CD4+ CD25+ Treg cells inhibit human memory gammadelta T cells to produce IFN-gamma in response to M tuberculosis antigen ESAT-6

T cells play an important role in innate immunity against infections; however, the regulation of these cells remains largely unknown. In the present study, we show that ESAT-6, an antigen of Mycobacterium tuberculosis, induces IFN- secretion by human T cells. In addition, ESAT-6 also induces the activation and proliferation of T cells. Phenotypic analysis indicates that IFN-–producing T cells are mainly effector memory cells with the surface phenotype of CD45RA^–CD62L^–CCR7^–. These results were further confirmed by the fact that naive T cells from cord blood did not produce IFN- in response to ESAT-6. Further studies indicated that stimulation with ESAT-6 directly induced purified T cells to produce IFN-, independent of both antigen-presenting cells and CD4⁺ T cells. Unexpectedly, depletion of CD4⁺ T cells markedly enhanced IFN- production by T cells, indicating that CD4⁺ T cells regulate the response of T cells. Importantly, CD4⁺CD25⁺ T regulatory (Treg) cells but not CD4⁺CD25^– T cells significantly inhibited IFN- production by T cells. Taken together, these data demonstrate for the first time that Treg cells can play an important role in the regulation of immune responses of antigen-specific human memory T cells.     

CD4+CD25+ T cells regulate colonic localization of CD4 T cells reactive to a microbial antigen

BACKGROUND: In patients with inflammatory bowel diseases, T-cell activation driven by microflora has been implicated as a mechanism causing clonal expansion and infiltration of CD4+ T cells in colonic lamina propria (LP). We explored a regulatory mechanism preventing infiltration of CD4+ T cells specific to a microbe-associated antigen in the gut. METHODS: SCID mice were reconstituted with CD4+ T cells specific to ovalbumin (OVA) and were orally administered with Escherichia coli engineered to produce OVA. RESULTS: OVA-specific CD4+ T cells (KJ1-26+) were recruited to colonic LP in an Ag-dependent manner, which was inhibited by adoptive transfer of naturally occurring CD4+CD25+ T (Treg) cells. KJ1-26+ T cells and Treg cells are localized preferentially to the colonic follicles that contain dendritic cells. In mice given Treg cells, LP CD4+ T cells showed a decrease in proliferative and interferon gamma response and an increase in transforming growth factor beta1 response to OVA stimulation. Treg cells inhibited both antigenic activation of effector CD4+ T cells and class II/CD80/CD86 up-regulation of dendritic cells. CONCLUSION:: Treg cells suppress recruitment of CD4+ T cells specific to a microbe-associated antigen to LP, which was associated with colocalization of effector CD4+ T cells and Treg cells in colonic follicles.     

Comparison of cytokine plasma levels in human African trypanosomiasis

BACKGROUND: Immunological studies suggest that human African trypanosomiasis (HAT) is associated with inflammatory responses. A better understanding of the complex cytokine interactions regulating HAT infections is essential to elucidate the mechanisms of generalized immunosuppression. METHOD: We determined levels of interleukin (IL)-2, IL-4, IL-6, IL-10, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma protein levels in plasma samples from three groups of individuals from the Democratic Republic of Congo: (i) HAT cases; (ii) seropositive individuals for whom parasite detection was negative and (ii) controls. RESULTS: Plasma levels of six cytokines were significantly higher in HAT cases than in both controls (P<0.003) and seropositive individuals (P<0.016). IL-2 and IL-10 concentrations were significantly lower (P<0.02) in the seropositive group than in the control one. CONCLUSION: Human African trypanosomiasis leads to the development of strong cytokine responses, indicating the potential involvement of IL-2 and IL-10 in the phenomenon of seropositivity without parasitological confirmation. This strongly suggests the involvement of immunity in this particular aspect of HAT epidemiology.     

CD25+CD4+ T cells contribute to the control of memory CD8+ T cells

Previously we demonstrated that IL-15 and IL-2 control the number of memory CD8+ T cells in mice. IL-15 induces, and IL-2 suppresses the division of these cells. Here we show that CD25+CD4+ regulatory T cells play an important role in the IL-2-mediated control of memory phenotype CD8+ T cell number. In animals, the numbers of CD25+CD4+ T cells were inversely correlated with the numbers of memory phenotype CD8+ T cells with age. Treatment with anti-IL-2 caused CD25+CD4+ T cells to disappear and, concurrently, increased the numbers of memory phenotype CD8+ T cells. This increase in the numbers of CD8+ memory phenotype T cells was not manifest in animals lacking CD4+ cells. Importantly, adoptive transfer of CD25+CD4+ T cells significantly reduced division of memory phenotype CD8+ T cells. Thus, we conclude that CD25+CD4+ T cells are involved in the IL-2-mediated inhibition of memory CD8+ T cell division and that IL-2 controls memory phenotype CD8+ T cell numbers at least in part through maintenance of the CD25+CD4+ T cell population.     

Maintenance of HIV-specific central and effector memory CD4 and CD8 T cells requires antigen persistence

The HIV-specific central and effector CD4 and CD8 memory T cell populations disappear from the peripheral blood of infected individuals under highly active antiretroviral therapy (HAART) with a mean half-life of 6.0 and 7.7 months, respectively. By contrast, cytomegalovirus (CMV)-specific responses are stable or increase. The striking quantitative differences between T cell memory to two persistent viral infections are instructive as to how antigen dosage contributes to the maintenance of antigen-specific memory T cell responses in humans.     

Abnormal γIFN and αTNF secretion in purified CD2+ cells from autoimmune thrombocytopenic purpura (ATP) patients: Their implication in the clinical course of the disease

Gamma inferferon (γIFN), alpha tumor necrosis factor (αTNF), and interleukin 6 (IL-60) are cytomines produced by a wide variety of cells, incuding T lymphocys and NK cells. These cytokines affect B-cell proliferation and differentiation into immunoglobulin seceting cells. In addition, γIFN and αTNF also enhance the function of macrophagesm, upregulating the expresson of their igG receptors. Abonormalities in the production of these cytokines may be involved in the clinical course of autoimmune thrombocytopenic purpura (ATP). This paper describes the production of these cytokines in PHA-stimulated peripheral blood CCD2+ cells from ATP patients. Both γIFN and αTNF were significantly increased in PHA-stimulated CD2+ cells from therapy-dependent ATP patients (platelet counts <50,000/μl), as compared to ATP patients with stable disease (sustained platelet counts >50,000/μl without need treatment) (P < 0.05). No significant differences were found in γlFN production by PHA-stimulated CD2+ cells between therapy-dependent ATP patients and healthy controls (P < 0.05). However, the production of αTNF by PHA-stimulated CD2+ cells from therapy-dependent ATP patients was significantly higher compared to that found in healthy controls (P < 0.05). There were no significant differences in IL-6 production by PHA-stimulated CD2+ cells from ATP patients and healthy controls (P < 0.05). These findings demonstrate abnormal γlFN and αTNF secretion in purified CD2 cells from ATP patients. The clinical severity of the disease is associated with the altered secretion of these lymphokines by CD2 cells. © 1995 Wiley-Liss, Inc.     

Altered pattern of cytokine production by peripheral blood CD2+ cells from B chronic lymphocytic leukemia patients

To determine if activation-induced cytokine production is altered in CD2+ lymphocytes from B-CLL patients, cytokine levels were determined by ELISA in supernatants of PHA-stimulated cultures of CD2+ cells from 33 B-CLL patients and 22 healthy controls. The production of Interferon γ (IFN-γ) and Tumor Necrosis Factor (TNF-α) by mitogen-activated CD2+ lymphocytes from B-CLL patients was higher than that found in healthy controls, while no differences were found in TNF-β production. IFN-γ and TNF-α levels determined at 72 h in PHA-stimulated CD2+ cell cultures from B-CLL patients statistically correlated with the percentages of CD3+CD45RO+ and CD3−CD56+ lymphocytes, respectively. Although there were differences in the production kinetics of interleukins (ILs) 2 and 4 between B-CLL patients and the healthy controls, no differences were found at the time when the levels of both interleukins peak. The production of both IFN-γ and IL-4 by PHA-stimulated CD2+ lymphocytes from non-smouldering B-CLL patients was significantly higher than that from smouldering B-CLL patients while no significant differences were found in the production of IL-2, TNF-α, and TNF-β between the two B-CLL patient groups. These data suggest that functional alterations in the production of cytokines by CD2+ cells from B-CLL patients could help to explain the expansion of leukemic cells in B-CLL patients. Am. J. Hematol. 57:93–100, 1998. © 1998 Wiley-Liss, Inc.     

Increased competition for antigen during priming negatively impacts the generation of memory CD4 T cells

The factors involved in the differentiation of memory CD4 T cells from na?ve precursors are poorly understood. We developed a system to examine the effect of increased competition for antigen by CD4 T cells on the generation of memory in response to infection with a recombinant vesicular stomatitis virus. Competition was initially regulated by increasing the precursor frequency of adoptively transferred na?ve T cell antigen receptor transgenic CD4 T cells. Despite robust proliferation at high precursor frequencies, memory CD4 T cells did not develop, whereas decreasing the input number of na?ve CD4 T cells promoted memory development after infection. The lack of memory development was linked to reduced blastogenesis and poor effector cell induction, but not to initial recruitment or proliferation of antigen-specific CD4 T cells. To prove that availability of antigen alone could regulate memory CD4 T cell development, we used treatment with an mAb specific for the epitope recognized by the transferred CD4 T cells. At high doses, this mAb effectively inhibited the antigen-specific CD4 T cell response. However, at a very low dose of mAb, primary CD4 T cell expansion was unaffected, although memory development was dramatically reduced. Moreover, the induction of effector function was concomitantly inhibited. Thus, competition for antigen during CD4 T cell priming is a major contributing factor to the development of the memory CD4 T cell pool.     

干扰素治疗慢性乙型肝炎患者HBeAg转阴率和CD4~+CD25~+调节性T淋巴细胞水平的关系

目的 观察干扰素抗病毒治疗前后慢性乙型肝炎患者外周血CD4+CD25+调节性T细胞(CD4+CD25+Treg)表达水平的变化和HBeAg转阴的关系.方法 选择用干扰素α-2b治疗的HBeAg阳性慢性乙型肝炎56例,分别于治疗前、48周时检测外周静脉血CD4+CD25+Treg占CD4+T细胞的比例,同时检测HBeAg、ALT和HBVdNA载量.结果 抗病毒治疗48周后HBeAg转阴组CD4+CD25+rreg水平[(9.12±2.45)％]较治疗前[(11.99±3.25)％]明显下降(P＜0.01);而HBeAg未转阴组较治疗前无明显下降(P＞0.05).结论 慢性乙型肝炎患者经干扰素α-2b抗病毒治疗,HBeAg血清转换者CD4+CD25+Treg水平降低,而未转阴者Treg下降不明显.     

日本血吸虫虫卵抗原诱导CD4+CD25+T细胞及其细胞因子表达

目的 探讨日本血吸虫虫卵抗原诱导宿主免疫应答下调的机制.方法 6～8周龄雌性队LB/c小鼠分为2组,实验组小鼠口服血吸虫虫卵10 000个以及尾静脉注射可溶性虫卵抗原(SEA)200μg,每周免疫1次,共4次;对照组注射PBS.流式细胞仪检测SEA免疫小鼠CD4+CD25+T细胞数量;与CD4+CD25-T细胞共同培养,检测CD4+CD25+T细胞抑制功能;流式细胞仪检测CD4+CD25+T细胞表达IL-4、IL-10与IFN-γ水平;酶联免疫吸附试验检测静脉血IL-10和转化生长因子-β表达水平.结果 实验组小鼠CD4+CD25+T细胞数量为14.7%,对照组为7.4%;实验组IL-10为29.2 pg/ml,对照组为11.0 pg/ml.与CD4+CD25-T细胞相比,CD4+CD25+T细胞主要合成IL-10及少量IFN-γ.CD4+CD25+T细胞显著抑制CD4+T细胞增殖. 结论 日本血吸虫虫卵抗原可能通过诱导CD4+CD25+T细胞和IL-10下调机体免疫应答.     

In vitro human memory CD8 T cell expansion in response to cytomegalovirus requires CD4+ T cell help

Requirements for human memory CD8(+) T cell expansion are incompletely understood. We found that human cytomegalovirus (HCMV) induced expansion of memory CD8(+) T cells in vitro without requiring intracellular viral peptide synthesis. Peptide-major histocompatibility complex class I tetramer binding confirmed expansion of cells with HCMV-peptide specificity. Expansion of memory CD8(+) T cells was completely dependent on the presence and function of CD4(+) T cells, whose "help" also could be induced by exposure to irrelevant antigen. Recombinant interleukin (IL)-2 or IL-15 could substitute for help provided by CD4(+) T cells, whereas CD8(+) T cell expansion was blocked by anti-IL-2 but not anti-IL-15 antibody. Human memory CD8(+) T cells expand dramatically in vitro in response to cross-presentation of HCMV antigens, and, in contrast to observations made in murine systems, this proliferation was critically dependent on CD4(+) T cells that provide essential IL-2. Thus, in humans, cross-presentation and expansion of memory CD8(+) T cells may be compromised in disease states that result in deficits in CD4(+) T cell numbers or function, such as may be seen in human immunodeficiency virus type 1 infection.     

Ablation of thymic export causes accelerated decay of naive CD4 T cells in the periphery because of activation by environmental antigen

A model of chemical thymectomy by inducible Rag ablation was used to study peripheral T cell homeostasis. Induction of Rag ablation was efficient and complete, leading to cessation of thymic T cell production within 3–4 weeks. The decay of peripheral T cells became apparent with a delay of an additional 2–3 weeks and was entirely accounted for by loss of naïve T cells, whereas numbers of memory phenotype and regulatory T cells were not decreased. Naïve CD4 T cells decayed with an average half-life of 50 days, whereas naïve CD8 T cells exhibited a considerably longer half-life. The rapid decay of naïve CD4 T cells was not caused by intrinsic survival differences compared with naïve CD8 T cells, but was caused by changes in the lymphopenic environment resulting in higher microbial load and consequential activation. This finding suggests that in lymphopenic conditions involving compromised thymic function replenishment and survival of a naïve CD4 T cell repertoire may be severely curtailed because of chronic activation. Such a scenario might play a role in the aging immune system and chronic viral infection, such as HIV infection, and contribute to loss of CD4 T cells and impaired immune function. As our data show, continued replenishment with cells from the thymus seems to be required to maintain efficient gut mucosal defense.     

Intrinsic defects in CD8 T cells with aging contribute to impaired primary antiviral responses

Aging is associated with altered immune responses, particularly with a diminished CD8 T cell response. Although both intrinsic and extrinsic factors are hypothesized to impact this decreased T cell response, the direct evidence of an intrinsic deficiency in virus-specific CD8 T cells is limited. In this study, a TCR transgenic (Tg) P14 mouse model was utilized to compare the activation and proliferation of the Tg CD8 T cells of young and aged P14 mice upon stimulation with antigen or infection with virus. The proliferation of purified Tg CD8 T cells of aged mice was significantly lower than that of young mice when cultured in vitro with both the LCMV specific peptide and antigen presenting cells from young wild type mice. In addition, expression of the activation markers, CD69, CD25, and CD44, was delayed on Tg T cells of aged mice after stimulation. Importantly, while adoptive transfer of purified Tg CD8 T cells of young or aged mice into young wild type mice resulted in expansion of the Tg CD8 T cells of both ages after LCMV infection, the expansion of the Tg T cells from aged mice was significantly decreased compared with that of the Tg T cells from young mice. However, while the number of IFN-γ secreting Tg CD8 T cells from aged mice was significantly decreased compared to that of young mice, the percentages of Tg CD8 T cells producing IFN-γ were similar in young and aged mice, demonstrating that proliferation, but not function, of the Tg CD8 T cells of aged mice was impaired. Importantly, chronological age alone was not sufficient to predict an altered proliferative response; rather, expression of high levels of CD44 on CD8 T cells of aged mice reflected a decreased proliferative response. These results reveal that alterations intrinsic to CD8 T cells can contribute to the age-associated defects in the primary CD8 T cell response during viral infection.     

Th1/Th2 cytokine profiles and their relationship to clinical features in patients with chronic hepatitis C virus infection

Purpose. An imbalance in helper T-cell type 1 (Th1) and type 2 (Th2) cytokines is suggested to play an important role in the pathogenesis of chronic viral infections, but this issue is not resolved in patients with hepatitis C virus (HCV) infection. The aim of this study was to clarify the relationship between the balance of Th1 and Th2 cytokines and liver damage. Methods. We investigated cytokine levels in the peripheral blood and liver tissue of patients with chronic HCV infection (n = 59) by three different methods; we used flow cytometry to detect intracellular cytokines, and we measured cytokine titers in sera and in the supernatants of lymphocyte cultures with enzyme-linked immunosorbent assays (ELISAs). Results. In both CD4+ and CD8+ cells, interferon (IFN) γ-producing cell populations increased, while there was no difference in interleukin (IL)-10 production, indicating a shift to a Th1 cytokine profile with the progression of liver disease. With respect to the ratio of IFN-γ to IL-10, a correlation was found in CD4+ cells between peripheral blood and liver tissue (r = 0.98; P = 0.0011). Th1 cytokine was predominant in intrahepatic CD4+ cells, while it was predominant in peripheral blood CD8+ cells. Conclusions. These findings indicate a correlation between dominant Th1 response and disease activity and progression. In addition, we suggest that intrahepatic CD4+ T cells play a pathogenetic role in the hepatic injury of HCV infection. Received: August 10, 2000 / Accepted: February 2, 2001