Rapamycin inhibits differentiation of Th17 cells and promotes generation of FoxP3+ T regulatory cells

Reciprocal differentiation of immunosuppressive CD4⁺CD25⁺FoxP3⁺ T regulatory cells (Tregs) and proinflammatory IL-17-producing cells (Th17) from naïve CD4 cells is contingent upon the cytokine environment. Using MACS-purified CD4 cells, we found that rapamycin and cyclosporine A (CsA) potently inhibited the TGFβ and IL-6-induced generation of IL-17-producing cells. Intriguingly, rapamycin promoted, while CsA markedly inhibited, TGFβ-mediated generation of Tregs. The aforementioned effects of rapamycin and CsA were also observed for Flow-sorted CD4⁺CD25⁻ T cells, indicating that the effect of these two immunosuppressive agents was based on their action on de novo generation of Tregs and Th17 cells from naïve CD4 cells. Our observation suggests a distinct mode of immunosuppressive action and tolerance induction by rapamycin and CsA. The capacity of rapamycin to generate immunosuppressive Tregs and to suppress differentiation of pathogenic Th17 cells furthers our understanding of the basis for the therapeutic immunosuppressive effects of rapamycin in patients with autoimmune diseases and allo-transplantation reactions.     

Alloantigen specific T regulatory cells in transplant tolerance

CD4⁺CD25⁺Foxp3⁺T cells are regulatory/suppressor cells (Treg) that include non-antigen(Ag)-specific as well as Ag-specific Tregs. How non-Ag-specific naïve CD4⁺CD25⁺Treg develop into specific Tregs is unknown. We have studied DA rats tolerant to fully allogeneic PVG cardiac grafts that survived with out immunosuppression for over 100 days and identified the cellular basis of alloantigen specific tolerance. Key observations from our studies will be reviewed including how CD4⁺CD25⁺Tregs were first identified and the cytokine dependence of CD4⁺T cells that transfer alloantigen specific transplant tolerance which died in culture unless stimulated with both cytokine rich ConA supernatant and specific donor alloantigen. Both the tolerant CD4⁺CD25⁺ and CD4⁺CD25⁻ T cell populations are required to transfer tolerance, yet alone the CD4⁺CD25⁻ T cell effect rejection. Tolerance transfer occurs with a low ratio of CD4⁺CD25⁺T cells (< 1:10), whereas to induce tolerance with naive CD4⁺CD25⁺T cells requires both a ratio of > 1:1 and is not alloantigen specific.Recent findings on how naïve CD4⁺CD25⁺T cells developed into two separated pathways of alloantigen specific Tregs, by culturing them with alloAg with either IL-2 or IL-4 and donor alloantigen are described. IL-2 enhances IFN-γR and IL-5 mRNA while IL-4 induced a reciprocal profile with de novo IL-5Rα and increased IFN-γ mRNA expression. Both IL-2 and IL-4 alloactivated CD4⁺CD25⁺Tregs within 3–4 days of culture can induce alloantigen specific tolerance at ratios of 1:10. Long term, CD4⁺CD25⁺T cells from tolerant hosts given IL-2 cultured cells have increased IL-5 and IFN-γR mRNA; whereas hosts given IL-4 cultured cells had enhanced IL-5Rα mRNA expression and IL-5 enhanced their proliferation to donor but not third party alloAg.These findings suggest that Th1 and Th2 responses activate two pathways of alloantigen specific Tregs that can mediate transplant tolerance but are dependent upon cytokines produced by ongoing Th1 and/or Th2 immune responses.     

CD4+ Foxp3+ regulatory T cells induced by TGF-β, IL-2 and all-trans retinoic acid attenuate obliterative bronchiolitis in rat trachea transplantation

Obliterative bronchiolitis (OB) is the major obstacle for long-term allograft survival in lung transplantation, and the underlying mechanism is still not well understood. Regulatory T cells (Tregs) have been shown to be essential in the maintenance of immune tolerance. In this study we investigated the role of Tregs in protecting OB in rat. We show that the combination of TGF-β, Interleukin (IL)-2, and all-trans retinoic acid (atRA) could induce naïve rat CD4⁺CD25⁻ T cells to differentiate into CD4⁺CD25⁺Foxp3⁺ T cells in vitro, and they acquired suppressive function. In a rat orthotopic tracheal transplantation OB model, the adoptive transfer of the induced Tregs reduced symptoms of airway obliteration and fibrication of grafts when compared with adoptive transfer of control cells without suppressive property. Moreover, recipients treated with the induced Tregs secreted high level of immunosuppressive cytokine TGF-β and IL-10, and low level of pro-inflammatory cytokines IL-17, IFN-γ, IL-6, and MCP-1, and had fewer effector T cells including Th17 cells and Th1 cells in the graft. Taken together, these findings suggest that in vitro induced Tregs by the combination of TGF-β, IL-2, and atRA are effective in protecting rat trachea allograft rejection through the inhibition of effector T cells and their function. These datas implicate new therapies to prevent OB and allograft rejection in human lung transplantation.     

T2 enhances in situ level of Foxp3+ regulatory cells and modulates inflammatory cytokines in Crohn's disease

BackgroundActing via IL-10 and transforming growth factor-β (TGF-β), t regulatory cells (Tregs) that express the Forkhead Box P3 (Foxp3) play a vital role in maintaining intestinal immune homeostasis. Many studies have found correlation between Foxp3⁺ Treg cells and Crohn's disease (CD). T2, extracted from the medicinal plant Tripterygium wilfordii Hook F, has already been proved to be therapeutically effective in inducing the remission of CD. However, the mechanisms in human studies remain largely unknown.AimWe aimed to explore the effect of T2 on the in situ levels of inflammatory cytokines and the number of Foxp3⁺ Tregs in inflamed mucosa of CD.MethodsMucosal biopsies from 20 patients treated with T2 were taken by colonoscopy. The changes of Foxp3⁺ Tregs as well as TNF-α and IL-10 in diseased tissue were visualized by immunochemistry. Western blot and ELISA were used to quantify levels of Foxp3 protein expression and inflammatory cytokines.ResultsT2 treatment ameliorated the pathological inflammation of CD. We observed that the significantly elevated Foxp3⁺ Tregs and IL-10 levels in the mucosa of CD patients after T2 treatment concurred with the down-regulation of proinflammatory TNF-α.ConclusionWe confirmed the efficacy of T2 treatment in CD and showed that microscopic inflammation was attenuated by the modulation of in situ levels of inflammatory cytokines. The therapeutic mechanisms might involve the up-regulation of Foxp3⁺ Tregs.     

CNI induced Th17/Treg imbalance and susceptibility to renal dysfunction in renal transplantation

Calcineurin inhibitors (CNI) prevent graft rejection by blocking interleukin-2 (IL-2), which was required for development and function of Foxp3⁺CD4⁺CD25⁺ regulatory T cells (Treg). Recently, IL-2 was reported to play a part in the inhibition of Th17 cells. The renal transplantation recipient who used CNI regularly might have Th17/Treg imbalance with increased Th17 cells and decreased Treg cells, which would cause renal dysfunction even rejection. To assess the effect of CNI on Th17 cells and Treg cells, we included 123 renal transplantation recipients (101 in a stable stage and 22 with renal dysfunction) and 27 healthy volunteers. Among all the recipients, 103 recipients used CNI and 20 recipients used sirolimus without CNI. The recipients who used CNI were further classified into four groups according to the blood levels of CNI: Of all these subjects, Th17 and Treg frequencies in the peripheral blood were analyzed by flow cytometry (FCM). Serums IL-17, IL-23, IL-6, IFN-r, and TGF-β were analyzed by ELISA. The results demonstrated that the transplantation recipient treated by CNI revealed an obvious increase in peripheral Th17 frequencies and a significant decrease in Treg frequencies when compared with the sirolimus group and healthy people (P < 0.05). Even more, the transplantation recipient with renal dysfunction had the highest level of Th17 cells (P < 0.05) while the lowest Treg cells compared with stable recipient and healthy control, with increased serums IL-6 and IL-17. Our results indicated that CNI was associated with Th17/Treg imbalance in peripheral blood, which supported the followed generation of renal dysfunction after transplantation.     

CD8+CD103+ regulatory T cells in spontaneous tolerance of liver allografts

It has been shown that rat liver allografts between certain inbred major histocompatibility complex (MHC) disparate strains are accepted spontaneously, and regulatory T cells (Tregs) have been suggested to play a role in the spontaneous liver tolerance. CD8⁺CD103⁺ T cells bear the phenotypes of effector cells, and they are implicated in allograft destruction. Here we provide evidence that CD8⁺CD103⁺ T cells possess regulatory function and may contribute to prevent liver allograft rejection. We show that the expression of CD103 in the CD8⁺ T cells was increased in spontaneous liver grafts tolerant recipients. We further show that CD8⁺CD103⁻ T cells can also upregulate the expression of CD103 and Foxp3 after stimulation with alloantigen or TGF-β in vitro, and the CD8⁺CD103⁺ T cells acquired regulatory properties. The suppressive function of the alloantigen or TGF-β conditioned CD8⁺CD103⁺ T cells was cell–cell contact dependent. These results imply that liver-specific factor(s) would be involved in the generation of CD8⁺CD103⁺ Tregs that contribute to spontaneous liver allografts tolerance.     

Pre-differentiated Th1 and Th17 effector T cells in autoimmune gastritis: Ag-specific regulatory T cells are more potent suppressors than polyclonal regulatory T cells

Naïve antigen-specific CD4⁺ T cells (TxA23) induce autoimmune gastritis when transferred into BALB/c nu/nu mice. Transfer of in vitro pre-differentiated Th1 or Th17 TxA23 effector T cells into BALB/c nu/nu recipients induces distinct histological patterns of disease. We have previously shown that co-transfer of polyclonal naturally occurring Treg (nTreg) suppressed development of Th1-, but not Th17-mediated disease. Therefore, we analysed the suppressive capacity of different types of Treg to suppress Th1- and Th17-mediated autoimmune gastritis. We compared nTreg with polyclonal TGFβ-induced WT Treg (iTreg) or TGFβ-induced antigen-specific TxA23 iTreg in co-transfer experiments with Th1 or Th17 TxA23 effector T cells. 6 weeks after transfer in vitro pre-differentiated TxA23 Th1 and Th17 effector cells induced destructive gastritis. Th1-mediated disease was prevented by co-transfer of nTreg and also antigen-specific iTreg, whereas WT iTreg did not show an effect. However, Th17-mediated disease was only suppressed by antigen-specific iTreg. Pre-activation of nTreg in vitro prior to transfer did not increase their suppressive activity in Th17-mediated gastritis. Thus, antigen-specific iTreg are potent suppressors of autoimmune gastritis induced by both, fully differentiated Th1 and Th17 effector cells.     

外源性LTB4对CIA小鼠Treg/Th17脾细胞分化的作用

目的探讨外源性白三烯B4(LTB4)对胶原诱导型关节炎(collagen-induced arthritis,CIA)小鼠脾细胞调节性T细胞(Treg)和Th17细胞分化的调节,进一步阐明LTB4在类风湿关节炎(RA)发病中的作用机制。方法建立CIA小鼠模型,取造模d28的脾细胞,体外实验分析外源性LTB4对Treg和Th17细胞分化的影响。应用流式细胞术检测CD4+CD25+Foxp3+细胞的数量,荧光定量PCR技术检测调控Treg和Th17细胞分化的特异性转录因子Foxp3和RORγt的mRNA的表达,酶联免疫吸附(ELISA)方法检测培养细胞上清IL-17的含量。结果成功建立CIA小鼠模型;造模d28分离小鼠脾细胞,体外培养加入鸡Ⅱ型胶原(CⅡ)共同孵育,随着LTB4浓度增加(0.01、0.1、1μmol·L-1),CD4+CD25+Foxp3+细胞数量相应减少,Foxp3 mRNA的表达相应降低;相反,IL-17的含量相应增加,RORγt mRNA的表达相应升高。结论LTB4抑制CIA模型脾细胞Treg细胞的分化,促进Th17细胞的分化,提示LTB4在CIA发病过程中具有一定的促炎活性。     

Oridonin inhibits 4T1 tumor growth by suppressing Treg differentiation via TGF-β receptor

The Chinese herbal medicine oridonin has potent anti-inflammatory and antitumor activities. In addition, oridonin treatment effectively suppresses breast cancer growth. However, the underlying mechanisms are poorly defined. Here, we reported that oridonin decreased Treg differentiation in vitro and in vivo. Oridonin inhibition of Treg differentiation was dependent on decreasing TGF-β receptor expression. Oridonin attenuated Tregs’ immunosuppressive ability; thus, oridonin did not inhibit CD8⁺ T cell proliferation very well in vitro. Oridonin greatly delayed the progression of 4T1 tumors in vivo. In addition, oridonin combined with anti-PD-1 activated a robust antitumor immune response and suppressed 4T1 tumor growth. Therefore, our results indicate that oridonin inhibits TNBC growth by modulating Treg differentiation, which provides new directions for the clinical treatment of TNBC.     

Upregulation of PD-1 on CD4+CD25+T cells is associated with immunosuppression in liver of mice infected with Echinococcus multilocularis

Alveolar echinococcosis is a zoonotic disease caused by Echinococcus multilocularis (E. multilocularis) infection. The relationship between PD-1/PD-L1 pathway and Tregs at different stages of E. multilocularis infection has rarely been reported. This study aims to investigate the role of PD-1/PD-L1 in immunosuppression of Tregs in E. multilocularis infection. Hematoxylin-eosin staining, flow cytometry, immunohistochemistry, quantitative RT-PCR analysis, cytometric bead array and MTT assay were used to analyze liver pathological changes, percentages of PD-1⁺ Tregs and PD-L1⁺ dendritic cells (DCs), expression levels of PD-1, PD-L1 and Foxp3, levels of interleukin-10 (IL-10) and transforming growth factor beta (TGF-β) and proliferation of lymphocytes. During middle-late stage (day 30 to day 330) the percentages of PD-1⁺ Tregs and PD-L1⁺ DCs together with levels of Foxp3, IL-10 and TGF-β increased significantly and maintained at high level. The expression of PD-1 and PD-L1 was increased with the enlarging erosion of E. multilocularis, and was mainly distributed in hepatic sinus, fibrous wall of alveolar hydatid and germinal layer around foci of infection. PD-1/PD-L1 promoted the secretion of IL-10 and TGF-β. Our results indicate that engagement of the PD-1 and PD-L1 correlates with inhibition of T-cell effector function, cytokine secretion and proliferation. High expression of PD-1/PD-L1 may play an important role in stimulating CD4⁺CD25⁺ T cells, and maintaining peripheral tolerance and immune evasion during chronic infection of E. multilocularis.     

Changes in regulatory T cells in patients with ovarian cancer undergoing surgery: Preliminary results

Regulatory T cells (Treg) suppress immune responses in patients with cancer. Surgery is the most effective therapeutic strategy for ovarian cancer (OC). However, the interplay between the Treg population and surgical resection remains unclear. 61 patients with OC who received no prior treatment were enrolled in the study. Treg percentages were characterized from peripheral blood mononuclear cells. We investigated CD4⁺ CD25⁺, CD4⁺ CD25⁺ Foxp3⁺, CD8⁺ CD28⁻, and CD8⁺ Foxp3⁺ Tregs in OC patients and their postoperative changes using flow cytometry. Treg percentages were significantly higher in OC patients than those in benign ovarian tumors (BOT) and healthy controls. Higher percentages of Tregs were found in patients with stage III/IV than stage I/II OC. Treg percentages were significantly decreased postoperatively. The postoperative Treg percentages in patients with stage I/II OC were similar to those in BOT patients, while postoperative Treg percentages in patients with stage III/IV OC remained higher. Tregs were markedly lower on postoperative day (POD) 3 than preoperatively. They increased slightly after 7 days, but remained lower than preoperative levels. These data suggested that Tregs continued to decline from POD 7 to POD 30. Treg percentages are correlated with the tumor burden and could be a key factor in monitoring the immunological status of patients with OC.     

Combined therapy of CD4+CD25+ regulatory T cells with low-dose sirolimus,but not calcineurin inhibitors,preserves suppressive function of regulatory T cells and prolongs allograft survival in mice

Our previous study proved that sirolimus is a potent immunosuppressant which induces long-term allograft survival depends on persistence of alloantigens. CD4⁺CD25⁺ regulatory T (Treg) cells are potent suppressors in transplantation. Our objectives focus on whether combined-therapy of Tregs with immunosuppressants could prolong allograft survival in mice.The study showed that inhibition of Tregs was maintained by co-cultured with sirolimus (1 nM) in vitro, but not tacrolimus (1 nM) or CsA (1 nM). When the concentration was increased > 100 nM, suppression was fallen. Based on the ability of sirolimus to target effector T cells, but retaining the inhibition of Tregs, an adoptive infusion of donor alloantigen specific Tregs combined with 30-day sirolimus (1 mg/kg) and 3-day ATG (20 mg/kg) was found to prolong heart allograft survival in mice. Even though the cell numbers of CD4⁺ T cells were found to decrease in sirolimus-treated mice, sirolimus selectively enhanced the numbers of CD4⁺CD25⁺ cells and increased the expression of Foxp3 in spleens and lymph nodes, respectively, in recipients. However, combined therapy with low-dose CsA (5 mg/kg) or tacrolimus (1 mg/kg) reduced significantly the expression of Foxp3 and failed to prolong the allograft survival.In summary, expanded Tregs exposed to sirolimus can survive, proliferate, and preserve inhibition in vitro. Tregs are more resistant to sirolimus than other T cells. Combined with Tregs, sirolimus rather than calcineurin inhibitors, prolongs the allograft survival. Sirolimus may be the best copartner for Tregs therapy. It also suggests calcineurin-dependent signals may be required in the development of Tregs.     

Immunoregulatory Cordyceps sinensis increases regulatory T cells to Th17 cell ratio and delays diabetes in NOD mice

Cordyceps sinensis (CS) is a parasitic fungus, and it has been used widely in traditional Chinese medicines (TCM) for centuries. Many studies have shown that CS has immunoregulatory activity in many disease models, but the underlying mechanism remains elusive. We studied whether CS could suppress the onset of diabetes by altering T lymphocyte subsets in non-obese diabetic (NOD) mice. We found that the onset of type1 diabetes in NOD mice was associated with an imbalance of CD4⁺CD25⁺FoxP3⁺ regulatory T (Treg) cells and IL-17 producing Th17 cells. Oral administration of CS resulted in reduction in the overall incidence of diabetes, and this was due to an increase in the ratio of Treg cells to Th17 in the spleen and pancreatic lymph nodes (PLNs). Taken together, these data imply that CS is able to modulate Treg to Th17 cell ratio in vivo, thus contributing to the inhibition of diabetes.     

Costunolide,a sesquiterpene lactone,inhibits the differentiation of pro-inflammatory CD4+ T cells through the modulation of mitogen-activated protein kinases

CD4⁺ T cell activation and adequate differentiation into effector T helper (Th) cells are crucial for mediating adaptive immune responses to cope with foreign pathogens. Despite the significant role of Th cells, excessive increases in their numbers result in inflammatory and autoimmune diseases. In this study, we investigated the effects of costunolide, a plant-derived natural compound with an anti-inflammatory activity, in regulating Th cells and the underlying mechanisms. Costunolide significantly decreased cell populations of differentiated Th1, Th2, and Th17 subsets under Th subset-polarizing conditions, while exerting statistically negligible effects on Treg cell differentiation. Furthermore, costunolide inhibited the expression level of Th subset-polarizing master genes such as T-bet, GATA3, and RORγt, indicating that costunolide inhibits the differentiation of CD4⁺ T cells into Th subsets. Additionally, costunolide suppressed the proliferative activity of CD4⁺ T cells and the expression of CD69 activation marker on CD4⁺ T cells. When the molecular targets of costunolide were investigated, phosphorylation of ERK and p38 was found to be decreased under Th subset-polarizing conditions, whereas activity of JNK remained unchanged. U0126, an ERK inhibitor, and SB203580, a p38 inhibitor, decreased the expression of CD69 upon TCR stimulation and inhibited CD4⁺ T cell differentiation, indicating that both ERK and p38 are suggested to be critical molecular targets of costunolide. Taken together, these results suggest that costunolide inhibits the differentiation of CD4⁺ T cells by suppressing ERK and p38 activities and can be an effective therapeutic agent for T cell-mediated immune diseases.     

Dysfunction of IL-10-producing type 1 regulatory T cells and CD4+CD25+ regulatory T cells in a mimic model of human multiple sclerosis in Cynomolgus monkeys

CD4⁺CD25⁺ Treg and IL-10⁺ Tr1 cells play a major role in controlling autoimmunity by suppressing self-reactive T cells. Dysfunction of Tregs appears to be a critical factor in the pathogenesis of autoimmune diseases. Multiple sclerosis (MS) is an inflammatory demyelinating disorder of CNS, where CD4⁺ T cells result in nervous tissue damage. The aim of this study was to investigate the protective role of Treg and Tr1 cells in a mimic model of human MS in Cynomolgus monkeys.This study indicated the suppressive capacity of Tregs from MS monkeys was impaired compared with naive controls. The population of CD4⁺CD25⁺ Tregs was decreased in acute stage of MS. However, they showed a restored function and percentage in remitting monkeys. In stable phase, CD4⁺CD25⁺ Tregs differentially expressed elevated level of CD62P cell adhesion molecule which contributes to the mechanism by which Treg cells inhibit CD4⁺ T cell responses. On the other hand, the percentage of CD4⁺IL-10⁺ Tr1 and suppressive function of Tr1 cells were found reduced in MS monkeys. IL-10 secretion was diminished almost 9-fold in active MS, and recovered in active MS. This deficit in IL-10 secretion was specific to CD3/CD46, but not to CD3/CD28 stimulation. The concentrations of IFN-γ secreted by CD3/CD46-activated T cells were also not affected.These results demonstrate that Tregs are dysfunctional in Cynomolgus monkey with MS. Loss of regulatory function appears to be an important factor in the pathogenesis of MS. Hence, to develop new approaches for induction of Tregs in vivo may be beneficial for the clinical treatment in autoimmune diseases.     

LncRNA XLOC_003810 modulates thymic Th17/Treg balance in myasthenia gravis with thymoma

Imbalance of T helper 17 (Th17)/regulatory T (Treg) cells is involved in the pathogenesis of myasthenia gravis with thymoma (MG-T). Long non-coding RNAs (lncRNAs) are implicated in the regulation of Th17/Treg balance. This study was designed to explore the role of XLOC_003810, a novel lncRNA, in regulating the Th17/Treg balance in MG-T. The thymic CD4⁺ T cells were isolated from control subjects and MG-T patients. The Th17/Treg balance was evaluated by determining proportions of Th17 and Treg cells and expression of Th17- and Treg- associated molecules. Lentivirus-mediated silencing and overexpression of XLOC_003810 in CD4⁺ T cells were performed. The results showed that XLOC_003810 expression was higher in MG-T thymic CD4⁺ T cells than that in the control group. Furthermore, the ratio of Th17/Treg cells, proportion of Th17 cells and levels of Th17-associated molecules were significantly increased, whereas the proportion of Treg cells and levels of Treg-associated molecules were decreased in MG-T thymic CD4⁺ T cells. Importantly, the Th17/Treg imbalance in MG-T thymic CD4⁺ T cells was aggravated by XLOC_003810 overexpression, whereas it was attenuated by XLOC_003810 silencing. Collectively, XLOC_003810 modulates thymic Th17/Treg balance in MG-T patients, providing the scientific basis for the clinical targeted therapy of MG-T.     

Minireview: Divergent roles of α7 nicotinic acetylcholine receptors expressed on antigen-presenting cells and CD4+ T cells in the regulation of T cell differentiation

α7 nAChRs expressed on immune cells regulate antigen-specific antibody and proinflammatory cytokine production. Using spleen cells from ovalbumin (OVA)-specific T cell receptor transgenic DO11.10 mice and the α7 nAChR agonist GTS-21, investigation of (1) antigen processing-dependent and (2) -independent, antigen presenting cell (APC)-dependent, naïve CD4⁺ T cell differentiation, as well as (3) non-specific APC-independent, anti-CD3/CD28 mAbs-induced CD4⁺ T cell differentiation, revealed the differential roles of α7 nAChRs expressed on T cells and APCs in the regulation of CD4⁺ T cell differentiation. GTS-21 suppressed OVA-induced antigen processing- and APC-dependent differentiation into regulatory T cells (Tregs) and effector T cells (Th1, Th2 and Th17) without affecting OVA uptake or cell viability. By contrast, GTS-21 upregulated OVA peptide-induced antigen processing-independent T cell differentiation into all lineages. During anti-CD3/CD28 mAbs-induced T cell differentiation in the presence of polarizing cytokines, GTS-21 promoted wild-type T cell differentiation into all lineages, but did not affect α7 nAChR-deficient T cell differentiation. These results demonstrate (1) that α7 nAChRs on APCs downregulate T cell differentiation by inhibiting antigen processing and thereby interfering with antigen presentation; and (2) that α7 nAChRs on T cells upregulate differentiation into Tregs and effector T cells. Thus, the divergent roles of α7 nAChRs on APCs and T cells likely regulate the intensity of immune responses. These findings suggest the possibility of using α7 nAChR agonists to harvest greater numbers of Tregs and Th1 and Th2 cells for adoptive immune therapies for treatment of autoimmune diseases and cancers.     

Effects of human umbilical cord-derived mesenchymal stem cells on anterior chamber-associated immune deviation

Introduction of antigen into anterior chamber (AC) induces a deviant immune response termed anterior chamber-associated immune deviation (ACAID) that protects the eye from inflammatory destruction consequent to a systemic immune response. Mesenchymal stem cells (MSCs) can modulate a variety of immune responses. However, the effects of systemic administration of MSCs on ACAID have not been explored. In this study, C57BL/6 mice were inoculated with ovalbumin in the AC to induce ACAID, control group received AC injection of solvent alone. Immediately after the AC injection, the mice were injected through the tail vein with human Umbilical Cord-derived MSCs (hUC-MSC) or phosphate buffer saline. All animals were subcutaneously immunized with ovalbumin one week later. Delayed-type hypersensitivity assay was performed another week following immunization. The splenic monocytes were then isolated, cultured and stimulated with ovalbumin. Levels of IL-10, TGF-β, and IFN-γ in culture media were measured by ELISA. The frequencies of CD4⁺CD25⁺Foxp3⁺ and CD8⁺Foxp3⁺ regulatory T cells (Tregs) were determined by flow cytometry. The results showed that the AC inoculation of ovalbumin induced significantly less ear swelling than controls, confirming the establishment of ACAID. MSCs potentiated IL-10 and TGF-β production, further suppressed IFN-γ secretion from splenic monocytes in ACAID mice, and enhanced expansion of CD4⁺CD25⁺Foxp3⁺ and CD8⁺Foxp3⁺ Tregs isolated from the spleen of ACAID mice. Therefore, our study, for the first time, provides clear evidence that systemic administration of MSCs augments cytokine production and Treg expansion from ACAID spleens, which may contribute to promotion and maintenance of ACAID.