IL-2 is essential for TGF-beta to convert naive CD4+CD25- cells to CD25+Foxp3+ regulatory T cells and for expansion of these cells

Vitamin A Impairs the Reprogramming of Tregs into IL-17-Producing Cells during Intestinal Inflammation

Maintaining the identity of Foxp3⁺ regulatory T cells (Tregs) is critical for controlling immune responses in the gut, where an imbalance between Tregs and T effector cells has been linked to inflammatory bowel disease. Accumulating evidence suggests that Tregs can convert into Th17 cells and acquire an inflammatory phenotype. In this study, we used an adoptive transfer model of Ag-specific T cells to study the contribution of different factors to the reprogramming of in vitro-generated Treg cells (iTreg) into IL-17-producing cells in a mouse model of gut inflammation in vivo. Our results show that intestinal inflammation induces the reprogramming of iTreg cells into IL-17-producing cells and that vitamin A restrains reprogramming in the gut. We also demonstrate that the presence of IL-2 during the in vitro generation of iTreg cells confers resistance to Th17 conversion but that IL-2 and retinoic acid (RA) cooperate to maintain Foxp3 expression following stimulation under Th17-polarizing conditions. Additionally, although IL-2 and RA differentially regulate the expression of different Treg cell suppressive markers, Treg cells generated under different polarizing conditions present similar suppressive capacity.

The Number of Immunoregulatory T Cells is Increased in Patients with Psoriasis after Goeckerman Therapy

Regulatory T cells (Treg) are a specialized subpopulation of T cells that act to suppress inadequate immune response. Psoriasis is recognized as a T-cell driven immune-mediated systemic inflammatory disease with skin manifestation. Effective therapeutical approach to treat psoriasis is Goeckerman therapy (GT). The aim of this study was to compare the number of Treg in the peripheral blood of 27 psoriatic patients and 19 controls and to evaluate the influence of GT on Treg population in peripheral blood of patients with psoriasis. There was no significant difference in the relative number of Treg cells in the peripheral blood of healthy blood donors and patients with psoriasis before initiation of GT (P = 0.2668). In contrary, the relative number of Treg cells in peripheral blood of patients with psoriasis after GT was significantly higher than those found in healthy blood donors (P = 0.0019). Moreover, the relative number of Treg is significantly increased in psoriatic patients after Goeckerman therapy compared to the pre-treatment level (P = 0.0042). In conclusion, this significant increase in Treg count after GT is probably associated with amelioration of inflammation by GT, as disease activity expressed as PASI decreased in our patients by GT (P = 0.0001).

Negative regulation of natural killer cell in tumor tissue and peripheral blood of oral squamous cell carcinoma

Natural killer (NK) cells are the key lymphocytes in solid tumors. Its activity is regulated by both germline encoded receptors and cytokine microenvironment. We conducted a case-control study to investigate the activation status of NK cell in oral squamous cell carcinoma (OSCC). NK cell activation was assessed in context of NK cell cytotoxicity and transcript expression of NK cell receptors (NKp46 and KIRs) and NK cell associated cytokines (IL-1β, IL-2, IL-10, IL-12β, IL-15, IL-18, IL-21, IFN-γ, TNF-α and TGF-β). The results revealed possible mechanisms involved in reduced NK cell activation in peripheral circulation: quantitative deficiency of NK cell number and lowered cytotoxicity together with qualitative NK impairments caused by--(1) decreased expression of NK activating receptor NKp46, (2) increased expression of NK suppressive cytokines--IL-10 and TGF-β and (3) induction of FOXP3(+)CTLA4(+) suppressor cells. On the other hand, in the tumor tissue, escape of NK immune surveillance appeared to be modulated by upregulation of TGF-β and IL-10 together with downregulation of NK cell activating cytokines (IL-2, IL-12β, IL-15, IL-18, IL-21 and IFN-γ) and NK receptors (NKp46 and KIRs). In addition, our study supported the earlier contention that TNF-α and IL-1β expression levels may be used as markers of malignant transformation in oral leukoplakia. In conclusion, the study provided an insight into the negative regulation of NK cell in tumor tissue and peripheral blood of OSCC patients, which can be exploited to boost the current NK cell and cytokine based immunotherapy for the treatment of oral cancer.

Impaired expansion of regulatory T cells in a neonatal thymectomy-induced autoimmune mouse model

Neonatal thymectomy in certain mouse strains is known to induce organ-specific autoimmunity due to impaired functions of T cells, including Foxp3(+) regulatory T (Treg) cells in the thymus. The precise mechanism underlying the induction of autoimmunity by neonatal thymectomy remains unclear. One possibility is that depletion of Treg cells breaks down peripheral tolerance. We examined the functions of Treg cells by using a murine Sjögren syndrome model of NFS/sld mice that underwent neonatal thymectomy. The ratio of Treg cells to effector memory phenotype T cells in thymectomy mice was significantly lower than that of nonthymectomy mice. In addition, in vitro induction of peripherally induced Treg cells by transforming growth factor-β (TGF-β) using naive T cells from Sjögren syndrome model mice was severely impaired. The mRNA expression of TGF-β receptor I and II and Smad3 and -4 in the TGF-β-induced signal transduction pathway of Treg cells in this Sjögren syndrome model were lower than those of control mice. In addition, Treg cells in this Sjögren syndrome model exhibited an interferon-γ-producing Th1-like phenotype that resembled effector T cells. In conclusion, these results suggest that abnormal expansion and differentiation of Treg cells and inflammatory cytokines produced by Treg cells contribute to the development of autoimmunity.

The role of all-trans retinoic acid in the biology of Foxp3+ regulatory T cells

Regulatory T (Treg) cells are necessary for immune system homeostasis and the prevention of autoimmune diseases. Foxp3 is specifically expressed in Treg cells and plays a key role in their differentiation and function. Foxp3(+) Treg cells are consisted of naturally occurring, thymus-derived Treg (nTreg) and peripheral-induced Treg (iTreg) cells that may have different functional characteristics or synergistic roles. All-trans retinoic acid (atRA), a vitamin A metabolite, regulates a wide range of biological processes, including cell differentiation and proliferation. Recent studies demonstrated that atRA also regulates the differentiation of T helper (Th) cells and Treg cells. Moreover, atRA also sustains nTreg stability under inflammatory conditions. In this review, we summarize the significant progress of our understanding of the role(s) and mechanisms of atRA in Treg biology.

Beyond regulatory T cells: the potential role for IL-2 to deplete T-follicular helper cells and treat autoimmune diseases

Low-dose IL-2 administration suppresses unwanted immune responses in mice and humans, thus evidencing the potential of IL-2 to treat autoimmune disorders. Increased Tregs activity is one of the potential mechanisms by which low-dose IL-2 immunotherapy induces immunosuppression. In addition, recent data indicate that IL-2 may contribute to prevent unwanted self-reactive responses by preventing the developing of T-follicular helper cells, a CD4(+) T-cell subset that expands in autoimmune disease patients and promotes long-term effector B-cell responses. Here we discuss the mechanisms underlying the clinical benefits of low-dose IL-2 administration, focusing on the role of this cytokine in promoting Treg-mediated suppression and preventing self-reactive T-follicular helper cell responses.

MAR binding protein SMAR1 favors IL-10 mediated regulatory T cell function in acute colitis

Treg cells are not only crucial for controlling immune responses to autoantigens but also prevent those directed towards commensal pathogens. Control of effector immune responses by Treg cells depend on their capacity to accumulate at inflammatory site and accordingly accommodate to inflammatory environment. Till date, the factors associated with maintaining these aspects of Treg phenotype is not understood properly. Here we have shown that a known nuclear matrix binding protein SMAR1 is selectively expressed more in colonic Treg cells and is required for their ability to accumulate at inflammatory site and to sustain high levels of Foxp3 and IL-10 expression during acute colitis. Elimination of anti-inflammatory subsets revealed a protective role for IL-10 producing Treg cells in SMAR1(-/-) mice. Moreover, a combined action of Foxp3 and SMAR1 restricts effector cytokine production and enhance the production of IL-10 by colonic Treg cells that controls acute colitis. This data highlights a critical role of SMAR1 in maintaining Treg physiology during inflammatory disorders.

Dexamethasone suppresses allergic rhinitis and amplifies CD4(+) Foxp3(+) regulatory T cells in vitro

BACKGROUND

Glucocorticosteroids (GCs) are highly effective in mitigating allergic inflammation. In this study, we investigate the effects of dexamethasone (DEX) on regulatory T cells (Tregs) in a murine model of allergic rhinitis (AR).

METHODS

BALB/c mice were sensitized to ovalbumin (OVA) followed by intranasal OVA challenge. Mice in the treatment group received DEX by intraperitoneal injection (5 mg/kg/day) 1 hour before the OVA challenge. Further, CD4(+) CD25(-) T cells from the spleens were cultured in presence of DEX. The effects of DEX on CD4(+) Foxp3(+) T cells were then assessed in vivo as well as in vitro.

RESULTS

Frequencies of sneezing and scratching decreased significantly in the DEX-treated group compared to that in the OVA group. Histopathological analyses showed that DEX restored the destroyed and discontinuous ciliated epithelium of the nasal mucosa in the OVA group. Moreover, DEX inhibited the production of interleukin (IL)-4, IL-5, and IL-13 in the nasal cavity lavage fluid in this group. We also observed a significant increase in the percentage of CD4(+) Foxp3(+) T cells in the OVA group. In vivo, DEX treatment significantly decreased the number of CD4(+) Foxp3(+) T cells. However, in vitro, the proportion of these cells increased in the presence of DEX. Furthermore, the number of late stage apoptotic CD4(+) T cells was also significantly increased upon exposure to DEX.

CONCLUSION

DEX therapy effectively suppresses AR symptoms, but does not result in the expected increase in the frequency of Tregs in vivo. Thus, whether GCs exert immunosuppressive effects by influencing the number of Tregs remains unresolved.

Prevention and Immunotherapy of Secondary Murine Alveolar Echinococcosis Employing Recombinant EmP29 Antigen

Alveolar echinococcosis (AE) is caused by infection with the larval stage of the tapeworm Echinococcus multilocularis. An increasing understanding of immunological events that account for the metacestode survival in human and murine AE infection prompted us to undertake explorative experiments tackling the potential of novel preventive and/or immunotherapeutic measures. In this study, the immunoprotective and immunotherapeutic ability of recombinant EmP29 antigen (rEmP29) was assessed in mice that were intraperitoneally infected with E. multilocularis metacestodes. For vaccination, three intraperitoneal injections with 20μg rEmP29 emulsified in saponin adjuvants were applied over 6 weeks. 2 weeks after the last boost, mice were infected, and at 90 days post-infection, rEmP29-vaccinated mice exhibited a median parasite weight that was reduced by 75% and 59% when compared to NaCl- or saponin–treated control mice, respectively. For immunotherapeutical application, the rEmP29 (20μg) vaccine was administered to experimentally infected mice, starting at 1 month post-infection, three times with 2 weeks intervals. Mice undergoing rEmP29 immunotherapy exhibited a median parasite load that was reduced by 53% and 49% when compared to NaCl- and saponin–treated control mice, respectively. Upon analysis of spleen cells, both, vaccination and treatment with rEmP29, resulted in low ratios of Th2/Th1 (IL-4/IFN-γ) cytokine mRNA and low levels of mRNA coding for IL-10 and IL-2. These results suggest that reduction of the immunosuppressive environment takes place in vaccinated as well as immunotreated mice, and a shift towards a Th1 type of immune response may be responsible for the observed increased restriction of parasite growth. The present study provides the first evidence that active immunotherapy may present a sustainable route for the control of AE.

Current medical management of AE that relies on surgery and continuous benzimidazole administration is of limited effectiveness. Therefore, alternative preventive and therapeutic tools need to be explored. Here, we demonstrate that vaccination with recombinant antigen EmP29 (rEmP29), prior or after secondary infection of BALB/c mice, resulted in a significant reduction of the median parasite weight when compared to different control groups. We then characterized the transcription level of splenic IL-4 and IFN-γ cytokines as hallmarks for AE-anti-protective humoral immune reaction (Th2) and for AE-effective (restrictive) cellular response (Th1), respectively. Results revealed that vaccinated mice in pre- or post-infection situation exhibited the lowest IL-4/IFN-γ mRNA ratios. In addition, those groups showed also significantly low levels of IL-10-encoding mRNA coding (immunosuppressive cytokine), as well as IL-2. These findings suggest that reduction of parasite load in rEmP29-vaccinated mice (in pre- or post-infection status) might be triggered by a decline of the immunosuppressive environment and a change of the host immune reaction towards a Th1-re-oriented cell-mediated immune defense. A similar non-specific effect appears also to be yielded by the immunostimulating adjuvants. This study provides the first insight into the potential benefits of antigen-specific immunotherapy as new treatment option of AE.

Apoptotic cell-linked immunoregulation: implications for promoting immune tolerance in transplantation

The induction of alloantigen-specific immune tolerance is the "Holy-Grail" in transplantation. Although it had been previously demonstrated that transient depletion of T cells through apoptosis could lead to long-term immune tolerance, the underlying mechanism responsible for this tolerance induction and maintenance was unknown. In this short article, a novel mechanism for long-term immune tolerance via transient T cell apoptosis will be discussed, based on our recent findings in a CD3-specific antibody treatment-induced immune tolerance mouse model. Transforming growth factor-β, which is produced by immature dendritic cells whilst they phagocytose apoptotic T cells and by macrophages, plays an important role in initiating long-term immune tolerance. A possible model of how allospecific-immune tolerance can be induced in order to prevent allograft rejection in transplantation will be also proposed.

HY-Specific Induced Regulatory T Cells Display High Specificity and Efficacy in the Prevention of Acute Graft-versus-Host Disease

Naturally derived regulatory T cells (Tregs) may prevent graft-versus-host disease (GVHD) while preserving graft-versus-leukemia (GVL) activity. However, clinical application of naturally derived regulatory T cells has been severely hampered by their scarce availability and nonselectivity. To overcome these limitations, we took alternative approaches to generate Ag-specific induced Tregs (iTregs) and tested their efficacy and selectivity in the prevention of GVHD in preclinical models of bone marrow transplantation. We selected HY as a target Ag because it is a naturally processed, ubiquitously expressed minor histocompatibility Ag (miHAg) with a proven role in GVHD and GVL effect. We generated HY-specific iTregs (HY-iTregs) from resting CD4 T cells derived from TCR transgenic mice, in which CD4 cells specifically recognize HY peptide. We found that HY-iTregs were highly effective in preventing GVHD in male (HY(+)) but not female (HY(-)) recipients using MHC II-mismatched, parent→F1, and miHAg-mismatched murine bone marrow transplantation models. Interestingly, the expression of target Ag (HY) on the hematopoietic or nonhematopoietic compartment alone was sufficient for iTregs to prevent GVHD. Furthermore, treatment with HY-iTregs still preserved the GVL effect even against pre-established leukemia. We found that HY-iTregs were more stable in male than in female recipients. Furthermore, HY-iTregs expanded extensively in male but not female recipients, which in turn significantly reduced donor effector T cell expansion, activation, and migration into GVHD target organs, resulting in effective prevention of GVHD. This study demonstrates that iTregs specific for HY miHAgs are highly effective in controlling GVHD in an Ag-dependent manner while sparing the GVL effect.

All-trans retinoic acid favors the development and function of regulatory T cells from liver transplant patients

Graft-versus-host disease (GVHD) is an intractable complication in transplant patients. Regulatory T cells (Tregs) have the ability to prevent GVHD and consist of two subsets: natural Tregs (nTregs) and induced Tregs (iTregs). In comparison to nTregs, iTregs originate in the periphery under certain conditions and show improved proliferative and suppressive abilities in an inflammatory milieu. All-trans retinoic acid (atRA) favors Treg expansion and FoxP3 expression in human Tregs. However, whether atRA can affect the function of iTregs from transplant patients remains inconclusive. Therefore, we sorted naïve T cells from liver transplant patients and cultured them in vitro. Further analyses were performed to assess the suppressive function of iTregs in vitro and in vivo. atRA favored expansion and forkhead box P3 expression in iTregs from transplant patients. In comparison to iTregs from healthy donors, iTregs from transplant patients showed decent suppressive abilities in vitro and in vivo. Our findings suggest that atRA can potentially improve the development and function of iTregs from transplant patients. Furthermore, our results provide novel insights into Treg therapy in GVHD clinical trials.

Regulatory T cells: Mechanisms of suppression and impairment in autoimmune liver disease

There are three classic liver diseases with probable autoimmune etiology: primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune hepatitis. The occurrence of these autoimmune conditions is determined by the breakdown of immune-regulatory mechanisms that in health are responsible for maintaining immunological tolerance against self-antigens. Among the multiple T cell subsets with suppressive function, the regulatory T cells (Tregs), defined by the expression of CD4, the IL-2 receptor α chain (CD25), and the transcription factor FOXP3, have emerged as having a central role in maintaining immune-tolerance to autoantigens. Tregs are equipped with an array of mechanisms of suppression, including the modulation of antigen presenting cell maturation and function, the killing of target cells, the disruption of metabolic pathways, and the production of anti-inflammatory cytokines. In all the three autoimmune liver diseases mentioned above, there is evidence pointing for either a reduced frequency and/or function of Tregs. Here, we review the definition, phenotypic characteristics, and mechanisms of suppression employed by Tregs and then we discuss the evidence available pointing to their impairment in patients with autoimmune liver disease.

Anti-CMV-IgG positivity of donors is beneficial for alloHSCT recipients with respect to the better short-term immunological recovery and high level of CD4+CD25high lymphocytes

Hematopoietic stem cell transplantation from anti-cytomegalovirus immunoglobulin G (anti-CMV-IgG) positive donors facilitated immunological recovery post-transplant, which may indicate that chronic CMV infection has an effect on the immune system. This can be seen in the recipients after reconstitution with donor lymphocytes. We evaluated the composition of lymphocytes at hematologic recovery in 99 patients with hematologic malignancies post hematopoietic stem cell transplantation (HSCT). Anti-CMV-IgG seropositivity of the donor was associated with higher proportions of CD4+ (227.963 ± 304.858 × 106 vs. 102.050 ± 17.247 × 106 cells/L, p = 0.009) and CD4+CD25high (3.456 ± 0.436 × 106 vs. 1.589 ± 0.218 × 106 cells/L, p = 0.003) lymphocytes in the blood at hematologic recovery. The latter parameter exerted a diverse influence on the risk of acute graft-versus-host disease (GvHD) if low (1.483 ± 0.360 × 106 vs. 3.778 ± 0.484 × 106 cells/L, p < 0.001) and de novo chronic GvHD (cGvHD) if high (3.778 ± 0.780 × 106 vs. 2.042 ± 0.261 × 106 cells/L, p = 0.041). Higher values of CD4+ lymphocytes in patients who received transplants from anti-CMV-IgG-positive donors translated into a reduced demand for IgG support (23/63 vs. 19/33, p = 0.048), and these patients also exhibited reduced susceptibility to cytomegalovirus (CMV), Epstein-Barr virus (EBV) and/or human herpes 6 virus (HHV6) infection/reactivation (12/50 vs. 21/47, p = 0.032). Finally, high levels (³0.4%) of CD4+CD25high lymphocytes were significantly associated with better post-transplant survival (56% vs. 38%, four-year survival, p = 0.040). Donors who experience CMV infection/reactivation provide the recipients with lymphocytes, which readily reinforce the recovery of the transplanted patients' immune system.

Regulatory T cells in early life: comparative study of CD4+CD25high T cells from foals and adult horses

The immune system of mammals is subject to continuous development during the postnatal phase of life. Studies following the longitudinal development of the immune system in healthy children are limited both by ethical considerations and sample volumes. Horses represent a particular valuable large animal model for T regulatory (Treg) cells and allergy research. We have recently characterised Treg cells from horses, demonstrated their regulatory capability and showed both their expansion and induction in vitro. Insect bite hypersensitivity (IBH) is a common allergy in horses resembling atopic dermatitis and studies have shown that first exposure to allergens in adult life results in an increased incidence of IBH. The aim of the present study was to characterize circulating CD4⁺CD25^highFoxP3⁺cells in foals, evaluate their suppressive capability and their in vitro induction compared to adult horses. 19 foals (age range, 1–5 months), their adult mothers and six one-year-old horses (yearlings) were included in the study. The proportion of FoxP3⁺ cells within the circulating CD4⁺CD25^high population was significantly higher in foals (47%) compared to their mothers (18%) and to yearlings (26%). Treg cells from foals also displayed a higher suppressive capability. Furthermore, CD4⁺CD25^high cells in foals could be induced in vitro from CD4⁺CD25⁻ cells in a significantly higher proportion compared to mares. These cells also displayed a significantly enhanced suppressive capability. In summary these findings support the notion that exposure of horses to allergens during maturation of the immune system assists the establishment of induced (i)Treg driven tolerance.

The environment of regulatory T cell biology: cytokines, metabolites, and the microbiome

Regulatory T cells (Tregs) are suppressive T cells that have an essential role in maintaining the balance between immune activation and tolerance. Their development, either in the thymus, periphery, or experimentally in vitro, and stability and function all depend on the right mix of environmental stimuli. This review focuses on the effects of cytokines, metabolites, and the microbiome on both human and mouse Treg biology. The role of cytokines secreted by innate and adaptive immune cells in directing Treg development and shaping their function is well established. New and emerging data suggest that metabolites, such as retinoic acid, and microbial products, such as short-chain fatty acids, also have a critical role in guiding the functional specialization of Tregs. Overall, the complex interaction between distinct environmental stimuli results in unique, and in some cases tissue-specific, tolerogenic environments. Understanding the conditions that favor Treg induction, accumulation, and function is critical to defining the pathophysiology of many immune-mediated diseases and to developing new therapeutic interventions.

The suppressive function of human CD8(+) iTregs is inhibited by IL-1β and TNFα

CD8(+) Tregs display an immunoregulatory activity and may play an essential role in the immunopathology of several diseases. Therefore, their therapeutic potential is exquisite and further studies on their differentiation and function are essential. The aim of this study was to evaluate the role of the innate immune system in CD8(+) iTreg differentiation and function. Naive human CD8(+) CD25(-) CD45RA(+) T cells were cultured in Treg-inducing conditions with or without IL-1β, TNFα or monocyte-derived dendritic cells (DCs). The differentiation of CD8(+) CD127(-) CD25(hi) FoxP3(hi) -induced Tregs (CD8(+) iTregs) is dependent on TGF-β1 and IL-2, which had synergistic effect upon their differentiation. CD8(+) iTregs were also induced in a coculture with allogeneic mature DCs (mDCs). The CD8(+) iTregs suppressive function was confirmed, which was diminished in the presence of IL-1β and TNFα. The IL-1β-prevented suppressive function was associated with reduced secretion of IL-10 and IFNγ, whereas the presence of TNFα did not affect their secretion. Furthermore, the presence of TNFα reduced IL-10 and TGF-β1 secretion by CD8(+) iTregs, whereas only IL-10 secretion was decreased by IL-1β. Together, these results suggest that IL-1β and TNFα prevent IL-2- and TGF-β1-driven CD8(+) iTregs suppressive function in human T cells. Such pro-inflammatory innate immune response possibly mediates its negative tolerogenic effect through reduced IFNγ-, IL-10- and TGF-β1-driven mechanism.

The protein tyrosine phosphatase PTPN22 controls forkhead box protein 3 T regulatory cell induction but is dispensable for T helper type 1 cell polarization

Protein tyrosine phosphatases (PTPs) regulate T cell receptor (TCR) signalling and thus have a role in T cell differentiation. Here we tested whether the autoimmune predisposing gene PTPN22 encoding for a PTP that inhibits TCR signalling affects the generation of forkhead box protein 3 (FoxP3)(+) T regulatory (Treg ) cells and T helper type 1 (Th1) cells. Murine CD4(+) T cells isolated from Ptpn22 knock-out (Ptpn22(KO) ) mice cultured in Treg cell polarizing conditions showed increased sensitivity to TCR activation compared to wild-type (WT) cells, and subsequently reduced FoxP3 expression at optimal-to-high levels of activation. However, at lower levels of TCR activation, Ptpn22(KO) CD4(+) T cells showed enhanced expression of FoxP3. Similar experiments in humans revealed that at optimal levels of TCR activation PTPN22 knock-down by specific oligonucleotides compromises the differentiation of naive CD4(+) T cells into Treg cells. Notably, in vivo Treg cell conversion experiments in mice showed delayed kinetic but overall increased frequency and number of Treg cells in the absence of Ptpn22. In contrast, the in vitro and in vivo generation of Th1 cells was comparable between WT and Ptpn22(KO) mice, thus suggesting PTPN22 as a FoxP3-specific regulating factor. Together, these results propose PTPN22 as a key factor in setting the proper threshold for FoxP3(+) Treg cell differentiation.

Secretion of immunoregulatory cytokines by mesenchymal stem cells

According to the minimal criteria of the International Society of Cellular Therapy, mesenchymal stem cells (MSCs) are a population of undifferentiated cells defined by their ability to adhere to plastic surfaces when cultured under standard conditions, express a certain panel of phenotypic markers and can differentiate into osteogenic, chondrogenic and adipogenic lineages when cultured in specific inducing media. In parallel with their major role as undifferentiated cell reserves, MSCs have immunomodulatory functions which are exerted by direct cell-to-cell contacts, secretion of cytokines and/or by a combination of both mechanisms. There are no convincing data about a principal difference in the profile of cytokines secreted by MSCs isolated from different tissue sources, although some papers report some quantitative but not qualitative differences in cytokine secretion. The present review focuses on the basic cytokines secreted by MSCs as described in the literature by which the MSCs exert immunodulatory effects. It should be pointed out that MSCs themselves are objects of cytokine regulation. Hypothetical mechanisms by which the MSCs exert their immunoregulatory effects are also discussed in this review. These mechanisms may either influence the target immune cells directly or indirectly by affecting the activities of predominantly dendritic cells. Chemokines are also discussed as participants in this process by recruiting cells of the immune systems and thus making them targets of immunosuppression. This review aims to present and discuss the published data and the personal experience of the authors regarding cytokines secreted by MSCs and their effects on the cells of the immune system.

Mathematical model of sarcoidosis

Sarcoidosis is a disease involving abnormal collection of inflammatory cells forming nodules, called granulomas. Such granulomas occur in the lung and the mediastinal lymph nodes, in the heart, and in other vital and nonvital organs. The origin of the disease is unknown, and there are only limited clinical data on lung tissue of patients. No current model of sarcoidosis exists. In this paper we develop a mathematical model on the dynamics of the disease in the lung and use patients' lung tissue data to validate the model. The model is used to explore potential treatments.

Low-dose interleukin-2 therapy: a driver of an imbalance between immune tolerance and autoimmunity

For many years, the role of interleukin-2 (IL-2) in autoimmune responses was established as a cytokine possessing strong pro-inflammatory activity. Studies of the past few years have changed our knowledge on IL-2 in autoimmune chronic inflammation, suggesting its protective role, when administered at low-doses. The disrupted balance between regulatory and effector T cells (Tregs and Teffs, respectively) is a characteristic of autoimmune diseases, and is dependent on homeostatic cytokines, including IL-2. Actually, inherent defects in the IL-2 signaling pathway and/or levels leading to Treg compromised function and numbers as well as Th17 expansion have been attributed to autoimmune disorders. In this review, we discuss the role of IL-2 in the pathogenesis of autoimmune diseases. In particular, we highlight the impact of the dysregulated IL-2 pathway on disruption of the Treg/Th17 balance, reversal of which appears to be a possible mechanism of the low-dose IL-2 treatment. The negative effects of IL-2 on the differentiation of follicular helper T cells (Tfh) and pathogenic Th17 cells, both of which contribute to autoimmunity, is emphasized in the paper as well. We also compare the current IL-2-based therapies of animal and human subjects with immune-mediated diseases aimed at boosting the Treg population, which is the most IL-2-dependent cell subset desirable for sufficient control of autoimmunity. New perspectives of therapeutic approaches focused on selective delivery of IL-2 to inflamed tissues, thus allowing local activity of IL-2 to be combined with its reduced systemic and pleiotropic toxicity, are also proposed in this paper.

Interleukin-2 drives immature double negative thymocytes into γδ T cells expressing Foxp3 on a stromal cell line in vitro

γδ T cells are exported from the thymus as innate-like lymphocytes that can immediately respond to antigens. In the thymus, γδ T cells diverge into functionally distinct lineages. It is not known whether γδ T cells differentiate into regulatory cells that express Foxp3, which is an essential transcription factor for CD4(+) regulatory T cells. In this study, we analyzed CD25(+) immature thymocytes that give rise to both αβ and γδ thymocytes. These precursor cells have the potential to differentiate into Foxp3(+) γδ T cells on a stromal cell line, TSt4-Dll1. Development of Foxp3(+) γδ thymocytes in this culture was dependent on IL-2. IL-2 stimulation induced Id3, Egr1, and Egr3 expression in CD25(+) immature thymocytes, suggesting that it could activate signaling molecules that are downstream of TCR signaling. The induction of Foxp3 in precursor γδ T cells suggested that IL-2 could activate the Foxp3 gene early in thymocyte development.

1α,25-dihydroxyvitamin D3 in combination with transforming growth factor-β increases the frequency of Foxp3⁺ regulatory T cells through preferential expansion and usage of interleukin-2

A high prevalence of vitamin D insufficiency and deficiency exists worldwide, which is associated with an increased incidence and severity of a range of immune-mediated diseases. This has resulted in considerable interest in the immunodulatory functions of vitamin D. The active form of vitamin D, 1α,25-dihydroxyvitamin D3 [1,25(OH)₂D3], has been shown to increase the frequency of Foxp3⁺ CD4⁺ T regulatory (Treg) cells when present at high concentrations or under strong T-cell stimulation in culture. Supporting evidence exists in vivo for a positive association between serum 25(OH)D and Foxp3⁺ Treg cell numbers in humans. The aim of this work was to identify the cytokine milieu required in vitro to promote Foxp3⁺ Treg cells in cultures containing 1,25(OH)₂D3 at more moderate concentrations (10⁻⁷ m). Stimulation of human CD4⁺ T cells with a combination of 1,25(OH)₂D3 and transforming growth factor-β (TGF-β) greatly increased the frequency of Foxp3⁺ Treg cells, which is proposed to result from the preferential expansion of Foxp3⁺ Treg cells, as compared with the Foxp3⁻ effector T cells, in culture. The differential effect on proliferation may result from enhanced availability and usage of interleukin-2 by the Foxp3⁺ Treg cells compared with Foxp3⁻ effector T cells. In summary, modulation of the cytokine environment to one high in TGF-β in the presence of 1,25(OH)₂D3 (10⁻⁷ m) significantly increased Foxp3⁺ Treg cell frequency. These data provide additional evidence for the important immunomodulatory properties of 1,25(OH)₂D3 that exist and may help to control inflammatory diseases.

Immunoevasive pericytes from human pluripotent stem cells preferentially modulate induction of allogeneic regulatory T cells

Isolated microvessel-residing pericytes and pericytes from human pluripotent stem cells (hPSCs) exhibit mesenchymal stem cell-like characteristics and therapeutic properties. Despite growing interest in pericyte-based stem cell therapy, their immunogenicity and immunomodulatory effects on nonactivated T cells are still poorly defined, in particular those of vasculogenic hPSC pericytes. We found that tissue-embedded and unstimulated cultured hPSC- or tissue-derived pericytes constitutively expressed major histocompatibility complex (MHC) class I and the inhibitory programmed cell death-ligand 1/2 (PD-L1/2) molecules but not MHC class II or CD80/CD86 costimulatory molecules. Pretreatment with inflammatory mediators failed to induce an antigen-presenting cell-like phenotype in stimulated pericytes. CD146+ pericytes from hPSCs did not induce activation and proliferation of allogeneic resting T cells independent of interferon (IFN)-γ prestimulation, similarly to pericytes from human brain or placenta. Instead, pericytes mediated a significant increase in the frequency of allogeneic CD25highFoxP3+ regulatory T cells when cocultured with nonactivated peripheral blood T cells. Furthermore, when peripheral blood CD25high regulatory T cells (Tregs) were depleted from isolated CD3+ T cells, pericytes preferentially induced de novo formation of CD4+CD25highFoxP3+CD127-, suppressive regulatory T cells. Constitutive expression of PD-L1/2 and secretion of transforming growth factor-β by hPSC pericytes directly regulated generation of pericyte-induced Tregs. Pericytes cotransplanted into immunodeficient mice with allogeneic CD25- T cells maintained a nonimmunogenic phenotype and mediated the development of functional regulatory T cells. Together, these findings reveal a novel feature of pericyte-mediated immunomodulation distinguished from immunosuppression, shared by native tissue pericytes and hPSC pericytes, and support the notion that pericytes can be applied for allogeneic cell therapy.

Review article: chemokines as orchestrators of autoimmune hepatitis and potential therapeutic targets

BACKGROUND

Chemokines contribute to the pathogenesis of autoimmune hepatitis by directing the migration and positioning of inflammatory and immune cells within the liver.

AIM

Describe the liver-infiltrating effector cell populations in autoimmune hepatitis, indicate the chemokines that influence their migration, describe the role of chemokines in hepatic fibrosis and identify chemokine-directed treatment opportunities.

METHODS

Studies cited in Pub Med from 1972 to 2014 for autoimmune hepatitis, chemokines in liver disease, pathogenesis of autoimmune hepatitis and chemokine therapy were selected.

RESULTS

T helper type 17 lymphocytes expressing CXCR3 and CCR6 are attracted to the liver by the secretion of CXCL9, CXCL10 and CXCL11. These cells recruit pro-inflammatory T helper type 1 lymphocytes expressing CXCR3 and CCR5 by secreting CXCL10. Resident natural killer T cells expressing CXCR6 migrate in response to the local secretion of CXCL16, and they modulate the inflammatory response. T helper type 2 lymphocytes expressing CCR4 are attracted by CCL17 and CCL22, and they dampen the expansion of pro-inflammatory cells. Regulatory T cells expressing CXCR3 are attracted by the secretion of CXCL9, and they help dampen the pro-inflammatory responses. CCL2, CCL3, CCL5, CXCL4, CXCL10 and CXCL16 promote fibrosis by activating or attracting hepatic stellate cells, and CX3CL1 may prevent fibrosis by affecting the apoptosis of monocytes.

CONCLUSIONS

Chemokines are requisites for mobilising, directing and positioning the effector cells in immune-mediated liver disease. They are feasible therapeutic targets in autoimmune hepatitis, and the evaluation of monoclonal antibodies that neutralise the pro-inflammatory ligands or designer peptides that block receptor activity are investigational opportunities.

Interleukin-2 and STAT5 in regulatory T cell development and function

Interleukin-2 and its downstream target STAT5 have effects on many aspects of immune function. This has been perhaps best documented in regulatory T cells. In this review we summarize the initial findings supporting a role for IL2 and STAT5 in regulatory T cell development and outline more recent studies describing how this critical signaling pathway entrains regulatory T cell differentiation and affects regulatory T cell function.

The roles of regulatory B cells in cancer

Regulatory B cells (Bregs), a newly described subset of B cells, have been proved to play a suppressive role in immune system. Bregs can inhibit other immune cells through cytokines secretion and antigen presentation, which give them the role in the pathogenesis of autoimmune diseases and cancers. There are no clear criteria to identify Bregs; different markers were used in the different experimental conditions. Massive researches had described the functions of immune cells such as regulatory T cells (Tregs), dendritic cells (DCs), and B cells in the autoimmune disorder diseases and cancers. More and more researches focused on the roles of Bregs and the cytokines such as Interleukin-10 (IL-10) and transforming growth factor beta (TGF-β) secreted by Bregs. The aim of this review is to summarize the characteristics of Bregs and the roles of Bregs in cancer.

Cord blood CD4(+)CD25(+) regulatory T cells fail to inhibit cord blood NK cell functions due to insufficient production and expression of TGF-beta1

Although CD4(+)CD25(+) Treg (Treg) cells are known to modulate NK cell functions, the modulation mechanism of these cells in cord blood has not been fully clarified. The purpose of this study was to clarify the mechanism whereby cord blood Treg cells modulate cord NK cells. By performing various cultures of purified NK cells with or without autologous Treg cells, diminished inhibitory effects of cord Treg cells towards cord NK cell functions, including activation, cytokine production, and cytotoxicity, were observed. We also observed lower secretion of sTGF-beta1 and lower expression of mTGF-beta1 by cord Treg cells than by adult Treg cells. These data revealed the capability of adult Treg cells to suppress rhIL-2-stimulated NK cell function by TGF-beta1, both membrane-bound and soluble types. The reduced inhibitory capabilities of cord Treg cells compared with adult Treg cells is thought to be due to insufficient expression of TGF-beta1.

Transforming growth factor beta (TGFβ) plays a crucial role in prolonging allograft survival in an allodepletion ("pruning") skin transplant model

Adoptive cell therapies involving cell manipulation to achieve tolerance are increasingly being studied in animal models and in human trials. We have demonstrated that the specific removal of allo-stimulated dividing cells (or "pruning") promotes long-term allograft survival across a major MHC mismatch in transplant models including skin, heart and islet transplants. In this study, we examine the role of transforming growth factor beta (TGFβ), an important regulatory cytokine, on allograft survival in our allodepletion or "pruning" skin transplant model. Increased proliferation of CD4(+) T cells was observed following allo-stimulation of BALB/c spleen cells (labeled with CFSE) in the presence of the regulatory cytokines TGFβ and (interleukin-2) IL-2 in a mixed lymphocyte culture (MLC). Expression of the regulatory gene forkhead box-3 (FoxP3) was increased in both the allo-stimulated non-dividing (ND) (CFSE(high)) and dividing (D) (CFSE(low)) CD4(+) T cell populations, with the highest expression found in the D CD4(+) T cell population. Mice reconstituted with allo-stimulated ND CD4(+) T cells following TGFβ/IL-2 stimulation showed prolonged allograft survival, similar to previous data. Significantly, TGFβ/IL-2 stimulation prevented acute rejection of allografts across a major MHC mismatch in the presence of highly activated allo-stimulated D CD4(+) T cells. Blockade of TGFβ promoted rejection of allografts even following depletion of allo-stimulated D CD4(+) T cells. These studies support a crucial role for TGFβ in the survival of allografts and shows that regulatory cytokines TGFβ/IL2 can delay the rejection of allografts, even in the presence of highly activated alloreactive T cells.

Dendritic cells decreased the concomitant expanded Tregs and Tregs related IL-35 in cytokine-induced killer cells and increased their cytotoxicity against leukemia cells

Regulatory T cells (Tregs) are potent immunosuppressive cells and essential for inducing immune tolerance. Recent studies have reported that Tregs and Tregs related cytokines can inhibit the antitumor activity of cytokine-induced killer (CIK) cells, but dendritic cells co-cultured CIK (DC-CIK) cells can be used for induction of a specific immune response by blocking of Tregs and TGF-β, IL-10. As a novel identified cytokine, IL-35 is specially produced by Tregs and plays an essential role in immune regulation. However, it remains unknown whether IL-35 roles in tumor immunotherapy mediated by CIK and DC-CIK cells. In this study, we cultured CIK and DC-CIK cells from the same healthy adult samples, and investigated their phenotype, proliferation, cytotoxic activity against leukemia cell lines K562 and NB4 by FCM and CCK-8, measured IL-35, TGF-β and IL-10 protein by ELISA, detected Foxp3, IL-35 and IL-35 receptor mRNA by Real-time PCR, respectively. We found Tregs and IL-35 concomitantly expanded by a time-dependent way during the generation of CIK cells, but DC significantly down-regulated the expression of them and simultaneously up-regulated the proliferation ability as well as cytotoxic activity of CIK cells against leukemia cell lines. Therefore, our data suggested that DC decreased concomitant expanded Tregs and Tregs related IL-35 in CIK cells and might contribute to improve their cytotoxicity against leukemia cells in vitro.

Vaccination strategies for Parkinson disease: induction of a swift attack or raising tolerance?

Parkinson disease is the second most common neurodegenerative disease in the world, but there is currently no available cure for it. Current treatments only alleviate some of the symptoms for a few years, but they become ineffective in the long run and do not stop the disease. Therefore it is of outmost importance to develop therapeutic strategies that can prevent, stop, or cure Parkinson disease. A very promising target for these therapies is the peripheral immune system due to its probable involvement in the disease and its potential as a tool to modulate neuroinflammation. But for such strategies to be successful, we need to understand the particular state of the peripheral immune system during Parkinson disease in order to avoid its weaknesses. In this review we examine the available data regarding how dopamine regulates the peripheral immune system and how this regulation is affected in Parkinson disease; the specific cytokine profiles observed during disease progression and the alterations documented to date in patients' peripheral blood mononuclear cells. We also review the different strategies used in Parkinson disease animal models to modulate the adaptive immune response to salvage dopaminergic neurons from cell death. After analyzing the evidence, we hypothesize the need to prime the immune system to restore natural tolerance against α-synuclein in Parkinson disease, including at the same time B and T cells, so that T cells can reprogram microglia activation to a beneficial pattern and B cell/IgG can help neurons cope with the pathological forms of α-synuclein.

Therapeutic potential of regulatory T cells in autoimmune disorders

Regulatory T cells (Tregs) play a dominant role in the regulation of immune responses. Quantitative and/or qualitative abnormalities of Tregs were observed in patients with autoimmune diseases and therapeutic interventions focusing Tregs are an attractive new target with the potential to cure these disorders. Biological agents approved for treatment of inflammatory rheumatic diseases transiently influence Treg prevalences and function and experimental therapies including novel biological agents, gene therapy, activation and ex vivo expansion of purified Tregs as well as substances influencing tolerogenic dendritic cells will be developed for selective Treg therapy. Although many of these interventions are effective in vitro, in animal models as well as in early clinical trials, significant concerns exist regarding the stability of Treg modifications as well as the long-term safety of Treg-based therapies.

Targeting regulatory T cells in cytokine-induced killer cell cultures (Review)

Regulatory T cells (Tregs) are potent immunosuppressive cells that promote tumor growth and invasion by inducing immune escape and suppressing the antitumor immune response. Cytokine-induced killer (CIK) cells are considered to be the primary candidate for adoptive immunotherapy due to their strong antitumor activity. It was recently reported that the concomitant presence of Tregs may decrease the cytotoxicity of CIK cells. Therefore, depletion or downregulation of Tregs in CIK cell cultures by optimizing the culture program may enhance CIK cell cytotoxicity in vitro and in vivo. The aim of the present review was to summarize the currently available studies on the optimal culture strategy for improving the antitumor activity of CIK cells through targeting Tregs.

Prevention of allogeneic cardiac graft rejection by transfer of ex vivo expanded antigen-specific regulatory T-cells

The rate of graft survival has dramatically increased using calcineurin inhibitors, however chronic graft rejection and risk of infection are difficult to manage. Induction of allograft-specific regulatory T-cells (Tregs) is considered an ideal way to achieve long-term tolerance for allografts. However, efficient in vitro methods for developing allograft-specific Tregs which is applicable to MHC full-mismatched cardiac transplant models have not been established. We compared antigen-nonspecific polyclonal-induced Tregs (iTregs) as well as antigen-specific iTregs and thymus-derived Tregs (nTregs) that were expanded via direct and indirect pathways. We found that iTregs induced via the indirect pathway had the greatest ability to prolong graft survival and suppress angiitis. Antigen-specific iTregs generated ex vivo via both direct and indirect pathways using dendritic cells from F1 mice also induced long-term engraftment without using MHC peptides. In antigen-specific Treg transferred models, activation of dendritic cells and allograft-specific CTL generation were suppressed. The present study demonstrated the potential of ex vivo antigen-specific Treg expansion for clinical cell-based therapeutic approaches to induce lifelong immunological tolerance for allogeneic cardiac transplants.

Phenotypic and functional characteristic of a newly identified CD8+ Foxp3- CD103+ regulatory T cells

TGF-β and Foxp3 expressions are crucial for the induction and functional activity of CD4(+)Foxp3(+) regulatory T (iTreg) cells. Here, we demonstrate that although TGF-β-primed CD8(+) cells display much lower Foxp3 expression, their suppressive capacity is equivalent to that of CD4(+) iTreg cells, and both Foxp3(-) and Foxp3(+) CD8+ subsets have suppressive activities in vitro and in vivo. CD8(+)Foxp3(-) iTreg cells produce little IFN-γ but almost no IL-2, and display a typical anergic phenotype. Among phenotypic markers expressed in CD8(+)Foxp3(-) cells, we identify CD103 expression particularly crucial for the generation and function of this subset. Moreover, IL-10 and TGF-β signals rather than cytotoxicity mediate the suppressive effect of this novel Treg population. Therefore, TGF-β can induce both CD8(+)Foxp3(-) and CD8(+)Foxp3(+) iTreg subsets, which may represent the unique immunoregulatory means to treat autoimmune and inflammatory diseases.

Tumor-induced perturbations of cytokines and immune cell networks

Until recently, the intrinsically high level of cross-talk between immune cells, the complexity of immune cell development, and the pleiotropic nature of cytokine signaling have hampered progress in understanding the mechanisms of immunosuppression by which tumor cells circumvent native and adaptive immune responses. One technology that has helped to shed light on this complex signaling network is the cytokine antibody array, which facilitates simultaneous screening of dozens to hundreds of secreted signal proteins in complex biological samples. The combined applications of traditional methods of molecular and cell biology with the high-content, high-throughput screening capabilities of cytokine antibody arrays and other multiplexed immunoassays have revealed a complex mechanism that involves multiple cytokine signals contributed not just by tumor cells but by stromal cells and a wide spectrum of immune cell types. This review will summarize the interactions among cancerous and immune cell types, as well as the key cytokine signals that are required for tumors to survive immunoediting in a dormant state or to grow and spread by escaping it. Additionally, it will present examples of how probing secreted cell-cell signal networks in the tumor microenvironment (TME) with cytokine screens have contributed to our current understanding of these processes and discuss the implications of this understanding to antitumor therapies.

Regulatory T-cell differentiation and their function in immune regulation

Regulatory T-cells (Treg) represent a subset of CD4+ T-cells characterized by high suppressive capacity, which can be generated in the thymus or induced in the periphery. The deleterious phenotype of the Scurfy mouse, which develops an X-linked lymphoproliferative disease resulting from defective T-cell tolerance, clearly demonstrates the importance of Treg cells for the maintenance of immune homeostasis. Although significant progress has been achieved, much information regarding the development, characteristics and function of Treg cells remain lacking. This chapter highlights the most recent discoveries in the field of Treg biology, focusing on the development and role of this cell subset in the maintenance of immune balance.

The multifaceted role of Th17 lymphocytes and their associated cytokines in cancer

While the role of T helper 17 lymphocytes (Th17) in the pathogenesis of autoimmune diseases and in infectious immunity has been relatively well defined, the impact of these cells and their associated cytokines on cancer development is still under debate. Although multiple reports have indicated that Th17 can promote anticancer immunity, others have argued that these cells may exhibit tumor-promoting properties. This dichotomy in the function of Th17 lymphocytes in cancer may be related to the versatile nature of these cells, being capable of differentiating into either proinflammatory Th1 or suppressive FoxP3-expressing Treg cells or hybrid T cell subsets depending on the underlying environmental conditions. In the current review, we examine the role of Th17 lymphocytes and Th17-associated cytokines in cancer and discuss how factors that control their final lineage commitment decision may influence the balance between their tumor-promoting versus tumor-suppressing properties.

The function of BAFF on T helper cells in autoimmunity

B cell-activating factor belonging to the TNF family (BAFF) exerts its pathogenic role in supporting the survival and proliferation of B cells, regulating class switch recombination as well as the selection of autoreactive B cells. Overexpression of BAFF induces a dramatic expansion of activated B cells, particularly marginal zone B cells, as well as hypergammaglobulinemia, autoantibody production and immune complex deposition. However, in addition to its effect on B cells, recent work has also demonstrated that BAFF can promote T cell activation, proliferation and differentiation. In this review, we have discussed the recent progress on the function and role of BAFF on T cells and T cell-mediated diseases.

Regulation of interferon gamma signaling by suppressors of cytokine signaling and regulatory T cells

Regulatory T cells (Tregs) play an indispensable role in the prevention of autoimmune disease, as interferon gamma (IFNγ) mediated, lethal auto-immunity occurs (in both mice and humans) in their absence. In addition, Tregs have been implicated in preventing the onset of autoimmune and auto-inflammatory conditions associated with aberrant IFNγ signaling such as type 1 diabetes, lupus, and lipopolysaccharide (LPS) mediated endotoxemia. Notably, suppressor of cytokine signaling-1 deficient (SOCS1^−/−) mice also succumb to a lethal auto-inflammatory disease, dominated by excessive IFNγ signaling and bearing similar disease course kinetics to Treg deficient mice. Moreover SOCS1 deficiency has been implicated in lupus progression, and increased susceptibility to LPS mediated endotoxemia. Although it has been established that Tregs and SOCS1 play a critical role in the regulation of IFNγ signaling, and the prevention of lethal auto-inflammatory disease, the role of Treg/SOCS1 cross-talk in the regulation of IFNγ signaling has been essentially unexplored. This is especially pertinent as recent publications have implicated a role of SOCS1 in the stability of peripheral Tregs. This review will examine the emerging research findings implicating a critical role of the intersection of the SOCS1 and Treg regulatory pathways in the control of IFN gamma signaling and immune system function.

Mathematical Models of the Impact of IL2 Modulation Therapies on T Cell Dynamics

Several reports in the literature have drawn a complex picture of the effect of treatments aiming to modulate IL2 activity in vivo. They seem to promote either immunity or tolerance, probably depending on the specific context, dose, and timing of their application. Such complexity might derive from the pleiotropic role of IL2 in T cell dynamics. To theoretically address the latter possibility, our group has developed several mathematical models for Helper, Regulatory, and Memory T cell population dynamics, which account for most well-known facts concerning their relationship with IL2. We have simulated the effect of several types of therapies, including the injection of: IL2; antibodies anti-IL2; IL2/anti-IL2 immune-complexes; and mutant variants of IL2. We studied the qualitative and quantitative conditions of dose and timing for these treatments which allow them to potentiate either immunity or tolerance. Our results provide reasonable explanations for the existent pre-clinical and clinical data, predict some novel treatments, and further provide interesting practical guidelines to optimize the future application of these types of treatments.

TGF-β activation and function in immunity

The cytokine TGF-β plays an integral role in regulating immune responses. TGF-β has pleiotropic effects on adaptive immunity, especially in the regulation of effector and regulatory CD4(+) T cell responses. Many immune and nonimmune cells can produce TGF-β, but it is always produced as an inactive complex that must be activated to exert functional effects. Thus, activation of latent TGF-β provides a crucial layer of regulation that controls TGF-β function. In this review, we highlight some of the important functional roles for TGF-β in immunity, focusing on its context-specific roles in either dampening or promoting T cell responses. We also describe how activation of TGF-β controls its function in the immune system, with a focus on the key roles for members of the integrin family in this process.

The IL-2/IL-2R system: from basic science to therapeutic applications to enhance immune regulation

IL-2 plays a critical role in the normal function of the immune system. A trophic factor for lymphocytes, IL-2 is required for mounting and sustaining adaptive T cell responses; however, IL-2 is also critical for immune regulation via its effects on regulatory T cells (Treg cells). Over the years, we have contributed to the understanding of the biology of IL-2 and its signaling through the IL-2 receptor and helped define the key role played by IL-2 in Treg development and function. Our data show that Treg cells have a heightened sensitivity to IL-2, which may create a therapeutic window to promote immune regulation by selective stimulation of Treg cells. We are now developing new efforts to translate this knowledge to the clinical arena, through our focused interest in Type 1 diabetes as a prototypic autoimmune disease. Specifically, we aim at developing IL-2-based therapeutic regimens and incorporate means to enhance antigen-specific Treg responses, for improved and more selective regulation of islet autoimmunity. In parallel, we are pursuing studies in preclinical models of autoimmunity and transplantation to define critical factors for successful adoptive Treg therapy and develop clinically applicable therapeutic protocols.

The imbalance between regulatory and IL-17-secreting CD4⁺T cells in multiple-trauma rat

BACKGROUND

It has been well recognised that a deficit of numbers and function of CD4(+)CD25(+)Foxp3(+)cells (Treg) is attributed to the development of auto-immune diseases, inflammatory diseases, tumour and rejection of transplanted tissue; however, there are controversial data regarding the suppressive effect of Treg cells on the T-cell response in auto-immune diseases. Additionally, interleukin-17 (IL-17)-producing cells (Th17) have a pro-inflammatory role. The balance between Th17 and Treg may be essential for maintaining immune homeostasis and has long been thought as one of the important factors in the development/prevention of auto-immune diseases, inflammatory diseases, tumour and rejection of transplanted tissue, but their role in multiple trauma remains unclear.

OBJECTIVE

This study aims to investigate whether an imbalance of Treg and Th17 effector cells is characteristic of rats suffering from multiple trauma.

METHODS AND SUBJECTIVE

Sixty Sprague-Dawley (SD) rats were randomly divided into three groups. The control group (n=20, group I) no received procedures (normal). The sham group (n=20, group II) only received anaesthesia, cannulation and observation. The bilateral femoral shaft fractures with haemorrhagic shock groups (n=20, group III). Rats in groups II and III were killed at the end of 4h after models were established. Peripheral blood samples were collected for assessment of Treg cells, Th17 cells and cytokines (IL-17, IL-6, IL-2, transforming growth factor beta (TGF-β)) and intestine tissue was collected for intestine histological analysis.

RESULTS

We observed decreased Treg/Th17 ratios in CD4(+)T cells in rats with multiple trauma and a strong inverse correlation with disease activity (intestinal histological scores).

CONCLUSION

We suggest a role for immune imbalance in the pathogenesis and development of multiple trauma. The alteration of the index of Treg/Th17 cells likely indicates the therapeutic response and progress in the clinic.

Water-soluble undenatured type II collagen ameliorates collagen-induced arthritis in mice

Earlier studies have reported the efficacy of type II collagen (C II) in treating rheumatoid arthritis (RA). However, a few studies have investigated the ability of the antigenic collagen to induce oral tolerance, which is defined as active nonresponse to an orally administered antigen. We hypothesized that water-soluble undenatured C II had a similar effect as C II in RA. The present study was designed to examine the oral administration of a novel, water-soluble, undenatured C II (commercially known as NEXT-II) on collagen-induced arthritis (CIA) in mice. In addition, the underlying mechanism of NEXT-II was also identified. After a booster dose (collagen-Freund's complete adjuvant), mice were assigned to control CIA group, or NEXT-II treatment group, to which saline and NEXT-II were administered, respectively. The arthritis index in the NEXT-II group was significantly lower compared with the CIA group. Serum IL-6 levels in the NEXT-II group were significantly lower compared with the CIA group, while serum IL-2 level was higher. Furthermore, oral administration of NEXT-II enhanced the proportion of CD4+CD25+T (Treg) cells, and gene expressions of stimulated dendritic cells induced markers for regulatory T cells such as forkhead box p3 (Foxp3), transforming growth factor (TGF)-β1, and CD25. These results demonstrated that orally administered water-soluble undenatured C II (NEXT-II) is highly efficacious in the suppression of CIA by inducing CD4+CD25+ Treg cells.

Pneumococcal components induce regulatory T cells that attenuate the development of allergic airways disease by deviating and suppressing the immune response to allergen

The induction of regulatory T cells (Tregs) to suppress aberrant inflammation and immunity has potential as a therapeutic strategy for asthma. Recently, we identified key immunoregulatory components of Streptococcus pneumoniae, type 3 polysaccharide and pneumolysoid (T+P), which suppress allergic airways disease (AAD) in mouse models of asthma. To elucidate the mechanisms of suppression, we have now performed a thorough examination of the role of Tregs. BALB/c mice were sensitized to OVA (day 0) i.p. and challenged intranasal (12-15 d later) to induce AAD. T+P was administered intratracheally at the time of sensitization in three doses (0, 12, and 24 h). T+P treatment induced an early (36 h-4 d) expansion of Tregs in the mediastinal lymph nodes, and later (12-16 d) increases in these cells in the lungs, compared with untreated allergic controls. Anti-CD25 treatment showed that Treg-priming events involving CD25, CCR7, IL-2, and TGF-β were required for the suppression of AAD. During AAD, T+P-induced Tregs in the lungs displayed a highly suppressive phenotype and had an increased functional capacity. T+P also blocked the induction of IL-6 to prevent the Th17 response, attenuated the expression of the costimulatory molecule CD86 on myeloid dendritic cells (DCs), and reduced the number of DCs carrying OVA in the lung and mediastinal lymph nodes. Therefore, bacterial components (T+P) drive the differentiation of highly suppressive Tregs, which suppress the Th2 response, prevent the Th17 response and disable the DC response resulting in the effective suppression of AAD.