Helicobacter pylori-specific CD4+ CD25high regulatory T cells suppress memory T-cell responses to H. pylori in infected individuals

Helicobacter pylori colonizes the gastric and duodenal mucosa. The infection normally persists for life and causes peptic ulcers and gastric cancer in a subset of infected individuals. We hypothesized that the inability to clear the infection may be a consequence of H. pylori-specific regulatory T cells that actively suppress T-cell responses. Therefore, we characterized the T-cell responses to H. pylori in H. pylori-infected individuals without any subjective symptoms and in uninfected control subjects and investigated the role of regulatory CD4+ CD25(high) T cells during infection. The stimulation of CD4+ peripheral blood T cells with monocyte-derived dendritic cells pulsed with a membrane preparation of H. pylori resulted in proliferation and gamma interferon production in both infected and uninfected individuals. Sorted memory cells from infected individuals responded less than cells from uninfected subjects, and the unresponsiveness could be abolished by depletion of CD4+ CD25(high) regulatory T cells or the addition of interleukin 2. Furthermore, CD4+ CD25(high) T cells suppressed H. pylori-induced responses in cocultures with CD25(low/-) cells. Tetanus toxoid induced comparable responses in memory cells from infected and uninfected individuals in both the presence and the absence of regulatory T cells, suggesting that the suppression was H. pylori specific. In conclusion, we have shown that H. pylori-infected individuals have impaired memory CD4+ T-cell responses to H. pylori that are linked to the presence of H. pylori-specific regulatory T cells that actively suppress the responses.     

Helicobacter pylori-specific CD4+ T cells home to and accumulate in the human Helicobacter pylori-infected gastric mucosa

Helicobacter pylori infects the stomach and duodenal mucosa. T cells are important components of the H. pylori-induced immune response, but little is currently known about how these cells are recruited to the infected mucosa. Here, we have characterized stomach and duodenal T cells isolated from H. pylori-infected and noninfected subjects with regard to subtype, expression of homing and chemokine receptors, and in vitro reactivity to H. pylori antigens. Higher numbers of CD4(+) but similar numbers of CD8(+) lamina propria T cells were isolated from stomach biopsies from H. pylori-positive compared to H. pylori-negative individuals. CD4(+) T cells from infected stomach expressed increased levels of the homing receptor L-selectin and the chemokine receptor CCR4 compared to CD4(+) T cells from uninfected stomach. Infected stomach mucosa also contained increased levels of the CCR4 chemokine ligand MDC/CCL22. In contrast, comparable numbers of CD4(+) T cells with similar receptor expression were isolated from the duodenum of H. pylori-positive and H. pylori-negative individuals. In vitro proliferation of mucosal T cells was strongly enhanced by the addition of interleukin-2 (IL-2) and IL-7 to the cell cultures. Using this approach, H. pylori-specific T-cell responses were detected in stomach CD4(+) T cells from H. pylori-positive but not H. pylori-negative individuals. Duodenal T cells from only a few individuals responded to H. pylori stimulation, and the responsiveness was not restricted to H. pylori-positive individuals, suggesting limited H. pylori specificity in the duodenum and possible cross-reactivity with antigens from other bacteria in this compartment. In conclusion, these results suggest that H. pylori-specific CD4(+) T cells preferentially home to and accumulate in the infected stomach and that L-selectin and CCR4/MDC are important for this recruitment.     

Function and recruitment of mucosal regulatory T cells in human chronic Helicobacter pylori infection and gastric adenocarcinoma

CD4(+)CD25(high) FOXP3-expressing regulatory T cells (Treg) can suppress immune responses to infections and tumors, thereby promoting microbial persistence and tumor progression. However, little is known about the phenotype and function of human mucosal Treg. Therefore, we analyzed the suppressive activity and homing phenotype of Treg in gastric mucosa of Helicobacter pylori-infected gastric adenocarcinoma patients. We found increased numbers of CD4(+)FOXP3(+) Treg in the tumor compared to tumor-free gastric mucosa. Gastric Treg cells were able to suppress H. pylori-induced T cell proliferation and IFN-gamma production. Furthermore, gastric Treg expressed increased levels of l-selectin and CCR4, compared to non-Treg cells, suggesting that these receptors contribute to Treg recruitment. The presence of functional antigen-specific Treg in H. pylori-infected gastric mucosa supports an important role for these cells in suppression of mucosal effector T cell responses, which probably contribute to bacterial persistence and possibly also to gastric tumor progression.     

CD4+ Foxp3+ regulatory T cells mediate Toxoplasma gondii-induced T-cell suppression through an IL-2-related mechanism but independently of IL-10

Acute Toxoplasma gondii infection comprises an immunosuppression stage, characterized by a reduction in T-cell proliferation in vitro. Treg cells maintain the homeostasis of the immune system, but their role in T. gondii-induced suppression has not been addressed. We show herein that immunosuppression, affecting both CD4(+) and CD8(+) T-cell proliferation, concurs with a reduction in Treg-cell number. The residual Treg cells, however, are activated and display an increased suppressive capacity. We show that selective elimination of Treg cells using Foxp3(EGFP) mice leads to a full recovery of CD4(+) and CD8(+) T-cell proliferation. After Treg-cell removal, a reduced production of IL-10 was observed, but IL-2 levels were unchanged. The numbers of IL-10-producing Treg cells also increased during infection, although the in vitro neutralization of this cytokine did not modify T-cell proliferation, suggesting that IL-10 does not mediate the Treg-mediated suppression. However, addition of rIL-2 in vitro fully restored T-cell proliferation from infected animals. Thus, we show that Treg cells mediate the T-cell suppression observed during acute T. gondii infection through an IL-2-dependent mechanism. Our results provide novel insights into the regulation of the immune response against T. gondii.     

Antigen-specific in vitro suppression of murine Helicobacter pylori-reactive immunopathological T cells by CD4CD25 regulatory T cells

A Helicobacter pylori-specific in vitro coculture system was established and used to study the role of CD4+CD25+ regulatory T cells (Treg) in gastritis development in mice with H. pylori infection. Effects of therapeutic immunization against H. pylori infection on the Treg function were also studied to better understand the mechanisms leading to postimmunization gastritis in these mice. Depletion of Treg led to extensive proliferation to H. pylori antigens of CD4+ T cells isolated from either na?ve, H. pylori-infected or H. pylori-immunized mice. Using the Treg-depleted CD4+ T cells from immunized mice as effector cells, we compared the suppressive efficacy of Treg isolated from na?ve, infected or immunized mice and found that Treg from na?ve mice, and slightly less efficiently from infected mice, suppressed the CD25- effector T-cell response and in most cases were distinctly more efficacious than Treg isolated from immunized mice. The suppressive efficacy of Treg isolated from the differently treated mice correlated closely with production of interleukin-5 (IL-5) by the Treg and suppression of interferon-gamma and IL-2 production by the CD25- effector T cells. Our study is the first to demonstrate in H. pylori-induced chronic infection, antigen-specific Treg with differential efficacy in suppressing H. pylori proinflammatory T effector cells.     

Mucosal FOXP3-expressing CD4+ CD25high regulatory T cells in Helicobacter pylori-infected patients

Helicobacter pylori chronically colonizes the stomach and duodenum and causes peptic ulcers or gastric adenocarcinoma in 10 to 20% of infected individuals. We hypothesize that the inability of patients to clear H. pylori infections is a consequence of active suppression of the immune response. Here we show that H. pylori-infected individuals have increased frequencies of CD4(+) CD25(high) T cells in both the stomach and duodenal mucosa compared to uninfected controls. These cells have the phenotype of regulatory T cells, as they express FOXP3, a key gene for the development and function of regulatory T cells, as well as high levels of the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) protein. In contrast, mucosal CD4(+) CD25(low) and CD4(+) CD25(-) cells express little FOXP3 mRNA and low levels of the CTLA-4 protein. Mucosal CD4(+) CD25(high) T cells are present in individuals with asymptomatic H. pylori infections as well as in duodenal ulcer patients. The frequencies of CD4(+) CD25(high) cells are also increased in the stomachs of H. pylori-infected patients with gastric adenocarcinoma, particularly in cancer-affected tissues. These findings suggest that regulatory T cells may suppress mucosal immune responses and thereby contribute to the persistence of H. pylori infections.     

CD4+ CD25+调节性T细胞在HIV/AIDS患者中的作用及其与HIV病毒载量的相关性研究

目的 研究HIV感染者／AIDS患者外周血CD4^＋ CD25^＋ 调节性T细胞（CD4^＋ CD25^＋ regulatory Tcell，Treg）频率、功能及其临床意义。方法 选择31例HIV感染者／AIDS患者和30例健康对照者，采用流式细胞仪检测各组外周血Treg的表型和频率。采取MACS磁珠分选CD4^＋CD25^＋T细胞，利用[^3H]胸腺嘧啶掺入法检测CD4^＋ CD25^＋T细胞在特异性HIV抗原刺激下对CD4^＋ CD25-T细胞的增殖影响。结果HIV／AIDS患者组与正常对照组相比较，外周血CD4^＋ CD25^＋ T细胞频率在统计学上差异无统计学意义。与正常对照组比较，HIV感染者外周血CD4^＋ CD25^＋ T细胞频率升高，差异有统计学意义（P〈0.01）；与正常对照组比较，AIDS患者者外周血CD4^＋ CD25^＋ T细胞频率降低，差异有统计学意义（P〈0．0001）。HIV RNA病毒载量与患者外周血CD4^＋ CD25^＋ T细胞数量呈正相关性（P〈0．01）。CD4^＋ CD25^＋ T细胞具有抑制HIV特异性的CD4^＋ CD25^- T细胞的增殖作用。结论HIV感染者／AIDS患者的细胞免疫功能紊乱，CD4^＋ CD25^＋ T细胞能抑制HIV感染者／AIDS患者的HIV特异性细胞免疫反应，促进HIV病毒复制，与形成持续HIV感染有关。     

Absence of CD4+CD25+ regulatory T cells is associated with a loss of regulation leading to increased pathology in Helicobacter pylori-infected mice

Helicobacter pylori induces symptomatic chronic gastritis in a subpopulation of infected individuals. The mechanism(s) determining the development and severity of pathology leading to symptoms are not fully understood. In a mouse model of H. pylori infection we analysed the influence of immunoregulatory CD4+CD25+ T cells on H. pylori colonization and gastritis. Athymic C57BL/6 nu/nu mice were reconstituted with (a) lymph node (LN) cells (b) LN cells depleted of CD25+ T cells (CD25(-) LN) or (c) not reconstituted at all. Mice were then infected orally with 3 x 10(8)H. pylori SS1 bacteria. At 2 and 6 weeks after the inoculation there was a significant (P < 0.001) reduction in H. pylori colonization in athymic mice transferred with CD25(-) LN cells compared to mice transferred with LN cells. Colonization was still reduced at 12 weeks after inoculation. Mice transferred with CD25(-) LN cells showed an earlier onset and increased severity of gastritis as compared to mice receiving LN cells. Splenic cells isolated from mice receiving CD25(-) LN cells produced the highest level of IFN-gamma on stimulation with H. pylori antigens in vitro, had a higher H. pylori-specific DTH response and increased infiltration of CD4+ T cells and macrophages in the gastric mucosa. Athymic mice not transferred with T cells had persistent high H. pylori colonization and displayed a normal gastric epithelium without inflammatory cells. In conclusion, CD4+CD25+ cells reduce immunopathology in H. pylori infection, possibly by reducing the activation of IFN-gamma producing CD4+ T cells, even at the expense of a higher H. pylori load in the gastric mucosa.     

Helicobacter pylori induces transendothelial migration of activated memory T cells

Helicobacter pylori infection is associated with pronounced infiltration of granulocytes and lymphocytes into the gastric mucosa, resulting in active chronic gastritis that may develop into duodenal ulcer disease or gastric adenocarcinoma. Infiltrating T cells play a major role in the pathology of these diseases, but the signals involved in recruitment of T cells from blood to H. pylori-infected tissues are not well understood. We therefore examined H. pylori-induced T-cell transendothelial migration (TEM). The Transwell system, employing a monolayer of human umbilical vein endothelial cells, was used as a model to study TEM. H. pylori induced a significant T-cell migration, compared to spontaneous migration. CD4+ and CD8+ T cells migrated to the same extent in response to H. pylori, whereas there was significantly larger transmigration of memory T cells compared to naive T cells. Both H. pylori culture filtrate and urease induced migration, and the presence of the H. pylori cag pathogenicity island increased TEM. T-cell TEM was mediated by LFA-1-ICAM-1 interactions in accordance with an increased ICAM-1 expression on the endothelial cells after contact with H. pylori. Migrating T cells had increased expression of activation marker CD69 and chemokine receptors CXCR3, CCR4, and CCR9. Furthermore, T cells migrating in response to H. pylori secreted Th1 but not Th2 cytokines upon stimulation. In conclusion, our data indicate that live H. pylori and its secreted products contribute to T-cell recruitment to the gastric mucosa and that the responding T cells have an activated memory Th1 phenotype.     

Changes of CD4+CD25+Foxp3+ regulatory T cells in aged Balb/c mice

A progressive decline in the integrity of the immune system is one of the physiologic changes during aging. The frequency of autoimmune diseases or immune disorders increases in the aging population, but the state of regulatory T (Treg) cells in aged individuals has not been well determined. In the present study, we investigated the levels, phenotypes, and function of CD4(+)CD25(+) Treg cells in Balb/c mice, which were older than 20 months. Significantly enhanced percentages of CD4(+)CD25(+) Treg cells in the periphery (blood, spleen, and lymph nodes) of the aged mice were observed. These Treg cells showed modified Vbeta family distribution, reduced levels of CD45 receptor B and CD62 ligand molecules, as well as normal levels of forkhead box p3. However, when the inhibiting function of Treg cells was assayed in the in vitro assays and in a delayed-type hypersensitivity (DTH) model, CD4(+)CD25(+) Treg cells of aged mice displayed significantly lower inhibiting ability on alloantigen-induced DTH reaction or cytokine productions (IL-2 and IFN-gamma) but not cell proliferation of effector T cells, as compared with CD4(+)CD25(+) Treg cells of young mice. In addition, the percentages of CD4(+)CD8(-)CD25(+) Treg cells in the thymi of aged mice increased significantly, but their total cell numbers decreased markedly in these mice. Our present studies indicated collectively that the percentages, phenotypes, the size of TCR repertoire, and function of CD4(+)CD25(+) Treg cells were altered significantly with aging in mice. The functional defects of CD4(+)CD25(+) Treg cells may shed light on the role of CD4(+)CD25(+) Treg cells in the increased sensitivity to autoimmune diseases of aged populations.     

Resistance of primary murine CD4+ T cells to Helicobacter pylori vacuolating cytotoxin

Persistent colonization of the human stomach by Helicobacter pylori is a risk factor for the development of gastric cancer and peptic ulcer disease. H. pylori secretes a toxin, VacA, that targets human gastric epithelial cells and T lymphocytes and enhances the ability of H. pylori to colonize the stomach in a mouse model. To examine how VacA contributes to H. pylori colonization of the mouse stomach, we investigated whether murine T lymphocytes were susceptible to VacA activity. VacA inhibited interleukin-2 (IL-2) production by a murine T-cell line (LBRM-33), similar to its effects on a human T-cell line (Jurkat), but did not inhibit IL-2 production by primary murine splenocytes or CD4+ T cells. VacA inhibited activation-induced proliferation of primary human CD4+ T cells but did not inhibit the proliferation of primary murine CD4+ T cells. Flow cytometry studies indicated that the levels of VacA binding to primary murine CD4+ T cells were significantly lower than levels of VacA binding to human CD4+ T cells. This suggests that the resistance of primary murine CD4+ T cells to VacA is attributable, at least in part, to impaired VacA binding to these cells.     

CD8+ Foxp3+ T cells share developmental and phenotypic features with classical CD4+ Foxp3+ regulatory T cells but lack potent suppressive activity

"Suppressor T cells" were historically defined within the CD8(+) T-cell compartment and recent studies have highlighted several naturally occurring CD8(+) Foxp3(-) Treg populations. However, the relevance of CD8(+) Foxp3(+) T cells, which represent a minor population in both thymi and secondary lymphoid organs of nonmanipulated mice, remains unclear. We here demonstrate that de novo Foxp3 induction in peripheral CD8(+) Foxp3(-) T cells is counter-regulated by DC-mediated co-stimulation via CD80/CD86. CD8(+) Foxp3(+) T cells fail to develop in TCR-transgenic mice with Rag1(-/-) background, similar to classical CD4(+) Foxp3(+) Tregs. Notably, both naturally occurring and induced CD8(+) Foxp3(+) T cells express bona fide Treg markers including CD25, GITR, CTLA4 and CD103, and show defective IFN-γ production upon restimulation when compared with their CD8(+) Foxp3(-) counterparts. However, utilizing DEREG transgenic mice for the isolation of Foxp3(+) cells by eGFP reporter expression, we demonstrate that induced CD8(+) Foxp3(+) T cells similar to activated CD8(+) Foxp3(-) T cells only mildly suppress T-cell proliferation and IFN-γ production. We therefore categorize CD8(+) Foxp3(+) T cells as a tightly controlled population sharing certain developmental and phenotypic properties with classical CD4(+) Foxp3(+) Tregs, but lacking potent suppressive activity.     

BALB/c mice have more CD4+CD25+ T regulatory cells and show greater susceptibility to suppression of their CD4+CD25- responder T cells than C57BL/6 mice

Increasing evidence indicates that CD4(+)CD25(+) T regulatory (Treg) cells control a wide spectrum of immune responses. The initial identification of CD4(+)CD25(+) Treg cell as a "professional suppressor" was based on observations made in BALB/c mice. This mouse strain is well known to preferentially develop T helper cell type 2 responses, to be more susceptible to intracellular parasite infection, to have a higher tumor incidence, and to be more resistant to the induction of autoimmune diseases, as compared with C57BL/6 (B6) mice. We therefore decided to compare Treg cell function of B6 and BALB/c mice. We observed that the frequency of CD4(+)CD25(+) T cells in the thymus and peripheral lymphoid organs of BALB/c mice was higher than in B6 mice. CD4(+)CD25(+) Treg cells from both mouse strains shared similar phenotypic properties, including expression of characteristic immunological markers and hyporesponsiveness to T cell receptor cross-linking and in their capacity to suppress proliferation of BALB/c CD4(+)CD25(-) T responder (Tres) cells. However, CD4(+)CD25(-) Tres cells from B6 mice were notably less susceptible to suppression by CD4(+)CD25(+) Treg cells from either mouse strain. Our data suggest that the number and the level of suppression of CD4(+)CD25(+) Treg cells for CD4(+)CD25(-) Tres cells may be dictated by genetic background. Our data also suggest that differences in the CD4(+)CD25(+) Treg cell number and the susceptibility of CD4(+)CD25(-) Tres cells may, at least in part, account for the differences in immune response between B6 and BALB/c strains of mice.     

人外周血CD4+CD25+调节性T细胞的分离、鉴定和功能特征

目的： 分离人外周血CD4＋ CD25＋ Treg细胞, 并检测其功能.方法： RT-PCR技术检测CD4＋ CD25＋ Treg细胞中Foxp3的mRNA表达;与CD8＋ T细胞和CD4＋ CD25- T细胞共同培养, 或加入外源性IL-2及IL- 4, 检测其抑制功能;流式细胞术检测IFN-γ、 IL- 4和IL-10.结果： CD4＋ CD25＋ Treg细胞高表达Foxp3, 主要分泌IL-10, 能够抑制CD8＋ T细胞和CD4＋ CD25- T细胞的增殖, 高浓度IL-2能够阻断CD4＋ CD25＋ Treg细胞的抑制功能.结论： CD4＋ CD25＋ Treg细胞是一群具有免疫抑制功能的调节性T细胞, 这种抑制作用能够被高浓度IL-2阻断.     

Characterization of T-regulatory cells, induced by immature dendritic cells, which inhibit enteroantigen-reactive colitis-inducing T-cell responses in vitro and in vivo

Regulatory T (Treg) cells, derived from co-cultures of unfractionated CD4(+) T cells and immature dendritic cells (DC), suppress enteroantigen-induced proliferation of CD4(+) CD25(-) T cells. The DC-induced Treg cells are a mixture of CD25(+) (10-20%) and CD25(-) (80-90%) T cells. However, all the suppressor activity in vitro and in vivo resides in the CD25(+) T-cell subset. The CD25(+) DC-induced Treg cells can inhibit enteroantigen-induced proliferation in vitro through a transwell membrane, and their function does not appear to depend on previous activation. DC-induced CD25(+) Treg cells display a naive phenotype, expressing high levels of CD45RB and l-selectin (CD62L). In addition, the DC-induced Treg cells mediate a stronger suppressive activity than prototype CD25(+) regulatory T cells. The DC-induced Treg cells, and hereof purified CD25(+) and CD25(-) T-cell fractions, were co-injected into severe combined immunodeficiency (SCID) mice with colitis-inducing CD4(+) CD25(-) T cells. Both unfractionated CD4(+) and purified CD25(+) Treg cells fully protected the recipients against the development of colitis. In contrast, co-transfer of fractionated CD25(-) T cells offered no protection against disease development. Enterobacterial antigen-exposed CD4(+) T cells of the protected mice secreted higher levels of interleukin-10 and lower levels of interferon-gamma than the unprotected mice. The present data demonstrate DC-induced CD4(+) CD25(+) Treg cells, which phenotypically and functionally differ from the generally accepted prototype of CD25(+) Treg cells. These data may initiate new procedures for the expansion of Treg cells for clinical use.     

Inhibition of phosphoantigen-mediated gammadelta T-cell proliferation by CD4+ CD25+ FoxP3+ regulatory T cells

Tumour growth promotes the expansion of CD4(+) CD25(+) FoxP3(+) regulatory T cells (Tregs) which suppress various arms of immune responses and might therefore contribute to tumour immunosurveillance. In this study, we found an inverse correlation between circulating Treg frequencies and phosphoantigen-induced gammadelta T-cell proliferation in cancer patients, which prompted us to address the role of Tregs in controlling the gammadelta T-cell arm of innate immune responses. In vitro, human Treg-peripheral blood mononuclear cell (PBMC) co-cultures strongly inhibited phosphoantigen-induced proliferation of gammadelta T cells and depletion of Tregs restored the impaired phosphoantigen-induced gammadelta T-cell proliferation of cancer patients. Tregs did not suppress other effector functions of gammadelta T cells such as cytokine production or cytotoxicity. Our experiments indicate that Tregs do not mediate their suppressive activity via a cell-cell contact-dependent mechanism, but rather secrete a soluble non-proteinaceous factor, which is independent of known soluble factors interacting with amino acid depletion (e.g. arginase-diminished arginine and indolamine 2,3-dioxygenase-diminished tryptophan) or nitric oxide (NO) production. However, the proliferative activity of alphabeta T cells was not affected by this cell-cell contact-independent suppressive activity induced by Tregs. In conclusion, these findings indicate a potential new mechanism by which Tregs can specifically suppress gammadelta T cells and highlight the strategy of combining Treg inhibition with subsequent gammadelta T-cell activation to enhance gammadelta T cell-mediated immunotherapy.     

The local and systemic T-cell response to Helicobacter pylori in gastric cancer patients is characterised by production of interleukin-10

Helicobacter pylori causes a life-long infection that may lead to development of gastric adenocarcinoma (GC) and thereby cause major worldwide health problems. The present study was designed to study whether those that develop GC have an altered immune response to H. pylori compared to individuals that remain asymptomatic. When stimulated with H. pylori antigens, T cells from both peripheral blood and gastric mucosa of H. pylori-infected GC patients produced high amounts of IL-10, while the IL-10 production from blood T cells of H. pylori-infected asymptomatic subjects was low. Furthermore, mRNA levels of IL-10 were increased in the gastric mucosa of GC patients. In addition, the frequency of activated CD8(+) T cells was markedly reduced in stomach mucosa of patients with GC compared to asymptomatic individuals. We propose that the increased production of the suppressive cytokine IL-10 in H. pylori-infected GC patients leads to a diminished cytotoxic anti-tumour T-cell response in the stomach, which may contribute to tumour progression in subjects suffering from GC.     

A clonal model for human CD8+ regulatory T cells: unrestricted contact-dependent killing of activated CD4+ T cells

Previous studies in murine systems have demonstrated that CD8(+) Treg cells down-regulate immune responses in vivo through suppressing activated CD4(+) T cells. Here we describe novel regulatory CD8(+) T-cell clones isolated from healthy human peripheral blood following in vitro stimulation with autologous Epstein-Barr virus (EBV)-specific CD4(+) T cells. TCR activation of CD4(+) target T cells was required for CD8(+) Treg cells to exert suppressive activity, which was mediated through lysis of CD4(+) targets in a cell contact-dependent manner. Suppression was independent of Foxp3 expression in CD8(+) Treg cells, HLA compatibility between CD8(+) Treg cells and CD4(+) target cells and antigen-specificity of CD4(+) target T cells. CD8(+) Treg clones expressed CD3 and a variety of TCR V(β) chains as well as CD56, CD69, CD62L and CD95 but did not express CD16, CD161, CXCR4 and CCR7. When used together, antibodies specific for CD11a/CD18 and CD8 inhibited suppressive activity of CD8(+) Treg clones. The ability to establish clonal CD8(+) T cells that maintain regulatory function in vitro will facilitate further studies to define this population in vivo and to identify the mechanisms used for recognition and suppression of activated target cells.     

B cells pulsed with Helicobacter pylori antigen efficiently activate memory CD8+ T cells from H. pylori-infected individuals

Helicobacter pylori infection causes chronic gastritis that may progress to peptic ulcers or gastric adenocarcinoma and thereby cause major world-wide health problems. Previous studies have shown that CD4+ T cells are important in the immune response to H. pylori in humans, but the role of CD8+ T cells is less clear. In order to study the CD8+ T cell response to H. pylori in greater detail, we have evaluated efficient conditions for activation of CD8+ T cells in vitro. We show that H. pylori-reactive CD8+ T cells can be activated most efficiently by B cells or dendritic cells pulsed with H. pylori antigens. We further show that the majority of CD8+ T cells in H. pylori-infected gastric mucosa are memory cells, and that memory CD8+ T cells sorted from peripheral blood of H. pylori-infected individuals respond 15-fold more to H. pylori urease compared to memory cells from uninfected subjects. We conclude that CD8+ T cells do participate in the immune response to H. pylori, and this may have implications for the development of more severe disease outcomes in H. pylori-infected subjects.     

Developmental changes of FOXP3-expressing CD4+CD25+ regulatory T cells and their impairment in patients with FOXP3 gene mutations

FOXP3 is required for the generation and function of CD4(+)CD25(+) regulatory T (Treg) cells. To elucidate the biological role of Treg cells, we used a monoclonal anti-FOXP3 antibody to examine the frequencies of Treg cells during child development. The percentages of CD4(+)CD25(+)FOXP3(+) T cells were constant shortly from after birth through adulthood. CD4(+)CD25(+)FOXP3(+) T cells in cord blood showed the naive CD45RA(+)CD45RO(-) phenotype, whereas adult CD4(+)CD25(+)FOXP3(+) T cells expressed mostly the memory CD45RA(-)CD45RO(+) phenotype. The age-dependent dominance of memory CD4(+)CD25(+)FOXP3(+) T cells implies functional differences between naive and memory Treg cells. Notably, four patients with FOXP3 gene mutations revealed a paucity of CD4(+)CD25(+)FOXP3(+) T cells. Importantly, one patient with a frame shift mutation, who showed typical symptoms of IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked), exhibited marked T cell activation, whereas others with missense mutations, who were clinically milder, did not. This observation suggests a possible genotype-phenotype correlation in IPEX.