Specialization in tolerance: innate CD(4+)CD(25+) versus acquired TR1 and TH3 regulatory T cells

Artesunate targets cellular metabolism to regulate the Th17/Treg cell balance

INTRODUCTION

Metabolic reprogramming is one of the important mechanisms of cell differentiation, and different cells have different preferences for energy sources. During the differentiation of naive CD4 + T cells into Th17 and Treg cells, these cells show specific energy metabolism characteristics. Th17 cells depend on enhanced glycolysis, fatty acid synthesis, and glutaminolysis. In contrast, Treg cells are dependent on oxidative phosphorylation, fatty acid oxidation, and amino acid depletion. As a potent antimalarial drug, artesunate has been shown to modulate the Th17/Treg imbalance and regulate cell metabolism.

METHODOLOGY

Relevant literatures on ART, cellular metabolism, glycolysis, lipid metabolism, amino acid metabolism, CD4 + T cells, Th17 cells, and Treg cells published from January 1, 2010 to now were searched in PubMed database.

CONCLUSION

In this review, we will highlight recent advances in which artesunate can restore the Th17/Treg imbalance in disease states by altering T-cell metabolism to influence differentiation and lineage selection. Data from the current study show that few studies have focused on the effect of ART on cellular metabolism. ART can affect the metabolic characteristics of T cells (glycolysis, lipid metabolism, and amino acid metabolism) and interfere with their differentiation lineage, thereby regulating the balance of Th17/Treg and alleviating the symptoms of the disease.

Critical appraisal of the clinical utility of sublingual immunotherapy in allergy

Since it was introduced by Noon in 1911, allergen-specific immunotherapy or desensitization has been widely prescribed in the management of allergic diseases. Aimed at the etiology, it represents the only effective treatment for allergy. The basic mechanisms of immunotherapy are becoming better understood and allow us to improve this technique in the future. The sublingual immunotherapy as an alternative to subcutaneous route has been widely studied. Several clinical trials confirmed that sublingual immunotherapy is efficient in reducing allergic respiratory symptoms. The sublingual immunotherapy reduces the risk of developing serious side effects due to desensitization. We performed a literature review in order to remind the mechanisms of action and to demonstrate efficacy and tolerability of the sublingual immunotherapy in the treatment of allergic rhinoconjunctivitis and asthma and its impact on the quality of life.

Immune Dysregulation in Patients Persistently Infected with Human Papillomaviruses 6 and 11

Human Papillomaviruses (HPVs) 6 and 11 are part of a large family of small DNA viruses, some of which are commensal. Although much of the population can contain or clear infection with these viruses, there is a subset of individuals who develop persistent infection that can cause significant morbidity and on occasion mortality. Depending on the site of infection, patients chronically infected with these viruses develop either recurrent, and on occasion, severe genital warts or recurrent respiratory papillomas that can obstruct the upper airway. The HPV-induced diseases described are likely the result of a complex and localized immune suppressive milieu that is characteristic of patients with persistent HPV infection. We review data that documents impaired Langerhans cell responses and maturation, describes the polarized adaptive T-cell immune responses made to these viruses, and the expression of class select II MHC and KIR genes that associate with severe HPV6 and 11 induced disease. Finally, we review evidence that documents the polarization of functional T_H2 and T-regulatory T-cells in tissues persistently infected with HPV6 and 11, and we review evidence that there is suppression of natural killer cell function. Together, these altered innate and adaptive immune responses contribute to the cellular and humoral microenvironment that supports HPV 6 and 11-induced disease.

Efficacy of telbivudine in the treatment of chronic hepatitis b and liver cirrhosis and its effect on immunological responses

This study was aimed to evaluate the long-term effects of telbivudine (LdT) in the treatment of chronic hepatitis B (CHB) and HBV-related liver cirrhosis (LC) and to observe the changes of immunological responses during LdT treatment. Clinical data of 80 CHB and 28 HBV-related LC patients who were administered with LdT for 108 weeks and followed up were retrospectively analyzed. The liver function indicators including ALT, AST and γ-GT, HBV DNA copy number in serum and the rates of hepatitis B e antigen (HBeAg) seroconversion were analyzed before and 12, 24, 36, 48, 60, 72, 84, 96 and 108 weeks after LdT treatment in CHB and LC groups. Four serum fibrosis-related markers, including hyaluronic acid (HA), human laminin (LN), human type IV collagen (IV-C) and human N-terminal procollagen III peptide (PC-III), were detected before and after LdT treatment in LC group. The results showed favorable viral suppression and biochemical responses after treatment with LdT for 12 weeks, and a high rate of virological and biochemical control was maintained during the course of 108-week treatment in both CHB and LC groups. The four fibrosis-related markers, especially HA and LN, were down-regulated to some degrees in LC group. Moreover, LdT treatment led to the fluctuation of the circulating interferon-γ (IFN-γ) and interleukin-10 (IL-10) levels at different time points in CHB group. It was concluded that LdT could favorably lead to the virological suppression and biochemical remission. Besides, IFN-γ and IL-10 may represent a suitable and effective predictor of responsiveness during LdT therapy.

Phenotype alterations in regulatory T-cell subsets in primary HIV infection and identification of Tr1-like cells as the main interleukin 10-producing CD4+ T cells

BACKGROUND

Conventional regulatory T cells (Tregs) can suppress human immunodeficiency virus type 1 (HIV-1)-specific immune responses but cannot control immune activation in primary HIV infection. Here, we characterized Treg subsets, using recently defined phenotypic delineation, and analyzed the relative contribution of cell subsets to the production of immunosuppressive cytokines in primary HIV infection.

METHODS

In a longitudinal prospective study, ex vivo phenotyping of fresh peripheral blood mononuclear cells from patients with primary HIV infection was performed at baseline and month 6 of follow-up to characterize Treg subsets, immune activation, and cytokine production in isolated CD4(+) T cells.

RESULTS

The frequency of CD4(+)CD25(+)CD127(low) Tregs and the distribution between the naive, memory, and activated/memory Treg subsets was similar in patients and healthy donors. However, Tregs from patients with primary HIV infection showed peculiar phenotypic profiles, such as elevated FoxP3, ICOS, and CTLA-4 expression, with CTLA-4 expression strikingly increased in all Treg subsets both at baseline and month 6 of follow-up. The great majority of interleukin 10 (IL-10)-producing CD4(+) T cells were FoxP3(neg) (ie, Tr1-like cells). In contrast to conventional Tregs, Tr1-like cells were inversely correlated with immune activation and not associated with lower effector T-cell responses.

CONCLUSION

FoxP3(neg) Tr1-like cells-major contributors to IL-10 production-may have a beneficial role by controlling immune activation in early HIV infection.

Liver type I regulatory T cells suppress germinal center formation in HBV-tolerant mice

The liver plays a critical role in inducing systemic immune tolerance, for example, during limiting hypersensitivity to food allergy and in rendering acceptance of allotransplant or even hepatotropic pathogens. We investigated the unknown mechanisms of liver tolerance by using an established hepatitis B virus (HBV)-carrier mouse model, and found that these mice exhibited an antigen-specific tolerance toward peripheral HBsAg vaccination, showing unenlarged draining lymph node (DLN), lower number of germinal centers (GC), and inactivation of GC B cells and follicular T helper (Tfh) cells. Both in vivo and in vitro immune responses toward HBsAg were suppressed by mononuclear cells from HBV-carrier mice, which were CD4(+) Foxp3(-) type 1 regulatory T (Tr1)-like cells producing IL-10. Using recipient Rag1(-/-) mice, hepatic Tr1-like cells from day 7 of HBV-persistent mice acquired the ability to inhibit anti-HBV immunity 3 d earlier than splenic Tr1-like cells, implying that hepatic Tr1-like cells were generated before those in spleen. Kupffer cell depletion or IL-10 deficiency led to impairment of Tr1-like cell generation, along with breaking HBV persistence. The purified EGFP(+)CD4(+) T cells (containing Tr1-like cells) from HBV-carrier mice trafficked in higher numbers to DLN in recipient mice after HBsAg vaccination, and subsequently inactivated both Tfh cells and GC B cells via secreting IL-10, resulting in impaired GC formation and anti-HB antibody production. Thus, our results indicate Tr1-like cells migrate from the liver to the DLN and inhibit peripheral anti-HBV immunity by negatively regulating GC B cells and Tfh cells.

Characterization of the immune response in human paracoccidioidomycosis

OBJECTIVES

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the dimorphic fungus Paracoccidioides brasiliensis that presents two main clinical forms: the adult form (AF) and the juvenile form (JF); and an asymptomatic form denominated PCM-infection (PI). These forms of PCM are related to the immune response developed after infection, which has been associated with Th1 and Th2 responses. However, some PCM characteristics cannot be explained by this balance. In this study we aimed to complement the characterization of the immune response in PCM, including the newly described T cells subpopulations (Th17, Th9 and Th22).

METHODS

We analyzed the expression of cytokines and transcription factors characteristics of these different subpopulations of CD4(+) T cells in PBMCs from PCM patients and a PI group.

RESULTS

The results showed that the PI group presented a predominant Th1 response; that JF patients were characterized by a mixed Th2/Th9 response; and AF patients were characterized by a predominant Th17/Th22 response, as well as substantial participation of Th1 cells.

CONCLUSIONS

These results contribute to the existing knowledge on the immune responses associated with resistance or susceptibility to the P. brasiliensis infection, and thus could lead to the development of new strategies for patient management.

Jacalin regulates IgA production by peripheral blood mononuclear cells

AIMS

In IgA nephropathy, circulating immune complexes containing IgA1 are deposited on the glomerular mesangium, causing mesangial cell proliferation and acceleration of extracellular matrix production. The suppressive effect of jacalin, a galactose-binding lectin, on IgA production in vitro was determined.

MATERIALS & METHODS

Normal human peripheral blood mononuclear cells were stimulated with plate-bound anti-CD3 and Th2 stimulation, with or without jacalin. Regulatory and effector cell subsets were determined by flow cytometry, and immunoglobulin production by ELISA.

RESULTS

Jacalin increased the ratio of CD4(+)CD25(+)CD152(+) Tregs:effector T cells in peripheral blood mononuclear cell cultures 60-fold. This CD4(+)CD25(+)CD152(+) Treg increase may have inhibited Th2-stimulated IgA production by B cells.

CONCLUSION

Immune tolerance induced by jacalin can suppress IgA production.

Heat shock proteins and regulatory T cells

Heat shock proteins (HSPs) are important molecules required for ideal protein function. Extensive research on the functional properties of HSPs indicates that HSPs may be implicated in a wide range of physiological functions including immune function. In the immune system, HSPs are involved in cell proliferation, differentiation, cytokine release, and apoptosis. Therefore, the ability of the immune system, in particular immune cells, to function optimally and in unison with other physiological systems is in part dependent on signaling transduction processes, including bidirectional communication with HSPs. Regulatory T cells (Tregs) are important T cells with suppressive functions and impairments in their function have been associated with a number of autoimmune disorders. The purpose of this paper is to examine the relationship between HSPs and Tregs. The interrelationship between cells and proteins may be important in cellular functions necessary for cell survival and expansion during diseased state.

Effects of telbivudine treatment on the circulating CD4⁺ T-cell subpopulations in chronic hepatitis B patients

CD4⁺ T cells serve as master regulators of the adaptive immune response to HBV. However, CD4⁺ T-cell subsets are heterogeneous, and it remains unknown how the antiviral agents affect the different CD4⁺ T cell subtypes. To this end, the expressions of signature transcription factors and cytokines of CD4⁺ T-cell subtypes were examined in hepatitis B patients before and after treatment with telbivudine. Results showed that, upon the rapid HBV copy decrease induced by telbivudine treatment, the frequencies and related cytokines of Th17 and Treg cells were dramatically decreased, while those for Th2 cells were dramatically increased. No obvious changes were observed in Th1 cell frequencies; although, IFN-γ expression was upregulated in response to telbivudine treatment, suggesting another cell source of IFN-γ in CHB patients. Statistical analyses indicated that Th17 and Tr1 (a Treg subtype) cells were the most sensitive subpopulations of the peripheral blood CD4⁺ T cells to telbivudine treatment over 52 weeks. Thus, Th17 and Tr1 cells may represent a suitable and effective predictor of responsiveness during telbivudine therapy. These findings not only improve our understanding of hepatitis pathogenesis but also can aid in future development of appropriate therapeutic strategies to control viral hepatitis.

B7-H4 induces donor-specific tolerance in mouse islet allografts

Negative cosignaling molecules play an important role in regulating T-cell responses to alloantigen stimulation. We recently reported that adenoviral-mediated transduction of islet allografts with B7-H4 inhibits allograft rejection. In this study, we investigate the mechanism for B7-H4-induced prolongation of mouse islet allograft survival. Streptozotocin-induced diabetic C57BL/6 mice were rendered normoglycemic by renal subcapsular implants of B7-H4-transduced BALB/c islets. Grafts and spleens were removed after days 2, 10, and 60 (n = 8 each) for characterization of kinetics of Foxp3 and interleukin 10 (IL-10) expression. Mixed lymphocyte reaction (MLR) was done at day 60. Ten mice were subjected to nephrectomy at 60 days and then five were implanted with secondary BALB/c islets and five were given third-party CBA/J islets. An increase in Foxp3 and IL-10 mRNA expression was detected in recipients' spleens at day 60 and this was associated with increased quantities of Foxp3(+) cells. Splenocytes at day 60 showed hyporesponsiveness during MLR to alloantigen stimulation. Proliferation was partially restored after CD25(+) T-cell depletion. Secondary BALB/c islets survived for 79 ± 29 days compared with 21 ± 3.6 days for CBA/J islets (p < 0.001). Local expression of B7-H4 induces long-term unresponsiveness to donor-specific alloantigens, and is associated with T regulatory cells, suggesting the development of tolerance.

Early acceptance of renal allografts in mice is dependent on foxp3(+) cells

Mouse renal allografts have a remarkable ability to promote acceptance across full major histocompatibility complex incompatibilities in certain strain combinations without immunosuppression. The mechanism is unknown but is believed to involve immunoregulation. This study tests whether Foxp3(+) T-regulatory cells are responsible in the early phase of graft acceptance, using B6.Foxp3(DTR) mice that express diphtheria toxin receptor (DTR) in Foxp3(+) cells. The administration of DT to B6.Foxp3(DTR) recipients with accepted DBA/2 kidneys, 3 weeks to 3 months after transplantation, caused a marked depletion of Foxp3 cells and triggered acute cellular rejection, manifested by a sudden increase in blood urea nitrogen within a week. None of the controls showed an increase in blood urea nitrogen, including DT-treated B6 wild-type recipients of DBA/2 kidneys or B6.Foxp3(DTR) recipients of isografts. Accepted DBA/2 allografts showed prominent lymphoid sheaths around arteries containing numerous CD3(+)Foxp3(+) cells, CD4(+) cells, dedritic cells, and B cells, which was independent of CCR4. The lymphoid sheaths disintegrate after Foxp3 depletion, accompanied by widespread CD8 interstitial mononuclear inflammation, tubulitis, and endarteritis. The Foxp3 depletion caused an increased frequency of donor-reactive cells in the spleen by interferon (IFN) γ enzyme-linked immunosorbent spot (ELISPOT) assays and increased expression of the maturation markers, CD86 and IA(b), on dendritic cells in the spleen and kidney. We conclude that Foxp3(+) cells are needed to maintain acceptance of major histocompatibility complex-incompatible renal allografts in the first 3 months after transplantation and may act by inhibiting DC maturation.

Blocking costimulatory pathways: prospects for inducing transplantation tolerance

Tolerance induction to alloantigens is a major challenge in transplant immunology. Whereas conventional immunosuppression inhibits the immune system in a nonspecific way, thereby also undermining an appropriate immune response towards potentially harmful infectious organisms, tolerance in a transplantation setting is restricted to alloantigens, while protective immunity is preserved. Moreover, tolerance implies an immunological status that is preserved after withdrawal of the tolerance-inducing therapy. Among the most promising strategies to induce immunological tolerance are costimulation blockade and establishment of mixed chimerism. Despite significant advances, we still know little about the mechanisms responsible for such tolerance. In this article, we discuss tolerance induction to transplantation antigens by costimulation blockade.

Suppression of allogeneic T cells proliferation by CD3/CD46-induced T-regulatory 1 cells

CD46 is not only identified as a complement regulatory protein which protects host cells from complement attack, but also a new co-stimulatory molecule for human T cells. CD3/CD46 co-stimulation can induce a T-regulatory 1 cell (Tr1)-specific cytokine phenotype in human CD4+ T cells. However, the role of CD46 as a co-stimulatory molecule in the modulation of the acquired immunity, such as transplant immunology, remains unclear. In this study, CD4+ T cells were isolated from human CD46-transgenic C57BL/6 mice by magnetic-activated cell sorting, and further induced by anti-CD3, anti-CD28 and anti-CD46 antibodies respectively, and anti-CD3/anti-CD28 antibodies, anti-CD3/anti-CD46 antibodies, or the monoclonal antibody panel against CD3/CD28/CD46. The levels of interleukin-2 (IL-2), gamma-interferon (gamma-IFN), interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) were detected in the supernatants of different groups. Suppression of allogeneic T cell proliferation were assessed by using mixed lymphocyte reaction (MLR) assay, in which monoclonal antibodies against CD46 were added to the culture. The results showed that CD3/CD28, CD3/CD46 and CD3/CD28/CD46 co-stimulation could significantly induce stronger proliferation of T cells than CD3 stimulation (P<0.05), and CD3/CD28/CD46 co-stimulation significantly increased the proliferation of T cells when compared with CD3/CD28 or CD3/CD46 co-stimulation (P<0.05 for each). IL-2 and gamma-IFN levels were much higher in CD3/CD28 co-stimulation group than in CD3, CD28, CD46 and CD3/CD46 groups (P<0.05 for each). IL-10 and TGF-beta levels were dramatically increased in CD3/CD46 co-stimulation group as compared with those in the CD3, CD28, CD46 and CD3/CD28 groups (P<0.05 for each). CD3/CD46 co-stimulation significantly inhibited the T cell proliferation and allogenic immune responses through the secretion of IL-10 and TGF-beta in MLR (P<0.05). These results suggested that CD3/CD46 can induce Tr1 cells to modulate allogenic immune responses, and it may become a novel target for the development of new therapeutic approach for T-cell-mediated diseases. CD46 plays an important role in regulating the T cell-mediated immune responses by bridging innate and acquired immunity.

Innate profiles of cytokines implicated on oral tolerance correlate with low- or high-suppression of humoral response

SUMMARY

Oral tolerance (OT) is being studied with great interest because of its therapeutic potential in allergy and autoimmunity. In the present study, two mouse strains with extreme phenotypes of OT susceptibility (TS) or resistance (TR) to ovalbumin (OVA) were used to demonstrate whether the tr and ts genes, cumulated during 18 generations of bi-directional genetic selection, influence expression of immunobiological traits in naive or antigen-gavaged TR/TS mice. The difference in anti-OVA titres was 2048-fold between OVA-gavaged TS and TR mice. Tolerance susceptibility to OVA gavage in individuals from a (TS x TR)F(2) population was 24% high-susceptibility, 62% low-susceptibility and 14% non-tolerant. Different antigens, unrelated to OVA, were tested by gavage and TS mice were generally susceptible while TR mice were resistant. The stability of TS and TR phenotypes was not affected by the use of strict protocols of intraperitoneal immunization or feeding over 30 consecutive days. The levels of interleukin-2 (IL-2), IL-4, interferon-gamma and IL-10 cytokines evaluated in concanavalin A-stimulated spleen cells from naive mice and in OVA-stimulated spleen cells from OVA-gavaged mice were higher in TS mice. Interleukin-10 was up-regulated in OVA-gavaged TS mice and down-regulated in TR mice. In naive mice, the percentage of CD4(+) CD25(+) and CD4(+) Foxp3(+) spleen cells and IL-10 expression by CD4(+) cells was significantly higher in TS mice. These results indicate that regulation of IL-10 expression could be an important factor contributing to the mechanisms controlling OT susceptibility, and that the OT responses of TR and TS individuals strongly correlate with their innate potential to secrete this cytokine.

Regulatory T Cells in children with intestinal parasite infection

Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4(+) CD25(high) and CD4(+) Foxp3(+) cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3(+) CD69(+), CD4(+) CTLA-4(+), and CD8(+) CD28(-) T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3(+) CD69(+), CD4(+) CTLA-4(+) and CD8(+) CD28(-) lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children.

Induction of type 2 T helper cell allergen tolerance by IL-10-differentiated regulatory dendritic cells

In mouse models of asthma, therapeutic use of allergen-presenting IL-10-differentiated dendritic cells (DCs) can abrogate airway hyperresponsiveness, and reduce other asthma-related responses to near background. Analogous human DCs can suppress human T cell responses in vitro, but the operative mechanisms are poorly defined. We investigated the ability of IL-10-treated human DCs to induce tolerance among autologous T cells of subjects with asthma and the mechanisms by which they do this. CD14(+) monocyte-derived DCs were differentiated in the presence of IL-10 (DC10) ex vivo from 11 donors with asthma and 4 control donors, and characterized for relevant markers. They were pulsed with specific or irrelevant allergen, and cultured with autologous peripheral blood CD4(+) T cells, either alone or together with autologous immunostimulatory DCs (DC-TNF), and the impact of this treatment on the T-cell responses was assessed for each donor. The DC10 expressed reduced levels of some relevant markers (CD40, CD80, human leukocyte antigen-DR) and stimulatory cytokines (IL-6 and IL-12), but augmented levels of Ig-like transcript-22/CD85j and IL-10 relative to DC-TNF. In cocultures, they dampened DC-TNF-driven T helper (Th) type 2 cell proliferation and cytokine (IL-4, -5, and -13) secretion. They also drove the development from atopic CD4(+)CD25(lo)Foxp3(lo) cells of a population of IL-10-secreting CD25(+)Foxp3(+)LAG-3(+)CTLA-4(+) regulatory T cells (Tregs). These Tregs suppressed stimulatory DC-induced autologous Th2 cell proliferation and cytokine secretion in a contact-dependent manner. Our data indicate that IL-10-treated human DCs induce Th2 cell allergen tolerance ex vivo by driving the differentiation of Tregs.

Differential control of allo-antigen-specific regulatory T cells and effector T cells by anti-CD4 and other agents in establishing transplantation tolerance

Donor-specific graft tolerance can be established by a combination of allo-antigen exposure and manipulation of T cell function, for example by donor-specific transfusion (DST) under the cover of a non-depleting anti-CD4 mAb. Yet, the cellular basis of this graft tolerance is still obscure. This report shows that T cell-deficient BALB/c nude mice reconstituted with naive unfractionated T cells are specifically tolerized to DBA/2 skin grafts by DST and anti-CD4 mAb treatment, whereas those transferred with T cell suspensions depleted of all Foxp3(+)CD25(+)CD4(+) natural regulatory T cells (Tregs) are not. The treatment inhibits Mls-1(a) allo-antigen-specific expansion of CD4(+) non-Tregs expressing Vbeta6 TCR subfamily but leaves the expansion of Vbeta6-expressing Tregs unaffected, allowing the latter to selectively expand and establish donor-specific tolerance. Furthermore, anti-CD4 mAb inhibits in vitro the selective expansion of allo-antigen-specific CD4(+) non-Tregs but not natural Tregs, as observed with in vitro anti-CD154 [CD40 ligand (CD40L)] mAb or rapamycin treatment. The results collectively indicate that the differential effect of biologicals and pharmacological substances on the expansion of allo-antigen-specific Tregs and effector T cells and resulting dominance of the former can be a key general mechanism underlying dominant transplantation tolerance.

Carcinoembryonic antigen-specific but not antiviral CD4+ T cell immunity is impaired in pancreatic carcinoma patients

Pancreatic carcinoma is a very aggressive disease with dismal prognosis. Although evidences for tumor-specific T cell immunity exist, factors related to tumor microenvironment and the presence of immunosuppressive cytokines in patients' sera have been related to its aggressive behavior. Carcinoembryonic Ag (CEA) is overexpressed in 80-90% of pancreatic carcinomas and contains epitopes recognized by CD4(+) T cells. The aim of this study was to evaluate the extent of cancer-immune surveillance and immune suppression in pancreatic carcinoma patients by comparing the anti-CEA and antiviral CD4(+) T cell immunity. CD4(+) T cells from 23 normal donors and 44 patients undergoing surgical resection were tested for recognition of peptides corresponding to CEA and viral naturally processed promiscuous epitopes by proliferation and cytokine release assays. Anti-CEA CD4(+) T cell immunity was present in a significantly higher number of normal donors than pancreatic cancer patients. Importantly, whereas CD4(+) T cells from normal donors produced mainly GM-CSF and IFN-gamma, CD4(+) T cells from the patients produced mainly IL-5, demonstrating a skew toward a Th2 type. On the contrary, the extent of antiviral CD4(+) T cell immunity was comparable between the two groups and showed a Th1 type. The immunohistochemical analysis of tumor-infiltrating lymphocytes showed a significantly higher number of GATA-3(+) compared with T-bet(+) lymphoid cells, supporting a Th2 skew also at the tumor site. Collectively, these results demonstrate that Th2-immune deviation in pancreatic cancer is not generalized but tumor related and suggests that the skew might be possibly due to factor(s) present at the tumor site.

Regulatory T cells and their role in rheumatic diseases: a potential target for novel therapeutic development

Regulatory T cells have an important role in limiting immune reactions and are essential regulators of self-tolerance. Among them, CD4+CD25high regulatory T cells are the best-described subset. In this article, we summarize current knowledge on the phenotype, function, and development of CD4+CD25high regulatory T cells. We also review the literature on the role of these T cells in rheumatic diseases and discuss the potential for their use in immunotherapy.

Induction of mucosal tolerance in SLE: a sniff or a sip away from ameliorating lupus?

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by aberrant immune responses against intracellularly derived self antigens. Treatment for SLE relies on the use of aggressive immunosuppressants and steroids that are nonspecific and can cause serious adverse effects. The observation that a systemic immune tolerance to self antigens or generation of regulatory T cells may follow mucosal (nasal or oral) exposure to self proteins or monoclonal antibody against CD3 respectively suggests that induction of mucosal tolerance offers the basis of a side effect-free therapy that could re-establish the ability to distinguish self from non-self and restore peripheral tolerance in individuals susceptible to developing autoimmune diseases. Here I review studies on mucosal tolerance in autoimmune diseases and discuss the therapeutic potential of inducing tolerance for the treatment of SLE.

Ovalbumin-protein sigma 1 M-cell targeting facilitates oral tolerance with reduction of antigen-specific CD4+ T cells

BACKGROUND & AIMS

The follicle-associated epithelium (FAE) plays key roles in antigen uptake and subsequent induction of mucosal immunity. In this study, we examined whether M-cell targeting using a protein antigen (Ag) delivery system would induce oral tolerance instead of enhancement of Ag-specific mucosal antibody (Ab) responses.

METHODS

Mice were fed different doses of a recombinant protein sigma 1 of reovirus genetically conjugated to ovalbumin (OVA-psigma1), psigma1 only, or phosphate-buffered saline (PBS) before oral challenge with OVA plus cholera toxin as mucosal adjuvant. OVA-specific Ab and CD4-positive (CD4(+)) T-cell responses were determined.

RESULTS

A low dose of OVA-psigma1 reduced anti-OVA Ab and CD4(+) T-cell responses in both mucosal and systemic lymphoid tissues. OVA/MHC I-A(d) tetramer staining showed that the numbers of OVA-specific CD4(+) T cells were significantly reduced in lamina propria of mice fed OVA-psigma1 than those fed psigma1 only or PBS only. In fact, Foxp3 expressing CD25(+) CD4(+) T cells were markedly increased in this tissue. Nonetheless, CD25(+) CD4(+) T cells from the spleen, mesenteric lymph nodes, and Peyer's patches of orally tolerized mice showed increased transforming growth factor beta1 (TGF-beta1) and interleukin-10 (IL-10) production compared with nontolerized mice.

CONCLUSIONS

These results show that an FAE M-cell targeting protein Ag delivery system facilitates oral tolerance induction because of a reduction in Ag-specific CD4(+) T cells and increased levels of TGF-beta1 and IL-10 producing, CD25(+) CD4(+) regulatory T cells in both systemic and mucosal lymphoid tissues.

Efficient generation of survivin-specific cytotoxic T lymphocytes from healthy persons in vitro: quantitative and qualitative effects of CD4+ T cells

For the adoptive immunotherapy and the study of cytotoxic T lymphocytes (CTLs) in human, efficient in vitro generation of CTLs is needed. However, it is still difficult to induce T cells specific for naïve antigens in vitro even though dendritic cells (DCs) as potent APCs are used. In this study, we investigated quantitative and qualitative effects of CD4+ T cells during in vitro stimulation of CD8+ T cells from healthy donors using DCs transduced with adenovirus vector expressing human survivin (Adv-survivin). CTLs were not efficiently induced in the absence of CD4+ T cells or in CD25+ depleted CD4+ T cells. When the ratio of CD4+:CD8+ T cells was quantitatively decreased from 2:1 to 1:2, proliferation of CTLs specific for survivin was gradually increased. Because DCs pulsed with HCMV pp65 protein could activate CD4+ T cells to secrete Th1 cytokines, the use of pp65 protein as an adjuvant induced higher numbers and frequencies of CTLs. Furthermore, Th1 conditioning of CD4+ T cells augmented this generation of CTLs. These results suggest that both quantitative and qualitative modulation of CD4+ T cells including the number and Th1 polarization may be required for the efficient induction of CTLs specific for tumor antigens in vitro.

Phenotype of CD4+ T cell subsets that develop following mouse facial nerve axotomy

We have previously shown that CD4(+) T helper (Th) 2 cells, but not Th1 cells, participate in the rescue of mouse facial motoneurons (FMN) from axotomy-induced cell death. Recently, a number of other CD4(+) T cell subsets have been identified in addition to the Th1 and Th2 effector subsets, including Th17, inducible T regulatory type 1 (Tr1), and naturally thymus-born Foxp3(+) regulatory (Foxp3(+) Treg) cells. These subsets regulate the nature of a T cell-mediated immune response. Th1 and Th17 cells are pro-inflammatory subsets, while Th2, Tr1, and Foxp3(+) Treg cells are anti-inflammatory subsets. Pro-inflammatory responses in the central nervous system are thought to be neurodestructive, while anti-inflammatory responses are considered neuroprotective. However, it remains to be determined if another CD4(+) T cell subset, other than the Th2 cell, develops after peripheral nerve injury and participates in FMN survival. In the present study, we used FACS analysis to determine the temporal frequency of Th1, Th17, Th2, Tr1 and Foxp3(+) Treg CD4(+) T cell subset development in C57BL/6 wild type mice after facial nerve transection at the stylomastoid foramen in the mouse. The results indicate that all of the known CD4(+) T cell subsets develop and expand in number within the draining lymph node, with a peak in number primarily at 7 days postoperative (dpo), followed by a decline at 9 dpo. In addition to the increase in subset frequency over time, FACS analysis of individual cells showed that the level of cytokine expressed per cell also increased for interferon-gamma (IFN-gamma), interleukin (IL)-10 and IL-17, but not IL-4. Additional control double-cytokine labeling experiments were done which indicate that, at 7dpo, the majority of cells indeed have committed to a specific phenotype and express only 1 cytokine. Collectively, our findings indicate for the first time that there is no preferential activation and expansion of any single CD4(+) T cell subset after peripheral nerve injury but, rather, that both pro-inflammatory and anti-inflammatory CD4(+) T cells develop.

Preferential migration of T regulatory cells induced by IL-16

As a natural ligand for CD4, IL-16 has been shown to preferentially induce migration in Th1 cells, and, in long-term cultures with IL-2, IL-16 facilitates the expansion of CD4(+)CD25(+) cells. In addition, IL-16 has an immunomodulatory role in asthmatic inflammation, as exogenous administration significantly reduces inflammation and airway hyperreactivity. The mechanism for this, however, is not clear. Based on its functional characteristics and potential immunomodulatory role, we investigated the ability of IL-16 to recruit and influence the development of T regulatory (Treg) cells. We now demonstrate that IL-16 preferentially induces migration in a CD25(+)CTLA-4(+) human T cell subset and that responding cells produce IFNgamma and TGFbeta but not IL-10. These cells are relatively unresponsive to antigenic stimulation and can suppress proliferation and IL-5, but not IFNgamma, production by autologous T cells. We further demonstrate that IL-16-recruited cells are enriched for Forkhead box P3 (Foxp3). In addition, we find that IL-16 stimulation may facilitate de novo induction of Foxp3(+) Treg cells, because the stimulation of FoxP3-negative T cells for 48 h results in the expression of FoxP3 mRNA and protein. These data indicate that at sites of inflammation IL-16 may contribute to selective Treg cell expansion through the preferential induction of a migratory response from existing Treg cells, as well as by the induction of de novo generation of FoxP3(+) cells. These findings offer a potential mechanism for the immunosuppressive effects of IL-16 seen in Th2-mediated inflammation.

Developmental exposure to noninherited maternal antigens induces CD4+ T regulatory cells: relevance to mechanism of heart allograft tolerance

We hypothesize that developmental exposure to noninherited maternal Ags (NIMA) results in alloantigen-specific natural and adaptive T regulatory (T(R)) cells. We compared offspring exposed to maternal H-2(d) (NIMA(d)) with nonexposed controls. In vitro assays did not reveal any differences in T cell responses pretransplant. Adoptive transfer assays revealed lower lymphoproliferation and greater cell surface TGF-beta expression on CD4(+) T cells of NIMA(d)-exposed vs control splenocytes. NIMA(d)-exposed splenocytes exhibited bystander suppression of tetanus-specific delayed-type hypersensitivity responses, which was reversed with Abs to TGF-beta and IL-10. Allospecific T effector cells were induced in all mice upon i.v. challenge with B6D2F1 splenocytes or a DBA/2 heart transplant, but were controlled in NIMA(d)-exposed mice by T(R) cells to varying degrees. Some (40%) NIMA(d)-exposed mice accepted a DBA/2 allograft while others (60%) rejected in delayed fashion. Rejector and acceptor NIMA(d)-exposed mice had reduced T effector responses and increased Foxp3(+) T(R) cells (CD4(+)CD25(+)Foxp3(+) T(R)) in spleen and lymph nodes compared with controls. The key features distinguishing NIMA(d)-exposed acceptors from all other mice were: 1) higher frequency of IL-10- and TGF-beta-producing cells primarily in the CD4(+)CD25(+) T cell subset within lymph nodes and allografts, 2) a suppressed delayed-type hypersensitivity response to B6D2F1 Ags, and 3) allografts enriched in LAP(+), Foxp3(+), and CD4(+) T cells, with few CD8(+) T cells. We conclude that the beneficial NIMA effect is due to induction of NIMA-specific T(R) cells during ontogeny. Their persistence in the adult, and the ability of the host to mobilize them to the graft, may determine whether NIMA-specific tolerance is achieved.

Detection of Foxp3+ cells on biopsies of kidney transplants with early acute rejection

This retrospective study was conducted to examine whether the presence of Foxp3+ cells in biopsies of kidney transplants displaying early acute rejection (AR) predicted the outcome of the episode. Seventeen biopsies showing AR included in this study were obtained at 42 +/- 30 days after transplantation. Lesions were graded according to the Banff classification. Foxp3 staining was performed on paraffin-embedded sections with a monoclonal antibody after antigen retrieval. We evaluated relationships between the number and the location of Foxp3+ cells, the type of rejection, and the serum creatinine value at 1 year. Foxp3+ cells were detected in 11 of 17 biopsies with AR (9.5 +/- 13.3 cells/mm(2)). These elements were mixed with other interstitial inflammatory cells. Intraepithelial tubular Foxp3+ cells were seen in 9 biopsies (1.5 +/- 2.5 cells/mm(2)). Foxp3+ cells were associated with borderline lesions (25.5 +/- 22.4/mm(2)); type 1 AR (7.18 +/- 9/mm(2)) and type 2 AR (1.99 +/- 3.46/mm(2)). The average number of cells per field was not different in C4d(+) and C4d(-) AR (6 +/- 8.35 vs 8.5 +/- 14.7/mm(2)). Graft loss within the first year was higher among the group of recipients without Foxp3+ cells (3/6) than those with Foxp3+ cells (0/11). All AR with intraepithelial tubular Foxp3 cells had favorable outcomes. Foxp3 has been proposed as a relevant marker of CD4(+)CD25(+) regulatory T cells. This study showed that Foxp3+ cells can be detected in kidney transplant biopsies with AR. The absence of Foxp3+ cells, especially in epithelial tubular cells, might indicate a poor prognosis following an AR episode.

Specific alloantigen self-control by regulatory T cells in organ transplantation: a review

Multidrug immunosuppressive protocols have increased short-term patient and graft survival rates from 50% to 90% in the past two decades. Unfortunately, chronic graft rejection still remains the main cause of long-term failure and patients must undergo lifelong immunosuppression. The severe side effects such as life-threatening infections, secondary malignancies, and cardiovascular dysfunction all together include roughly 50% of deaths among kidney transplant patients with functioning grafts. Therefore, it should be of crucial importance to reduce immunosuppression and seek induction of specific tolerance to donor alloantigens. Several investigations have suggested that the acquisition of tolerance to self and/or foreign antigens is dependent on the number and function of naturally occurring and acquired regulatory T cells, which can control all aggressive T cells. The regulatory T cells together with their receptors, costimulatory molecules, cytokines, chemokines, and growth factors all contribute to maintain an equilibrium between aggressive and suppressive effector immune responses. As a consequence of increased knowledge, new immunosuppressive approaches based on either alloantigen-specific regulatory T-cell expansion in vivo or in vitro have been proposed to achieve donor-specific transplantation tolerance in kidney allograft recipients. This contribution attempted to summarize knowledge about regulatory T cells and developing methods to induce specific tolerance in kidney transplantation.

CD4+CD25+ regulatory T cells in health and disease

1. Over the past 5 years, tremendous progress has been made in understanding the suppressive mechanisms of T regulatory (Treg) cells. The Treg cells, a subpopulation of T cells, have been shown to play an important role in maintaining peripheral tolerance and the prevention of autoimmunity. 2. Various populations of Treg cells have been described, including thymically derived CD4(+)CD25(+) Treg cells. These naturally occurring Treg cells are present in the periphery and are capable of suppressing proliferation and effector T cell responses both in vitro and in vivo. 3. In addition, a second subset of Treg cells, type 1 T regulatoary (Tr1) and Th3 cells, exert their suppressive capacity via cytokines such as interleukin-10 and transforming growth factor-beta and are contact independent. 4. The present review summarizes the characteristics and molecular basis of CD4(+)CD25(+) Treg cells, as well as their therapeutic potential in modulating inflammatory diseases, such as inflammatory bowel disease and rheumatoid arthritis.

Prevention of red cell alloimmunization by CD25 regulatory T cells in mouse models

Transfusion therapy is currently an effective therapeutic intervention in a number of diseases, including sickle cell disease. However, its use is complicated by a high incidence of red blood cell (RBC) alloimmunization in the transfusion recipients. The identification of T regulatory cells (Tregs) among the CD4(+) CD25(+) T cell subset as key regulators of peripheral tolerance in mice as well as humans has opened an exciting era in the prevention and treatment of autoimmune disease and for improving organ transplantation. However, their potential in inducing transfusion tolerance remains to be explored. We used red cells from mice transgenic for human glycophorin A blood group antigen as donor cells and transfused wild-type mice to induce alloantibodies, as an experimental system to study RBC alloimmunization. We found that depletion with anti-CD25 enhanced the alloantibody production, indicating that CD25 Tregs play an important role in regulation of alloantibody responses. More importantly, adoptive transfer of purified population of CD4(+)CD25(+) but not CD4(+)CD25(-) cells from naïve mice prevented the induction of IgG and IgM alloantibody production in transfusion recipients, with a concomitant reduction in activated splenic B cells and macrophages. Similarly, adoptive transfer of purified populations of CD4(+)CD25(+) cells from naïve mice into naïve syngeneic recipients inhibited the anti-Ig response to rat RBCs in the recipients but transfer of control CD4(+)CD25(-) cells did not. Altogether, our results demonstrate that Tregs participate in the control of transfusion-associated RBC alloantibody responses, opening up the possibility that Treg immunotherapy may be exploited for suppressing transfusion immunization events.

Initiating mechanisms of food allergy: Oral tolerance versus allergic sensitization

Immediately after birth the mucosa of the gastrointestinal tract, which represents the greatest body surface area exposed to the outside environment, is confronted with a large variety of foreign antigens. The immune system of the intestine now has to meet the task of discriminating between pathogens and harmless antigens, such as food proteins and commensal bacteria, and to respond accordingly. This important job is fulfilled by cells of the gut-associated lymphoid tissue, the largest immunologic organ in the body. Despite the large extent of food antigen exposure, only a small percentage of individuals experience adverse immunologic reactions to food. This is due to the fact that the normal immune response to dietary proteins is associated with the induction of oral tolerance, which refers to a state of active inhibition of immune responses to an antigen by means of prior exposure to that antigen via the oral route. Abrogation of oral tolerance or failure to induce oral tolerance may result in the development of food hypersensitivity. In the present review, factors that may play a role in the outcome of oral tolerance versus sensitization to food proteins are discussed.

Significance of CD25 positive cells and macrophages in noncrescentic IgA nephropathy

The aim of this study was to determine whether infiltration by CD25 positive cells, macrophages, and activated macrophages in the kidney is predictive of chronic histological injury and renal prognosis in adults with noncrescentic IgA nephropathy. Renal biopsies of 36 patients with noncrescentic IgA nephropathy were examined by immunohistochemistry for glomerular and interstitial CD4, CD8, and CD25 positive cells, monocytes/macrophage (Mac387), and activated macrophages (27E10). Renal injury (glomerulosclerosis, mesangial cell hypercellularity, tubular atrophy, and interstitial fibrosis) at the time of biopsy and renal prognosis (follow-up creatinine and creatinine clearance) were assessed. The mean follow-up period was 22.5 +/- 16.5 months. The number of interstitial CD8 positive cells was the best predictor of renal injury at the time of biopsy, and was positively correlated with glomerulosclerosis (p = 0.04), tubular atrophy (p = 0.04), and interstitial fibrosis (p = 0.01) but not with mesangial cell hypercellularity. The number of interstitial Mac387 and 27E10 positive cells were the best predictors of renal prognosis (r2 = 0.33 and 0.34 respectively, both p < 0.01). These data suggest the presence of CD8 cells and macrophages in the kidney at the time of biopsy could potentially serve as pathological markers to identify patients with IgA nephropathy, which may warrant more aggressive medical therapy.

Regulating regulatory T cells

Regulatory T cells (Tregs) are a specialized subpopulation of T cells that act to suppress activation of other immune cells and thereby maintain immune system homeostasis, self-tolerance as well as control excessive response to foreign antigens. The mere concept of Tregs was the subject of significant controversy among immunologists for many years owing to the paucity of reliable markers for defining these cells and the ambiguity of the nature and molecular basis of suppressive phenomena. However, recent advances in the molecular characterization of this cell population have firmly established their existence and their vital role in the vertebrate immune system. Of interest, accumulating evidence from both humans and experimental animal models has implicated the involvement of Tregs in the development of graft-versus-host disease (GVHD). The demonstration that Tregs could separate GVHD from graft-versus-tumor (GVT) activity suggests that their immunosuppressive potential could be manipulated to reduce GVHD without detrimental consequence on GVT effect. Although a variety of T lymphocytes with suppressive capabilities have been reported, the two best-characterized subsets are the naturally arising, intrathymic-generated Tregs (natural Tregs) and the peripherally generated, inducible Tregs (inducible Tregs). This review summarizes our current knowledge of the generation, function and regulation of these two populations of Tregs during an immune response. Their role in the development of GVHD and their therapeutic potential for the prevention and treatment of GVHD will also be described.

Reduced function of CD4+25+ regulatory T cell fraction in silicosis patients

The quality and quantity of CD4+25+ regulatory T cells (Treg) in silicosis patients (SIL) were examined and compared with results from healthy donors (HD) because SIL often develop autoimmune diseases along with pulmonary disorders. Peripheral blood mononuclear cells from 57 SIL and 50 HD were analyzed for Treg. Treg frequency and clinical parameters were subjected to a factor analysis. Treg and CD4+25- T cells (Tneg) from five HD and five SIL, sorted by flow-cytometer, were used for functional assays of Treg, the expression pattern of Treg specific genes (FoxP3, GITR and CTLA-4) and activation-related genes (CD122 and CD123). Although the actual frequency of Treg did not differ between SIL and HD, the age-corrected level was reduced in SIL. The factor analysis showed that Treg frequency was positively associated with the serum level of IL-2. The inhibitory effect of Treg on Tneg activation was decreased when the Treg:Tneg ratio was 1:1/4 to 1/2. In addition, Treg dominancy of FoxP3 and CTLA-4 expression and Tneg dominancy of CD132 expression found in HD were lost in SIL. These results indicated that the Treg fraction in SIL may be substituted with chronically activated T cells due to recurrent exposure to silica, resulting in a reduction in the frequency and function of Treg. Since the reduction of Treg may precede the clinical manifestation, as silicosis may be a pre-clinical status for autoimmune diseases, control of Treg function using cell and/or gene therapy may be a good way to manage autoimmune disease.

Cutting Edge: Critical Role for A2A Adenosine Receptors in the T Cell-Mediated Regulation of Colitis

A(2A) adenosine receptors (A(2A)AR) inhibit inflammation, although the mechanisms through which adenosine exerts its effects remain unclear. Although the transfer of regulatory Th cells blocks colitis induced by pathogenic CD45RB(high) Th cells, we show that CD45RB(low) or CD25+ Th cells from A(2A)AR-deficient mice do not prevent disease. Moreover, CD45RB(high) Th cells from A(2A)AR-deficient mice were not suppressed by control CD45RB(low) Th cells. A(2A)AR agonists suppressed the production of proinflammatory cytokines by CD45RB(high) and CD45RB(low) T cells in association with a loss of mRNA stability. In contrast, anti-inflammatory cytokines, including IL-10 and TGF-beta, were minimally affected. Oral administration of the A(2A)AR agonist ATL313 attenuated disease in mice receiving CD45RB(high) Th cells. These data suggest that A(2A)AR play a novel role in the control of T cell-mediated colitis by suppressing the expression of proinflammatory cytokines while sparing anti-inflammatory activity mediated by IL-10 and TGF-beta.

Function of tumor necrosis factor receptor family members on regulatory T-cells

Effector cells play a crucial role in the immune system of higher vertebrates in eliminating invading pathogens and transformed cells that could cause disease or death of the individual. To be effective and specific, immune responses have to distinguish between self and nonself. Mechanisms of central and peripheral tolerance have evolved to control effector cells that could respond to autoantigens. Regulatory T-cells (Treg cells) are critical modulators of effector cells in the periphery that suppress autoreactive T-cells but are also involved in modulating immune responses against invading pathogens. Identification of surface markers of Treg cells and the development of in vitro systems to study the suppressive function of Treg cells have revealed distinct phenotypic and functional subsets of Treg cells. Several tumor necrosis factor receptor (TNFR) family members have been shown to play a role in the development, homeostasis, and suppressor function of Treg cells. Recent findings suggest that TNFRs and other cell-surface molecules of Treg cells can be explored for therapeutic strategies targeting autoimmune disorders, cancer, and immune responses against pathogens.

Adaptive islet-specific regulatory CD4 T cells control autoimmune diabetes and mediate the disappearance of pathogenic Th1 cells in vivo

Adaptive regulatory T cells that develop from naive CD4 cells in response to exposure to Ag can act as immunotherapeutic agents to control immune responses. We show that effectors generated from murine islet-specific CD4 cells by TCR stimulation with IL-2 and TGF-beta1 have potent suppressive activity. They prevent spontaneous development of type 1 diabetes in NOD mice and inhibit development of pancreatic infiltrates and disease onset orchestrated by Th1 effectors. These regulatory T cells do not require innate CD25+ regulatory cells for generation or function, nor do they share some characteristics typically associated with them, including expression of CD25. However, the adaptive population does acquire the X-linked forkhead/winged helix transcription factor, FoxP3, which is associated with regulatory T cell function and maintains expression in vivo. One mechanism by which they may inhibit Th1 cells is via FasL-dependent cytotoxicity, which occurs in vitro. In vivo, they eliminate Th1 cells in lymphoid tissues, where Fas/FasL interactions potentially play a role because Th1 cells persist when this pathway is blocked. The results suggest that adaptive regulatory CD4 cells may control diabetes in part by impairing the survival of islet-specific Th1 cells, and thereby inhibiting the localization and response of autoaggressive T cells in the pancreatic islets.

Clinical application of human CD4+ CD25+ regulatory T cells for the treatment of inflammatory bowel diseases

As our understanding of the immunological and genetic basis of inflammatory bowel disease (IBD) grows, potential therapeutic options are being developed at a rapid pace. Nevertheless, new drugs for IBD are needed because about half of all patients with severe ulcerative colitis (UC) eventually undergo colectomy, and a significant part of Crohn's disease (CD) patients do not respond to standard medical therapies, including immunosuppressants and TNF-alpha neutralising antibodies, or suffer from significant side effects. Finally, recurrence of disease activity following remission is frequent in both UC and CD, and there is an unmet need for effective maintenance strategies. It is well-known that immune responses in the intestine remain in a state of controlled inflammation, suggesting that not only does active suppression by regulatory T (TR) cells play an important role in the normal intestinal homeostasis, but also its dysregulation might lead to the development of IBD. TR cells are functional subsets of T cells that downregulate adaptive immune responses by interfering with the activation of dendritic cells and proliferation of T cells. From experimental work it is now clear that TR cells play a critical role in maintaining immune homeostasis, and several therapeutic approaches have been targeted at the induction of TR cells in order to control mucosal inflammation. Before using TR cells clinically as living immunosuppressants for the treatment of IBD, however, we have to pass many critical checkpoints, such as the in vitro expansion of TR cells and the confirmation of their safety. This paper will discuss recently gained knowledge of human TR cells and the possibility of their clinical usages as a new strategy for the treatment of IBD.

Cutting edge: an alternative pathway of CD4+ T cell differentiation is induced following activation in the absence of gamma-chain-dependent cytokine signals

This report addresses the role of gamma-chain cytokine signals in regulating CD4(+) T cell differentiation following activation. Using murine CD4(+) T cells lacking the Jak3 tyrosine kinase, we show that activation of these cells in the absence of gamma-chain-dependent cytokine signals induces an alternative pathway of T cell differentiation. Specifically, activated Jak3(-/-) CD4(+) T cells produce IL-10, TGF-beta, and IFN-gamma, but not IL-2 or IL-4, and are unable to proliferate in vitro. In addition, Jak3(-/-) CD4(+) T cells express high levels of programmed death-1 and lymphocyte activation gene-3 and modestly suppress the proliferation of wild-type CD4(+) T cells in coculture assays. Together, these features demonstrate a striking similarity between Jak3(-/-) CD4(+) T cells and the regulatory T cells that have been shown to suppress immune responses in vitro and in vivo. We conclude that Jak3 is a critical component of signaling pathways that regulate T cell differentiation into effector vs regulatory lineages.

Frequency of Natural Regulatory CD4+CD25+ T Lymphocytes Determines the Outcome of Tolerance across Fully Mismatched MHC Barrier through Linked Recognition of Self and Allogeneic Stimuli

We show in this study that long-term tolerance to allogeneic skin grafts can be established in the absence of immunosuppression by the combination of the following elements: 1) augmenting the frequency of regulatory CD4(+)CD25(+) T cells (Treg) and 2) presentation of the allogeneic stimuli through linked recognition of allo- and self-epitopes on semiallogeneic F(1) APCs. BALB/c spleen cells enriched for CD4(+)CD25(+) T lymphocytes were transferred either to BALB/c nu/nu mice or to BALB/c nu/nu previously injected with F(1)(BALB/c x B6.Ba) spleen cells, or else grafted with F(1)(BALB/c x B6.Ba) skin (chimeric BALB/c nu/nu-F(1)). Chimeric BALB/c nu/nu-F(1) reconstituted with syngeneic CD25(+)-enriched spleen cells were unable to reject the previously transferred F(1)(BALB/c x B6.Ba) spleen cells or F(1)(BALB/c x B6.Ba) skin grafts, and a specific tolerance to a secondary B6 graft was obtained, with rejection of third-party CBA grafts. BALB/c nu/nu mice reconstituted only with syngeneic CD25(+)-enriched spleen cells rejected both B6 and CBA skin grafts. In contrast, when chimeric BALB/c nu/nu-F(1) were reconstituted with spleen populations comprising normal frequencies of Treg cells, the linked recognition of allo and self resulted in breaking of self tolerance and rejection of syngeneic grafts, strongly suggesting that linked recognition works in both directions, either to establish tolerance to allo, or to break tolerance to self, the critical parameter being the relative number of Treg cells.

[T regulatory lymphocytes, atopy and asthma: a new concept in three dimensions]

BACKGROUND

Allergic inflammation is considered to be the result of a pattern of Th2 lymphocyte activation. However this inflammation, relevant for atopy and infiltration of affected tissues by eosinophils, is insufficient by itself to explain the clinical features of asthma. Several studies have demonstrated that Th2 type inflammation was also associated in asthma with a Th1 response, with production of gamma interferon. It has recently been shown that the regulatory T lymphocytes (Treg) which produce IL-10 and/or TGF-beta and induce tolerance are defective in allergic patients. In addition, these lymphocytes increase during specific immunotherapy. Their decrease could explain the Th2 activation found in atopic patients.

PERSPECTIVE

We review the potential importance of Treg cells in atopy and also asthma, and propose a concept whereby the allergic inflammatory response would not be due to a Th1/Th2 imbalance, but rather to a Treg deficiency progressively rising from normal to atopic, from atopy to asthma and from asthma to acute exacerbations.

CONCLUSION

Three dimensions of inflammation need therefore to be taken into account: Th1, Th2 and Treg.