致耐受性树突状细胞和调节性T细胞在支气管哮喘中的作用

支气管哮喘是树突状细胞(dendritic cells,DC)介导的以辅助性T细胞2(T-helper type2,Th2)优势免疫为特征的气道炎症性疾病,DC在变应原触发哮喘的始动环节中发挥中心作用.调节性T细胞(regulatory T cells,Treg)是一种特殊的T细胞,能够通过多种机制影响DC和效应性T细胞,从而发挥免疫抑制作用.DC不仅对入侵病原体产生免疫应答,而且对无害物质维持免疫耐受.这些具有致耐受性的DC通过多种不同的路径诱导Treg,上调Treg数目和(或)功能,从而抑制免疫应答.应用致耐受性DC作为靶点,有望为哮喘免疫治疗开辟新的途径.     

Selective ERK activation differentiates mouse and human tolerogenic dendritic cells,expands antigen‐specific regulatory T cells,and suppresses experimental inflammatory arthritis

Objective

Most therapeutic treatments for autoimmune arthritis rely on immunosuppressive drugs, which have side effects. Although a previous study by our group showed that specific ERK activation suppressed immune responses, its application in a therapeutic setting has never been tested. The aim of the present study was to define the ERK‐dependent immunosuppressive mechanisms and to apply selective ERK activation for the treatment of experimental inflammatory arthritis.

Methods

A constitutively active ERK activator was coexpressed with a model antigen using lentivectors. Immunosuppressive mechanisms were characterized at the level of dendritic cell (DC) function, differentiation of antigen‐specific Treg cells, and inhibition of inflammatory T cells. Administration of the ERK activator with antigen as a strategy to suppress inflammatory arthritis was tested in an experimental mouse model.

Results

Selective ERK activation induced mouse and human DCs to secrete bioactive transforming growth factor β, a process required for suppression of T cell responses and differentiation of antigen‐specific Treg cells. Treg cells strongly proliferated after antigen reencounter in inflammatory conditions, and these cells exhibited antigen‐dependent suppressive activities. Inflammatory arthritis was effectively inhibited through antigen‐specific mechanisms. Importantly, this strategy did not rely on identification of the initiating arthritogenic antigen. Equivalent mechanisms were demonstrated in human monocyte–derived DCs, setting the scene for a possible rapid translation of this approach to patients with rheumatoid arthritis.

Conclusion

This strategy of selective ERK activation resulted in an effective therapeutic protocol, with substantial advantages over DC or T cell vaccination.

     

Modified myeloid dendritic cells act as regulatory dendritic cells to induce anergic and regulatory T cells

To exploit a novel strategy to regulate T cell-mediated immunity, we established human and murine modified dendritic cells (DCs) with potent immunoregulatory properties (designed as regulatory DCs), which displayed moderately high expression levels of major histocompatibility complex (MHC) molecules and extremely low levels of costimulatory molecules compared with their normal counterparts. Unlike human normal DCs, which caused the activation of allogeneic CD4(+) and CD8(+) T cells, human regulatory DCs not only induced their anergic state but also generated CD4(+) or CD8(+) regulatory T (Tr) cells from their respective naive subsets in vitro. Although murine normal DCs activated human xenoreactive T cells in vitro, murine regulatory DCs induced their hyporesponsiveness. Furthermore, transplantation of the primed human T cells with murine normal DCs into severe combined immunodeficient (SCID) mice enhanced the lethality caused by xenogeneic graft-versus-host disease (XGVHD), whereas transplantation of the primed human T cells with murine regulatory DCs impaired their ability to cause XGVHD. In addition, a single injection of murine regulatory DCs following xenogeneic or allogeneic transplantation protected the recipients from the lethality caused by XGVHD as well as allogeneic acute GVHD. Thus, the modulation of T cell-mediated immunity by regulatory DCs provides a novel therapeutic approach for immunopathogenic diseases.     

Abnormal presence of semimature dendritic cells that induce regulatory T cells in HIV-infected subjects

Dendritic cells (DCs), because they orchestrate the immune response to microbes, represent an ideal target for pathogens attempting to evade the immune system. We hypothesized that interactions between human immunodeficiency virus (HIV) and DCs lead to the development of a semimature state, in which DCs migrate to lymph nodes but induce tolerance in T cells, rather than immunity. We found that lymph nodes from untreated HIV-infected subjects contained an abundance of semimature DCs, the disappearance of which correlated with the initiation of highly active antiretroviral therapy (HAART). Such lymph nodes also contained an abundance of T cells that had a regulatory phenotype and that persisted after HAART. Lymph node DCs from untreated HIV-infected subjects cultured with normal allogeneic T cells induced these T cells to adopt the phenotype of regulatory T cells, an ability that was lost after HAART. We conclude that HIV infection correlates with the presence of semimature DCs that stimulate T cell tolerance rather than immunity. These regulatory T cells may contribute to the lack of effective HIV immune responses.     

Vasoactive intestinal peptide generates human tolerogenic dendritic cells that induce CD4 and CD8 regulatory T cells

Induction of antigen-specific tolerance is critical for autoimmunity prevention and immune tolerance maintenance. In addition to their classical role as sentinels of the immune response, dendritic cells (DCs) play important roles in maintaining peripheral tolerance through the induction/activation of regulatory T (T(reg)) cells. The possibility of generating tolerogenic DCs opens new therapeutic perspectives in autoimmune/inflammatory diseases. Characterizing endogenous factors that contribute to the development of tolerogenic DCs is highly relevant. We here report that the immunosuppressive neuropeptide vasoactive intestinal peptide (VIP) induces the generation of human tolerogenic DCs with the capacity to generate CD4 and CD8 T(reg) cells from their respective naive subsets. The presence of VIP during the early stages of DC differentiation from blood monocytes generates a population of IL-10-producing DCs unable to fully mature after the effects of inflammatory stimuli. CD4 T(reg) cells generated with VIP-differentiated DCs resemble the previously described Tr1 cells in terms of phenotype and cytokine profile. CD8 T(reg) cells generated with tolerogenic VIP DCs have increased numbers of IL-10-producing CD8(+)CD28(-)-CTLA4(+) T cells. CD4 and CD8 T(reg) cells primarily suppress antigen-specific T(H)1-mediated responses. Therefore, the possibility of generating or expanding ex vivo tolerogenic DC(VIPs) opens new therapeutic perspectives for treating autoimmune diseases and graft-versus-host disease after allogeneic transplantation in humans.     

Myeloma cells act as tolerogenic antigen‐presenting cells and induce regulatory T cells in vitro

Regulatory T cells (Tregs) are essential for maintenance of self‐tolerance; however, tumor cells can exploit the tolerance to escape the immune system. We investigated the Tregs frequency in patients with multiple myeloma (MM) and in those with monoclonal gammopathy of undetermined significance (MGUS), and found that CD4⁺FoxP3⁺ and CD8⁺FoxP3⁺ Tregs were significantly increased in patients with MM and correlated with the active phase. Both Tregs subsets were expanded in cocultures of CD3⁺ lymphocytes and fresh CD138⁺ MM plasma cells or RPMI8226 and U266 cell lines and functioned as natural (n) and inducible (i) Tregs insofar as they inhibited the proliferation of stimulated CD3 lymphocytes via contact‐dependent and contact‐independent pathways. Induction of Tregs by MM plasma cells required a contact‐dependent pathway, implying antigen recognition by T cells. MM plasma cells acted as immature and tolerogenic antigen‐presenting cells (APCs), in that they displayed low CD80/CD86 expression associated with a phagocytic activity. By acting as immature APCs, MM plasma cells plausibly expand (n)Tregs and (i)Tregs both through conversion of CD3⁺FoxP3^? into CD3⁺FoxP3⁺ T cells and proliferation of CD3⁺FoxP3⁺ T cells, which may suppress the anti‐MM immune response.     

CCL17 and CCL22 chemokines within tumor microenvironment are related to infiltration of regulatory T cells in esophageal squamous cell carcinoma

It has been reported that an increased population of regulatory T cells (T‐regs) is one of the reasons for impaired anti‐tumor immunity. We investigated the frequency of Foxp3⁺ T‐regs in tumor‐infiltrating lymphocytes (TILs) and peripheral blood lymphocytes (PBLs) of patients with esophageal squamous cell carcinoma (ESCC). Furthermore, in order to elucidate the mechanisms behind T‐regs accumulation within tumors, we evaluated the relationship between CCL17 or CCL22 expression and the frequency of Foxp3⁺ T‐regs. CD4⁺CD25⁺Foxp3⁺ T‐regs as a percentage of CD4⁺ cells were counted by flow cytometry. The frequency of CCL17⁺ or CCL22⁺ cells among CD14⁺ cells in tumors was also evaluated by flow cytometry. Moreover, an in vitro migration assay using T‐regs derived from ESCC was performed in the presence of CCL17 or CCL22. The frequency of Foxp3⁺ T‐regs in TILs was significantly higher than that in the normal esophageal mucosa (24.6 ± 10.0 vs 7.1 ± 5.9%, P < 0.01). The frequency of Foxp3⁺ T‐regs in PBLs of ESCC patients was significantly higher than that in normal healthy donors (7.0 ± 4.2 vs 2.5 ± 1.0%, P < 0.01). Furthermore, the frequency of CCL17⁺ or CCL22⁺ cells among CD14⁺ cells within tumors was significantly higher than that of normal esophageal mucosa, and there was a significant correlation between the frequency of CCL17⁺ or CCL22⁺ cells and Foxp3⁺ T‐regs in TILs. In addition, the in vitro migration assay indicated that T‐regs were significantly induced to migrate by CCL17 or CCL22. In conclusion, CCL17 and CCL22 within the tumor are related to the increased population of Foxp3⁺ T‐regs in ESCC.     

Toso controls encephalitogenic immune responses by dendritic cells and regulatory T cells

The ability to mount a strong immune response against pathogens is crucial for mammalian survival. However, excessive and uncontrolled immune reactions can lead to autoimmunity. Unraveling how the reactive versus tolerogenic state is controlled might point toward novel therapeutic strategies to treat autoimmune diseases. The surface receptor Toso/Faim3 has been linked to apoptosis, IgM binding, and innate immune responses. In this study, we used Toso-deficient mice to investigate the importance of Toso in tolerance and autoimmunity. We found that Toso^−/− mice do not develop severe experimental autoimmune encephalomyelitis (EAE), a mouse model for the human disease multiple sclerosis. Toso^−/− dendritic cells were less sensitive to Toll-like receptor stimulation and induced significantly lower levels of disease-associated inflammatory T-cell responses. Consistent with this observation, the transfer of Toso^−/− dendritic cells did not induce autoimmune diabetes, indicating their tolerogenic potential. In Toso^−/− mice subjected to EAE induction, we found increased numbers of regulatory T cells and decreased encephalitogenic cellular infiltrates in the brain. Finally, inhibition of Toso activity in vivo at either an early or late stage of EAE induction prevented further disease progression. Taken together, our data identify Toso as a unique regulator of inflammatory autoimmune responses and an attractive target for therapeutic intervention.More than 5% of the populations of Western countries suffer from inflammatory autoimmune diseases (1). In all cases, a hyperactivated immune system is responsible for the initiation of autoimmunity. In the periphery, inflammatory T cells such as IL-17–producing Th (Th17) and IFN-γ–producing Th1 cells are controlled by suppressive regulatory T (Treg) cells (2). Numeric or functional imbalance of these various T-cell populations can result in autoimmunity or immunodeficiency. How the immune system limits self-reactive inflammatory responses in healthy individuals, and how these mechanisms fail in patients, is still under intensive investigation.The transmembrane receptor Toso belongs to the Ig superfamily, and its cytoplasmic domain shows homology to Fas-activated serine/threonine kinase (3). Toso has been implicated in the regulation of CD95 (Fas/Apo1)- and TNF receptor (TNFR)-dependent T-cell apoptosis, and is highly overexpressed in apoptosis-resistant B-cell lymphomas (3–6). Toso also functions as an Fc receptor for IgM, and so may be important for B-cell development (7–10). Recently, Toso expression was detected on granulocytes and monocytes and Toso was linked to the homeostasis and activation of the innate immune system (11–13). However, the precise physiological relevance of Toso’s multifaceted functionality is still unknown.In this study, we investigated the impact of loss of Toso on inflammatory autoimmune responses. Toso-deficient (Toso^−/−) mice were less susceptible to the induction of experimental autoimmune encephalomyelitis (EAE). Disease resistance was dependent on Toso’s function in dendritic cells (DCs). DCs from Toso^−/− mice initiated less intense inflammatory CD4⁺ and CD8⁺ T-cell responses that were associated with reduced immunopathology. Toso^−/− DCs induced more Tregs than controls. Finally, interference with Toso activity in vivo significantly decreased the burden of EAE disease following induction. Our findings indicate that Toso is a crucial mediator of inflammatory autoimmune responses in vivo.     

Virus-stimulated plasmacytoid dendritic cells induce CD4+ cytotoxic regulatory T cells

Immune responses to pathogens need to be maintained within appropriate levels to minimize tissue damage, whereas such controlled immunity may allow persistent infection of certain types of pathogens. Interleukin 10 (IL-10) plays an important role in such immune regulation. We previously showed that HSV-stimulated human plasmacytoid dendritic cells (pDCs) induced naive CD4+ T cells to differentiate into interferon gamma (IFN-gamma)/IL-10-producing T cells. Here we show that HSV-stimulated pDCs induce allogeneic naive CD4+ T cells to differentiate into cytotoxic regulatory T cells that poorly proliferate on restimulation and inhibit proliferation of coexisting naive CD4+ T cells. IL-3-stimulated pDCs or myeloid DCs did not induce such regulatory T cells. Both IFN-alpha and IL-10 were responsible for the induction of anergic and regulatory properties. High percentages of CD4+ T cells cocultured with HSV-stimulated pDCs, and to a lesser extent those cocultured with IL-3-stimulated pDCs, expressed granzyme B and perforin in an IL-10-dependent manner. CD4+ T cells cocultured with HSV-stimulated pDCs accordingly exhibited cytotoxic activity. The finding that virus-stimulated pDCs are capable of inducing CD4+ cytotoxic regulatory T cells suggests that this DC subset may play an important role in suppressing excessive inflammatory responses and also in inducing persistent viral infection.     

Mitomycin C-treated dendritic cells inactivate autoreactive T cells: Toward the development of a tolerogenic vaccine in autoimmune diseases

Treatment of autoimmune diseases remains a challenge for immunological research. An ideal therapy should inhibit the immune reaction against the diseased organ and leave the rest of the immune response intact. Our previous studies showed that donor-derived dendritic cells (DCs) treated in vitro with mitomycin C (MMC) suppress rat heart allograft rejection if injected into recipients before transplantation. Here we analyze their efficacy in controlling autoimmunity. MMC-DCs loaded with myelin-basic-protein (MBP) inhibited specific T cells derived from multiple sclerosis patients in vitro. If coincubated with MMC-DCs, T cells were arrested in the G₀/G₁ cell cycle phase. Microarray gene scan showed that MMC influences the expression of 116 genes in DCs, one main cluster comprising apoptotic and the second cluster immunosuppressive genes. Apparently, the combination of apoptosis with expression of tolerogenic molecules renders MMC-DCs suppressive. MBP-loaded MMC-DCs also inhibited mouse T cells in vitro and, in contrast to MBP-loaded naïve DCs, did not induce experimental autoimmune encephalitis. Most importantly, mice vaccinated with inhibitory DCs became resistant to the disease. Whereas this is not the first report on generation of suppressive DCs, it delineates a method using a clinically approved drug at nontoxic concentrations, which yields irreversibly changed DCs, effective across species in vitro and in vivo.     

Heavy chain ferritin activates regulatory T cells by induction of changes in dendritic cells

Heavy chain ferritin (H-ferritin) is a component of the iron-binding protein, ferritin. We have previously shown that H-ferritin inhibits anti-CD3-stimulated lymphocyte proliferation and that this was due to increased production of interleukin-10 (IL-10). In the present study we have shown that induction of IL-10 production was due to effects of H-ferritin on adherent antigen-presenting cells (APCs) in blood and monocyte-derived dendritic cells (MoDCs). IL-10 was produced by a subpopulation of CD4 T cells, which expressed the CD25 component of the IL-2 receptor and the CTLA-4 receptor characteristic of regulatory T cells. The changes induced in MoDCs were compared with those induced by CD40L and their significance tested by inhibition with monoclonal antibodies. These studies indicated that H-ferritin induced relatively greater expression of CD86 and B7-H1 on MoDCs and that monoclonal antibodies against their receptors, CTLA-4 and programmed death receptor-1 (PD-1), inhibited IL-10 production from the regulatory T cells. H-ferritin did not appear to induce direct production of the cytokines IL-2, IL-4, IL-6, IL-10, IL-12, or interferon-gamma from the DCs. These results are consistent with the thesis that H-ferritin induces B7-H1 and CD86 (B7-2) on APCs, which in turn induce IL-10 production from regulatory T cells. This is possibly one mechanism by which melanoma cells may induce changes in APCs in the vicinity of the tumor and result in suppression of immune responses by induction of regulatory T cells.     

树突状细胞和调节性T细胞在自身抗原所致小鼠免疫耐受模型中的作用

目的:探讨树突状细胞(DC)及CD4 CD25 调节性T细胞在胰岛素自身抗原sc所诱导的小鼠胰岛素依赖性糖尿病(IDDM)的免疫耐受中的重要作用．方法:低剂量链脲佐菌素(STZ)(40 mg／kg)ip 连续5次在Balb／c小鼠体内建立IDDM模型,胰岛素(100 μg)与不完全弗氏佐剂(IFA,1:1)混合液sc 1次／wk,连续4 wk．模型建立后每周测定血糖,5 wk时处死动物,取胰腺进行病理组织学检查．分离骨髓DC前体及脾脏T淋巴细胞并进行体外培养．采用流式细胞术测定DC表型和CD4 CD25 调节性T细胞,以同种淋巴细胞刺激实验检测DC刺激淋巴细胞增殖功能．结果:胰岛素sc 4 wk后可明显降低小鼠的血糖,与模型对照组有极显著差异(13．79± 2．71 mmol/L vs 20．98±1．43 mmol／L,P<0．05), 胰岛内炎症细胞浸润减少,组织结构完整． IDDM模型建立后,小鼠骨髓来源树突状细胞CD11c表达为26．4％,DC分化异常,而正常小鼠CD11c表达为47．5％;混合淋巴细胞反应中DC刺激能力减弱,刺激指数分别为1．47± 0．01和1．32±0．01(刺激细胞和反应细胞比例分别为1:10和1:20),与正常小鼠相比,差别具有极显著性意义(P值均小于0．01)．脾脏 CD4 CD25 调节性T细胞减少到1．43％,而正常小鼠为5．09％．与此相反,胰岛素自身抗原连续应用后,不仅使血糖得到控制,表达 CD11c的树突状细胞数量增加,CD86和MHC- Ⅱ表面分子表达降低到26．6％和28．8％,刺激淋巴细胞反应的能力弱于正常DC,但强于模型小鼠的DC,刺激指数分别为2．30±0．06(1: 10)和2．17±0．02(1:20),CD4 CD25 调节性T 细胞数量上升到7．15％．结论:胰岛素sc可预防STZ所致小鼠IDDM的发生,自身抗原可以通过改善功能异常的树突状细胞．诱导CD4 CD25 调节性T细胞分化在模型小鼠体内建立免疫耐受．     

Regulatory T cells control tolerogenic versus autoimmune response to sperm in vasectomy

Vasectomy is a well accepted global contraceptive approach frequently associated with epididymal granuloma and sperm autoantibody formation. To understand the long-term sequelae of vasectomy, we investigated the early immune response in vasectomized mice. Vasectomy leads to rapid epithelial cell apoptosis and necrosis, persistent inflammation, and sperm granuloma formation in the epididymis. Vasectomized B6AF1 mice did not mount autoimmune response but instead developed sperm antigen-specific tolerance, documented as resistance to immunization-induced experimental autoimmune orchitis (EAO) but not experimental autoimmune encephalomyelitis. Strikingly, tolerance switches over to pathologic autoimmune state following concomitant CD4(+)CD25(+)Foxp3(+) regulatory T cell (Treg) depletion: unilaterally vasectomized mice produce dominant autoantibodies to an orchitogenic antigen (zonadhesin), and develop CD4 T-cell- and antibody-dependent bilateral autoimmune orchitis. Therefore, (i) Treg normally prevents spontaneous organ-specific autoimmunity induction by persistent endogenous danger signal, and (ii) autoantigenic stimulation with sterile autoinflammation can lead to tolerance. Finally, postvasectomy tolerance occurs in B6AF1, C57BL/6, and A/J strains. However, C57BL/6 mice resisted EAO after 60% Treg depletion, but developed EAO after 97% Treg reduction. Therefore, variance in intrinsic Treg function--a possible genetic trait--can influence the divergent tolerogenic versus autoimmune response to vasectomy.