滤泡辅助性T细胞在器官移植免疫中的研究进展

滤泡辅助性T(Tfh)细胞是从人类扁桃体中发现的一类辅助性T(Th)细胞,Tfh细胞通过分泌白细胞介素21(IL-21)促进B细胞分化为浆母细胞,产生免疫球蛋白并促进生发中心形成。抗体介导的体液排异反应是移植物功能丧失的重要原因,而抗体的产生有赖于Tfh细胞的辅助,并且IL-21受体的抑制剂抑制Tfh细胞和B细胞在同种异体反应中的功能。本文将对近年来Tfh细胞在分化、亚型及器官移植中在抗体介导的排异反应中的作用进行综述,并推测其在未来移植后发生体液免疫排异患者中的意义。     

IL-21在滤泡辅助性T细胞分化发育及功能中的作用

抗原刺激B细胞产生抗体需要T细胞辅助,近年来人们逐渐认识到一个命名为滤泡辅助性T细胞（Tfh）的CD4^＋T细胞亚群在B细胞诱导的免疫应答中具有重要作用。Tfh细胞的主要特征包括表达趋化因子受体与（CXCR5）,迁移定位于B细胞滤泡辅助B细胞产生抗体。Tfh细胞产生的细胞因子IL-21能够促进B细胞分化为抗体形成细胞,这种辅助性细胞因子在Tfh细胞的分化发育、效应发挥及Tfh细胞功能失调相关的疾病中具有重要意义。     

IL-21在滤泡辅助性T细胞分化发育及功能中的作用

抗原刺激B细胞产生抗体需要T细胞辅助,近年来人们逐渐认识到一个命名为滤泡辅助性T细胞(Tfh)的CD4+T细胞亚群在B细胞诱导的免疫应答中具有重要作用.Tfh细胞的主要特征包括表达趋化因子受体与(CXCR5),迁移定位于B细胞滤泡辅助B细胞产生抗体.Tfh细胞产生的细胞因子IL-21能够促进B细胞分化为抗体形成细胞,这种辅助性细胞因子在Tfh细胞的分化发育、效应发挥及Tfh细胞功能失调相关的疾病中具有重要意义.     

滤泡辅助性T细胞(T_(fh))的研究进展

T细胞辅助B细胞抗体的生成是体液免疫应答的中心环节.但直到最近,科学家们才对T细胞辅助B细胞的细胞及分子机制有了更清楚的认识.滤泡辅助性T细胞(T follicular helper cells,Tfh)是最近明确的一种新的CD4+T细胞亚群,其主要功能是辅助B细胞参与体液免疫.Tfh的表型和功能与其他CD4+T细胞亚群有所不同,包括趋化因子受体的表达(如CXCR5)、定位和迁移(Tfh存在于B细胞滤泡)及其辅助B细胞的功能.Tfh产生的细胞因子IL-21在Tfh功能中处于核心地位,通过与其受体IL-21R结合,可有效地刺激B细胞分化成抗体形成细胞.因此Tfh细胞相关分子(如ICOS或IL-21)的高表达或低表达,很可能与某些自身免疫性疾病或免疫缺陷疾病的发病有关.     

外周血循环滤泡辅助性T 细胞及IL-21 在银屑病中的表达及意义

目的:探讨外周血循环滤泡辅助性T 细胞(Follicular helper T cells,Tfh)及相关细胞因子IL-21 在银屑病患者中的表达水平及其与疾病活动度的关系。方法:收集38 例银屑病患者及32 例健康对照者,流式细胞术检测外周血循环CD4+CXCR5+ Tfh 和CD4+ CXCR5+ ICOS+ Tfh 细胞比例以及Th17 细胞比例;ELISA 检测血清IL-21 浓度;分析这些指标间及与银屑病疾病活动度评分PASI 间的相关性。结果:与健康对照者相比,银屑病患者外周血循环CD4+ CXCR5+ Tfh 和CD4+ CXCR5+ ICOS+Tfh 细胞比例更高,血清IL-21 浓度和Th17 细胞比例亦显著高于对照组(P<0.05);IL-21 浓度与CD4+ CXCR5+ Tfh 和CD4+CXCR5+ ICOS+ Tfh 细胞比例均显著正相关,而与Th17 细胞比例间无显著相关性(P>0.05);且CD4+ CXCR5+ ICOS+ Tfh 细胞比例和血清IL-21 与银屑病疾病活动度PASI 评分显著正相关,而CD4+ CXCR5+ Tfh 则与之无显著相关性(P>0.05)。结论:银屑病患者外周血循环Tfh 比例、IL-21 浓度上调与银屑病患者疾病活动度密切相关,提示Tfh 可能参与银屑病的发生发展过程,这一效应可能是通过分泌高水平IL-21 实现;IL-21 浓度与Tfh 细胞比例相关,而与Th17 细胞比例无相关性提示银屑病患者IL-21可能主要由Tfh 细胞分泌。     

滤泡辅助T细胞的分化和功能及其在疾病中的作用

CD4~+辅助T(Th)细胞在抗原的刺激下会分化为不同的效应T细胞亚群。体液免疫应答具有很好的持久性,持久性的维持依赖于一群特殊的CD4~+T细胞提供辅助,即滤泡辅助性T(Tfh)细胞。树突状细胞(DC)提呈抗原并促进活化的Tfh前体细胞迁移到B细胞滤泡区域分化为成熟的Tfh细胞,辅助生发中心(GC)形成以及浆细胞和记忆性B细胞的分化,从而形成完整的体液免疫应答。Tfh细胞分化和功能上的失调均会导致多种疾病的发生。本文主要从Tfh细胞分化、功能以及在疾病中的作用三个方面对Tfh细胞的研究进展进行阐述。     

哮喘患者急性加重期滤泡辅助型T细胞的分化水平及临床意义

目的观察滤泡辅助型T细胞(Tfh细胞)在支气管哮喘患者急性发作期和治疗后的分化水平,探讨Tfh细胞是否在哮喘中存在分化异常及其临床意义。方法采用流式细胞术检测健康志愿者、哮喘患者急性发作期及治疗后外周血单个核细胞中CD4~~+CXCR5~~+T细胞、CD4~~+ICOS~+T细胞、CD4~~+CXCR5~~+ICOS~~+T细胞的比例;反转录PCR法检测CD4~+T细胞中Bcl-6mRNA的水平;ELISA检测血浆白细胞介素21(IL-21)的水平;采用直线回归统计学分析IL-21与患者第一秒用力呼气容积/用力肺活量百分比(FEV1/FVC)及第一秒用力呼气容积/预计值百分比(FEV1/Pre)之间的相关性。结果哮喘患者CD4~~+CXCR5~~+细胞、CD4~~+CXCR5~~+ICOS~~+T细胞比例、Bcl-6 mRNA表达水平、IL-21水平均显著高于正常对照组;治疗后哮喘患者CD4~~+CXCR5~~+细胞、CD4~~+ICOS~~+细胞、CD4~~+CXCR5~~+ICOS~~+T细胞表达比例、Bcl-6 mRNA表达水平、IL-21水平均显著低于急性发作时;哮喘患者IL-21表达水平与患者FEV1/FVC、FEV1/Pre存在负相关。结论 Tfh细胞在哮喘急性期存在分化增强,治疗后Tfh细胞分化减弱,提示Tfh细胞可能参与哮喘的炎症反应,其水平可能反映哮喘患者气道受限程度。     

滤泡辅助性T细胞的分化及其与免疫性疾病的关系

初始B细胞迁移至外周淋巴器官后发生一系列的变化,其参与体液免疫应答的过程需要滤泡辅助性T细胞（Tfh）的辅助.Tfh是一类以高水平表达CXCR5为特征的T细胞亚群,其分化除了由转录因子Bcl-6调控外尚有多种因素参与,如IL-21、ICOS、T-B细胞间接触、抗体亲和力等.Tfh细胞在体内正常的免疫应答中起着重要作用,一旦其相关因子表达发生异常,将导致机体免疫功能紊乱,引发多种免疫性疾病和肿瘤.     

滤泡辅助性T细胞相关分子与类风湿性关节炎相关性研究进展

类风湿性关节炎(RA)患者体内滤泡辅助性T(Tfh)细胞异常表达,与RA的发生发展相关。目前, Tfh细胞调控RA发生机制的研究仍处于初级阶段。此外, Tfh细胞表面分子CXC趋化因子受体5(CXCR5)、诱导性共刺激分子(ICOS)和程序性死亡蛋白1(PD-1)及其分泌的白细胞介素21(IL-21)、 B细胞淋巴瘤因子6(BCL6)均被证实与RA的发生有关。我们主要从Tfh细胞表面分子及其分泌的因子的角度研究其调控RA发生的机制,分析与Tfh细胞相关的各分子对RA发生的作用,探讨各分子对RA临床诊断的意义和以各分子为靶点治疗RA的潜在途径。     

表观遗传学调控滤泡辅助性T细胞分化的研究进展

滤泡辅助性T细胞(Tfh细胞)定位于淋巴滤泡的辅助性T细胞亚群,主要功能为辅助B细胞参与体液免疫应答,对免疫球蛋白的产生有着重要作用。表观遗传学主要研究在基因的核苷酸序列不发生改变的情况下,基因表达的可遗传性变化,是免疫细胞的分化调控机制之一。研究发现Tfh细胞的分化具有可塑性,本文主要综述了表观遗传学调控在Tfh细胞分化方面的研究进展。     

A fundamental role for interleukin-21 in the generation of T follicular helper cells

T cell help to B cells is a fundamental property of adaptive immunity, yet only recently have many of the cellular and molecular mechanisms of T cell help emerged. T follicular helper (Tfh) cells are the CD4(+) T helper cells that provide cognate help to B cells for high-affinity antibody production in germinal centers (GC). Tfh cells produce interleukin-21 (IL-21), and we show that IL-21 was necessary for GC formation. However, the central role of IL-21 in GC formation reflected its effects on Tfh cell generation rather than on B cells. Expression of the inducible costimulator (ICOS) was necessary for optimal production of IL-21, indicative of interplay between these two Tfh cell-expressed molecules. Finally, we demonstrate that IL-21's costimulatory capacity for T helper cell differentiation operated at the level of the T cell receptor signalosome through Vav1, a signaling molecule that controls T cell helper function. This study reveals a previously unappreciated role for Tfh cells in the formation of the GC and isotype switching through a CD4(+) T cell-intrinsic requirement for IL-21.     

The role of the T follicular helper cells in allergic disease

T follicular helper (Tfh) cells were discovered just over a decade ago as germinal centre T cells that help B cells make antibodies. Included in this role is affinity maturation and isotype switching. It is here that their functions become less clear. Tfh cells principally produce IL-21 which inhibits class switching to IgE. Recent studies have questioned whether the germinal centre is the main site of IgE class switching or IgE affinity maturation. In this review, I will examine the evidence that these cells are responsible for regulating IgE class switching and the relationship between Tfh cells and T helper 2 (Th2) effector cells.     

Interleukin (IL)-21 promotes intestinal IgA response to microbiota

Commensal microbiota-specific T helper type 17 (Th17) cells are enriched in the intestines, which can convert into T follicular helper (Tfh) in Peyer's patches, and are crucial for production of intestinal immunoglobulin A (IgA) against microbiota; however, the role of Th17 and Tfh cytokines in regulating the mucosal IgA response to enteric microbiota is still not completely known. In this study, we found that intestinal IgA was impaired in mice deficient in interleukin (IL)-17 or IL-21 signaling. IL-21, but not IL-17, is able to augment B-cell differentiation to IgA⁺ cells as mediated by transforming growth factor β1 (TGFβ1) and accelerate IgA class switch recombination (CSR). IL-21 and retinoic acid (RA) induce IgA⁺ B-cell development and IgA production and drives autocrine TGFβ1 production to initiate IgA CSR. Repletion of T-cell-deficient TCRβxδ^−/− mice with Th17 cells specific for commensal bacterial antigen increased the levels of IgA⁺ B cells and IgA production in the intestine, which was blocked by neutralizing IL-21. Thus IL-21 functions to strongly augment IgA production under intestinal environment. Furthermore, IL-21 promotes intestinal B-cell homing through α₄β₇ expression, alone or with TGFβ and RA. Together, IL-21 from microbiota-specific Th17 and/or Tfh cells contributes to robust intestinal IgA levels by enhancing IgA⁺ CSR, IgA production and B-cell trafficking into the intestine.     

Interleukin-2 inhibits germinal center formation by limiting T follicular helper cell differentiation

T follicular helper (Tfh) cells promote T?cell-dependent humoral immune responses by providing T?cell help to B cells and by promoting germinal center (GC) formation and long-lived antibody responses. However, the cellular and molecular mechanisms that control Tfh cell differentiation in?vivo are incompletely understood. Here we show that interleukin-2 (IL-2) administration impaired influenza-specific GCs, long-lived IgG responses, and Tfh cells. IL-2 did not directly inhibit GC formation, but instead suppressed the differentiation of Tfh cells, thereby hindering the maintenance of influenza-specific GC B cells. Our data demonstrate that IL-2 is a critical factor that regulates successful Tfh and B cell responses in?vivo and regulates Tfh cell development.