Th17细胞与Th1、Treg细胞关系的研究进展

CD4~+T细胞在不同细胞因子环境中可分化为Th1、Th2、Treg、Th17四种亚群,在一定条件下,各Th细胞亚群之间可以互相转化,从而使机体的免疫效应和免疫抑制处于精细而复杂的平衡状态。Th17细胞与自身免疫性疾病和肿瘤的发生发展关系密切,研究Th17细胞与Th1细胞、Treg细胞之间的相互关系,对于预防和治疗自身免疫性疾病和肿瘤等临床难题意义重大。     

川芎嗪对小鼠哮喘模型Th17细胞的调控作用以及对Th17、Treg细胞平衡的影响

目的：研究川芎嗪对小鼠哮喘模型外周血中Th17、Treg细胞比例以及特征性细胞因子IL-17、IL-10水平的影响。方法：雄性BALB/c小鼠随机分成四组：正常对照组、哮喘模型组、川芎嗪治疗组以及激素治疗组。 OVA诱导激发哮喘,治疗组小鼠在第0、7、14天以及每次雾化吸入前30 min腹腔注射川芎嗪或地塞米松注射液,正常对照组用生理盐水替代OVA进行腹腔注射以及雾化吸入。小鼠的肺组织HE染色,分离外周血淋巴细胞做流式细胞学检测并ELISA法检测血清中IL-17、IL-10的水平。结果：哮喘模型组造模成功,川芎嗪治疗组及激素治疗组哮喘表现较轻微。 HE染色显示哮喘模型组小鼠肺组织在支气管以及小血管周围发现大量的嗜酸性粒细胞、中性粒细胞、巨噬细胞等炎性细胞浸润;而川芎嗪治疗组和激素治疗组小鼠的肺组织切片中仅发现少量的炎性细胞。流式细胞仪检测显示哮喘组小鼠的Treg细胞较正常组小鼠比例明显降低,而Th17细胞占CD4＋T细胞显著升高;川芎嗪治疗组小鼠以及激素治疗组小鼠的变化趋势一致,Treg细胞和Th17细胞的比例趋于正常。 ELISA结果显示哮喘组小鼠的IL-17的水平显著高于正常组,IL-10的水平较正常组显著降低,川芎嗪治疗组小鼠的IL-17水平较哮喘模型组明显降低,而IL-10的水平显著升高,激素治疗组小鼠的变化趋势与川芎嗪治疗组一致。结论：在OVA诱导小鼠哮喘模型中,川芎嗪可以通过增强Treg细胞的功能,增加Treg细胞的数量,进而抑制Th17细胞的数量以及功能,减轻Th17细胞的应答,降低IL-17细胞因子的分泌,从而起到预防/控制哮喘发作的作用。     

Treg/Th17平衡在巨细胞病毒感染发病机制中的作用

目的:研究调节性T细胞(Treg/Th17)细胞失衡在巨细胞病毒感染(CMV)免疫调节机制中的作用。方法:将CMV感染患儿按诊断标准分为激活感染组与潜伏感染组,同时设立正常对照组,采用流式细胞术(FCM)分析各组外周血Treg、Th17的百分比,并计算Treg/Th17比值;同时采用ELISA和RT-PCR法检测Treg主要相关因子(IL-10、Foxp3)和Th17主要相关因子(TGF-β、IL-17、IL-6、IL-23及ROR-γt)表达水平。结果:与对照组比较,CMV感染后Treg细胞百分率降低,Th17细胞升高,致Treg/Th17比值下降(P<0.05);CMV感染后两组间比较,激活感染组Treg/Th17比值和Treg主要相关因子表达水平下降更明显,而Th17主要相关因子表达水平显著上调,差异均有统计学意义(P<0.05)。结论:Treg/Th17平衡参与了CMV感染发病免疫机制,并可能与病毒潜伏-激活状态相关。     

Antigen‐specific Treg regulate Th17‐mediated lung neutrophilic inflammation,B‐cell recruitment and polymeric IgA and IgM levels in the airways

Th17 cells play key roles in mediating autoimmunity, inflammation and mucosal host defense against pathogens. To determine whether naturally occurring Treg (nTreg) limit Th17‐mediated pulmonary inflammation, OVA‐specific CD4⁺ Th17 cells and expanded CD4⁺CD25⁺Foxp3⁺ nTreg were cotransferred into BALB/c mice that were then exposed to OVA aerosols. Th17 cells, when transferred alone, accumulated in the lungs and posterior mediastinal LN and evoked a pronounced airway hyperreactivity and neutrophilic inflammation, characterized by B‐cell recruitment and elevated IgA and IgM levels. Cotransfer of antigen‐specific nTreg markedly reduced the Th17‐induced pulmonary inflammation and associated neutrophilia, B‐cell influx and polymeric Ig levels in the airways, but did not inhibit airway hyperreactivity. Moreover, the regulation appeared restricted to the site of mucosal inflammation, since transfer of nTreg did not affect the Th17 response developing in the lung draining LN, as evidenced by unaltered levels of IL‐17 production and low numbers of Foxp3⁺ Treg. Our findings suggest a crucial role for Th17 cells in mediating airway B‐cell influx and IgA response, and demonstrate that antigen‐specific nTreg suppress Th17‐mediated lung inflammation. These results provide new insights into how Th17 responses are limited and may facilitate development of novel approaches for controlling Th17‐induced inflammation.     

IL‐6: Regulator of Treg/Th17 balance

IL‐6 is a pleiotropic cytokine involved in the physiology of virtually every organ system. Recent studies have demonstrated that IL‐6 has a very important role in regulating the balance between IL‐17‐producing Th17 cells and regulatory T cells (Treg). The two T‐cell subsets play prominent roles in immune functions: Th17 cell is a key player in the pathogenesis of autoimmune diseases and protection against bacterial infections, while Treg functions to restrain excessive effector T‐cell responses. IL‐6 induces the development of Th17 cells from naïve T cells together with TGF‐β; in contrast, IL‐6 inhibits TGF‐β‐induced Treg differentiation. Dysregulation or overproduction of IL‐6 leads to autoimmune diseases such as multiple sclerosis (MS) and rheumatoid arthritis (RA), in which Th17 cells are considered to be the primary cause of pathology. Given the critical role of IL‐6 in altering the balance between Treg and Th17 cells, controlling IL‐6 activities is potentially an effective approach in the treatment of various autoimmune and inflammatory diseases. Here, we review the role of IL‐6 in regulating Th17/Treg balance and describe the critical functions of IL‐6 and Th17 in immunity and immune‐pathology.     

Serotonin decreases the production of Th1/Th17 cytokines and elevates the frequency of regulatory CD4+ T‐cell subsets in multiple sclerosis patients

Excessive levels of proinflammatory cytokines in the CNS are associated with reduced serotonin (5‐HT) synthesis, a neurotransmitter with diverse immune effects. In this study, we evaluated the ability of exogenous 5‐HT to modulate the T‐cell behavior of patients with MS, a demyelinating autoimmune disease mediated by Th1 and Th17 cytokines. Here, 5‐HT attenuated, in vitro, T‐cell proliferation and Th1 and Th17 cytokines production in cell cultures from MS patients. Additionally, 5‐HT reduced IFN‐γ and IL‐17 release by CD8⁺ T cells. By contrast, 5‐HT increased IL‐10 production by CD4⁺ T cells from MS patients. A more accurate analysis of these IL‐10‐secreting CD4⁺ T cells revealed that 5‐HT favors the expansion of FoxP3⁺CD39⁺ regulatory T cells (Tregs) and type 1 regulatory T cells. Notably, this neurotransmitter also elevated the frequency of Treg17 cells, a novel regulatory T‐cell subset. The effect of 5‐HT in upregulating CD39⁺ Treg and Treg17 cells was inversely correlated with the number of active brain lesions. Finally, in addition to directly reducing cytokine production by purified Th1 and Th17 cells, 5‐HT enhanced in vitro Treg function. In summary, our data suggest that serotonin may play a protective role in the pathogenesis of MS.     

Translational Mini‐Review Series on Th17 Cells: CD4+ T helper cells: functional plasticity and differential sensitivity to regulatory T cell‐mediated regulation

Atherosclerosis is a chronic inflammatory disease. Immunomodulation of atherosclerosis emerges as a promising approach to prevention and treatment of this widely prevalent disease. The function of high‐density lipoprotein (HDL) to promote reverse cholesterol transport may explain the ability of its protection against atherosclerosis. Findings that HDL and apolipoprotein A‐I (apoA‐I) inhibited the ability of antigen presenting cells (APCs) to stimulate T cells might be attributed to lipid raft, a cholesterol‐rich microdomain exhibiting functional properties depending largely upon its lipid composition. Thus, modulating cholesterol in lipid raft may provide a promising anti‐atherogenic strategy.     

Expansion of Foxp3+ T‐cell populations by Candida albicans enhances both Th17‐cell responses and fungal dissemination after intravenous challenge

Candida albicans remains the fungus most frequently associated with nosocomial bloodstream infection. In disseminated candidiasis, the role of Foxp3⁺ regulatory T (Treg) cells remains largely unexplored. Our aims were to characterize Foxp3⁺ Treg‐cell activation in a murine intravenous challenge model of disseminated C. albicans infection, and determine the contribution to disease. Flow cytometric analyses demonstrated that C. albicans infection drove in vivo expansion of a splenic CD4⁺Foxp3⁺ population that correlated positively with fungal burden. Depletion from Foxp3^hCD2 reporter mice in vivo confirmed that Foxp3⁺ cells exacerbated fungal burden and inflammatory renal disease. The CD4⁺Foxp3⁺ population expanded further after in vitro stimulation with C. albicans antigens (Ags), and included at least three cell types. These arose from proliferation of the natural Treg‐cell subset, together with conversion of Foxp3^? cells to the induced Treg‐cell form, and to a cell type sharing effector Th17‐cell characteristics, expressing ROR‐γt, and secreting IL‐17A. The expanded Foxp3⁺ T cells inhibited Th1 and Th2 responses, but enhanced Th17‐cell responses to C. albicans Ags in vitro, and in vivo depletion confirmed their ability to enhance the Th17‐cell response. These data lead to a model for disseminated candidiasis whereby expansion of Foxp3⁺ T cells promotes Th17‐cell responses that drive pathology.     

Reverse plasticity: TGF‐β and IL‐6 induce Th1‐to‐Th17‐cell transdifferentiation in the gut

Th17 cells are a heterogeneous population of pro‐inflammatory T cells that have been shown to mediate immune responses against intestinal bacteria. Th17 cells are highly plastic and can transdifferentiate to Th1/17 cells or unconventional Th1 cells, which are highly pathogenic in animal models of immune‐mediated diseases such as inflammatory bowel diseases. A recent European Journal of Immunology article by Liu et al. (Eur. J. Immunol. 2015. 45:1010–1018) showed, surprisingly, that Th1 cells have a similar plasticity, and could transdifferentiate to Th17 cells. Thus, IFN‐γ‐producing Th1 effector cells specific for an intestinal microbial antigen were shown to acquire IL‐17‐producing capacities in the gut in a mouse model of colitis, and in response to TGF‐β and IL‐6 in vitro. TGF‐β induced Runx1, and together with IL‐6 was shown to render the ROR‐γt and IL‐17 promoters in Th1 cells accessible for Runx1 binding. In this commentary, we discuss how this unexpected plasticity of Th1 cells challenges our view on the generation of Th1/17 cells with the capacity to co‐produce IL‐17 and IFN‐γ, and consider possible implications of this Th1‐to‐Th17‐cell conversion for therapies of inflammatory bowel diseases and protective immune responses against intracellular pathogens.     

Th17细胞的生物学特性

近年来发现有一种不同于Th1和Th2细胞、产生IL-17的Th细胞亚群:Th17。其在促炎症反应和自身免疫病中发挥重要作用。IL-6和TGF-β的联合作用能诱导初始T细胞分化成Th17细胞。RORγt为目前已确定的Th17细胞分化所需要的特异性转录因子。了解Th17细胞分化的影响因素、产生的细胞因子、在自身免疫病中的作用以及与调节性T细胞(Treg)的相互作用关系很重要。     

Metabolic control of the Treg/Th17 axis

The interplay of the immune system with other aspects of physiology is continually being revealed and in some cases studied in considerable mechanistic detail. A prime example is the influence of metabolic cues on immune responses. It is well appreciated that upon activation, T cells take on a metabolic profile profoundly distinct from that of their quiescent and anergic counterparts; however, a number of recent breakthroughs have greatly expanded our knowledge of how aspects of cellular metabolism can shape a T-cell response. Particularly important are findings that certain environmental cues can tilt the delicate balance between inflammation and immune tolerance by skewing T-cell fate decisions toward either the T-helper 17 (Th17) or T-regulatory (Treg) cell lineage. Recognizing the unappreciated immune-modifying potential of metabolic factors and particularly those involved in the generation of these functionally opposing T-cell subsets will likely add new and potent therapies to our repertoire for treating immune mediated pathologies. In this review, we summarize and discuss recent findings linking certain metabolic pathways, enzymes, and by-products to shifts in the balance between Th17 and Treg cell populations. These advances highlight numerous opportunities for immune modulation.     

Translational Mini‐Review Series on Th17 Cells: Function and regulation of human T helper 17 cells in health and disease

T helper (Th) cell have a central role in modulating immune responses. While Th1 and Th2 cells have long been known to regulate cellular and humoral immunity, Th17 cells have been identified only recently as a Th lineage that regulates inflammation via production of distinct cytokines such as interleukin (IL)-17. There is growing evidence that Th17 cells are pathological in many human diseases, leading to intense interest in defining their origins, functions and developing strategies to block their pathological effects. The cytokines that regulate Th17 differentiation have been the focus of much debate, due primarily to inconsistent findings from studies in humans. Evidence from human disease suggests that their in vivo development is driven by specialized antigen-presenting cells. Knowledge of how Th17 cells interact with other immune cells is limited, but recent data suggest that Th17 cells may not be subject to strict cellular regulation by T regulatory cells. Notably, Th17 cells and T regulatory cells appear to share common developmental pathways and both cell types retain significant plasticity. Herein, we will discuss the molecular and cellular regulation of Th17 cells with an emphasis on studies in humans.     

Expression of Th17 and Treg Lymphocyte Subsets in Hypertrophied Adenoids of Children and its Clinical Significance

Adenoid hypertrophy is the most common cause of upper airway obstruction and sleep-disordered breathing in children, yet its pathogenesis remains unclear. The identification of the novel helper T cell subsets, Th17 cells and regulatory T cells (Tregs) could provide new insight into our understanding of the mechanisms involved in the development of this condition. The purpose of this study is to evaluate the adenoidal lymphocyte subsets to describe the percentage of various lymphocyte subsets in hypertrophied adenoids and correlate them with symptom severity. Twenty consecutive children undergoing adenoidectomy were included, and lymphocytes were isolated from their adenoids. T cell subpopulations were detected by flow cytometry using a fluoresceinated monoclonal antibody directed against a number of cell markers (CD4+, CD8+, CD25+, FOXP3 IL17+, and others). We found a significant negative linear correlation between the Th17/Treg ratio and the patients’ clinical scores (R = ?0.71 p < 0.005). The correlation was independent of age and gender. Decreased ratios of Th17/Treg subpopulations may play a role in the pathogenesis of adenoid hypertrophy.     

T‐bet is essential for Th1‐mediated,but not Th17‐mediated,CNS autoimmune disease

T cells that produce both IL‐17 and IFN‐γ, and co‐express ROR‐γt and T‐bet, are often found at sites of autoimmune inflammation. However, it is unknown whether this co‐expression of T‐bet with ROR‐γt is a prerequisite for immunopathology. We show here that T‐bet is not required for the development of Th17‐driven experimental autoimmune encephalomyelitis (EAE). The disease was not impaired in T‐bet^?/? mice and was associated with low IFN‐γ production and elevated IL‐17 production among central nervous system (CNS) infiltrating CD4⁺ T cells. T‐bet^?/? Th17 cells generated in the presence of IL‐6/TGF‐β/IL‐1 and IL‐23 produced GM‐CSF and high levels of IL‐17 and induced disease upon transfer to naïve mice. Unlike their WT counterparts, these T‐bet^?/– Th17 cells did not exhibit an IL‐17→IFN‐γ switch upon reencounter with antigen in the CNS, indicating that this functional change is not critical to disease development. In contrast, T‐bet was absolutely required for the pathogenicity of myelin‐responsive Th1 cells. T‐bet‐deficient Th1 cells failed to accumulate in the CNS upon transfer, despite being able to produce GM‐CSF. Therefore, T‐bet is essential for establishing Th1‐mediated inflammation but is not required to drive IL‐23‐induced GM‐CSF production, or Th17‐mediated autoimmune inflammation.     

Mycobacterium tuberculosis RpfE promotes simultaneous Th1‐ and Th17‐type T‐cell immunity via TLR4‐dependent maturation of dendritic cells

Reciprocal induction of the Th1 and Th17 immune responses is essential for optimal protection against Mycobacterium tuberculosis (Mtb); however, only a few Mtb antigens are known to fulfill this task. A functional role for resuscitation‐promoting factor (Rpf) E, a latency‐associated member of the Rpf family, in promoting naïve CD4⁺ T‐cell differentiation toward both Th1 and Th17 cell fates through interaction with dendritic cells (DCs) was identified in this study. RpfE induces DC maturation by increasing expression of surface molecules and the production of IL‐6, IL‐1β, IL‐23p19, IL‐12p70, and TNF‐α but not IL‐10. This induction is mediated through TLR4 binding and subsequent activation of ERK, p38 MAPKs, and NF‐κB signaling. RpfE‐treated DCs effectively caused naïve CD4⁺ T cells to secrete IFN‐γ, IL‐2, and IL‐17A, which resulted in reciprocal expansions of the Th1 and Th17 cell response along with activation of T‐bet and RORγt but not GATA‐3. Furthermore, lung and spleen cells from Mtb‐infected WT mice but not from TLR4^?/? mice exhibited Th1 and Th17 polarization upon RpfE stimulation. Taken together, our data suggest that RpfE has the potential to be an effective Mtb vaccine because of its ability to activate DCs that simultaneously induce both Th1‐ and Th17‐polarized T‐cell expansion.     

Th17与自身免疫性疾病

Th17细胞是新近发现的一类新型的能够分泌白细胞介素17(interleukin 17,IL-17)的CD4+T细胞。在IL-6和TGF-β作用下,初始CD4+T细胞分化为Th17细胞。分化成熟的Th17细胞可以分泌IL-17,IL-17F和IL-22等多种细胞因子,其中IL-17和IL-17F是其主要效应分子。临床前和临床数据均表明:Th17细胞与一些自身免疫性疾病(如系统性红斑狼疮、类风湿性关节炎、多发性硬化、银屑病、炎症性肠病、自身免疫性甲状腺疾病)有关。