vitro with tumor antigen come as no surprise. The recent identification of tolerogenic subsets of DCs and their generation in culture may allow a novel approach to induce tolerance in autoimmune diseases. By selective in vitro manipulation of DCs and their subsequent reinfusion, DC-mediated tolerance has been achieved in animal models of human autoimmune diseases, including experimental autoimmune encephalomyelitis in Lewis rats and SJL/J mice and spontaneous diabetes in NOD mice. In vitro observations of human blood DCs are promising for DC-based treatment of MS and other diseases with an autoimmune component. Data from animal models and human materials suggest that DC-based immunotherapy could be beneficial at least as a complement to conventional therapy. Molecular-biological approaches to tolerogenic DCs could provide a rationale for designing immunotherapeutic strategies in autoimmune diseases.