Emerging possibilities in the development and function of regulatory T cells

Emerging roles of T helper subsets in the pathogenesis of asthma

The cardinal features of asthma include pulmonary inflammation and airway hyperresponsiveness (AHR). Classically, asthma, specifically allergic asthma, has been attributed to a hyperactive Th2 cell immune response. However, the Th2 cell-mediated inflammation model has failed to adequately explain many of the clinical and molecular aspects of asthma. In addition, the outcomes of Th2-targeted therapeutic trials have been disappointing. Thus, asthma is now believed to be a complex and heterogeneous disorder, with several molecular mechanisms underlying the airway inflammation and AHR that is associated with asthma. The original classification of Th1 and Th2 pathways has recently been expanded to include additional effector Th cell subsets. These include Th17, Th9 and Treg cells. Emerging data highlight the involvement of these new Th cell subsets in the initiation and augmentation of airway inflammation and asthmatic responses. We now review the roles of these recently classified effector Th cell subsets in asthmatic inflammation and the insights they may provide in addition to the traditional Th2 paradigm. The hope is that a clearer understanding of the inflammatory pathways involved and the mediators of inflammation will yield better targeted therapeutics.

Smad2 positively regulates the generation of Th17 cells

Development of Foxp3(+) regulatory T cells and pro-inflammatory Th17 cells from naive CD4(+) T cells requires transforming growth factor-β (TGF-β) signaling. Although Smad4 and Smad3 have been previously shown to regulate Treg cell induction by TGF-β, they are not required in the development of Th17 cells. Thus, how TGF-β regulates Th17 cell differentiation remains unclear. In this study, we found that TGF-β-induced Foxp3 expression was significantly reduced in the absence of Smad2. More importantly, Smad2 deficiency led to reduced Th17 differentiation in vitro and in vivo. In the experimental autoimmune encephalomyelitis model, Smad2 deficiency in T cells significantly ameliorated disease severity and reduced generation of Th17 cells. Furthermore, we found that Smad2 associated with retinoid acid receptor-related orphan receptor-γt (RORγt) and enhanced RORγt-induced Th17 cell generation. These results demonstrate that Smad2 positively regulates the generation of inflammatory Th17 cells.

Genetic control of the inflammatory T-cell response in regulatory T-cell deficient scurfy mice

IPEX (Immunodysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome is a rare, recessive disorder in patients with mutations in the foxp3 gene, the normal expression of which is required for the generation of functional regulatory T-cells. Scurfy mice also bear a mutation in the foxp3, and like IPEX patients, spontaneously develop multi-organ inflammation. As reviewed herein, breeding immune response genes into Scurfy mice has provided useful insight into how the inflammatory T-cell response is regulated in the absence of regulatory T-cells and post regulatory T-cell checkpoint. Of particular interest are those that preferentially affect the inflammatory T-cell response in an "apparent" organ-specific manner, implying that specific mechanisms of control exist for individual organs during multi-organ inflammation.

TGF-beta1 gene-modified, immature dendritic cells delay the development of inflammatory bowel disease by inducing CD4(+)Foxp3(+) regulatory T cells

Inflammatory bowel disease (IBD) is caused by an uncontrolled immune response in the intestinal lumen, leading to inflammation in genetically predisposed individuals. Immunotherapy may be a promising approach to the treatment of IBD. Here, we show that transforming growth factor-beta1 (TGF-beta1) gene-modified immature dendritic cells (imDCs) could enhance the inhibitory function of imDCs and delay the progress of IBD induced by dextran sodium sulfate in mice. The results of fluorescence-activated cell sorter (FACS) demonstrated that this protective effect is mediated partially by inducing CD4(+)Foxp3(+) regulatory T cells (Tregs) in mesentery lymph nodes to control inflammation. In vitro experiments also supported this hypothesis. In conclusion, we provide evidence that TGF-beta1-modified bone marrow-derived imDCs may have a therapeutic effect to IBD.

Pharmacological modification of dendritic cells to promote their tolerogenicity in transplantation

Dendritic cells (DCs) are uniquely specialized antigen-presenting cells (APC) that play critical roles in both the stimulation and regulation of immune responses, including T-cell responses to transplanted organs. The inherent tolerogenicity of non-activated or "immature" DCs is well documented. Importantly, the infusion of DCs that are made resistant to activating inflammatory stimuli by "conditioning" through exposure to clinically approved immunosuppressants, such as corticosteroids, deoxyspergualin, and recently, rapamycin (RAPA), has produced encouraging outcomes in experimental models. Indeed, the infusion of RAPA-conditioned, host-derived DCs, pulsed with alloantigen, prolongs allograft survival. In particular, when the RAPA-conditioned DCs are delivered repeatedly or in combination with a short course of immunosuppression indefinite allograft survival is observed, typically associated with increased Foxp3(+) T-regulatory cells (Treg). Herein, we detail the procedures to generate and characterize RAPA-conditioned murine DCs (RAPA-DCs) ex vivo and in vivo. RAPA-DCs represent a pharmacologically conditioned DC population that promotes allograft survival and enriches for antigen-specific T-regulatory cells (Treg). DCs conditioned with immunosuppressive agents, like RAPA, represent novel and clinically applicable vectors or "negative" cellular vaccines, which can be loaded with donor antigen, and potentially used to promote/maintain organ transplant tolerance.

Immune stimulatory receptor CD40 is required for T-cell suppression and T regulatory cell activation mediated by myeloid-derived suppressor cells in cancer

Immune tolerance to tumors is often associated with accumulation of myeloid-derived suppressor cells (MDSC) and an increase in the number of T-regulatory cells (Treg). In tumor-bearing mice, MDSCs can themselves facilitate the generation of tumor-specific Tregs. In this study, we demonstrate that expression of the immune stimulatory receptor CD40 on MDSCs is required to induce T-cell tolerance and Treg accumulation. In an immune reconstitution model, adoptive transfer of Gr-1+CD115+ monocytic MDSCs derived from CD40-deficient mice failed to recapitulate the ability of wild-type MDSCs to induce tolerance and Treg development in vivo. Agonistic anti-CD40 antibodies phenocopied the effect of CD40 deficiency and also improved the therapeutic efficacy of IL-12 and 4-1BB immunotherapy in the treatment of advanced tumors. Our findings suggest that CD40 is essential not only for MDSC-mediated immune suppression but also for tumor-specific Treg expansion. Blockade of CD40-CD40L interaction between MDSC and Treg may provide a new strategy to ablate tumoral immune suppression and thereby heighten responses to immunotherapy.

Programmed Death-1 antibody blocks therapeutic effects of T-regulatory cells in cockroach antigen-induced allergic asthma

We recently reported that the adoptive transfer of T-regulatory cells (Tregs) isolated from lung and spleen tissue of green fluorescent protein-transgenic mice reversed airway hyperresponsiveness and airway inflammation. Because Programmed Death-1 (PD-1) is a pivotal receptor regulating effector T-cell activation by Tregs, we evaluated whether PD-1 is involved in the therapeutic effect of naturally occurring Tregs (NTregs) and inducible Tregs (iTregs) in cockroach (CRA)-sensitized and challenged mice. The CD4(+)CD25(+) NTregs and CD4(+)CD25(-) iTregs isolated from the lungs and spleens of BALB/c mice were adoptively transferred into CRA-sensitized and CRA-challenged mice with and without anti-PD-1 antibody (100 μg/mice). The CD4(+)CD25(+) T cells in the lung were phenotyped after adoptive transfer. Concentrations of IL-4, IL-5, IL-10, IFN-γ, and IL-13 in bronchoalveolar lavage fluid (BALF) were measured using ELISA. The NTregs and iTregs from either lung or spleen tissue reversed airway hyperresponsiveness for at least 4 wk. However, the therapeutic effect was blocked by administering the anti-PD-1 antibody. The administration of Tregs-recipient mice with anti-PD-1 antibody significantly decreased cytotoxic T-lymphocyte antigen-4 expression, with low concentrations of Forkhead-winged transcriptional factor box 3 (Foxp3) mRNA transcripts in lung CD4(+)CD25(+) T cells. These mice had substantially higher concentrations of BALF IL-4, IL-5, and IL-13, but significantly decreased levels of BALF IL-10. Adoptive therapy recipients without the anti-PD-1 antibody exhibited high levels of CTLA-4 expression and Foxp3 transcripts in lung CD4(+)CD25(+) T cells, with a significant decrease in BALF IL-4, IL-5, and IL-13 concentrations and a substantial increase in BALF IL-10 concentrations. These data suggest that the reversal of airway hyperresponsiveness and airway inflammation by Tregs is mediated in part by PD-1, because other costimulatory molecules (e.g., inducible costimulatory molecule [ICOS] or CTLA-4) have been shown to play a role in Treg-mediated suppression.

Does BCG vaccination protect against the development of childhood asthma? A systematic review and meta-analysis of epidemiological studies

BACKGROUND

Results have been conflicting as to whether Bacillus Calmette-Guérin (BCG) vaccine, a non-specific stimulator of the immune function, protects, predisposes or is unrelated to the development of childhood asthma. In this systematic review and meta-analysis, we qualitatively and quantitatively appraised the epidemiological evidence.

METHODS

Eligible studies were identified using a search strategy that included a computerized literature search and a manual search of each article's reference list, up to June 2008. A total of 23 studies were included (10 cohort, 5 case-control and 8 cross-sectional). Each study was summarized and rated for methodological quality. Pooled odds ratio (OR) estimates and 95% confidence intervals (CIs) were calculated using fixed-effects (FE) or random-effects (RE) models; if heterogeneity was present, the latter was used. Three indicators of BCG exposure were considered including BCG vaccination, tuberculin response and scar diameter.

RESULTS

The pooled estimate of association for 23 studies reporting on any of the three indicators suggested a protective effect of BCG exposure on childhood asthma occurrence. The studies were heterogeneous, especially when tuberculin response was considered. Restriction to a subgroup of 16 studies that considered BCG vaccination indicated a protective effect with no evidence of heterogeneity. The overall pooled OR using an FE model was 0.86 (95% CI 0.79-0.93). Exclusion of three studies with the lowest quality scores showed a similar association.

CONCLUSION

These results strengthen the epidemiological evidence in support of the hypothesis that exposure to the BCG vaccine in early life prevents asthma, possibly through a modulation of the immune maturation process.

IL-2 regulates CD103 expression on CD4+ T cells in Scurfy mice that display both CD103-dependent and independent inflammation

Scurfy (Sf) mice lack CD4(+)Foxp3(+) regulatory T cells and develop fatal multiorgan inflammation (MOI) mediated by CD4(+) T cells. Introducing Il2(-/-) gene into Sf mice (Sf.Il2(-/-)) inhibited inflammation in skin and lung. As a major integrin receptor for the organs, we compared CD103 expression on the CD4(+) T cells of B6, Il2(-/-), Sf, and Sf.Il2(-/-) mice. CD103(+)CD4(+) T cells, but not CD8(+) T cells or CD11c(+) dendritic cells, were significantly up-regulated only in Sf mice, indicating Il2(-/-) dominantly and specifically inhibited CD103 up-regulation in Sf CD4(+) T cells. In addition, CD4(+)Foxp3(+) regulatory T cell CD103 expression was not reduced in Il2(-/-) mice. Introducing CD103(-/-) into Sf mice inhibited inflammation in skin and lung as compared with age-matched Sf mice, but they died at approximately 7 wk old with inflammation developed in skin, lungs, and colon, demonstrating fatal MOI induced by CD103-independent mechanism. Transfer of Sf CD4(+) T cells induced MOI more rapidly than CD103(-)CD4(+) T cells, indicating the presence of CD103-dependent mechanism for inflammation. In vitro stimulation with anti-CD3 plus anti-CD28 beads confirmed that CD103 induction in the CD4(+)Foxp3(-) T cells in Il2(-/-) and Sf.Il2(-/-) is defective and cannot be restored by rIL-2 or rIL-15. The data indicate that IL-2 is required for optimal CD103 induction on CD4(+) T cells in Sf mice and this effect contributes to inflammation in an organ-specific manner. IL-2 also has additional roles because the protection of skin and lung inflammation in Sf.Il2(-/-), but not Sf.CD103(-/-) mice is lifelong and Sf.Il2(-/-) mice have longer lifespan than Sf.CD103(-/-) mice.

Aging and human CD4(+) regulatory T cells

Alterations in immunity that occur with aging likely contribute to the development of infection, malignancy and inflammatory diseases. Naturally occurring CD4(+) regulatory T cells (Treg) expressing high levels of CD25 and forkhead box P3 (FOXP3) are essential for regulating immune responses. Here we investigated the effect of aging on the number, phenotypes and function of CD4(+) Treg in humans. The frequency and phenotypic characteristics of CD4(+), FOXP3(+) T cells as well as their capacity to suppress inflammatory cytokine production and proliferation of CD4(+), CD25(-) T cells (target cells) were comparable in young (age <or=40) and elderly (age >or=65) individuals. However, when CD4(+), FOXP3(+) Treg and CD4(+), CD25(-) T cells were co-cultured at a ratio of 1:1, the production of anti-inflammatory cytokine IL-10 from CD4(+), CD25(-) T cells was more potently suppressed in the elderly than in the young. This finding was not due to changes in CTLA-4 expression or apoptosis of CD4(+), FOXP3(+) Treg and CD4(+), CD25(-) T cells. Taken together, our observations suggest that aging may affect the capacity of CD4(+), FOXP3(+) T cells in regulating IL-10 production from target CD4(+) T cells in humans although their other cellular characteristics remain unchanged.

Regulatory T cells: key players in tolerance and autoimmunity

CD4 + CD25 + regulatory T (TR) lymphocytes are essential to the maintenance of immunologic tolerance in the host. The discovery of Foxp3 as a transcription factor essential to the differentiation of TR ushered in detailed studies of the molecular mechanisms of TR cell development, peripheral homeostasis, and effector functions. In humans, loss of function mutations in genes that regulate T-cell development and function have been associated with TR cell deficiency or dysfunction and syndromes of autoimmunity and immune dysregulation. Augmentation of TR cells by immunotherapy and pharmacologic agents is a promising strategy for the treatment of allergic and autoimmune diseases.

Gamma irradiation alters the phenotype and function of CD4+CD25+ regulatory T cells

To examine the effects of gamma irradiation on Tregs, changes in phenotype and suppression function in Tregs treated with or without gamma ray were analyzed. Purified CD4(+)CD25(+) regulatory T cells were irradiated at different dosages with a (137)Cs source gamma ray at 4.8 Gy/min. After culture, the phenotype and function changes were determined by flow cytometry and [(3)H]-thymidine incorporation, respectively. A dose-dependent reduction of Tregs proliferation in response to gamma irradiation was noted, which paralleled the apoptosis induction of Tregs. Gamma irradiation downregulated the Tregs expression of CD45RO, CD62L, FOXP3, membrane TGF-beta, but upregulated Bax and GITR. High dose gamma irradiation (30 Gy) significantly abolished the suppression of Tregs on CD4(+)CD25(-) T cells proliferation. Thus Tregs not only influences the phenotype but also alters their suppressive capacities. Our findings suggest that radiotherapy may be an important strategy to alter the immunologic balance of Tregs and effector cells in cancer therapy.

Naturally occurring regulatory dendritic cells regulate murine cutaneous chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a limiting factor in allogeneic hematopoietic stem cell transplantation (alloHSCT) for the treatment of leukemia and other malignancies. Relative to the process that initiates and promotes cGVHD, the regulation is poorly understood. In this study, we examined the role of naturally occurring regulatory dendritic cells (DC(regs)) in murine major histocompatibility complex (MHC)-compatible and multiple minor histocompatibility antigen (miHAg)-incompatible model of cGVHD in alloHSCT. DC(regs) generated from bone marrow in vitro (BM-DC(regs)) exclusively expressed CD200 receptor 3 (CD200R3), which exerted a suppressive function in the Ag-specific CD4(+) T-cell response. CD49(+)CD200R3(+) cells showed similarities in phenotype and function to BM-DC(regs), which formally distinguishes them from other leukocytes, suggesting that they are the natural counterpart of BM-DC(regs). Treatment of the recipient mice after alloHSCT with the recipient-type CD49(+)CD200R3(+) cells as well as BM-DC(regs) protected against cGVHD, and the protection was associated with the generation of Ag-specific anergic CD4(+) T cells as well as CD4(+)CD25(+)Foxp3(+) regulatory T cells (T(regs)) from donor-derived alloreactive CD4(+)CD25(-)Foxp3(-) T cells. In addition, the depletion of CD49(+)CD200R3(+) cells before alloHSCT enhanced the progression of cGVHD. In conclusion, CD49(+)CD200R3(+) cells act as naturally occurring DC(regs) to regulate the pathogenesis of cGVHD in alloHSCT mediated through the control of the transplanted alloreactive CD4(+) T cells.

The Immune Response to Autologous Bacteroides in Ankylosing Spondylitis Is Characterized by Reduced Interleukin 10 Production

Objective.

Ileocolitis is a recognized feature of ankylosing spondylitis (AS) and is likely to play a role in the pathogenesis of AS, in conjunction with the normal intestinal microbiota. In order to investigate the host immune response in AS, we measured cytokines in tissue culture following exposure of peripheral blood mononuclear cells (PBMC) to autologous colonic bacteria.

Methods.

Twenty-one patients with AS and 21 matched controls were recruited. Subjects in the AS group were assessed clinically.Bacteroidesspecies belonging to theB. fragilisgroup were selectively cultured from stool samples and paired with blood samples from each participant. Ten cultures of autologousBacteroideswere randomly selected from cultures grown from the fecal specimens of each of the 21 patients with AS and 21 controls. These were then tested for reactivity with PBMC and the cytokines produced by proliferating lymphocytes [interleukin 10 (IL-10), IL-17, interferon-γ, tumor necrosis factor-α] were measured in cell culture supernatants. Differences between groups were analyzed using censored normal regression analysis.

Results.

The patients with AS had severe active AS with Bath AS Disease Activity Index 5.5 (± 1.6) and C-reactive protein (mg/l) 13.8 (± 12.2) (mean ± standard deviation). IL-10 concentrations inex vivoassay supernatants were lower in the AS group compared with controls (p = 0.047). There were no statistically significant differences between the groups for other cytokines.

Conclusion.

In AS, reduced IL-10 production in response to stimulation with autologousBacteroidescultures may represent a mechanism by which intestinal inflammation develops and persists, a situation analogous to inflammatory bowel disease.

CCR6 regulates the migration of inflammatory and regulatory T cells

Th17 and regulatory T (Treg) cells play opposite roles in autoimmune diseases. However, the mechanisms underlying their proper migration to inflammatory tissues are unclear. In this study, we report that these two T cell subsets both express CCR6. CCR6 expression in Th17 cells is regulated by TGF-beta and requires two nuclear receptors, RORalpha and RORgamma. Th17 cells also express the CCR6 ligand CCL20, which is induced synergistically by TGF-beta and IL-6, which requires STAT3, RORgamma and IL-21. Th17 cells, by producing CCL20, promote migration of Th17 and Treg cells in vitro in a CCR6-dependent manner. Lack of CCR6 in Th17 cells reduces the severity of experimental autoimmune encephalomyelitis and Th17 and Treg recruitment into inflammatory tissues. Similarly, CCR6 on Treg cells is also important for their recruitment into inflammatory tissues. Our data indicate an important role of CCR6 in Treg and Th17 cell migration.

Hypocalcemia impacts heart failure control in DiGeorge 2 syndrome

Chromosome 10p terminal deletion accounts for a rare subset among patients presenting with DiGeorge syndrome, and is designated as DiGeorge 2 syndrome. We report a neonate with DiGeorge-like phenotype having a deletion of distal 10p (p13-pter) and a duplication of terminal 3q (q29-qter) derived from paternal balanced translocation between 3q29 and 10p13. She had facial dysmorphism, atrial and ventricular septal defect, impaired T-cell function, hypoparathyroidism, sensorineural hearing loss, renal abnormalities and developmental delay. Her phenotype corresponded well with the typical characteristics of partial monosomy 10p and the small duplication of terminal 3q did not involve the critical region of 3q duplication syndrome. Clinically, hypoparathyroidism-related hypocalcemia lasted for three weeks and resulted in repeated episodes of heart failure. It was not until the calcium level was normalized that her heart failure improved markedly.

CONCLUSION

Cytogenetic analysis can help to recognize patients early on who have terminal 10p deletion when microdeletion of 22q11.2 is not the cause of DiGeorge syndrome. Hypoparathyroidism-related hypocalcemia impacts heart failure control in partial monosomy 10p and should be managed aggressively on critical care.

Development of CD4+CD25+FoxP3+ regulatory T cells from cord blood hematopoietic progenitor cells

Adult stem cells are capable of generating all of the cells of the hematopoietic system, and this process is orchestrated in part by the interactions between these cells and the stroma. T cell progenitors emerge from the stem cell compartment and migrate to the thymus, where their terminal differentiation and maturation occur, and it is during this phase that selection shapes the immune repertoire. Notch ligands, including Delta-like 1 (DL1), play a critical role in this lymphoid differentiation. To mimic this in vitro, stroma-expressing DL1 have been used to generate CD4(+)CD8(+) double-positive and single-positive T cells from hematopoietic stem/progenitor cells. This system provides a robust tool to investigate thymopoiesis; however, its capacity to generate regulatory T cells (Tregs) has yet to be reported. Natural Tregs (nTregs) develop in the thymus and help maintain immune homeostasis and have potential clinical use as a cell therapy for modulation of autoimmune disease or for transplant tolerization. Here, we describe for the first time the development of a population of CD4(+)CD25(+) CD127(lo)FoxP3(+) cells that emerge in coculture of cord blood (CB) CD34(+) progenitors on OP9-DL1 stroma. These hematopoietic progenitor-derived CD4(+)CD25(+) Tregs have comparable suppressor function with CB nTregs in vitro. The addition of IL-2 to the coculture enhanced the expansion and survival of this population significantly. This manipulable culture system, therefore, generates functional Tregs and provides a system to elucidate the mechanism of Treg development.

Allergies and childhood leukemia

A majority of studies to date have reported an inversed association between allergies and childhood leukemia. However, this association is likely an indirect one and may represent some shared underlying immune mechanisms that have been explained in the context of the "hygiene hypothesis", which has been thought to play an important role in the development of both allergies and childhood leukemia. This review focuses on what we know so far about the role of various immune cells (Th1, Th2, T regulatory and Th17 cells) in the development of allergies and how they may potentially be related to the etiology of childhood leukemia. In addition, the utilities of genetic and molecular studies to disentangle the association between allergies and childhood leukemia and to elucidate the biological mechanisms are also discussed.

In vitro suppression of xenoimmune-mediated macrophage activation by human CD4+CD25+ regulatory T cells

BACKGROUND

Macrophages are important effector cells in T cell-mediated xenograft rejection. The aim of this study was to determine whether CD4+CD25+ regulatory T cells (Tregs) were capable of suppressing macrophage activation in vitro.

METHODS

Porcine cell or xenoantigen-primed human peripheral blood mononuclear cells, CD4+ T cell-depleted peripheral blood mononuclear cells, or CD14+ macrophages plus autologous CD4+CD25- T cells were cultured with or without expanded autologous Tregs. Transwell cultures were used to separate the various components to determine the need for cell-cell contact.

RESULTS

Pig cell primed CD14+ macrophages required the presence of CD4+CD25- T cells for activation and increased expression of CD40, interleukin-12, and tumor necrosis factor-alpha. This up-regulated expression of macrophage activation markers was reduced substantially in the presence of autologous Tregs. Coculture with Tregs did not alter macrophage viability but reduced the capacity of macrophages to stimulate proliferation of responder T cells. Tregs required direct contact with CD4+CD25- T cells to inhibit macrophage activation but activated macrophage phenotype was not altered by separating the stimulated human peripheral blood mononuclear cells or CD14+ macrophages from Tregs in a transwell system. Macrophages did not require direct cell contact with porcine stimulator cells for full activation by CD4+CD25- T cells.

CONCLUSIONS

Human Tregs were able to suppress xenoantigen-primed and CD4+ T-cell-mediated macrophage activation and antigen-presenting cell function. However, Tregs had no direct effect on macrophages in vitro.

The effects of immunosuppression on regulatory CD4(+)CD25(+) T cells: impact on immunosuppression selection in transplantation

During immune response and T-cell activation, both effector T cells and regulatory T(T(reg)) cells are activated and regulated simultaneously by both positive and negative pathways. CD4(+)CD25(+) T(reg) cells play a critical role in immune tolerance to self antigens as well as to allografts in some transplant settings. Effective immunosuppressive regimens significantly reduced the incidence of acute allograft rejection in patients following organ transplantation. However, the impact of immunosuppressive treatment on the potential induction of transplant tolerance has not been well determined. In this review we summarize the effects of immunosuppressive reagents on CD4(+)CD25(+) T(reg) cells in order to bring attention to this issue, which may affect the choice of immunosuppressive regimen in the clinical setting.

Molecular antagonism and plasticity of regulatory and inflammatory T cell programs

Regulatory T (Treg) and T helper 17 (Th17) cells were recently proposed to be reciprocally regulated during differentiation. To understand the underlying mechanisms, we utilized a Th17 reporter mouse with a red fluorescent protein (RFP) sequence inserted into the interleukin-17F (IL-17F) gene. Using IL-17F-RFP together with a Foxp3 reporter, we found that the development of Th17 and Foxp3(+) Treg cells was associated in immune responses. Although TGF-beta receptor I signaling was required for both Foxp3 and IL-17 induction, SMAD4 was only involved in Foxp3 upregulation. Foxp3 inhibited Th17 differentiation by antagonizing the function of the transcription factors RORgammat and ROR*. In contrast, IL-6 overcame this suppressive effect of Foxp3 and, together with IL-1, induced genetic reprogramming in Foxp3(+) Treg cells. STAT3 regulated Foxp3 downregulation, whereas STAT3, RORgamma, and ROR* were required for IL-17 expression in Treg cells. Our data demonstrate molecular antagonism and plasticity of Treg and Th17 cell programs.

TH17 cells in development: an updated view of their molecular identity and genetic programming

Following activation, CD4+ T cells differentiate into different lineages of helper T (T(H)) cells that are characterized by distinct developmental regulation and biological functions. T(H)17 cells have recently been identified as a new lineage of effector T(H) cells, and they have been shown to be important in immune responses to infectious agents, as well as in various immune diseases. Over the past two to three years, there has been a rapid progress in our understanding of the differentiation programme of T(H)17 cells. Here, I summarize our current knowledge of the unique gene expression, cytokine-mediated regulation and transcriptional programming of T(H)17 cells, and provide my personal perspectives on the future studies that are required to elucidate this lineage in more detail.

IL-12-impaired and IL-12-secreting dendritic cells produce IL-23 upon CD154 restimulation

Experimental studies in monkeys on the basis of ex vivo-generated, reinjected dendritic cells (DCs) allow investigations of primate DC biology in vivo. To study in vitro and in vivo properties of DCs with a reduced capacity to produce IL-12, we adapted findings obtained in vitro with human cells to the rhesus macaque model. Following exposure of immature monocyte-derived monkey DCs to the immunomodulating synthetic polypeptide glatiramer acetate (GA) and to dibutyryl-cAMP (d-cAMP; i.e., a cAMP enhancer that activates DCs but inhibits the induction of Th1 immune responses), the resulting DCs displayed a mature phenotype with enhanced Ag-specific T cell stimulatory function, notably also for memory Th1 cells. Phosphorylation of p38 MAPK was not induced in GA/d-cAMP-activated DCs. Accordingly, these cells secreted significantly less IL-12p40 (p < or = 0.001) than did cytokine-activated cells. However, upon restimulation with rhesus macaque CD154, GA/d-cAMP-activated DCs produced IL-12p40/IL-23. Additionally, DCs activated by proinflammatory cytokines following protocols for the generation of cells used in clinical studies secreted significantly more IL-23 upon CD154 restimulation than following prior activation. Two days after intradermal injection, GA/d-cAMP-activated fluorescence-labeled DCs were detected in the T cell areas of draining lymph nodes. When similarly injected, GA/d-cAMP as well as cytokine-activated protein-loaded DCs induced comparable Th immune responses characterized by secretion of IFN-gamma, TNF, and IL-17, and transiently expanded FOXP3(+) regulatory T cells. Reactivation of primate DCs through CD154 considerably influences their immmunostimulatory properties. This may have a substantial impact on the development of innovative vaccine approaches.

Mechanisms in allergic airway inflammation - lessons from studies in the mouse

Asthma is a chronic inflammatory disease of the airways, involving recurrent episodes of airway obstruction and wheezing. A common pathological feature in asthma is the presence of a characteristic allergic airway inflammatory response involving extensive leukocyte infiltration, mucus overproduction and airway hyper-reactivity. The pathogenesis of allergic airway inflammation is complex, involving multiple cell types such as T helper 2 cells, regulatory T cells, eosinophils, dendritic cells, mast cells, and parenchymal cells of the lung. The cellular response in allergic airway inflammation is controlled by a broad range of bioactive mediators, including IgE, cytokines and chemokines. The asthmatic allergic inflammatory response has been a particular focus of efforts to develop novel therapeutic agents. Animal models are widely used to investigate inflammatory mechanisms. Although these models are not perfect replicas of clinical asthma, such studies have led to the development of numerous novel therapeutic agents, of which some have already been successful in clinical trials.

A novel role of IL-2 in organ-specific autoimmune inflammation beyond regulatory T cell checkpoint: both IL-2 knockout and Fas mutation prolong lifespan of Scurfy mice but by different mechanisms

Mutation of the Foxp3 transcription factor in Scurfy (Sf) mice results in complete absence of the CD4+Foxp3+ regulatory T cells (Tregs), severe multiorgan autoimmune syndrome, and early death at 4 wk of age. However, Sf mice simultaneously bearing the Il2-/- (Sf.Il2-/-) or Faslpr/lpr gene (Sf.Faslpr/lpr) have extended lifespan despite totally lacking Tregs, indicating a role of IL-2 and CD95 (Fas) signaling pathways in the multiorgan autoimmune syndrome beyond the Treg checkpoint. IL-2 has been implicated in regulating lymphoproliferation and CD178 (FasL) expression. However, Sf.Il2-/- mice have increased lymphoproliferation and FasL expression. Importantly, the pattern of organ-specific autoimmune response of Sf.Il2-/-mice resembled IL-2 knockout mice whereas that of Sf.Faslpr/lpr was similar to Sf mice, indicating that the distinct and weakened autoimmune manifestation in IL-2 knockout mice was not caused by the residual Tregs. Our study demonstrated a novel role of IL-2 in regulating multiorgan autoimmune inflammation beyond the Treg checkpoint and indicated that both Il2-/- and Faslpr/lpr genes prolong the lifespan of Sf mice but by different mechanisms.

Cancer treatment: the combination of vaccination with other therapies

Harnessing of the immune system by the development of ‘therapeutic’ vaccines, for the battle against cancer has been the focus of tremendous research efforts over the past two decades. As an illustration of the impressive amounts of data gathered over the past years, numerous antigens expressed on the surface of cancer cells, have been characterized. To this end, recent years research has focussed on characterization of antigens that play an important role for the growth and survival of cancer cells. Anti-apoptotic molecules like survivin that enhance the survival of cancer cells and facilitate their escape from cytotoxic therapies represent prime vaccination candidates. The characterization of a high number of tumor antigens allow the concurrent or serial immunological targeting of different proteins associated with such cancer traits. Moreover, while vaccination in itself is a promising new approach to fight cancer, the combination with additional therapy could create a number of synergistic effects. Herein we discuss the possibilities and prospects of vaccination when combined with other treatments. In this regard, cell death upon drug exposure may be immunogenic or non-immunogenic depending on the specific chemotherapeutics. Also, chemotherapy represents one of several options available for clearance of CD4⁺ Foxp3⁺ regulatory T cells. Moreover, therapies based on monoclonal antibodies may have synergistic potential in combination with vaccination, both when used for targeting of tumor cells and endothelial cells. The efficacy of therapeutic vaccination against cancer will over the next few years be studied in settings taking advantage of strategies in which vaccination is combined with other treatment modalities. These combinations should be based on current knowledge not only regarding the biology of the cancer cell per se, but also considering how treatment may influence the malignant cell population as well as the immune system.

Treatment strategies for allergy and asthma

Allergic diseases have reached epidemic proportions worldwide. An understanding of the cellular and soluble mediators that are involved in allergic inflammatory responses not only helps in understanding the mechanisms of current treatments, but is also important for the identification of new targets that are amenable to both small-molecule and biological interventions. There is now considerable optimism with regards to tackling the allergy epidemic in light of improvements in systemic and mucosal allergen-specific immunotherapy, the identification of key cytokines and their receptors that drive T-helper-2-cell polarization, a clearer understanding of the pathways of leukocyte recruitment and the signalling pathways that are involved in cell activation and mediator secretion, and new approaches to vaccine development.

Suppression of allergic inflammation by allergen-DNA-modified dendritic cells depends on the induction of Foxp3+ Regulatory T cells

CD4(+)CD25(+)Foxp3(+)Regulatory T cells (Tregs) play important roles in regulating allergic inflammation. To analyse if allergen-DNA-modified dendritic cells (DC) can suppress allergic responses and what roles Treg cells play in DC-based allergen-specific immunotherapy. Immature DC were transfected with retrovirus encoding Der p2 DNA, and administered to mice that sensitized and challenged with Der p2 protein. After Treg cells were depleted with anti-CD25 mAb, mice were re-challenged to observe the airway inflammation, and Treg cells in spleen CD4(+) T cells. And responses of spleen CD4(+) T cells to Der p2 were determined. Co-culture of naïve CD4(+) T cells with allergen-modified DC induced Foxp3+ Tregs. Sensitized and challenged mice developed allergic airway inflammation and Th2 responses, and decreased Foxp3(+) Tregs. Treatment with allergen-modified-DC suppressed airway inflammation and Th2 responses, and increased IL-10 and IFN-gamma production and Foxp3(+) Tregs significantly; and eliminated the responses of CD4(+) T cells to allergen. Administration of anit-CD25 mAb eliminated all the effects of modified-DC except for the increasing of IFN-gamma. Allergen-modified DC can induce immune tolerance to allergens and reverse the established Th2 responses induced by allergen, with dependence on the induction of Foxp3(+) Tregs.

CD4+CD25+ regulatory T cells in the small intestinal lamina propria show an effector/memory phenotype

CD4(+)CD25(+) regulatory T cells (Tregs) have been implicated in the suppression of pathogenic responses to both self- and non-self-antigens in the intestine. However, their precise properties and functions in the gut, as well as the molecular basis of their recruitment to the gut, are poorly understood. Here, we found that most of the CD4(+)CD25(+) T cells in the small intestinal lamina propria (LP) express Foxp3 and exhibit an 'effector/memory' phenotype, CD44(hi)CD45RB(lo)CD62L(-), whereas only a minority of the Foxp3(+)CD4(+)CD25(+) T cells in the spleen and mesenteric lymph nodes showed this phenotype. The Tregs in the small intestinal LP (LP-Tregs) expressed higher levels of CCR4 and CCR9 and a substantially lower level of CCR7 than the Tregs in the spleen. In vitro, the LP-Tregs showed chemotaxis to CCL25/thymus-expressed chemokine. In addition, they showed efficient chemotaxis to the CCR4 ligands, CCL17/thymus and activation-regulated chemokine and CCL22/macrophage-derived chemokine, which are abundantly expressed by dendritic cells (DCs) in the small intestinal LP. In vivo, approximately 50% of the LP-Tregs were closely associated or in direct contact with LP-DCs. These findings demonstrate that LP-Tregs are phenotypically and functionally unique and raise the possibility that they are retained in the small intestinal LP through the action of CCL17 and CCL22, which are locally produced by LP-DCs.

Overcoming immune tolerance against multiple myeloma with lentiviral calnexin-engineered dendritic cells

The key to successful cancer immunotherapy is to induce an effective anticancer immunity that will overcome the acquired cancer-specific immune tolerance. In this study, we found that dendritic cells (DCs) from multiple myeloma (MM) patients suppressed rather than induced a cancer cell-specific immune response. We demonstrated that CD4(+)CD25(high) T cells from MM patients suppressed the proliferation of activated peripheral blood lymphocytes. Further analysis illustrated that MM cell lysates or MM-specific idiotype immunoglobulins (MM Id-Ig) specifically induced the expansion of peripheral CD4(+)CD25(high)FoxP3(high) T regulatory (Treg) cells in vitro. Supraphysiological expression of calnexin (CNX) using lentiviral (LV) vectors in DCs of MM patients overcame the immune suppression and enhanced MM-specific CD4 and CD8 T-cell responses. However, overexpression of CNX did not affect the peripheral expansion of Treg cells stimulated by MM antigens. Thus, the immune suppression effect of Treg cells in cancer patients may be overcome by improving antigen processing in DCs, which in turn may lower the activation threshold of the immune effector cells. This concept of modulating anticancer immunity by genetically engineering cancer patients' DCs may improve immunotherapeutic regimens in cancer treatment.

Dynamics of the immune reaction to pancreatic cancer from inception to invasion

The dynamics of cancer immunosurveillance remain incompletely understood, hampering efforts to develop immunotherapy of cancer. We evaluated the evolving in vivo immune response to a spontaneous tumor in a genetically defined mouse model of pancreatic ductal adenocarcinoma from the inception of preinvasive disease to invasive cancer. We observed a prominent leukocytic infiltration even around the lowest grade preinvasive lesions, but immunosuppressive cells, including tumor-associated macrophages, myeloid-derived suppressor cells (MDSC), and regulatory T cells (Treg), dominated the early response and persisted through invasive cancer. Effector T cells, however, were scarce in preinvasive lesions, found in only a subset of advanced cancers, and showed no evidence of activation. The lack of tumor-infiltrating effector T cells strongly correlated with the presence of intratumoral MDSC with a near mutual exclusion. In vitro, we found that MDSC suppressed T-cell proliferation. Overall, our results show that suppressive cells of the host immune system appear early during pancreatic tumorigenesis, preceding and outweighing antitumor cellular immunity, and likely contribute to disease progression. Thus, in contrast to the hypothesis that an early "elimination phase" of cancer immunosurveillance is eventually overwhelmed by a growing invasive tumor, our findings suggest that productive tumor immunity may be undermined from the start. Efforts to test potent inhibitors of MDSC, tumor-associated macrophages, and Treg, particularly early in the disease represent important next steps for developing novel immunotherapy of cancer.

A regulatory role of interleukin 15 in wound healing and mucosal infection in mice

IL-15 plays a critical role in the development and maturation of gammadelta intraepithelial T lymphocytes (IEL), which are known to play important roles in wound healing and resolving inflammation in mice. In this study, we found that IL-15 transgenic (Tg) mice, under the control of a MHC Class I promoter, exhibited accelerated wound healing but were highly susceptible to genital infection with HSV-2. The IEL in the skin and reproductive organs of IL-15 Tg mice produced an aberrantly higher level of TGF-beta1 upon TCR triggering than in control mice. In vivo neutralization of TGF-beta ameliorated the susceptibility of IL-15 Tg mice to genital HSV-2 infection. Taken together, overexpression of IL-15 may stimulate IEL to produce TGF-beta1, promoting wound healing but impeding protection against genital HSV-2 infection.

Induction of oral tolerance to HSP60 or an HSP60-peptide activates T cell regulation and reduces atherosclerosis

OBJECTIVE

HSP60-specific T cells contribute to the development of the immune responses in atherosclerosis. This can be dampened by regulatory T cells activated via oral tolerance induction, and we explored the effect of oral tolerance induction to HSP60 and the peptide HSP60 (253 to 268) on atherosclerosis.

METHODS AND RESULTS

HSP60 and HSP60 (253 to 268) were administered orally to LDLr(-/-) mice before induction of atherosclerosis and resulted in a significant 80% reduction in plaque size in the carotid arteries and in a 27% reduction in plaque size at the aortic root. Reduction in plaque size correlated with an increase in CD4(+)CD25(+)Foxp3(+) regulatory T cells in several organs and in an increased expression of Foxp3, CD25, and CTLA-4 in atherosclerotic lesions of HSP60-treated mice. The production of interleukin (IL)-10 and transforming growth factor (TGF)-beta by lymph node cells in response to HSP60 was observed after tolerance induction.

CONCLUSIONS

Oral tolerance induction to HSP60 and a small HSP60-peptide leads to an increase in the number of CD4(+)CD25(+)Foxp3(+) regulatory T cells, resulting in a decrease in plaque size as a consequence of increased production of IL-10 and TGF-beta. We conclude that these beneficial results of oral tolerance induction to HSP60 and HSP60 (253 to 268) may provide new therapeutic approaches for the treatment of atherosclerosis.

Evaluation of tumour-infiltrating CD4+CD25+FOXP3+ regulatory T cells in human cutaneous benign and atypical naevi, melanomas and melanoma metastases

BACKGROUND

CD4+CD25+FOXP3+ regulatory T cells (Tregs) are thought to induce immunotolerance in melanoma. They have not yet been investigated in the entire spectrum of melanocytic cutaneous lesions within a tumour site.

OBJECTIVES

To evaluate CD4+CD25+FOXP3+ Tregs among tumour-infiltrating lymphocytes in cutaneous melanocytic lesions.

METHODS

We analysed 128 lesions (10 benign junctional common naevi, 10 benign compound common naevi, 10 compound Spitz naevi, 10 junctional atypical naevi, 20 compound atypical naevi, 20 radial growth phase melanomas, 30 vertical growth phase melanomas and 18 melanoma metastases). Tregs were identified by CD25-FOXP3 double immunostains.

RESULTS

This study indicates that CD4+/CD25+FOXP3+ Tregs are present in all groups of lesions. Junctional atypical naevi, compound atypical naevi and radial growth phase melanomas showed the highest percentages of CD4+CD25+FOXP3+ Tregs (junctional atypical naevi vs. junctional common naevi, compound common naevi, compound Spitz naevi, melanoma metastases: P < 0.0001; junctional atypical naevi vs. vertical growth phase melanomas: P = 0.001; compound atypical naevi vs. junctional common naevi, compound common naevi: P < 0.0001; compound atypical naevi vs. compound Spitz naevi, melanoma metastases: P = 0.002; compound atypical naevi vs. vertical growth phase melanomas: P = 0.02; radial growth phase melanomas vs. junctional common naevi, compound common naevi, compound Spitz naevi, melanoma metastases: P < 0.0001; radial growth phase melanomas vs. vertical growth phase melanomas: P = 0.008).

CONCLUSIONS

The strong prevalence of CD25+FOXP3+ Tregs both in junctional and compound atypical naevi and radial growth phase melanomas, suggests that they induce immunotolerance early during melanoma genesis, favouring melanoma growth. Their evaluation within a tumour site could be useful for prognostic and therapeutic purposes.

Regulatory dendritic cells protect against cutaneous chronic graft-versus-host disease mediated through CD4+CD25+Foxp3+ regulatory T cells

Chronic graft-versus-host disease (cGVHD) is a common cause of morbidity and mortality in allogeneic bone marrow transplantation (alloBMT). However, effective strategies for the treatment of cGVHD have not been established. In this study, we examined the therapeutic utility of modified dendritic cells (DCs) with a greater capacity to regulate immune responses than previously known tolerogenic DCs, regulatory DCs (DC(regs)), in the major histocompatibility complex-compatible, and multiple minor histocompatibility antigen-incompatible model of cGVHD in alloBMT. Treatment of the recipient mice after alloBMT with the recipient-type DC(regs) led to greater suppression of the incidence and severity of cutaneous cGVHD than rapamycin, whereas treatment with the recipient-type mature DCs promoted the pathogenesis. Analysis of the recipient mice suggested that the protective effect of the recipient-type DC(regs) involved the peripheral generation of alloreactive CD4(+)CD25(+)Foxp3(+)regulatory T (T(R)) cells from donor-derived CD4(+)CD25(-)Foxp3(-) T cells. Thus, immunotherapy with DC(regs) is a promising strategy for the treatment of cGVHD in alloBMT mediated through the induction of a dominant tolerance involving CD4(+)CD25(+)Foxp3(+) T(R) cells.

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.

The cross-talk between dendritic and regulatory T cells: good or evil?

Immune responses against pathogens require fine regulation to avoid excessive inflammation, which could be harmful to the host. Moreover, the immune system must be tolerant to nonpathogenic antigens to prevent allergy, autoimmunity, and transplant rejection. There is accumulating evidence that interactions between dendritic cells (DC) and regulatory T (Treg) cells play a crucial role in the balance between immune response and tolerance. Communications between these cells are complex, bidirectional, and mediated by soluble or cell surface molecules. The maturation status of DC, which may be influenced by different microenvironmental factors, is considered as an important checkpoint for the induction of peripheral tolerance through modifications of the activation status of T cells. Moreover, several lines of experimental evidence suggest that different subsets or the functional status of DC are also involved in the promotion of Treg cell differentiation. A better knowledge of the regulatory mechanisms of the immune response induced or inhibited by DC via their interactions with Treg cells could be relevant for the development of new, immunotherapeutic approaches.

Rapamycin-conditioned dendritic cells are poor stimulators of allogeneic CD4+ T cells, but enrich for antigen-specific Foxp3+ T regulatory cells and promote organ transplant tolerance

The ability of dendritic cells (DC) to regulate Ag-specific immune responses via their influence on T regulatory cells (Treg) may be key to their potential as therapeutic tools or targets for the promotion/restoration of tolerance. In this report, we describe the ability of maturation-resistant, rapamycin (RAPA)-conditioned DC, which are markedly impaired in Foxp3(-) T cell allostimulatory capacity, to favor the stimulation of murine alloantigen-specific CD4(+)CD25(+)Foxp3(+) Treg. This was distinct from control DC, especially following CD40 ligation, which potently expanded non-Treg. RAPA-DC-stimulated Treg were superior alloantigen-specific suppressors of T effector responses compared with those stimulated by control DC. Supporting the ability of RAPA to target effector T and B cells, but permit the proliferation and suppressive function of Treg, an infusion of recipient-derived alloantigen-pulsed RAPA-DC followed by a short postoperative course of low-dose RAPA promoted indefinite (>100 day) heart graft survival. This was associated with graft infiltration by CD4(+)Foxp3(+) Treg and the absence of transplant vasculopathy. The adoptive transfer of CD4(+) T cells from animals with long-surviving grafts conferred resistance to rejection. These novel findings demonstrate that, whereas maturation resistance does not impair the capacity of RAPA-DC to modulate Treg, it profoundly impairs their ability to expand T effector cells. A demonstration of this mechanism endorses their potential as tolerance-promoting cellular vaccines.

In vivo treatment with a nonapeptide thymic hormone, facteur thymique serique (FTS), ameliorates chronic colitis induced by dextran sulphate sodium in mice

Facteur thymique serique (FTS), a thymic hormone with nonapeptide is involved in T cell differentiation in intestine. Here we investigated the effect of FTS on dextran sulphate sodium (DSS)-induced colitis. BALB/c mice were subcutaneously treated with 1 mug/mouse/day of FTS daily. FTS did not affect the course of acute colitis induced by DSS as assessed by survival rate, clinical activity of diseases, extent of tissue damage of colons. On the other hand, FTS significantly ameliorated chronic colitis induced by multiple cycles of DSS as reflected by lower lethality, weight loss, clinical scores and histological scores. The levels of interferon (IFN)-gamma, interleukin 1(IL-1)-beta, and IL-12p40 in the culture supernatants of lamina propria (LP) cells of colon without any stimulation and IFN-gamma by T cells in the LP T cells under T cell receptor (TCR) triggering were reduced in FTS-treated mice, whereas the levels of IL-10 by LP cells and LPT cells were higher in FTS-treated mice. Thus, FTS may serve to suppress inflammation in DSS-induced chronic colitis accompanied by increased IL-10 production.

Large functional repertoire of regulatory T-cell suppressible autoimmune T cells in scurfy mice

Scurfy mice which lacks functional Foxp3 transcription factor and CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells, spontaneously develop autoimmune responses against skin, lung, liver and tail. However, many organs/tissues are spared from autoimmune attack. Here, we demonstrate that scurfy mice contain dormant autoimmune T cells that induced new diseases such as sialoadenitis, dacryoadenitis, pancreatitis, gastritis, intestinal inflammation, colitis, and myositis in RAG-1 KO mice. Inflammation in as many as 12 organs/tissues was consistently induced in individual recipients with scurfy lymph node cells containing as few as 1.25 x 10(6) CD4(+) T cells. Moreover, transfer of the multiple organ autoimmune diseases could be suppressed by as little as 0.5 x 10(6) CD4(+)CD25(+) Treg cells, mediated by inhibiting autoimmune T-cell expansion. Our study provides evidence for the presence of a large repertoire of autoimmune lymphocytes against various organs/tissues in scurfy mice as well as Treg cells in B6 mice capable of suppressing the expansion of these autoimmune lymphocytes. Various conditions that control the expression of autoimmune T cells are discussed.

Epicutaneous immunization with type II collagen inhibits both onset and progression of chronic collagen-induced arthritis

Epicutaneous immunization is a potential non-invasive technique for antigen-specific immune-modulation. Topical application of protein antigens to barrier-disrupted skin induces potent antigen-specific immunity with a strong Th2-bias. In this study, we investigate whether the autoimmune inflammatory response of chronic collagen-induced arthritis (CCIA) in DBA/1-TCR-β Tg mice can be modified by epicutaneous immunization. We show that epicutaneous immunization with type II collagen (CII) inhibited development and progression of CCIA and, importantly, also ameliorated ongoing disease as indicated by clinical scores of disease severity, paw swelling and joints histology. Treated mice show reduced CII-driven T cell proliferation and IFN-γ production, as well as significantly lower levels of CII-specific IgG2a serum antibodies. In contrast, CII-driven IL-4 production and IgE antibody levels were increased consistent with skewing of the CII response from Th1 to Th2 in treated mice. IL-4 production in treated mice was inversely correlated with disease severity. Moreover, T cells from treated mice inhibited proliferation and IFN-γ production by T cells from CCIA mice, suggesting induction of regulatory T cells that actively inhibit effector responses in arthritic mice. The levels of CD4⁺CD25⁺ T cells were however not increased following epicutaneous CII treatment. Together, these results suggest that epicutaneous immunization may be used as an immune-modulating procedure to actively re-programme pathogenic Th1 responses, and could have potential as a novel specific and simple treatment for chronic autoimmune inflammatory diseases such as rheumatoid arthritis.