The influence of regulatory T cells and diurnal hormone rhythms on T helper cell activity

Symptoms of diseases such as rheumatoid arthritis, which is T helper 1 (Th1) dependent, and asthma, which is T helper 2 (Th2) dependent, are influenced by diurnal rhythms and natural regulatory T cells (nTreg). However, the mechanisms responsible for the diurnal rhythm of disease activity have not been identified and it is unclear whether nTreg activity is diurnal rhythm‐dependent. We therefore investigated whether a 24‐hr diurnal cycle affected the ability of various helper T‐cell populations to generate immunomodulatory and pro‐inflammatory cytokines, as well as its suppression by nTreg cells. Using a within‐subject crossover design, sleep versus continuous wakefulness was compared over a 24‐hr period in healthy young volunteers under defined environmental conditions. Venous blood was drawn periodically every 5 hr and the function of T cells was explored in vitro. We demonstrated that interleukin (IL)‐2, interferon‐γ (IFN‐γ), tumour necrosis factor‐α (TNF‐α) and IL‐10 secretion by naïve CD4⁺ T cells follows a diurnal rhythm. Furthermore, multiple regression analysis, as well as subsequent in vitro experiments, suggested that serum levels of cortisol and prolactin are part of the underlying mechanism. Additionally, we observed that nTreg suppressed the secretion of IFN‐γ, IL‐2 and TNF‐α, but not the secretion of IL‐4, IL‐6, IL‐10 and IL‐17A. However, the abrogation of IL‐2 release was reversed upon inhibiting CD25 on nTreg. Highly purified nTreg secreted IL‐6, IL‐10 and IL‐17A, but not IL‐2, IL‐4, IFN‐γ or TNF‐α. Taken together, our results demonstrate that hormones and nTreg modulate the diurnal rhythm of T helper cell activity.     

TLR2 engagement on CD4+ T cells enhances effector functions and protective responses to Mycobacterium tuberculosis

We have previously demonstrated that mycobacterial lipoproteins engage TLR2 on human CD4⁺ T cells and upregulate TCR‐triggered IFN‐γ secretion and cell proliferation in vitro. Here we examined the role of CD4⁺ T‐cell‐expressed TLR2 in Mycobacterium tuberculosis (MTB) Ag‐specific T‐cell priming and in protection against MTB infection in vivo. Like their human counterparts, mouse CD4⁺ T cells express TLR2 and respond to TLR2 costimulation in vitro. This Th1‐like response was observed in the context of both polyclonal and Ag‐specific TCR stimulation. To evaluate the role of T‐cell TLR2 in priming of CD4⁺ T cells in vivo, naive MTB Ag85B‐specific TCR transgenic CD4⁺ T cells (P25 TCR‐Tg) were adoptively transferred into Tlr2^?/? recipient C57BL/6 mice that were then immunized with Ag85B and with or without TLR2 ligand Pam₃Cys‐SKKKK. TLR2 engagement during priming resulted in increased numbers of IFN‐γ‐secreting P25 TCR‐Tg T cells 1 week after immunization. P25 TCR‐Tg T cells stimulated in vitro via TCR and TLR2 conferred more protection than T cells stimulated via TCR alone when adoptively transferred before MTB infection. Our findings indicate that TLR2 engagement on CD4⁺ T cells increases MTB Ag‐specific responses and may contribute to protection against MTB infection.     

Cytokine profile,HLA restriction and TCR sequence analysis of human CD4+ T clones specific for an immunodominant epitope of Mycobacterium tuberculosis 16-kDa protein

The identification of immunodominant and universal mycobacterial peptides could be applied to vaccine design and have an employment as diagnostic reagents. In this paper we have investigated the fine specificity, clonal composition and HLA class II restriction of CD4+ T cell clones specific for an immunodominant epitope spanning amino acids 91-110 of the 16-kDa protein of Mycobacterium tuberculosis. Twenty-one of the tested 28 clones had a Th1 profile, while seven clones had a Th0 profile. None of the clones had a Th2 profile. While the TCR AV gene usage of the clones was heterogeneous, a dominant TCR BV2 gene family was used by 18 of the 28 clones. The CDR3 regions of BV2+ T cell clones showed variation in lengths, but a putative common motif R-L/V-G/S-Y/W-E/D was detected in 13 of the 18 clones. Moreover, the last two to three residues of the putative CDR3 loops, encoded by conserved BJ sequences, could also play a role in peptide recognition. Antibody blockade and fine restriction analysis using HLA-DR homozygous antigen-presenting cells established that 16 of 18 BV2+ peptide-specific clones were DR restricted and two clones were DR-DQ and DR-DP restricted. Additionally, five of the 18 TCRBV2+ clones recognized peptide 91-110 in association with both parental and diverse HLA-DR molecules, indicating their promiscuous recognition pattern. The ability of peptide 91-110 to bind a wide range of HLA-DR molecules, and to stimulate a Th1-type interferon (IFN)-gamma response more readily, encourage the use of this peptide as a subunit vaccine component.     

Anti-CD4 monoclonal antibody treatment in acute and early chronic antigen-induced arthritis: influence on T helper cell activation

To examine the effects of anti-CD4 mAb treatment in acute and chronic antigen-induced arthritis (AIA), C57BL/6 mice were treated intraperitoneally either with the depleting anti-CD4 mAb GK1.5 or with rat-IgG (control) on Days -1, 0, 1, 3, 5, and 7. Arthritis was monitored by assessment of joint swelling and histological evaluation in the acute (Day 3) and the chronic phase (Day 21) of AIA. To determine the effects on cellular immune responses, in vivo T-cell reactivity (delayed type hypersensitivity; DTH) was measured, as well as protein levels of TH1- (IL-2, IFN-gamma) and TH2-cytokines (IL-4, IL-10) in joint extracts and supernatants of ex vivo stimulated spleen and lymph node cells. The humoral immune response was analysed by measuring serum antibodies against methylated bovine serum albumine (mBSA) and extracellular matrix proteins. Treatment with GK1.5 reduced swelling, inflammation, and destruction of the arthritic joint. Unexpectedly, the effects were even more pronounced in the acute than in the chronic phase. The anti-inflammatory effect was accompanied by a diminished DTH against the arthritogen mBSA and a decrease of TH1-cytokine production in spleen and pooled body lymph nodes, whereas the TH2-cytokine production in these organs was unchanged and the humoral immune response was only moderately reduced. There was a failure of depleting CD4+ T-cells in the joint, reflected also by unchanged local cytokine levels. Therefore, systemic rather than local effects on the TH1/TH2 balance appear to underlie the therapeutic efficacy of anti-CD4 treatment in AIA.     

Expression of OX40 (CD134) on CD4+ T-cells from patients with myasthenia gravis

Myasthenia gravis (MG) is commonly regarded as the prototype of an antibody-mediated, organ-specific autoimmune disease. Antibodies against the acetylcholine receptor (AChR) on the muscle endplate trigger its typical clinical manifestations of weakness and fatiguability. T-B cell interactions are thought to play a crucial role in the pathogenesis of MG. OX40 (CD134), a costimulatory molecule that is expressed on activated CD4+ T-cells, might contribute to the development or pathogenesis of immune-mediated diseases such as rheumatoid arthritis and graft-versus-host disease. In the present study, we investigated the expression of OX40 on CD4+ T-cells from patients with MG and healthy individuals. Results from 36 MG patients and 28 healthy controls revealed that more freshly isolated CD4+ T-cells from MG patients expressed OX40 than cells from healthy individuals. High levels of antibodies against the AChR, thymic hyperplasia and onset at an early age were associated with elevated expression of OX40. Upon activation by various concentrations of anti-CD3 antibodies, CD4+ T-cells from MG patients showed a tendency toward higher levels of OX40 expression than cells from healthy individuals. Given the role of OX40 in the immune system, we conclude that OX40 might contribute to the development of MG.     

Multifunctional CD4+ T cells correlate with active Mycobacterium tuberculosis infection

Th1 CD4⁺ T cells and their derived cytokines are crucial for protection against Mycobacterium tuberculosis. Using multiparametric flow cytometry, we have evaluated the distribution of seven distinct functional states (IFN‐γ/IL‐2/TNF‐α triple expressors, IFN‐γ/IL‐2, IFN‐γ/TNF‐α or TNF‐α/IL‐2 double expressors or IFN‐γ, IL‐2 or TNF‐α single expressors) of CD4⁺ T cells in individuals with latent M. tuberculosis infection (LTBI) and active tuberculosis (TB). We found that triple expressors, while detectable in 85–90%TB patients, were only present in 10–15% of LTBI subjects. On the contrary, LTBI subjects had significantly higher (12‐ to 15‐fold) proportions of IL‐2/IFN‐γ double and IFN‐γ single expressors as compared with the other CD4⁺ T‐cell subsets. Proportions of the other double or single CD4⁺ T‐cell expressors did not differ between TB and LTBI subjects. These distinct IFN‐γ, IL‐2 and TNF‐α profiles of M. tuberculosis‐specific CD4⁺ T cells seem to be associated with live bacterial loads, as indicated by the decrease in frequency of multifunctional T cells in TB‐infected patients after completion of anti‐mycobacterial therapy. Our results suggest that phenotypic and functional signatures of CD4⁺ T cells may serve as immunological correlates of protection and curative host responses, and be a useful tool to monitor the efficacy of anti‐mycobacterial therapy.     

CD8+ CD28- and CD8+ CD57+ T cells and their role in health and disease

Chronic antigenic stimulation leads to gradual accumulation of late-differentiated, antigen-specific, oligoclonal T cells, particularly within the CD8(+) T-cell compartment. They are characterized by critically shortened telomeres, loss of CD28 and/or gain of CD57 expression and are defined as either CD8(+) CD28(-) or CD8(+) CD57(+) T lymphocytes. There is growing evidence that the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population plays a significant role in various diseases or conditions, associated with chronic immune activation such as cancer, chronic intracellular infections, chronic alcoholism, some chronic pulmonary diseases, autoimmune diseases, allogeneic transplantation, as well as has a great influence on age-related changes in the immune system status. CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population is heterogeneous and composed of various functionally competing (cytotoxic and immunosuppressive) subsets thus the overall effect of CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell-mediated immunity depends on the predominance of a particular subset. Many articles claim that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells have lost their proliferative capacity during process of replicative senescence triggered by repeated antigenic stimulation. However recent data indicate that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells can transiently up-regulate telomerase activity and proliferate under certain stimulation conditions. Similarly, conflicting data is provided regarding CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell sensitivity to apoptosis, finally leading to the conclusion that this T-cell population is also heterogeneous in terms of its apoptotic potential. This review provides a comprehensive approach to the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population: we describe in detail its origins, molecular and functional characteristics, subsets, role in various diseases or conditions, associated with persistent antigenic stimulation.     

gammadelta T cells condition dendritic cells in vivo for priming pulmonary CD8 T cell responses against Mycobacterium tuberculosis

gammadelta T cells and dendritic cells are quickly recruited to the lungs shortly after intranasal vaccination with BCG, but the functional in vivo interplay between these two cell populations and its role in the induction of adaptive immune responses is unclear. Using TCR-deficient mice and bone marrow chimeras, we show here that gammadelta T cells provide a non-redundant early source of IFN-gamma in vivo, which enhances IL-12 production by lung dendritic cells. The in vivo-conditioned dendritic cells, in turn, prime a more efficient lung CD8 T cell response against Mycobacterium tuberculosis. Thus, strategies exploiting gammadelta T cell function and IFN-gamma production could be valuable for the design and testing of mucosal vaccines.     

The phenotypic and functional consequences of tumour necrosis factor receptor type 2 expression on CD4(+) FoxP3(+) regulatory T cells

Cytokine receptors expressed by CD4(+) FoxP3(+) regulatory T cells (Treg cells) not only serve as a phenotypic marker for the identification of this important population of immunosuppressive cells, they also promote the function of Treg cells. CD25, the α-chain of interleukin-2 receptor, is a prototype of such a receptor, which enables Treg cells to be activated by interleukin-2. We and others have found that tumour necrosis factor receptor type 2 (TNFR2) is another important cytokine receptor preferentially expressed by Treg cells with important phenotypic and functional roles. TNFR2 is preferentially expressed by highly functional human and mouse Treg cells, and mediates the activating effect of TNF on Treg cells. We review here the studies of the regulation of expression of TNFR2 on functional Treg cells as well as on CD4(+) FoxP3(-) effector T cells (Teff cells). We document the critical role of this receptor in the activation, proliferative expansion and survival of Treg cells. The contribution of TNFR2 expression on Treg and Teff cells to the beneficial and detrimental effects of anti-TNF treatment in autoimmune disorders will also be discussed.     

HIV-1 infection alters CD4+ memory T-cell phenotype at the site of disease in extrapulmonary tuberculosis

HIV-1-infected people have an increased risk of developing extrapulmonary tuberculosis (TB), the immunopathogenesis of which is poorly understood. Here, we conducted a detailed immunological analysis of human pericardial TB, to determine the effect of HIV-1 co-infection on the phenotype of Mycobacterium tuberculosis (MTB)-specific memory T cells and the role of polyfunctional T cells at the disease site, using cells from pericardial fluid and blood of 74 patients with (n = 50) and without (n = 24) HIV-1 co-infection. The MTB antigen-induced IFN-γ response was elevated at the disease site, irrespective of HIV-1 status or antigenic stimulant. However, the IFN-γ ELISpot showed no clear evidence of increased numbers of antigen-specific cells at the disease site except for ESAT-6 in HIV-1 uninfected individuals (p = 0.009). Flow cytometric analysis showed that CD4+ memory T cells in the pericardial fluid of HIV-1-infected patients were of a less differentiated phenotype, with the presence of polyfunctional CD4+ T cells expressing TNF, IL-2 and IFN-γ. These results indicate that HIV-1 infection results in altered phenotype and function of MTB-specific CD4+ T cells at the disease site, which may contribute to the increased risk of developing TB at all stages of HIV-1 infection.     

LIGHT, a new TNF superfamily member, is essential for memory T helper cell-mediated activation of dendritic cells

LIGHT is a recently identified member of the TNF superfamily that is up-regulated on activated T cells and can cooperate with CD40L to condition DC for the priming of CTL. In this report, we show that an intracellular pool of LIGHT is found selectively in some CD45RA-CD27+CD4+ "central" memory T cells and to a greater extent in some CD45RA-CD27-CD4+ effector memory T cells. LIGHT, like CD40L, is rapidly up-regulated on memory CD4+ T cells upon activation. Unlike CD40L, LIGHT up-regulation on naive T cells is delayed. Stimulation of DC with each subset of memory T cells in the presence of superantigen revealed that CD40L and LIGHT are required for optimal secretion of IL-12. Moreover, effector memory T cells, which can interact with DC in peripheral tissues, contribute to CCR7 induction on DC. LIGHT and CD40L can also regulate IL-12 production by CCR7+ DC capable of migration to lymph nodes. These data suggest that both LIGHT and CD40L may be involved in the maintenance or reactivation of secondary Th1 responses.     

协同刺激分子CD28在结核杆菌抗原体外激活人外周血γδT细胞中的作用

目的 :为了探讨CD2 8协同刺激分子在结核杆菌 (Mtb)低分子多肽抗原体外激活人外周血γδ T细胞中的作用。方法 :采用激发型抗CD2 8单抗模拟第二信号 ,Mtb低分子多肽抗原作为刺激原 ,对纯化的人外周血T细胞进行体外刺激和培养 ;用流式细胞仪检测γδ T细胞上CD2 8分子的表达、γδ T细胞的增殖效应及活化的γδ T细胞上CD6 9分子的表达。结果 :人外周血γδ T细胞中有 5 0 %左右表达CD2 8分子 ;抗CD2 8单抗协同Mtb抗原可刺激γδ T细胞的活化和增殖 ;但抗CD2 8单抗或Mtb抗原单独刺激则无作用。活化的γδ T细胞表面表达CD6 9分子。结论 :Mtb抗原在选择性活化人外周血γδ T细胞时需要第二信号的参与 ;CD2 8在Mtb抗原激活γδ T细胞时可提供协同刺激信号 ;CD6 9可作为γδ T细胞的早期活化标志。     

活动性肺结核病人外周血CD4~+/CD8~+Tim-3~+ T细胞群内记忆细胞分布特点

目的研究活动性肺结核病人外周血CD4+/CD8+Tim-3+T细胞群内记忆细胞分布特点。方法分离22例初治活动性肺结核病人PBMCs,用流式细胞仪分析比较CD4+/CD8+Tim-3+/Tim-3-T细胞群内的中央型记忆细胞(Tcm)和效应型记忆细胞(Tem)的分布。结果活动期初治肺结核病人外周血CD4+Tim-3+T细胞群包含更少的中央型记忆细胞(P<0.0001)和较多的效应型记忆细胞(P=0.0139),CD8+Tim-3+T细胞群包含较少的效应型记忆细胞(P=0.0065)。结论活动期初治肺结核CD4+Tim-3+T细胞群内含有更多的效应型记忆细胞可能会促使Tem对抗原的快速保护性免疫应答效应下降,从而促进结核分枝杆菌潜伏感染向活动性病变转变。Tim-3对记忆性T细胞分化、形成及功能的影响尚需进一步研究。     

Deficiencies in CD4+ and CD8+ T cell subsets in ataxia telangiectasia

Chronic sinopulmonary infections that are associated with immunodeficiency are one of the leading causes of death in the multi-systemic disease ataxia telangiectasia (AT). Immunological investigations of AT patients revealed a broad spectrum of defects in the humoral and the cellular immune system. Based on their important role in host defence the aim of our study was an extensive analysis of cell distribution and function of CD4+ and CD8+ T lymphocytes and NK cells. We found that naive (CD45RA+) CD4+ lymphocytes, as well as CD8+/CD45RA+ lymphocytes, are decreased, whereas NK cells (CD3-/CD16+CD56+) are significantly elevated in AT patients. In our culture system proliferation and cytokine production was normal in purified memory (CD45RO+) lymphocytes after stimulation with phorbol-12,13-dibutyrate (PBu2) and after PHA activation, indicating that differences in proliferation and cytokine production are due solely to reduced numbers of CD45RA+ lymphocytes. However, activation, and especially intracellular interferon production of AT lymphocytes, seem to follow different kinetics compared to controls. In contrast to polyclonal activation, stimulation via the T cell receptor results consistently in a reduced immune response. Taken together, our results suggest that deficiency of immunocompetent cells and an intrinsic immune activation defect are responsible for the immunodeficiency in AT.     

Daily subcutaneous injections of peptide induce CD4+ CD25+ T regulatory cells

Peptide immunotherapy is being explored to modulate varied disease states; however, the mechanism of action remains poorly understood. In this study, we investigated the ability of a subcutaneous peptide immunization schedule to induce of CD4(+) CD25(+) T regulatory cells. DO11.10 T cell receptor (TCR) transgenic mice on a Rag 2(-/-) background were injected subcutaneously with varied doses of purified ovalbumin (OVA(323-339)) peptide daily for 16 days. While these mice have no CD4(+) CD25(+) T regulatory cells, following this injection schedule up to 30% of the CD4(+) cells were found to express CD25. Real-time quantitative polymerase chain reaction (QPCR) analysis of the induced CD4(+) CD25(+) T cells revealed increased expression of forkhead box P3 (FoxP3), suggesting that these cells may have a regulatory function. Proliferation and suppression assays in vitro utilizing the induced CD4(+) CD25(+) T cells revealed a profound anergic phenotype in addition to potent suppressive capability. Importantly, co-injection of the induced CD4(+) CD25(+) T cells with 5,6-carboxy-succinimidyl-fluorescence-ester (CFSE)-labelled naive CD4(+) T cells (responder cells) into BALB/c recipient mice reduced proliferation and differentiation of the responder cells in response to challenge with OVA(323-339) peptide plus adjuvant. We conclude that repeated subcutaneous exposure to low-dose peptide leads to de novo induction of CD4(+) CD25(+) FoxP3(+) T regulatory cells with potent in vitro and in vivo suppressive capability, thereby suggesting that one mechanism of peptide immunotherapy appears to be induction of CD4(+) CD25(+) Foxp3(+) T regulatory cells.     

Effector T lymphocytes in well-nourished and malnourished infected children

The mechanisms involved in impaired immunity in malnourished children are not well understood. CD4(+) CD62L(-) and CD8(+) CD28(-) do not express the naive cell markers CD62L and CD28, suggesting that they function as effector T cells. Using a flow cytometry-based analysis we examined the proportions of CD4(+) CD62L(-) and CD8(+) CD28(-) T cell subsets in well-nourished infected (WNI) and malnourished infected (MNI) children. Here we report that WNI children had a higher percentage of CD4(+) CD62L(-) (11.1 +/- 1.0) and CD8(+) D28(-) (40.2 +/- 5.0) T cell subsets than healthy (6.5 +/- 1.0 and 23.9 +/- 4.8) and MNI children (7.4 +/- 1.1 and 23.1 +/- 6.2, respectively) (P < 0.5). Data suggest that WNI children respond efficiently against pathogenic microbes. In contrast, relatively low numbers of circulating of CD4(+) CD62L(-) and CD8(+) CD28(-) T cells in MNI children may represent an ineffective response to infection. Levels of effector T cells in children with gastrointestinal infections versus those suffering from respiratory infections were also significantly different within the WNI group. While WNI children with gastrointestinal infections had higher absolute and relative values of CD8(+), and CD8(+) CD28(-) T subsets, by those with respiratory infections had higher values of CD4(+) lymphocytes. However, due to the small number of subjects examined, our results in WNI children should be interpreted with caution and confirmed using a larger sample size. Our data suggest that altered expression of CD62L and CD28 receptors may contribute to impaired T cell function observed in MNI children.     

Characterization of HLA-DR- and TCR-binding residues of an immunodominant and genetically permissive peptide of the 16-kDa protein of Mycobacterium tuberculosis

The 16-kDa protein of Mycobacterium tuberculosis represents an important antigenic target during bacillary latency and, consequently, should be considered as candidate subunit vaccine component. In this study, we have used CD4 T cell clones that recognize the peptide p91-110, an immunodominant and genetically permissive epitope, in the context of five different HLA-DR molecules and truncated and substituted variants of this peptide, to identify the minimal binding sequence (HLA-DR-binding core) and the minimal stimulatory sequence (TCR-binding core), as well as the residues that contact HLA-DR molecules and the TCR. We have found a common 9-mer sequence, spanning amino acids 93-101, as the binding core for HLA-DR1, -DR11, -DR13 and -DR7, but a longer (13-mer) sequence spanning amino acids 92-104 was required for binding to the HLA-DR15 molecules. F(93) was required for binding to all the tested HLA-DR molecules, hence allowing us to identify it as the N-terminal primary anchor residue (P1). Additionally, the binding requirements for other residues varied considerably between the tested alleles: A(94) for HLA-DR15, V(99) for HLA-DR1, -DR15, -DR11 and -DR7, R(100) for HLA-DR11 and -DR13, and L(104) for HLA-DR15. Concerning the residues of p91-110 peptide required for binding to the TCR, the pepscan analysis results would support the contention that P(-1) E(92), P6 F(98) would be important TCR contact sites because their substitutions led to full loss of T cell activation. Moreover, P8 R(100) is found to be critical residue in binding to HLA-DR11- and -DR13-restricted T cell clones, without influencing binding to the relevant HLA-DR molecule. Our results could be useful to design peptides with altered HLA anchor residues or TCR interaction sites to achieve remarkable increase in activity and to study their vaccine potential.     

Gamma/delta T cell subsets in patients with active Mycobacterium tuberculosis infection and tuberculin anergy

Earlier data suggest that gamma/delta T cells may play an important role in the immune response to Mycobacterium tuberculosis. The aim of this study was to determine the percentage of different gamma/delta subsets in peripheral blood of active tuberculosis patients with a positive or negative tuberculin reaction. Thirty-eight patients infected with M. tuberculosis and 22 healthy controls were included in the study. Venous blood was taken before starting antimycobacterial treatment. Lymphocytes were reacted with monoclonal antibodies specific for different gamma/delta V chains (Vdelta1, Vdelta2, Vgamma9 and Vgamma4). The results were analysed in the context of tuberculin reactivity and X-ray findings. Our results revealed a selective loss of Vgamma9/Vdelta2 T cells in the peripheral blood of tuberculin-negative patients with active tuberculosis compared to healthy controls, while the ratio of Vgamma9/Vdelta2 T cells in the peripheral blood of patients with a positive skin test did not differ from that of healthy controls. These findings demonstrate a relationship between the loss of the major M. tuberculosis-reactive subset of gammadelta T cells and the absence of tuberculin reactivity. The data are consistent with the hypothesis that gammadelta T cells play a role in the protective immune response to M. tuberculosis infection.     

外周血辅助性T细胞亚群与肺结核严重性及疗效的关系

目的:探讨外周血的Th1和Th2细胞与肺结核病变严重程度及疗效的关系。方法:应用细胞内细胞因子的检测方法对62例肺结核患者外周血的Th1和Th2细胞亚群进行检测,根据患者治疗前影像学肺部病灶累及程度及治疗前后影像学变化进行分组比较,30例健康者作为对照。结果:治疗前肺结核组的Th1细胞计数和Th2细胞计数均明显低于健康对照组(P0.01,t检验)。治疗前多叶受累组的Th1细胞计数较局限组低(P0.05,t检验);治疗后病灶吸收明显组的Th1细胞计数均恢复至健康水平(P0.05,t检验);病灶吸收不明显组的Th1细胞计数仍低于健康水平(P0.01,t检验);治疗后无论病灶吸收明显组或病灶吸收不明显组的Th2细胞计数均仍低于健康组(P0.05,t检验)。结论:推测结核病的发生和进展可能与Th1细胞低下有关,非Th2型免疫反应增强所致,成功的抗结核治疗后,Th1细胞随之恢复。     

Equine CD4(+) CD25(high) T cells exhibit regulatory activity by close contact and cytokine-dependent mechanisms in vitro

Horses are particularly prone to allergic and autoimmune diseases, but little information about equine regulatory T cells (Treg) is currently available. The aim of this study therefore was to investigate the existence of CD4(+) Treg cells in horses, determine their suppressive function as well as their mechanism of action. Freshly isolated peripheral blood mononuclear cells (PBMC) from healthy horses were examined for CD4, CD25 and forkhead box P3 (FoxP3) expression. We show that equine FoxP3 is expressed constitutively by a population of CD4(+) CD25(+) T cells, mainly in the CD4(+) CD25(high) subpopulation. Proliferation of CD4(+) CD25(-) sorted cells stimulated with irradiated allogenic PBMC was significantly suppressed in co-culture with CD4(+) CD25(high) sorted cells in a dose-dependent manner. The mechanism of suppression by the CD4(+) CD25(high) cell population is mediated by close contact as well as interleukin (IL)-10 and transforming growth factor-β1 (TGF-β1) and probably other factors. In addition, we studied the in vitro induction of CD4(+) Treg and their characteristics compared to those of freshly isolated CD4(+) Treg cells. Upon stimulation with a combination of concanavalin A, TGF-β1 and IL-2, CD4(+) CD25(+) T cells which express FoxP3 and have suppressive capability were induced from CD4(+) CD25(-) cells. The induced CD4(+) CD25(high) express higher levels of IL-10 and TGF-β1 mRNA compared to the freshly isolated ones. Thus, in horses as in man, the circulating CD4(+) CD25(high) subpopulation contains natural Treg cells and functional Treg can be induced in vitro upon appropriate stimulation. Our study provides the first evidence of the regulatory function of CD4(+) CD25(+) cells in horses and offers insights into ex vivo manipulation of Treg cells.