IL‐15‐dependent CD8+CD122+ T cells ameliorate experimental autoimmune encephalomyelitis by modulating IL‐17 production by CD4+ T cells

Interleukin‐15 (IL‐15) is an inflammatory cytokine whose role in autoimmune diseases has not been fully elucidated. Th17 cells have been shown to play critical roles in experimental autoimmune encephalomyelitis (EAE) models. In this study, we demonstrate that blockade of IL‐15 signaling by TMβ‐1 mAb treatment aggravated EAE severity. The key mechanism was not NK‐cell depletion but depletion of CD8⁺CD122⁺ T cells. Adoptive transfer of exogenous CD8⁺CD122⁺ T cells to TMβ‐1‐treated mice rescued animals from severe disease. Moreover, transfer of preactivated CD8⁺CD122⁺ T cells prevented EAE development and significantly reduced IL‐17 secretion. Naïve effector CD4⁺CD25^? T cells cultured with either CD8⁺CD122⁺ T cells from wild‐type mice or IL‐15 transgenic mice displayed lower frequencies of IL‐17A production with lower amounts of IL‐17 in the supernatants when compared with production by effector CD4⁺CD25^? T cells cultured alone. Addition of a neutralizing antibody to IL‐10 led to recovery of IL‐17A production in Th17 cultures. Furthermore, coculture of CD8⁺CD122⁺ T cells with effector CD4⁺ T cells inhibited their proliferation significantly, suggesting a regulatory function for IL‐15 dependent CD8⁺CD122⁺ T cells. Taken together, these observations suggest that IL‐15, acting through CD8⁺CD122⁺ T cells, has a negative regulatory role in reducing IL‐17 production and Th17‐mediated EAE inflammation.     

天然CD4+CD25+Treg细胞的研究进展

天然CD4+ CD25+ Treg细胞在针对自身抗原和外来抗原的免疫应答中起关键控制作用,其缺乏或功能性的缺陷将导致多重病理性的失调.本文就近年在其产生、作用机制以及与免疫耐受的诱导关系等方面的研究进展进行了综述.     

Steady‐state antigen‐expressing dendritic cells terminate CD4+ memory T‐cell responses

CD4⁺ T cells are important effectors of inflammation and tissue destruction in many diseases of immune dysregulation. As memory T cells develop early during the preclinical stages of autoimmune and inflammatory diseases, immunotherapeutic approaches to treatment of these diseases, once established, must include the means to terminate memory T‐cell responses. Traditionally, it has been considered that, due to their terminally differentiated nature, memory T cells are resistant to tolerance induction, although emerging evidence indicates that some immunotherapeutic approaches can terminate memory T‐cell responses. Here, we demonstrate that CD4⁺ memory T‐cell responses can be terminated when cognate antigen is transgenically expressed in steady‐state DC. Transfer of in‐vitro‐generated CD4⁺ memory T cells establishes, in nontransgenic recipients, a stable and readily recalled memory response to cognate antigen. In contrast, upon transfer to mice expressing cognate antigen targeted to DC, memory CD4⁺ T cells undergo a phase of limited proliferation followed by substantial deletion, and recall responses are effectively silenced. This finding is important in understanding how to effectively apply immunotherapy to ongoing T‐cell‐mediated autoimmune and inflammatory diseases.     

Phenotypic switch of CD8+ T cells reactivated under hypoxia toward IL‐10 secreting,poorly proliferative effector cells

CD8⁺ T cells controlling pathogens or tumors must function at sites where oxygen tension is frequently low, and never as high as under atmospheric culture conditions. However, T‐cell function in vivo is generally analyzed indirectly, or is extrapolated from in vitro studies under nonphysiologic oxygen tensions. In this study, we delineate the role of physiologic and pathologic oxygen tension in vitro during reactivation and differentiation of tumor‐specific CD8⁺ T cells. Using CD8⁺ T cells from pmel‐1 mice, we observed that the generation of CTLs under 5% O₂, which corresponds to physioxia in lymph nodes, gave rise to a higher effector signature than those generated under atmospheric oxygen fractions (21% O₂). Hypoxia (1% O₂) did not modify cytotoxicity, but decreasing O₂ tensions during CTL and CD8⁺ tumor‐infiltrating lymphocyte reactivation dose‐dependently decreased proliferation, induced secretion of the immunosuppressive cytokine IL‐10, and upregulated the expression of CD137 (4‐1BB) and CD25. Overall, our data indicate that oxygen tension is a key regulator of CD8⁺ T‐cell function and fate and suggest that IL‐10 release may be an unanticipated component of CD8⁺ T cell‐mediated immune responses in most in vivo microenvironments.     

IL‐12‐mediated STAT4 signaling and TCR signal strength cooperate in the induction of CD40L in human and mouse CD8+ T cells

CD40L is one of the key molecules bridging the activation of specific T cells and the maturation of professional and nonprofessional antigen‐presenting cells including B cells. CD4⁺ T cells have been regarded as the major T‐cell subset that expresses CD40L upon cognate activation; however, we demonstrate here that a putative CD8⁺ helper T‐cell subset expressing CD40L is induced in human and murine CD8⁺ T cells in vitro and in mice immunized with antigen‐pulsed dendritic cells. IL‐12 and STAT4‐mediated signaling was the major instructive cytokine signal boosting the ability of CD8⁺ T cells to express CD40L both in vitro and in vivo. Additionally, TCR signaling strength modulated CD40L expression in CD8⁺ T cells after primary differentiation in vitro as well as in vivo. The induction of CD40L in CD8⁺ T cells regulated by IL‐12 and TCR signaling may enable CD8⁺ T cells to respond autonomously of CD4⁺ T cells. Thus, we propose that under proinflammatory conditions, a self‐sustaining positive feedback loop could facilitate the efficient priming of T cells stimulated by high affinity peptide displaying APCs.     

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.     

CD4+CD25+调节性T细胞在肿瘤免疫中的作用

CD4+CD25+调节性T细胞(Tr)是体内自然发生的调节性T细胞的重要亚群,具有无反应性和免疫抑制两大特性,主要通过与靶细胞的直接接触而起作用,其在体内不仅参与自身免疫性疾病、移植排斥反应等,还在肿瘤的发生、发展及免疫治疗中发挥重要作用.近几年来,Tr在肿瘤免疫中的作用倍受关注.     

IL‐12 and IL‐4 activate a CD39‐dependent intrinsic peripheral tolerance mechanism in CD8+ T cells

Immune responses to protein antigens involve CD4⁺ and CD8⁺ T cells, which follow distinct programs of differentiation. Naïve CD8 T cells rapidly develop cytotoxic T‐cell (CTL) activity after T‐cell receptor stimulation, and we have previously shown that this is accompanied by suppressive activity in the presence of specific cytokines, i.e. IL‐12 and IL‐4. Cytokine‐induced CD8⁺ regulatory T (Treg) cells are one of several Treg‐cell phenotypes and are Foxp3^? IL‐10⁺ with contact‐dependent suppressive capacity. Here, we show they also express high level CD39, an ecto‐nucleotidase that degrades extracellular ATP, and this contributes to their suppressive activity. CD39 expression was found to be upregulated on CD8⁺ T cells during peripheral tolerance induction in vivo, accompanied by release of IL‐12 and IL‐10. CD39 was also upregulated during respiratory tolerance induction to inhaled allergen and on tumor‐infiltrating CD8⁺ T cells. Production of IL‐10 and expression of CD39 by CD8⁺ T cells was independently regulated, being respectively blocked by extracellular ATP and enhanced by an A2A adenosine receptor agonist. Our results suggest that any CTL can develop suppressive activity when exposed to specific cytokines in the absence of alarmins. Thus negative feedback controls CTL expansion under regulation from both nucleotide and cytokine environment within tissues.     

Post-thymic in vivo proliferation of naive CD4+ T cells constrains the TCR repertoire in healthy human adults

In spite of thymic involution early in life, the numbers of naive CD4(+) T cells only slowly decline in ageing humans implying peripheral post-thymic naive CD4(+) T cell expansion. This proliferation may compensate for continuous activation and death of naive CD4(+) T cells but may also have negative consequences for protective immunity. Here we show that naive CD4(+) T cells that have proliferated in the periphery are characterized by a highly restricted oligoclonal TCR repertoire. Additionally these cells, which constitute the majority of naive CD4(+) T cells in the elderly, display signatures of recent TCR engagement. Our results demonstrate for the first time that peripheral post-thymic proliferation of naive CD4(+) T cells in healthy human individuals causes a significant contraction of the peripheral TCR repertoire. This age-dependent deterioration of CD4(+) T cell immunity could entail ageing-associated autoimmunity, increased susceptibility to infection or cancer and decreased efficiency of vaccination.     

CD4+ CD25+调节性T细胞对树突状细胞的杀伤作用

目的 探讨CD4^＋CD25^＋调节性T细胞是否对树突状细胞发挥免疫调节作用及其可能的机制。方法 用MACS（magnetic cell sorting）从BALB／c小鼠静息T细胞分离纯化CD4^＋CD25^＋T细胞，体外细胞增殖实验观察其对CD4^＋CD25^＋T细胞的免疫抑制作用；GM-CSF／IL-4培养自体小鼠骨髓来源DC，FACS（fluorescence-activated cell sorting）鉴定其表面分子特性；以CD3／CD28单克隆抗体活化CD4^＋CD25^＋调节性T细胞，FACS体外杀伤实验研究其对自体DC的调节作用，并观察穿孔素抑制剂EGTA对上述作用的影响。结果 用MACS法成功分离出CD4^＋CD25^＋T细胞，纯度可达98％，特异性表达而Faxp3基因，能明显抑制CD4^＋CD25^＋T细胞的体外增殖；骨髓来源的DC表达CDllc、MHCⅡ及少量协同刺激分子CD80、CD86；FACS体外杀伤实验证实以CD3／CD28抗体体外活化的CD4^＋CD25^＋调节性T细胞对自体DC有显著杀伤作用（P〈0．05），穿孔素抑制剂EGTA能部分抑制该杀伤效应（P〈0．05）。结论 CD4^＋CD25^＋调节性T细胞可通过杀伤作用对自体DC发挥免疫调节作用，穿孔素／颗粒酶杀伤途径可能参与其中。     

The regulation of regulation: interleukin‐10 increases CD4+ CD25+ regulatory T cells but impairs their immunosuppressive activity in murine models with schistosomiasis japonica or asthma

CD4⁺ CD25⁺ Foxp3⁺ regulatory T (Treg) cells play an important role in maintaining immune homeostasis. Interleukin‐10 (IL‐10), a cytokine with anti‐inflammatory capacities, also has a critical role in controlling immune responses. In addition, it is well known that production of IL‐10 is one of the suppression mechanisms of Treg cells. However, the action of IL‐10 on Treg cells themselves remains insufficiently understood. In this study, by using a Schistosoma japonicum‐infected murine model, we show that the elevated IL‐10 contributed to Treg cell induction but impaired their immunosuppressive function. Our investigations further suggest that this may relate to the up‐regulation of serum transforming growth factor (TGF‐β) level but the decrease in membrane‐bound TGF‐β of Treg cells by IL‐10 during S. japonicum infection. In addition, similar IL‐10‐mediated regulation on Treg cells was also confirmed in the murine model of asthma. In general, our findings identify a previously unrecognized opposing regulation of IL‐10 on Treg cells and provide a deep insight into the precise regulation in immune responses.     

CD4~+CD25~+T细胞在CD8~+T细胞抗肿瘤免疫中的调节作用

实验旨在研究CD4+CD25+T细胞在CD8+T细胞抗肿瘤免疫中的调节作用。将小鼠脾脏中分离的单个核细胞分为两组,即去除CD4+CD25+T细胞组和未去除CD4+CD25+T细胞组,测定树突状细胞提呈的肿瘤抗原多肽刺激不同T细胞增殖活性、细胞因子IFN-γ分泌,以及多肽特异性CD8+T细胞对同源性胃癌细胞株MFC的杀伤活性。结果显示预先去除未致敏T细胞中的CD4+CD25+T细胞,所诱导的特异性CD8+CTL对肿瘤细胞免疫应答增强,表现为反应性T细胞对树突状细胞提呈的肿瘤抗原多肽增殖反应增强,IFN-γ分泌量提高及CD8+T细胞对MFC杀伤活性增强。这些结果表明,预先去除未致敏T细胞中的CD4+CD25+T细胞,肿瘤抗原多肽修饰的树突状细胞肿瘤疫苗效能可明显增加。CD4+CD25+T细胞在CD8+T细胞抗肿瘤免疫中起下调作用。     

Involvement of CD91 and scavenger receptors in Hsp70‐facilitated activation of human antigen‐specific CD4+ memory T cells

Hsp70 plays several roles in the adaptive immune response. Based on the ability to interact with diverse peptides, extracellular Hsp70:peptide complexes exert profound effects both in autoimmunity and in tumor rejection by evoking potent T cell responses to the chaperoned peptide. The interaction with receptors on APC represents the basis for the immunological functions of Hsp70 and a critical point where the immune response can be regulated. Various surface proteins (e.g. CD91, scavenger receptors (SR)) have been implicated in binding of Hsp70. In this study, antigenic peptides from tetanus toxin and influenza hemagglutinin complexed to human stress‐inducible Hsp70 were found to enhance the proliferation and cytokine production of human antigen‐specific CD4⁺ T cells. This was demonstrated in proliferation experiments using human monocytes as APC. Proliferated antigen‐specific cells were detected combining HLA‐DRB1^*0401 or HLA‐DRB1^*1101 tetramer and CFSE staining. Treating monocytes with CD91 siRNA diminished these effects. Additional blocking of SR by the SR ligand fucoidan completely abolished enhanced proliferation and production of Th1 and Th2 cytokines. Taken together, our data indicate that in the human system, CD91 and members of the SR family efficiently direct Hsp70:peptide complexes into the MHC class II presentation pathway and thus enhance antigen‐specific CD4⁺ T cell responses.     

Interleukin‐4 downregulates CD127 expression and activity on human thymocytes and mature CD8+ T cells

Signaling via the IL‐7 receptor complex (IL‐7Rα/CD127 and IL‐2Rγ/CD132) is required for T‐cell development and survival. Decreased CD127 expression has been associated with persistent viral infections (e.g. HIV, HCV) and cancer. Many IL‐2Rγ‐sharing (γ_C) cytokines decrease CD127 expression on CD4⁺ and CD8⁺ T cells in mice (IL‐2, IL‐4, IL‐7, IL‐15) and in humans (IL‐2, IL‐7), suggesting a common function. IL‐4 is of particular interest as it is upregulated in HIV infection and in thyroid and colon cancers. The role of IL‐4 in regulating CD127 expression and IL‐7 activity in human thymocytes and mature CD8⁺ T cells is unknown and was therefore investigated. IL‐4 decreased CD127 expression on all thymocyte subsets tested and only on naïve (CD45RA⁺) CD8⁺ T cells, without altering membrane‐bound CD127 mRNA expression. Pre‐treatment of thymocytes or CD8⁺ T cells with IL‐4 inhibited IL‐7‐mediated phosphorylation of STAT5 and decreased proliferation of CD8⁺ T cells. By downregulating CD127 expression and signaling on developing thymocytes and CD8⁺ T cells, IL‐4 is a potential contributor to impaired CD8⁺ T‐cell function in some anti‐viral and anti‐tumor responses. These findings are of particular consequence to diseases such as HIV, HCV, RSV, measles and cancer, in which CD127 expression is decreased, IL‐7 activity is impaired and IL‐4 concentrations are elevated.     

CD4+ CD25+调节性T细胞在肾脏疾病中的作用

CD4+ CD25+ 调节性T细胞(Tr)是一个具有独立功能的T细胞亚群,是机体维持自身免疫耐受的重要组成部分,在免疫病理、移植物耐受、阻止自身免疫反应和维持机体免疫平衡方面都有一定作用,其T细胞亚群在多种免疫性疾病中发挥重要的调节作用,但国内外有关该群细胞在肾脏疾病中作用的报道较少.     

Communication between human mast cells and CD4+ T cells through antigen‐dependent interactions

Mast cells (MCs) are immune cells residing in tissues where pathogens are first encountered. It has been indicated that MCs might also be involved in setting the outcome of T‐cell responses. However, little is known about the capacity of human MCs to express MHC class II and/or to capture and present antigens to CD4⁺ T cells. To study the T‐cell stimulatory potential of human MCs, CD34⁺ stem cell derived MCs were generated. These cells expressed HLA‐DR when stimulated with IFN‐γ, and, importantly, presented peptide and protein for activation of antigen‐specific CD4⁺ T cells. The interplay between MC and T cell led to increased HLA‐DR expression on MCs. MCs were present in close proximity to T cells in tonsil and expressed HLA‐DR and CD80, indicating their ability to present antigens to CD4⁺ T cells in T‐cell areas of human LNs. Our data show that MCs can present native antigens to human CD4⁺ T cells and that HLA‐DR expressing MCs are present in tonsil tissue, indicating that human MCs can directly activate T cells and provide a rationale to study the potential of MCs to prime and/or skew human T‐cell responses.     

小鼠CD4＋ CD25＋免疫调节性T细胞体外扩增及功能检测的研究

目的 探讨小鼠CD4＋ CD25＋调节性T细胞（Tregs）的体外扩增方法及扩增后Tregs的免疫功能.方法 利用免疫磁珠法分离小鼠Tregs;采用anti-CD3mAb＋rIL-2和Allo-APC＋rIL-2两种方法进行体外扩增,通过TRANSWELL培养系统、细胞因子表达及CFSE染色标记等方法检测Tregs免疫抑制作用的机制.结果 体外分离的Tregs纯度为89.5％;活细胞率约为98％.Tregs扩增的倍数在两组各时间点差异无统计学意义.扩增后CD4＋ CD25＋T细胞、CD4＋T细胞和CD4＋ CD25-T细胞的每分钟计数（CPM）分别为1 470、12 700和14 300.混合淋巴细胞反应（MLR）中当CD4＋：CD25＋T细胞的比例为1∶1时,抑制率为79％,比例为8∶1时,抑制率为33％.CFSE标记后,进入分裂周期的CD4＋T细胞的百分比在未加入CD4＋ CD25＋T细胞组为83.7％,加入CD4＋ CD25＋T细胞组为31.7％,差异具有统计学意义（P=0.0006）.CD4＋ CD25＋T细胞对CD4＋T细胞的增殖抑制率在Transwell和Non-Transwell的培养系统中分别为＜5％和95％.Transwell培养组中IL-2含量高于Non-Transwell组,差异具有统计学意义[Transwell培养组为（158.33±2.08）pg/mL,Non-Transwell组为（23.00±2.00） pg/mL,P ＜0.0001].结论 采用免疫磁珠法分离小鼠Tregs可行,Tregs可有效扩增;Tregs的作用机制为抑制CD4＋T细胞的增殖及抑制CD4＋T细胞分泌IL-2;其抑制作用需要细胞-细胞间接触;体外扩增后的Tregs仍具有免疫特性,其体外免疫抑制作用增强.     

Genetically modified human CD4+ T cells can be evaluated in vivo without lethal graft‐versus‐host disease

Adoptive cell immunotherapy for human diseases, including the use of T cells modified to express an anti‐tumour T‐cell receptor (TCR) or chimeric antigen receptor, is showing promise as an effective treatment modality. Further advances would be accelerated by the availability of a mouse model that would permit human T‐cell engineering protocols and proposed genetic modifications to be evaluated in vivo. NOD‐scid IL2rγ^null (NSG) mice accept the engraftment of mature human T cells; however, long‐term evaluation of transferred cells has been hampered by the xenogeneic graft‐versus‐host disease (GVHD) that occurs soon after cell transfer. We modified human primary CD4⁺ T cells by lentiviral transduction to express a human TCR that recognizes a pancreatic beta cell‐derived peptide in the context of HLA‐DR4. The TCR‐transduced cells were transferred to NSG mice engineered to express HLA‐DR4 and to be deficient for murine class II MHC molecules. CD4⁺ T‐cell‐depleted peripheral blood mononuclear cells were also transferred to facilitate engraftment. The transduced cells exhibited long‐term survival (up to 3 months post‐transfer) and lethal GVHD was not observed. This favourable outcome was dependent upon the pre‐transfer T‐cell transduction and culture conditions, which influenced both the kinetics of engraftment and the development of GVHD. This approach should now permit human T‐cell transduction protocols and genetic modifications to be evaluated in vivo, and it should also facilitate the development of human disease models that incorporate human T cells.