CD4+ T-cell subsets in intestinal inflammation

Intestinal CD4⁺ T cells are essential mediators of immune homeostasis and inflammation. Multiple subsets of CD4⁺ T cells have been described in the intestine, which represents an important site for the generation and regulation of cells involved in immune responses both within and outside of the gastrointestinal tract. Recent advances have furthered our understanding of the biology of such cells in the intestine. Appreciation of the functional roles for effector and regulatory populations in health and disease has revealed potential translational targets for the treatment of intestinal diseases, including inflammatory bowel disease. Furthermore, the role of dietary and microbiota-derived factors in shaping the intestinal CD4⁺ T-cell compartment is becoming increasingly understood. Here, we review recent advances in understanding the multifaceted roles of CD4⁺ T cells in intestinal immunity.     

溃疡性结肠炎患者外周血IL-22及相关CD4+ T细胞亚群的表达

目的 通过检测溃疡性结肠炎(UC)患者外周血中IL-22及相关CD4+T细胞亚群的表达,探讨其在UC发病机制中的可能作用.方法 以我院住院治疗的35例UC患者及35例健康对照者为研究对象,应用ELISA法检测外周血血浆中IL-22的含量,采用流式细胞术检测Th1、Th17、Th22细胞亚群的比例,并分析其与疾病活动度的关系.结果 UC组患者血浆中IL-22的含量为(354.12±104.22) pg/ml,显著高于对照组(P＜0.05),其中重度患者增高明显;UC组患者外周血Th17细胞比例[(2.36±0.94)％]显著高于对照组(P＜0.05),其中,中、重度患者增高明显;UC组患者外周血Th22细胞比例[(2.27±0.87)％]显著高于对照组(P＜0.05),其中,重度患者增高明显;而UC组患者Th1细胞比例与对照组比较尤明显差异.结论 UC患者外周血中IL-22水平、Th17、Th22细胞比例明显升高,且与疾病活动度密切相关.     

Type I interferon supports primary CD8+ T-cell responses to peptide-pulsed dendritic cells in the absence of CD4+ T-cell help

CD8(+) T-cell responses to non-pathogen, cell-associated antigens such as minor alloantigens or peptide-pulsed dendritic cells (DC) are usually strongly dependent on help from CD4(+) T cells. However, some studies have described help-independent primary CD8(+) T-cell responses to cell-associated antigens, using immunization strategies likely to trigger natural killer (NK) cell activation and inflammatory cytokine production. We asked whether NK cell activation by MHC I-deficient cells, or administration of inflammatory cytokines, could support CD4(+) T-cell help-independent primary responses to peptide-pulsed DC. Injection of MHC I-deficient cells cross-primed CD8(+) T-cell responses to the protein antigen ovalbumin (OVA) and the male antigen HY, but did not stimulate CD8(+) T-cell responses in CD4-depleted mice; hence NK cell stimulation by MHC I-deficient cells did not replace CD4(+) T-cell help in our experiments. Dendritic cells cultured with tumour necrosis factor-α (TNF-α) or type I interferon-α (IFN-α) also failed to prime CD8(+) T-cell responses in the absence of help. Injection of TNF-α increased lymph node cellularity, but did not generate help-independent CD8(+) T-cell responses. In contrast, CD4-depleted mice injected with IFN-α made substantial primary CD8(+) T-cell responses to peptide-pulsed DC. Mice deficient for the type I IFN receptor (IFNR1) made CD8(+) T-cell responses to IFNR1-deficient, peptide-pulsed DC; hence IFN-α does not appear to be a downstream mediator of CD4(+) T-cell help. We suggest that primary CD8(+) T-cell responses will become help-independent whenever endogenous IFN-α secretion is stimulated by tissue damage, infection, or autoimmune disease.     

Elevated circulating Th17 and follicular helper CD4+ T cells in patients with rheumatoid arthritis

It remains not fully elucidated the potential functions of Th17 cells and follicular helper T (Tfh) cells and secreting cytokines in the pathogenesis of rheumatoid arthritis (RA) and their association with disease activity. In this study, the frequencies of Th17 and Tfh cells were determined by flow cytometry, and the levels of interleukin (IL)‐17, IL‐21, and IL‐22 were measured by ELISA in RA patients with different disease activities. The dynamic changes of cell subsets were also detected in response to disease‐modify antirheumatic drugs (DMARDs) therapy. The percentages of CD3⁺CD4⁺IL‐17A⁺ (Th17) cells and CD3⁺CD4⁺CXCR5⁺ICOS^high (Tfh) cells, as well as the concentrations of IL‐17, IL‐21, and IL‐22 were significantly elevated in RA patients than those in healthy individuals. Furthermore, Tfh cells, IL‐21, and IL‐22 in the serum was positively correlated with the values of disease activity score. Concentrations of IL‐21 and IL‐22 in the serum were remarkably reduced following the DMARDs therapies. Our data suggested that Th17 cells, Tfh cells as well as the secreting cytokines may be involved in the pathogenesis of RA. The frequency of circulating Tfh cells and the productions of IL‐21 and IL‐22 were associated with the disease activity of RA patients, and might be potential therapeutic targets for treatment of RA.     

Normal human pregnancy is associated with an elevation in the immune suppressive CD25+ CD4+ regulatory T-cell subset

Summary CD4+ CD25+ T regulatory cells (TReg), suppress antigen-specific immune responses and are important for allograft tolerance. During pregnancy the mother tolerates an allograft expressing paternal antigens (the fetus) requiring substantial changes in immune regulation over a programmed period of time. We analysed whether immune-suppressive TReg cells were altered during pregnancy and therefore might play a part in this tolerant state. The presence of TReg cells was assessed in the blood of 25 non-pregnant, 63 pregnant and seven postnatal healthy women by flow cytometry. We observed an increase in circulating TReg cells during early pregnancy, peaking during the second trimester and then a decline postpartum. Isolated CD25+ CD4+ cells expressed FoxP3 messenger RNA, a marker of TReg cells, and suppressed proliferative responses of autologous CD4+ CD25- T cells to allogeneic dendritic cells. These data support the concept that normal pregnancy is associated with an elevation in the number of TReg cells which may be important in maintaining materno-fetal tolerance.     

Galectin-9对活化的CD4+T细胞免疫调节作用的机制研究

目的 研究Galectin-9对活化的CD4+T细胞的免疫调节作用,并进一步探讨其作用机制.方法 获取野生型C57BL/6小鼠淋巴细胞,利用MACS分选CD4+ na(i)ve T细胞,给予anti-CD3 (2.5 μg/ml)抗体、anti-CD28(5μg/ml)抗体和IL-2(100 ng/ml)刺激,培养3d.将活化的CD4+T细胞分为3组:正常对照组、Galectin-9组和Galectin-9+α-乳糖组.利用CFSE检测T细胞增殖情况,并动态观察细胞形态变化;检测CD4+ CD69+T细胞、Th1、Th2和Th17细胞的比例;并利用ELISA检测淋巴细胞分泌IFN-γ 、IL-4、IL-10、IL-12、IL-17A和TGF-β1等细胞因子的水平;利用Western blot检测T-bet、GATA-3和ROR-yt等T细胞分化调控蛋白的变化.结果 与正常对照组和Galectin-9+α-乳糖组相比,Galectin-9组于2h时开始出现细胞形态改变,同时CD4+ CD69+T细胞、Th1和Th17细胞表达减少(P＜0.05),但Th2细胞无明显变化;培养上清液中IFN-γ、IL-12、IL-17A和TGF-β1的表达水平降低(P＜0.05),而IL-4和IL-10等Th2型细胞因子水平无明显变化;同时T-bet和ROR-γt的表达水平减少(P＜0.05).结论 Galectin-9抑制活化CD4+T细胞的Th1和Th17型免疫应答,而对Th2型免疫应答无影响,免疫调节的机制可能与其在转录水平影响Th1和Th17特定转录因子的表达有关.     

PARP-1 inhibitor-AG14361 suppresses acute allograft rejection via stabilizing CD4+FoxP3+ regulatory T cells

Acute allograft rejection is the most common complication in organ transplantation leading to organ loss. Treg cells play an important role in preventing acute rejection, but they are unstable and easily lose function. Poly(ADP-ribose) polymerase 1(PARP-1) is involved in the differentiation stabilization of Treg cells, it has been suggested that PARP-1 inhibition could prevent acute rejection and prolong allograft survival. This study investigated AG14361 effects on acute allograft rejection. We used a fully MHC-mismatched murine heart transplantation model to compare the effect of PARP-1 inhibitor-AG14361 on alloimmunity to the control. Mice treated with PARP-1 inhibitors showed a longer median survival time of allografts (MS14 compared with the control group, MST was 8 days, and AG14361 was 6 days, P = 0.019). The combination of sirolimus and AG14361 significantly delayed allograft MST (AG14361 + sirolimus for 30 days, sirolimus for 16 days, P = 0.002). AG14361 markedly augmented the number of the CD25+FoxP3+ Treg cells in the graft and periphery. In addition, it could enhance the suppressive function of Treg cells by upregulating the level of CTLA-4, PD-1 and ICOS. In vivo, the Treg/Th17 ratio increased significantly in the AG14351 group compared to the control. In the combination with sirolimus treatment, AG14361 promoted the long-term allograft survival. Our results highlight novel effects of a PARP-1 inhibitor. PARP-1 inhibitor AG14361 may be a promising agent to attenuate acute allograft rejection as it can maintain the number and function of Treg cells in allografts.     

CD4+ T helper 2 cells--microbial triggers, differentiation requirements and effector functions

Over the past 10 years we have made great strides in our understanding of T helper cell differentiation, expansion and effector functions. Within the context of T helper type 2 (Th2) cell development, novel innate‐like cells with the capacity to secrete large amounts of interleukin‐5 (IL‐5), IL‐13 and IL‐9 as well as IL‐4‐producing and antigen‐processing basophils have (re)‐emerged onto the type 2 scene. To what extent these new players influence αβ⁺ CD4⁺ Th2 cell differentiation is discussed throughout this appraisal of the current literature. We highlight the unique features of Th2 cell development, highlighting the three necessary signals, T‐cell receptor ligation, co‐stimulation and cytokine receptor ligation. Finally, putting these into context, microbial and allergenic properties that trigger Th2 cell differentiation and how these influence Th2 effector function are discussed and questioned.     

Neuropilin-1在CD4+ CD25+ T细胞上的表达

目的 探讨neuropilin-1(NRPl)在外周血中CIM+ CD25+ T细胞上的表达以及意义.方法 收集肾移植术后长期存活、慢性移植物肾病和急性排斥患者以及健康成年人的外周血,分离外周血淋巴细胞,用流式细胞仪检测外周血淋巴细胞中CD4+ CD25+ T细胞上NRPl和Foxp3的阳性细胞的百分比.结果 各组CD4+ CD25+ T细胞NRPl的表达率差异有统计学意义(P＜0.05);各组CD4+ CD25+ T细胞Foxp3的表达率差异亦有统计学意义(P＜0.05).长期存活组CD4+ CD25+ T细胞上NRP1和Foxp3表达率分别为19.6%±3.84%、50.19 ±3.90%,显著高于对照及慢性移植物肾病和急性排斥组(P＜0.05);急性排斥组的CD4+ CD25+ T细胞NRP1和Foxp3表达率最低4.64%±1.26%、17.24%±5.29%.各组CD4+ CD25+ T细胞NRP1表达变化趋势与Foxp3变化趋势相同.结论 NRP1在长期存活组的外周血淋巴细胞中CD4+ CD25+ T细胞的表达上调,在急性排斥组时表达下调,且其在各组的表达变化趋势与Foxp3的表达变化趋势是一致的,这就提示CD4+ CD25+ NRP1+ 细胞是一群调节性T细胞,即NRP1是CD4+ CD25+ Treg的一个重要的表面标志.     

类风湿关节炎患者外周血CD4+T细胞亚群的分析

目的 研究类风湿性关节炎(RA)患者不同时期外周血Treg和Th1、Th2、Th17细胞以及中性粒细胞上CD64的表达水平,及它们与RA的活动性指标和自身抗体的相关性.方法 采集78例RA患者和21例健康人外周静脉血,采用流式细胞术检测淋巴细胞亚群(Treg,Th1、Th2、Th17细胞)的变化.结果 RA的CD3+ CD4+T细胞和CD4+ CD25+T细胞增多,活动期RA组Treg比率高于缓解期RA组和健康对照组,缓解期RA组Th2细胞减少,RA中Th1,TH17细胞与健康对照组相比无统计学意义,Treg和Th1、Th2、Th17细胞与RA的活动性指标(ESR,CRP和PLT)均无关联.结论 CD4+T细胞亚群数量异常可能与RA疾病发展有关.     

Depletion of CD4+CD25+CD127lo regulatory T cells does not increase allergen‐driven T cell activation

Background It has been suggested that allergic diseases are caused by defective suppression of allergen‐specific Th2 cells by CD4⁺CD25⁺ regulatory T cells. However, such studies have been hampered by the difficulty in distinguishing regulatory T cells from CD25‐expressing activated T cells. Recently, it was shown that conventional T cells expressed high levels of CD127, whereas regulatory T cells were CD127^lo, allowing discrimination between these distinct T cell subpopulations. Objective The aim of this study was to study whether the putative regulatory subset defined as CD4⁺CD25⁺CD127^lo was involved in grass pollen‐reactive T cell responses. Methods Peripheral blood mononuclear cells (PBMCs) were obtained from allergic donors and non‐atopic controls out of season. Grass pollen‐induced cytokine production and proliferation were compared in cultures of undepleted cells and cells depleted of CD4⁺CD25⁺, CD4⁺CD25⁺CD127^hi or CD4⁺CD25⁺CD127^lo T cells. Results Undepleted cell cultures from allergic patients showed significantly increased proliferation and Th2 cytokine production compared with non‐atopic controls. Depletion of all CD25⁺ T cells did not increase cytokine production or proliferation, and more importantly, no increase in Th2 cytokine production or proliferation was observed in cell cultures depleted of CD4⁺CD25⁺CD127^lo cells (putative regulatory T cells) compared with undepleted PBMCs in both the allergic and the non‐atopic group. Conclusion Our study showed that T cells from grass pollen‐allergic patients and non‐atopic controls responded very differently to grass pollen extract, but this difference could not be explained by differences in regulatory T cell function. Further studies are needed to understand the importance of regulatory T cells in allergy.     

Reduced levels of both circulating CD4+ CD25+ CD127(low/neg) and CD4+ CD8(neg) invariant natural killer regulatory T cells in stable heart transplant recipients

A cross-regulation between two regulatory T cell (T(reg) ) subsets [CD4(+) CD25(+) and invariant natural killer (NK) T - iNK T] has been described to be important for allograft tolerance induction. However, few studies have evaluated these cellular subsets in stable recipients as correlates of favourable clinical outcome after heart transplantation. T(reg) and iNK T cell levels were assayed by flow cytometry in peripheral blood samples from 44 heart transplant recipients at a 2-year interval in 38 patients, and related to clinical outcome. Multi-parameter flow cytometry used CD4/CD25/CD127 labelling to best identify T(reg) , and a standard CD3/CD4/CD8/Vα24/Vβ11 labelling strategy to appreciate the proportions of iNK T cells. Both subtypes of potentially tolerogenic cells were found to be decreased in stable heart transplant recipients, with similar or further decreased levels after 2 years. Interestingly, the patient who presented with several rejection-suggesting incidents over this period displayed a greater than twofold increase of both cell subsets. These results suggest that CD4(+) CD25(+) CD127(low/neg) T(reg) and iNK T cells could be involved in the local control of organ rejection, by modulating immune responses in situ, in clinically stable patients. The measurement of these cell subsets in peripheral blood could be useful for non-invasive monitoring of heart transplant recipients, especially in the growing context of tolerance-induction trials.     

CD4+ T-cell subsets and host defense in the lung

CD4⁺ T-helper subsets are lineages of T cells that have effector function in the lung and control critical aspects of lung immunity. Depletion of these cells experimentally or by drugs or human immunodeficiency virus (HIV) infection in humans leads to the development of opportunistic infections as well as increased rates of bacteremia with certain bacterial pneumonias. Recently, it has been proposed that CD4⁺ T-cell subsets may also be excellent targets for mucosal vaccination to prevent pulmonary infections in susceptible hosts. Here, we review recent findings that increase our understanding of T-cell subsets and their effector cytokines in the context of pulmonary infection.     

CD4+ CD25+ [corrected] regulatory T cells render naive CD4+ CD25- T cells anergic and suppressive

CD4(+) CD25(+) Foxp3(+) naturally occurring regulatory T cells (nTreg) are potent inhibitors of almost all immune responses. However, it is unclear how this minor population of cells is capable of exerting its powerful suppressor effects. To determine whether nTreg mediate part of their suppressor function by rendering naive T cells anergic or by converting them to the suppressor phenotype, we cocultured mouse nTreg with naive CD4(+) CD25(-) T cells from T-cell receptor (TCR) transgenic mice on a RAG deficient (RAG(-/-)) background in the presence of anti-CD3 and interleukin-4 (IL-4) to promote cell viability. Two distinct responder cell populations could be recovered from the cocultures. One population remained undivided in the coculture and was non-responsive to restimulation with anti-CD3 or exogenous IL-2, and could not up-regulate IL-2 mRNA or CD25 expression upon TCR restimulation. Those responder cells that had divided in the coculture were anergic to restimulation with anti-CD3 but responded to restimulation with IL-2. The undivided population was capable of suppressing the response of fresh CD4(+) CD25(-) T cells and CD8(+) T cells, while the divided population was only marginally suppressive. Although cell contact between the induced regulatory T cell (iTreg) and the responders was required for suppression to be observed, anti-transforming growth factor-beta partially abrogated their suppressive function. The iTreg did not express Foxp3. Therefore nTreg are not only able to suppress immune responses by inhibiting cytokine production by CD4(+) CD25(-) responder cells, but also appear to modulate the responder cells to render them both anergic and suppressive.     

CD4+ T-cell inhibitory ligands: a tool for characterizing dysfunctional CD4+ T cells during chronic infection

T helper type 17 (Th17) lymphocytes are found in high frequency in tumour‐burdened animals and cancer patients. These lymphocytes, characterized by the production of interleukin‐17 and other pro‐inflammatory cytokines, have a well‐defined role in the development of inflammatory and autoimmune pathologies; however, their function in tumour immunity is less clear. We explored possible opposing anti‐tumour and tumour‐promoting functions of Th17 cells by evaluating tumour growth and the ability to promote tumour infiltration of myeloid‐derived suppressor cells (MDSC), regulatory T cells and CD4⁺ interferon‐γ⁺ cells in a retinoic acid‐like orphan receptor γt (RORγt) ‐deficient mouse model. A reduced percentage of Th17 cells in the tumour microenvironment in RORγt‐deficient mice led to enhanced tumour growth, that could be reverted by adoptive transfer of Th17 cells. Differences in tumour growth were not associated with changes in the accumulation or suppressive function of MDSC and regulatory T cells but were related to a decrease in the proportion of CD4⁺ T cells in the tumour. Our results suggest that Th17 cells do not affect the recruitment of immunosuppressive populations but favour the recruitment of effector Th1 cells to the tumour, thereby promoting anti‐tumour responses.     

The regulatory roles of B cell subsets in transplantation

Introduction: B cells mediate allograft rejection through antigen presentation, and production of cytokines and antibodies. More and more immunosuppressive agents specifically targeting B cells and plasma cells have been applied in clinical transplantation. However, recent studies have indicated the regulatory roles of B cells. Therefore, it is vital to clarify the different effects of B cell subsets in organ transplantation so that we can completely understand the diverse functions of B cells in transplantation.

Areas covered: This review focuses on the regulatory roles of B cells in transplantation. B cell subsets with immune modulation and factors mediating immunosuppressive functions of regulatory B (Breg) cells were analyzed. Therapies targeting B cells and the application of B cells for transplant tolerance induction were discussed.

Expert commentary: Besides involving rejection, B cells could also play regulatory roles in transplantation. Breg cells and the related markers may be used to predict the immune tolerant state in transplant recipients. New therapeutic strategies targeting B cells should be explored to promote tolerance induction with less impact on the host’s protective immunity in organ transplanted patients.