Th2 responses in schistosomiasis

Schistosomiasis is caused by infection with parasitic flatworms of the genus Schistosoma. It is characterized by the development of strong CD4⁺ T cell and B cell responses that, during primary infection, fail to eliminate the parasites, but in collaboration with cells of the innate immune system allow survival in the face of ongoing tissue damage caused by the lodging of parasite eggs in the liver and the passage of eggs across the intestinal epithelium. Mounting a tightly controlled Th2 response is key to this outcome, and while this type of response is a risk factor for the development of fibrosis, it also underpins the development of resistance to further infection; as such, understanding how Th2 responses are induced and regulated in schistosomiasis remains a critical area of research.     

Transcriptional regulation of Th17 cell differentiation

The paradigm of effector T helper cell differentiation into either Th1 or Th2 lineages has been profoundly shaken by the discovery of T cells that secrete IL-17 and other inflammatory cytokines. This subset, referred to as Th17, is centrally involved in autoimmune disease and is important in host defense at mucosal surfaces. In mouse, a series of cytokines, including IL-6, IL-21, IL-23, and TGF-beta, function sequentially or synergistically to induce the Th17 lineage. Other cytokines, including IL-2, IL-4, IFNgamma, and IL-27, inhibit differentiation of this lineage. Here we review how the nuclear orphan receptor RORgammat functions to coordinate the diverse cytokine-induced signals and thus controls Th17 cell differentiation.     

Phenotypic differences between Th1 and Th17 cells and negative regulation of Th1 cell differentiation by IL-17

Recent evidence from several groups indicates that IL-17-producing Th17 cells, rather than, as once was thought, IFN-gamma-producing Th1 cells, can represent the key effector cells in the induction/development of several autoimmune and allergic disorders. Although Th17 cells exhibit certain phenotypic and developmental differences from Th1 cells, the extent of the differences between these two T cell subsets is still not fully understood. We found that the expression profile of cell surface molecules on Th17 cells has more similarities to that of Th1 cells than Th2 cells. However, although certain Th1-lineage markers [i.e., IL-18 receptor alpha, CXCR3, and T cell Ig domain, mucin-like domain-3 (TIM-3)], but not Th2-lineage markers (i.e., T1/ST2, TIM-1, and TIM-2), were expressed on Th17 cells, the intensity of expression was different between Th17 and Th1 cells. Moreover, the expression of CTLA-1, ICOS, programmed death ligand 1, CD153, Fas, and TNF-related activation-induced cytokine was greater on Th17 cells than on Th1 cells. We found that IL-23 or IL-17 can suppress Th1 cell differentiation in the presence of exogenous IL-12 in vitro. We also confirmed that IL-12 or IFN-gamma can negatively regulate Th17 cell differentiation. However, these cytokines could not modulate such effects on T cell differentiation in the absence of APC.     

Th17细胞的分化调控与自身免疫性疾病

Th17细胞是最近发现的一种在分化和功能上均不同于Th1和Th2的新型CD4＋T细胞亚群.该群细胞以主要分泌细胞因子IL-17而得名.IL-6、TGF-β、IL-21及IL-23等对Th17细胞的分化调控发挥重要作用.研究表明,Th17细胞可参与多种自身免疫性疾病的发生、发展与转归.     

Dendritic cell subsets and the regulation of Th1/Th2 responses

Cells of the dendritic family are suited to perform two distinct functions at two discrete locations. In the peripheral tissues, dendritic cells (DC) act as sentinels for "dangerous" antigens. They then migrate into the lymphoid organ, where they initiate activation of T lymphocytes which are specific for these antigens. During their migration, DC shift from an antigen-capturing mode to a T cell sensitizing mode. In addition to switching on the immune response, subtypes of DC appear to influence the character of T cell differentiation, i.e. the Th1/Th2 balance. We will review the cellular and molecular bases of Th1-Th2 development by DC subsets, and will focus primarily, although not exclusively, on mouse DC.     

Interleukin-17C promotes Th17 cell responses and autoimmune disease via interleukin-17 receptor E

Although several interleukin-17 (IL-17) family members and their receptors have been recently appreciated as important regulators in inflammatory diseases, the function of other IL-17 cytokines and IL-17 receptor-like molecules is unclear. Here we show that an IL-17 cytokine family member, IL-17C, was induced in a Th17 cell-dependent autoimmune disease and was required for its pathogenesis. IL-17C bound to IL-17RE, a member of IL-17 receptor family whose full-length isoform was selectively expressed in Th17 cells and signaled via an IL-17RA-RE receptor complex and the downstream adaptor Act1. IL-17C-IL-17RE induced the expression of?a nuclear IkappaB family member, IκBζ, in Th17 cells to potentiate the Th17 cell response. Thus, our work has identified a cytokine-receptor pair with important function in regulating proinflammatory responses. This pathway may be targeted to treat autoimmune diseases.     

Th细胞及其分化调节

幼稚CD4^＋T细胞可分化为Th1和Th2细胞，Th1主要产生IL-2、IFN-γ、TNF，增强吞噬细胞介导的抗感染机制，促进细胞免疫，也在器官特异性自身免疫疾病中起作用；Th2细胞主要产生IL-4、IL-5、IL-10、IL-13，促进B细胞增殖、分化和产生抗体，增强B细胞介导的体液免疫应答，在变态反应和机体抗寄生虫免疫中发挥作用。Th细胞分化主要由局部环境中的细胞因子及细胞内关键转录因子调控。转录因子STAT1、STAT4、IRF1和T—bet促使Th1细胞分化；转录因子STAT6、IRF4和GATA-3促使Th2细胞分化。     

Mast cells promote Th1 and Th17 responses by modulating dendritic cell maturation and function

Mast cells (MCs) play an important role in the regulation of protective adaptive immune responses against pathogens. However, it is still unclear whether MCs promote such host defense responses via direct effects on T cells or rather by modifying the functions of antigen-presenting cells. To identify the underlying mechanisms of the immunoregulatory capacity of MCs, we investigated the impact of MCs on dendritic cell (DC) maturation and function. We found that murine peritoneal MCs underwent direct crosstalk with immature DCs that induced DC maturation as evidenced by enhanced expression of costimulatory molecules. Furthermore, the MC/DC interaction resulted in the release of the T-cell modulating cytokines IFN-γ, IL-2, IL-6 and TGF-β into coculture supernatants and increased the IL-12p70, IFN-γ, IL-6 and TGF-β secretion of LPS-matured DCs. Such MC-"primed" DCs subsequently induced efficient CD4+ T-cell proliferation. Surprisingly, we observed that MC-primed DCs stimulated CD4+ T cells to release high levels of IFN-γ and IL-17, demonstrating that MCs promote Th1 and Th17 responses. Confirming our in vitro findings, we found that the enhanced disease progression of MC-deficient mice in Leishmania major infection is correlated with impaired induction of both Th1 and Th17 cells.     

Th17细胞与Th1细胞在慢性阻塞性肺疾病炎症发病机制中的调控作用

慢性阻塞性肺疾病(COPD)发病的分子机制目前仍不甚清楚,大量证据表明,T淋巴细胞介导的免疫反应贯穿于COPD的各个阶段,导致炎症反应持续放大.近来研究发现,Th1细胞和Th17细胞均参与了COPD的免疫发病过程,通过相互间作用调控COPD的炎症反应.因此,深入了解COPD炎症发病过程中Th17、Th1细胞免疫应答特征、分化及调控功能,对探讨COPD的致病机制以及免疫调节治疗的靶点具有重要意义.     

Induction of a Th17 cell response by Helicobacter pylori Urease subunit B

Th17 cells represent a novel subset of CD4⁺ T cells, which is associated with Helicobacter pylori infection. In the present study, we investigated the potential role of Urease subunit B (UreB) in the induction of Th17 cell response. Co-cultured splenic lymphocytes from H. pylori-infected mice with the recombinant UreB (rUreB) elevated IL-17 secretion and caused an increase in the number of Th17 cells. The expression of IL-6 and IL-23 p19 was significantly increased in rUreB-stimulated macrophages. Whole cell protein (WCP) of UreB-deficient strain (UreB⁻ strain) induced less Th17 cell responses than that of wild-type strain. In addition, subcutaneous and intranasal immunization of rUreB elicited antigen-specific Th17 cell responses. Intranasal immunization of rUreB reduced H. pylori colonization in the stomach, which was closely related with the increased rUreB-specific Th17 cell responses. These results suggest that UreB is an important protein which is able to elicit Th17 cell responses against H. pylori both in vivo and in vitro.     

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。     

Enhanced Th1 and dampened Th2 responses synergize to inhibit acute granulomatous and fibrotic responses in murine schistosomiasis mansoni

In murine schistosomiasis mansoni, CD4(+) Th1 and Th2 cells participate in the ovum-induced granulomatous inflammation. Previous studies showed that the interleukin-12 (IL-12)-induced Th1 response strongly suppressed the Th2-cell-mediated pulmonary granuloma development in naive or primed mice. However, liver granulomas were only moderately suppressed in egg-vaccinated, recombinant IL-12 (rIL-12)-treated infected mice. The present study shows that repeated rIL-12 injections given during early granuloma development at 5 to 7 weeks after infection prolonged the Th1 phase and resulted in gamma interferon-mediated suppression of liver granulomas. The timing is crucial: if given at 6 to 8 weeks, during the Th2-dominated phase of florid granuloma growth, the treatment is ineffective. Daily injections of rIL-12 given between 5 and 7.5 weeks during the period of granuloma growth achieved a somewhat-stronger diminution in granuloma growth with less deposition of collagen but caused 60% mortality and liver pathology. In contrast, combined treatment with rIL-12 and anti-IL-4-anti-IL-10 monoclonal antibody (MAb) injections given during the Th2 phase strongly inhibited liver granuloma growth without mortality. The diminished inflammatory response was accompanied by less deposition of collagen in the liver. Moreover, neutralization of endogenous IL-12 by anti-IL-12 MAbs effectively decreased the early Th1 phase (between 5 and 6 weeks after infection) but not the developing Th2 phase (5 to 7 weeks) of granuloma development. These studies indicate that the granulomatous response in infected mice can be manipulated by utilizing the Th1-Th2-subset antagonism with potential salutary results in the amelioration of fibrous pathology.     

C-型凝集素家族在Th17细胞免疫反应中的作用

Th17细胞是近年来发现的一群新的细胞亚群,在感染、自身免疫性及肿瘤等疾病中发挥重要作用,是目前研究的热点之一.而C-型凝集素是一类重要的模式识别受体,能调节Th1细胞和Th17细胞间的免疫平衡,识别真菌等多种病原体,在抗感染免疫中具有重要作用.近年来有大量的研究发现,多种C-型凝集素受体参与Th17细胞的分化.因而对其深入研究可明确疾病的发病机制,为疾病的治疗提供了新的思路和靶点.     

抗原特异性Th17细胞的分化与调节

目的: 探讨影响抗原特异性Th17细胞分化和调节的因素.方法: T细胞受体转基因小鼠(DO11.10)CD4 T细胞, 与同背景正常小鼠的脾细胞混合, 经OVA多肽刺激后, 在不同的Th17极化的培养条件下, 观察Th17细胞及细胞因子的产生. 结果: 单纯OVA抗原刺激主要诱导特异性Th1型反应, 在TGF-β和IL-6存在的条件下, 主要诱导Th17反应; 当加入IL-23之后, 促进了Th17细胞的分化.阻断了IFN-γ和IL-4之后, Th17细胞的百分率明显增加.LPS可以促进Th1型细胞因子的产生, 但对抗原特异性Th17细胞的分化没有明显的促进作用.结论: 抗原特异性Th17细胞是与Th1、 Th2相对独立的细胞亚群, TGF-β、 IL-6和 IL-23可诱导或促进Th17的分化, 而Th1和Th2细胞因子抑制其分化.     

Human monocytes promote Th1 and Th17 responses to Streptococcus pneumoniae

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, and sepsis in children. Human immunity to pneumococcal infections has been assumed to depend on anticapsular antibodies. However, recent findings from murine models suggest that alternative mechanisms, dependent on T helper cells, are also involved. Although the immunological events in which T helper cells contribute to acquired immunity have been studied in mice, little is known about how these responses are generated in humans. Therefore, we examined bacterial and host factors involved in the induction of Th1 and Th17 responses, using a coculture model of human monocytes and CD4(+) T cells. We show that monocytes promote effector cytokine production by memory T helper cells, leading to a mixed Th1/Th17 (gamma interferon [IFN-γ]/interleukin-17 [IL-17]) profile. Both T helper cytokines were triggered by purified pneumococcal peptidoglycan; however, the balance between the two immune effector arms depended on bacterial viability. Accordingly, live pneumococci triggered a Th1-biased response via monocyte production of IL-12p40, whereas heat-killed pneumococci triggered a Th17 response through TLR2 signaling. An increased understanding of human T helper responses is essential for the development of novel pneumococcal vaccines designed to elicit cell-mediated immunity.     

Th1 and Th2 responses in pathogenesis and regulation of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) in animals can be induced by immunization with retinal antigens or their fragments and represents human uveitis of putative autoimmune origin. The pathogenesis of EAU, and likely also of human uveitis, involves cell-mediated destruction of retinal tissues that is dependent on retinal antigen-specific T cells. Because in most cases a Th1-type response has been implicated in pathogenesis, the prevailing consensus has been that immunoregulatory manipulations designed to enhance the Th2 response at the expense of the Th1 response will be beneficial in clinical treatment of uveitis. This assumption may not always be correct. The present review will summarize the evidence that, despite a central role for Th1 response in uveitis, an unopposed Th2-like response can be equally or more destructive to the retinal tissues. Furthermore, the Th1 response itself triggers regulatory circuits that feed back and dampen further recruitment of antigen-specific T cells into the Th1 effector pool. Thus, although the Th1 effector response can and does result in retinal pathology, immunoregulatory strategies must take into account that immune deviation therapies designed to replace the Th1 with a Th2 response might result in exchanging one type of pathology for another rather than in achieving the desired therapeutic effect.     

The matricellular protein SPARC supports follicular dendritic cell networking toward Th17 responses

Lymphnode swelling during immune responses is a transient, finely regulated tissue rearrangement, accomplished with the participation of the extracellular matrix. Here we show that murine and human reactive lymph nodes express SPARC in the germinal centres. Defective follicular dendritic cell networking in SPARC-deficient mice is accompanied by a severe delay in the arrangement of germinal centres and development of humoral autoimmunity, events that are linked to Th17 development. SPARC is required for the optimal and rapid differentiation of Th17 cells, accordingly we show delayed development of experimental autoimmune encephalomyelitis whose pathogenesis involves Th17. Not only host radioresistant cells, namely follicular dendritic cells, but also CD4⁺ cells are the relevant sources of SPARC, in vivo. Th17 differentiation and germinal centre formation mutually depend on SPARC for a proper functional crosstalk. Indeed, Th17 cells can enter the germinal centres in SPARC-competent, but not SPARC-deficient, mice. In summary, SPARC optimizes the changes occurring in lymphoid extracellular matrix harboring complex interactions between follicular dendritic cells, B cells and Th17 cells.     

The inflammasome drives protective Th1 and Th17 cellular responses in disseminated candidiasis

The Nlrp3 inflammasome has been proposed to play an important role in antifungal host defense. However, studies exploring the role of the inflammasome in antifungal host defense have been limited to the direct effects on IL-1β processing. Although IL-1β has important direct effects on the innate immune response, important effects of the caspase-1-dependent cytokines IL-1β and IL-18 are exerted on the initiation of the adaptive Th1 and Th17 cellular responses. No studies have been employed to assess the impact of the inflammasome on the Th1/Th17 defense mechanisms in vivo during candidiasis. In the present study, we demonstrate an essential role for caspase-1 and ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) in disseminated candidiasis through regulating antifungal Th1 and Th17 responses. Caspase-1(-/-) and ASC(-/-) mice display diminished Th1/Th17 responses, followed by increased fungal outgrowth and lower survival. These observations identify a critical role for the inflammasome in controlling protective adaptive immune responses during invasive fungal infection.