CD8+ T cells produce IL-2, which is required for CD(4+)CD25+ T cell regulation of effector CD8+ T cell development for contact hypersensitivity responses

Interleukin (IL)-2 functions to promote, as well as down-regulate, expansion of antigen-reactive CD4+ and CD8+ T cells, but the role of IL-2 in hapten-specific CD8+ T cell priming for contact hypersensitivity (CHS) responses remains untested. Using enzyme-linked immunospot to enumerate numbers of hapten-specific CD4+ and CD8+ T cells producing IL-2 in hapten-sensitized mice, the number of IL-2-producing CD8+ T cells was tenfold that of CD4+ T cells. Hapten-primed CD4+ T cells produced low amounts of IL-2 during culture with hapten-presenting Langerhans cells, whereas production by hapten-primed CD8+ T cells was fivefold greater. CD8+ T cells did not express CD25 during hapten priming, but treatment with anti-IL-2 or anti-CD25 monoclonal antibodies during hapten sensitization increased hapten-specific effector CD8+ T cells as well as the magnitude and duration of the CHS response. These results indicate that CD8+ T cells are the primary source of IL-2 and that this IL-2 is required for the function of a population of CD(4+)CD25+ T cells to restrict the development of the hapten-reactive effector CD8+ T cells that mediate CHS responses.     

Regulatory function of CD4+CD25+ T cells from Class II MHC-deficient mice in contact hypersensitivity responses

Contact hypersensitivity (CHS) is a CD8+ T cell-mediated, inflammatory response to hapten sensitization and challenge of the skin. During sensitization, the magnitude and duration of hapten-specific CD8+ T cell expansion in the skin-draining lymph nodes (LN) are restricted by CD4+CD25+ T regulatory cells (Treg). The regulation of hapten-specific CD8+ T cell priming in Class II MHC-deficient (MHC-/-) mice was investigated. Although hapten-specific CD8+ T cell priming and CHS responses were elevated in Class II MHC-/- versus wild-type mice, presensitization depletion of CD4+ or CD25+ cells in Class II MHC-/- mice further increased CD8+ T cell priming and the elicited CHS response. Flow cytometry analyses of LN cells from Class II MHC-/- mice revealed a population of CD4+ T cells with a majority expressing CD25. Forkhead box p3 mRNA was expressed in LN cells from Class II MHC-/- and was reduced to background levels by depletion of CD4+ or CD25+ cells. Isolated CD4+CD25+ T cells from wild-type and Class II MHC-/- mice limited in vitro proliferation of alloantigen- and hapten-specific T cells to antigen-presenting stimulator cells. These results identify functional CD4+CD25+ Treg in Class II MHC-/- mice, which restrict hapten-specific CD8+ T cell priming and the magnitude of CHS responses.     

Pertussis toxin as an adjuvant suppresses the number and function of CD4+CD25+ T regulatory cells

We observed a remarkable reduction in the frequency and immunosuppressive activity of splenic CD4+CD25+ T cells in C57BL/6 mice with MOG33-55-induced experimental autoimmune encephalomyelitis (EAE). Our study revealed that pertussis toxin (PTx), one component of the immunogen used to induce murine EAE, was responsible for down-regulating splenic CD4+CD25+ cells. Treatment of normal BALB/c mice with PTx in vivo reduced the frequency, suppressive activity and FoxP3 expression by splenic CD4+CD25+ T cells. However, PTx treatment did not alter the expression of characteristic phenotypic markers (CD45RB, CD103, GITR and CTLA-4) and did not increase the expression of CD44 and CD69 by the residual splenic and lymph node CD4+CD25+ T cells. This property of PTx was attributable to its ADP-ribosyltransferase activity. PTx did not inhibit suppressive activity of purified CD4+CD25+ T regulatory (Treg) cells in vitro, but did so in vivo, presumably due to an indirect effect. Although the exact molecular target of PTx that reduces Treg activity remains to be defined, our data suggests that alteration of both distribution and function of splenic immunocytes should play a role. This study concludes that an underlying cause for the immunological adjuvanticity of PTx is down-regulation of Treg cell number and function.     

Diversion of CD4+ T cell development from regulatory T helper to effector T helper cells alters the contact hypersensitivity response

Cutaneous sensitization to reactive haptens and subsequent challenge results in a T cell-mediated response, contact hypersensitivity (CHS). Recent results from this laboratory have indicated that hapten sensitization induces two populations of reactive T cells: CD8⁺ T cells producing interferon (IFN)-γ which mediate the response and CD4⁺ T cells producing interleukin (IL)-4 and IL-10 which negatively regulate the magnitude and duration of the response. Since CD4⁺ T cell development to either IFN-γ- (Th1) or IL-4/IL-10- (Th2)-producing cells is dependent upon the cytokine environment during antigen priming, we hypothesized that CD4⁺ T cell induction in a Th1-promoting environment would not only alter the CD4⁺ T cell cytokine-producing phenotype but also the course of the CHS response. Administration of the Th1-promoting cytokine IL-12 during hapten sensitization resulted in a CHS response of greater magnitude following challenge and extended the duration of the response. In hapten-sensitized mice depleted of CD8⁺ T cells, treatment with IL-12 induced effector CD4⁺ T cells. Histological examination of challenged ear tissue from these mice indicated minimal edema and an acute mononuclear cell infiltration more typical of classical delayed-type hypersensitivity than CHS. Hapten-primed CD4⁺ T cells from IL-12 treated, sensitized mice produced IFN-γ, but not IL-4 in response to T cell receptor-mediated stimulation. Use of neutralizing anti-IFN-γ antibody indicated that IL-12 not only directly promoted Th1 development but also indirectly inhibited Th2 development through stimulation of IFN-γ production at the time of hapten sensitization. Overall, these results demonstrate that diversion of CD4⁺ T cell development to Th1 effector cells rather than to Th2 cells alters the efferent nature of CHS and removes a primary regulatory mechanism of the immune response.     

血红素加氧酶-1上调CD4~+ CD25~+ Treg foxp3表达以增强Treg的免疫抑制功能

本研究探讨血红素加氧酶-1(heme oxygenase-1,HO-1)诱导CD4+CD25+调节性T细胞(regulatory T cells,Treg)foxp3表达,增加IL-10分泌,提高CD4+CD25+Treg的免疫抑制功能。选用磁珠分离正常BALB/c小鼠脾脏CD4+CD25+Treg,转染含HO-1质粒pcDNA3HO-1,或用血红素(hemin)、锡-原卟啉(Sn-protoporphyrin,SnPP)干预,培养48 h。用卵清蛋白致敏、激发BALB/c小鼠建立哮喘模型,并在致敏、激发阶段分别经血红素和SnPP干预。用Real-Time PCR和Western blot方法分别测定培养细胞内HO-1、foxp3 mRNA及蛋白量;ELISA方法分别测定细胞上清液和动物血清中IL-10、TGF-β水平;用磁珠分离哮喘动物脾脏CD4+CD25+Treg进行功能抑制试验。结果显示:经pcDNA3HO-1和血红素上调CD4+CD25+Treg HO-1表达,foxp3表达及蛋白水平相应增加,上清液IL-10水平明显升高。而OVA致敏、激发的哮喘小鼠模型,经血红素干预后,血清IL-10分泌亦增多,CD4+CD25+Treg功能抑制作用显著增强。该结果表明HO-1诱导CD4+CD25+Treg特异性转录因子foxp3表达,促进IL-10分泌,增强CD4+CD25+Treg的调节功能,具有显著的免疫抑制作用。     

Interleukin-2 is essential for CD4+CD25+ regulatory T cell function

Constitutive expression of CD25, the IL-2 receptor alpha-chain, defines a distinct population of CD4+ T cells (Treg) with suppressive activity in vitro and in vivo. IL-2 has been implicated in the generation and maintenance of Treg, however, a functional contribution of the IL-2 receptor during suppression is thus far unknown. We show that IL-2 is required for Treg function in vitro, since suppression is completely abrogated by selective blocking of the IL-2 receptor on Treg during co-culture with responder T cells. We demonstrate that Treg, which do not produce IL-2, compete for IL-2 secreted by responder T cells. In accordance with the idea of competition being part of the suppressive mechanism, in vitro neutralization of IL-2 mimics all effects of Treg. Conversely, recombinant IL-2 abrogates inhibition of IL-2 production in responder T cells, the hallmark of Treg suppression. Finally, activation in the presence of IL-2 primes Treg to produce IL-10 upon secondary stimulation, indicating that IL-2 uptake is also required to induce additional suppressive factors that might be more relevant for suppression in vivo. We propose the parakrine uptake of soluble mediators as a flexible mechanism to adapt Treg activity to the strength of the responder T cell reaction.     

急性淋巴细胞白血病患者外周血CD4+CD25+T调节细胞与白细胞介素2、白细胞介素10、转化生长因子β的检测*

背景：目前急性淋巴细胞白血病的病因尚未完全清楚,而CD4+CD25+T调节细胞对机体的免疫反应可能起着一定的调节作用。 目的：观察急性淋巴细胞白血病患者外周血CD4+CD25+T调节细胞分泌白细胞介素2、白细胞介素10及转化生长因子β的情况。 方法：采用密度梯度离心法分离22例B细胞系列的急性淋巴细胞白血病(B-ALL)患者、13例T细胞系列的急性淋巴细胞白血病(T-ALL)患者和18名正常人外周血单个核细胞。采用免疫磁珠法分离出CD4+CD25+T调节细胞进行培养,同时用双抗体夹心酶联免疫吸附试验检测细胞培养上清中白细胞介素2、白细胞介素10及转化生长因子β的水平。 结果与结论：B-ALL患者和T-ALL患者外周血CD4+CD25+T调节细胞培养上清中白细胞介素10和转化生长因子β水平显著高于正常人水平,而白细胞介素2水平显著低于正常人水平(P < 0.05);B-ALL和T-ALL患者的CD4+CD25+T调节细胞培养上清中3种因子表达差异无显著性意义(P > 0.05)。提示CD4+CD25+T调节细胞可能通过增加分泌白细胞介素10和转化生长因子β、减少分泌白细胞介素2等干扰抗肿瘤的免疫反应。      

Opposing effect of mesenchymal stem cells on Th1 and Th17 cell polarization according to the state of CD4+ T cell activation

Mesenchymal stem cells (MSCs) are multipotent progenitors with broad immunosuppressive properties. However, their therapeutic use in autoimmune disease models has shown dissimilar effects when applied at different stages of disease. We therefore investigated the effect of the addition of MSCs on the differentiation of Th1, Treg and Th17 cells in vitro, at different states of CD4(+) T cell activation. CD4(+) T lymphocytes purified by negative selection from mouse C57BL/6 splenocytes were cultured under Th1, Th17 and Treg inducing conditions with IL-12, TGF-β+IL-6 or TGF-β, respectively. C57BL/6 bone marrow derived MSCs were added to CD4(+) T cell cultures at day 0 or after 3 days of T cell polarizing activation. Intracellular cytokines for Th1, Th17 and Treg cells were quantitated at day 6 by flow cytometry. While early addition (day 0) of MSCs suppressed all CD4(+) T cell lineages, addition at day 3 only decreased IFN-γ production by Th1 polarized cells by 64% (p<0.05) while markedly increased IL-17 production by Th17 polarized cells by 50% (p<0.05) and left IL-10 production by Treg polarized cells unchanged. MSCs exhibit their typical suppressive phenotype when added early to cell cultures in the presence of CD4(+) T cell polarizing stimuli. However, once T cell activation has occurred, MSCs show an opposite stimulating effect on Th17 cells, while leaving Treg IL-10 producing cells unchanged. These results suggest that the therapeutic use of MSCs in vivo might exert opposing effects on disease activity, according to the time of therapeutic application and the level of effector T cell activation.     

Antigen-specific in vitro suppression of murine Helicobacter pylori-reactive immunopathological T cells by CD4CD25 regulatory T cells

A Helicobacter pylori-specific in vitro coculture system was established and used to study the role of CD4+CD25+ regulatory T cells (Treg) in gastritis development in mice with H. pylori infection. Effects of therapeutic immunization against H. pylori infection on the Treg function were also studied to better understand the mechanisms leading to postimmunization gastritis in these mice. Depletion of Treg led to extensive proliferation to H. pylori antigens of CD4+ T cells isolated from either na?ve, H. pylori-infected or H. pylori-immunized mice. Using the Treg-depleted CD4+ T cells from immunized mice as effector cells, we compared the suppressive efficacy of Treg isolated from na?ve, infected or immunized mice and found that Treg from na?ve mice, and slightly less efficiently from infected mice, suppressed the CD25- effector T-cell response and in most cases were distinctly more efficacious than Treg isolated from immunized mice. The suppressive efficacy of Treg isolated from the differently treated mice correlated closely with production of interleukin-5 (IL-5) by the Treg and suppression of interferon-gamma and IL-2 production by the CD25- effector T cells. Our study is the first to demonstrate in H. pylori-induced chronic infection, antigen-specific Treg with differential efficacy in suppressing H. pylori proinflammatory T effector cells.     

Essential role of MHC II-independent CD4+ T cells, IL-4 and STAT6 in contact hypersensitivity induced by fluorescein isothiocyanate in the mouse

Contact hypersensitivity (CHS) induced by a hapten is thought to be mediated by T helper type 1 (Th1) cells. However, FITC can induce contact allergy in vivo, and in vitro studies suggest that this response is Th2-type driven. We compared CHS reactions induced by FITC or dinitrofluorobenzene (DNFB), a well-known Th1 inducing hapten, in Balb/c mice, C57/B6 mice, and several gene knock-out mice, and investigated the role of Th1/Th2 cytokines, T cell populations, eosinophils, and mast cells. Balb/c mice (Th2 dominant strain) had a stronger response to FITC than C57/B6 mice (Th1 dominant strain). The skin inflammation was characterized by edema and eosinophilia, and serum IgE levels were elevated following FITC challenge. All responses were enhanced by a second round of sensitization. Anti-TNF-alpha or anti-very late antigen-4 (VLA-4) antibody partly inhibited both FITC- and DNFB-induced CHS. Pretreatment of mice with anti-IL-4 antibody, anti-IL-5 antibody, recombinant INF-gamma, or the mast-cell depleting agent 48/80 significantly diminished edema formation, and Stat6(-/-) mice were fully protected from FITC-induced CHS, while DNFB-induced CHS was enhanced (Stat6(-/-), mast cell depletion) or not affected (anti-IL-5 antibody). Further, mice lacking CD4(+) T cells and mice lacking both CD8 and MHC II showed very little reaction at all to FITC, while the absence of CD8 T cells alone or MHC II alone conferred partial protection only. These findings indicate a contribution of MHC II-independent CD4(+) T cells and/or CD4(+) NKT cells to the Th2 response triggered by FITC in vivo, and makes FITC-induced CHS a suitable animal model for atopic dermatitis.     

IL-4 deficiency does not impair the ability of dendritic cells to initiate CD4+ and CD8+ T cell responses in vivo

Several reports have described a role of IL-4 in dendritic cell function. We have examined the number and phenotype of dendritic cells from C57Bl/6 wild-type and IL-4-/- mice, and compared their ability to induce T cell immune responses in vivo and in vitro. We observed that the number of dendritic cells in the spleens and lymph nodes of IL-4-/- mice is comparable to the number found in wild-type mice. In addition, the expression of maturation markers such as MHC II, CD40, CD80 and CD86, and of differentiation markers such as CD4, CD8 and CD11b, was also comparable in the two populations. Splenic wild-type and IL-4-/- dendritic cells were both able to present antigen to T cell receptor transgenic CD4+ or CD8+ T cells in culture. When pulsed with antigen in vitro and then injected subcutaneously into C57BL/6 host mice, both populations of dendritic cells were able to induce the division of T cell receptor transgenic CD4+ or CD8+ T cells in vivo. This was the case regardless of whether the antigen used in these experiments was a low or a high affinity T cell receptor ligand. Similarly, both populations of dendritic cells were able to activate antigen-specific cytotoxic T cell responses and initiate tumor-protective immune responses in vivo. We conclude that IL-4-/- and wild-type dendritic cells have a comparable ability to initiate T cell immune responses when in an IL-4-sufficient environment.     

The ex vivo Microenviroments in MLTC of Poorly Immunogenic Tumor Cells Facilitate Polarization of CD4^＋ CD25^＋ Regulatory T Cells

CD4^＋CD25^＋ regulatory T （TR） cells play an important role in maintaining a balanced peripheral immune system. Recent studies have shown that TR cells may also play a key role in suppressing anti-tumor immune response. In order to investigate the tumor immune microenvironment and its influence on TR polarization, poorly immunogenic tumor cell line Ds （C57BL/6, H-2^b）, immunogenic tumor cell lines FBL3 （C57BL/6, H-2^b） and H22 BALB/c, H-2^d） were used to establish the syngeneic/allogeneic, poorly immunogenic/immunogenic mixed lymphocytes-tumor cell culture （MLTC）. Our results revealed that the proportion of CD4^＋CD25^＋ T cells in MLTC of syngeneic primed splenocytes stimulated with D5 tumor cells was higher than that with H22 cells （0.43% vs 0.044%, and the similar results appeared in allogeneic splenocytes stimulated with D5 tumor cells （0.39% vs 0.04%）. The splenocytes stimulated with supernatant from syngeneic MLTC of D5 tumor cells demonstrated higher proportion of CD4^＋CD25^＋ cells than that from allogeneic MLTC of D5 tumor cells, and the splenocytes stimulated with supernatant from syngeneic or allogeneic MLTC of H22 tumor cells generated lower proportion of CD4^＋CD25^＋ T cells than that of D5 tumor cells. The TGF-β1 and Th2-oriented cytokines （IL-4 and IL-10） were dominated in supernatants of syngeneic MLTC of poorly immunogenic tumor cells. Our results provided useful information for studying the mechanisms underlying tumor immune surveillance as well as for the tumor immunotherapy.     

IL-2 induces in vivo suppression by CD4(+)CD25(+)Foxp3(+) regulatory T cells

Interleukin-2 (IL-2) treatment is currently used to enhance T cell-mediated immune responses against tumors or in viral infections. At the same time, IL-2 is essential for the peripheral homeostasis of CD4(+)CD25(+)Foxp3(+ )regulatory T cells (Treg). In our study, we show that IL-2 is also an important activator of Treg suppressive activity in vivo. IL-2 treatment induces Treg expansion as well as IL-10 production and increases their suppressive potential in vitro. Importantly, in vivo application of IL-2 via gene-gun vaccination using IL-2 encoding DNA plasmids (pIL-2) inhibited naive antigen-specific T cell proliferation as well as a Th1-induced delayed type hypersensitivity response. The suppressive effect can be transferred onto naive animals by Treg from IL-2-treated mice and the suppression depends on the synergistic action of IL-10 and TGF-beta. These data highlight that during therapeutic treatment with IL-2 the concomitant activation of Treg may indeed counteract the intended activation of cellular immunity.     

CD52 is a novel costimulatory molecule for induction of CD4+ regulatory T cells

We previously reported that 4C8 monoclonal antibody (mAb) provides a costimulatory signal to human CD4+ T cells and consequently induces regulatory T (Treg) cells, which are hypo-responsive and suppress the polyclonal response of bystander CD4+ cells in a contact-dependent manner. In this study, we identified the antigen of 4C8 mAb as CD52. Costimulation with Campath-1H, a humanized anti-CD52 mAb, also induced Treg cells. Anti-CD52-induced Treg cells suppressed the proliferation of both CD4+ and CD8+ T cells provided with polyclonal or allogeneic stimulation. When Treg cells were induced from Staphylococcal enterotoxin B (SEB) treated cells, they suppressed the response to SEB more efficiently than that to another superantigen, SEA. Furthermore, anti-CD52-induced Treg cells could be expanded by culture with IL-2 followed by CD52-costimulation, and co-injection of expanded Treg cells suppressed lethal xenogeneic graft versus host disease (GvHD) reactions in SCID mice caused by human peripheral blood mononuclear cells (PBMCs).     

Chronic exposure to superantigen induces regulatory CD4(+) T cells with IL-10-mediated suppressive activity

The repeated injection of bacterial superantigens (SAg), such as staphylococcus enterotoxin (SE) A or B, has been shown in mice to induce a state of unresponsiveness characterized by the lack of secretion of Th1 lymphokines, such as IL-2 and IFN-gamma, following subsequent SAg challenge. We made the observation, in vivo as well as in vitro, that unresponsiveness to SAg could be transferred from SEA- to SEB-reactive T cells (and reversibly from SEB- to SEA-specific T cells) in C57BL/6 mice but not in BALB/c mice. Since C57BL/6 mice, unlike BALB/c mice, possess TCR V(beta)3+ and V(beta)11+ T cells able to react with both SEA and SEB, we hypothesized that SAg-unresponsive V(beta)3(+) and V(beta)11+ T cells could mediate linked suppression of other SAg-reactive T cells. To analyze further this possibility, spleen cells from BALB/c mice made unresponsive to SEB were tested for their capacity to suppress the response of normal BALB/c cells to SEB. The production of both IFN-gamma and IL-2 following SEB stimulation was greatly impaired in co-cultures containing CD4(+) T cells, but not CD8(+) T cells, isolated from unresponsive animals. In vivo, the production of both IFN-gamma and IL-2 responses to SEB was dramatically reduced in animals adoptively transferred with unresponsive spleen cells. This suppression was abrogated in recipients injected with neutralizing anti-IL-10 antibodies. Moreover, in animals made unresponsive to SEB, SAg-reactive CD4(+) T cells were found to express high levels of CTLA-4, a molecule recently described to play an essential role in the suppressive function of regulatory T cells. Taken together these results demonstrate that the repetitive injection of SAg induces the differentiation of regulatory CD4(+) T cells capable of suppressing SAg-reactive naive T cells.     

Cytotoxic CD8+ T cell ablation enhances the capacity of regulatory T cells to delay viral elimination in Theiler's murine encephalomyelitis

Theiler's murine encephalomyelitis (TME) of susceptible mouse strains is a commonly used infectious animal model for multiple sclerosis. The study aim was to test the hypothesis whether cytotoxic T cell responses account for the limited impact of regulatory T cells on antiviral immunity in TME virus‐induced demyelinating disease (TMEV‐IDD) resistant C57BL/6 mice. TME virus‐infected C57BL/6 mice were treated with (i) interleukin‐2/‐anti‐interleukin‐2‐antibody‐complexes to expand regulatory T cells (“Treg‐expansion”), (ii) anti‐CD8‐antibodies to deplete cytotoxic T cells (“CD8‐depletion”) or (iii) with a combination of Treg‐expansion and CD8‐depletion (“combined treatment”) prior to infection. Results showed that “combined treatment”, but neither sole “Treg‐expansion” nor “CD8‐depletion,” leads to sustained hippocampal infection and virus spread to the spinal cord in C57BL/6 mice. Prolonged infection reduces myelin basic protein expression in the spinal cord together with increased accumulation of β‐amyloid precursor protein in axons, characteristic of myelin loss and axonal damage, respectively. Chronic spinal cord infection upon “combined treatment” was also associated with increased T and B cell recruitment, accumulation of CD107b⁺ microglia/macrophages and enhanced mRNA expression of interleukin (IL)‐1α, IL‐10 and tumor necrosis factor α. In conclusion, data revealed that the suppressive capacity of Treg on viral elimination is efficiently boosted by CD8‐depletion, which renders C57BL/6 mice susceptible to develop chronic neuroinfection and TMEV‐IDD.     

Regulation of CD4+CD25+ regulatory T cell activity: it takes (IL-)two to tango

Although CD4(+)CD25(+) regulatory T cells (Treg) represent a well-characterized population of T cells with in vitro and in vivo suppressive capacity, the basic mechanisms of suppression are still not understood. The constitutive expression of the high-affinity receptor for IL-2 has raised the question about the role of IL-2 in Treg function. Here, we review recent data indicating that IL-2 is not only necessary for the homeostasis of Treg but is also critical for the activation of Treg function. Since Treg do not produce IL-2 by themselves, their capacity to utilize IL-2 secreted by other T cells appears to be an essential component of Treg biology. This indicates that Treg suppressive activity is controlled by interaction with activated target cells via the soluble mediator IL-2. In Treg, IL-2 has been identified as a potent inducer of the immunosuppressive cytokine IL-10, an important mediator of Treg suppression in vivo. The efficient capture of IL-2 by Treg may, under conditions of limited IL-2 supply, cause IL-2 deprivation of responder T cells. This competition can explain some of the currently discussed discrepancies between in vivo and in vitro activity of Treg.     

树突状细胞扩增抗原特异性CD4+ CD25+调节性T细胞研究进展

CD4+CD25+调节性T细胞(Tr)是同时具有免疫低反应性和免疫抑制性功能两大特征的T细胞.研究证实,CD4+ CD25+ Tr在抑制器官特异性自身免疫性疾病及GVHD是抗原特异性的,因此,应用器官特异性而不是多克隆性的Tr将大大促进以Tr为基础的免疫治疗.而具有调节活性的CD4+ CD25+ Tr仅占人类外周血CIM+ T细胞的1%～2%,因此,研究体外大量扩增的方法 对于以Tr基础的治疗至关重要.研究表明,树突状细胞(DC)作为机体强有力的专职抗原递呈细胞可以扩增具有抗原特异性的CD4+ CD25+ Tr且能增加后者的抑制活性,这为治疗自身免疫性疾病及GVHD提供了新的治疗前景.     

Regulatory T cells suppress autoreactive CD4+ T cell response to bladder epithelial antigen

AIM: To investigate the role of regulatory T (Treg) cells in CD4⁺ T cell-mediated bladder autoimmune inflammation. METHODS: Urothelium-ovalbumin (URO-OVA)/OT-II mice, a double transgenic line that expresses the membrane form of the model antigen (Ag) OVA as a self-Ag on the urothelium and the OVA-specific CD4⁺ T cell receptor specific for the I-A^b/OVA_323-339 epitope in the periphery, were developed to provide an autoimmune environment for investigation of the role of Treg cells in bladder autoimmune inflammation. To facilitate Treg cell analysis, we further developed URO-OVA^GFP-Foxp3/OT-II mice, a derived line of URO-OVA/OT-II mice that express the green fluorescent protein (GFP)-forkhead box protein P3 (Foxp3) fusion protein. RESULTS: URO-OVA/OT-II mice failed to develop bladder inflammation despite the presence of autoreactive CD4⁺ T cells. By monitoring GFP-positive cells, bladder infiltration of CD4⁺ Treg cells was observed in URO-OVA^GFP-Foxp3/OT-II mice. The infiltrating Treg cells were functionally active and expressed Treg cell effector molecule as well as marker mRNAs including transforming growth factor-β, interleukin (IL)-10, fibrinogen-like protein 2, and glucocorticoid-induced tumor necrosis factor receptor (GITR). Studies further revealed that Treg cells from URO-OVA^GFP-Foxp3/OT-II mice were suppressive and inhibited autoreactive CD4⁺ T cell proliferation and interferon (IFN)-γ production in response to OVA Ag stimulation. Depletion of GITR-positive cells led to spontaneous development of bladder inflammation and expression of inflammatory factor mRNAs for IFN-γ, IL-6, tumor necrosis factor-α and nerve growth factor in URO-OVA^GFP-Foxp3/OT-II mice. CONCLUSION: Treg cells specific for bladder epithelial Ag play an important role in immunological homeostasis and the control of CD4⁺ T cell-mediated bladder autoimmune inflammation.     

Regulation of microglia by CD4+ and CD8+ T cells: selective analysis in CD45-congenic normal and Toxoplasma gondii-infected bone marrow chimeras

Microglia, the resident macrophage population of the central nervous system, is rapidly activated in murine Toxoplasma encephalitis (TE). However, the precise contribution of microglia to intracerebral immune reactions and the in vivo regulation of microglial activity are still poorly understood. To selectively analyse microglial reactions in TE, we have established a model of radiation-induced CD45-congenic bone marrow chimeras between CD45.2+ C57BL/6 (recipient) and CD45.1+ B6.SJL (donor) mice. These chimeras allow a differentiation of radioresistant CD45.2+ microglia from all other leukocytes, which exhibit the CD45.1+ haplotype. In the normal brain, microglia produced tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-10, and IL-15 mRNA. In TE, marked microglial activation was observed with a de novo expression of IL-12p40 and inducible nitric oxide synthase mRNA, upregulation of IL-1beta and TNF-alpha mRNA, a continuous production of IL-10, and IL-15 mRNA, an induction of major histocompatibility class I and II antigens, intercellular adhesion molecule-1, and leukocyte function-associated antigen-1. Furthermore, selective depletion of CD4+ and/or CD8+ T cells in the chimeras revealed that microglial cytokine production was critically regulated by CD8+T cells, whereas expression of cell surface molecules was less dependent on T cells. These findings demonstrate a specific regulation of microglia by T lymphocytes during the course of TE.