CD4+CD25+调节性T细胞和TLRs在幽门螺杆菌 免疫逃逸中的作用

宿主感染幽门螺杆菌(H.pylori)后,会产生炎症反应和免疫反应,但宿主不能完全清除H.pylori,原因之一为H.pylori可逃逸宿主免疫形成持续慢性感染。H.pylori免疫逃逸机制尚不明确,目前此机制研究热点为CD4+CD25+调节性T细胞和TLRs在H.pylori免疫逃逸中的作用。     

CD8+ T cells are associated with severe gastritis in Helicobacter pylori-infected mice in the absence of CD4+ T cells

Helicobacter pylori infection results in the development of chronic gastritis, and CD4⁺ T cells are a major component of the gastric cellular infiltrate. To examine whether CD4⁺ T cells are important in initiating and maintaining H. pylori-induced gastritis, mice deficient in CD4⁺ T cells (B6.BM1.GK 1.5 mice [GK 1.5 mice]) were infected with H. pylori. We found that as in normal mice, H. pylori-specific antibodies, mostly of the immunoglobulin M isotype, developed in GK 1.5 mice but were unable to cure H. pylori infection. Further, while the stomachs of H. pylori-infected GK 1.5 mice were more heavily infiltrated with CD8⁺ T cells and B cells, mice deficient in both CD4⁺ and CD8⁺ T cells developed mild inflammation comparable to the level observed for C57BL/6 mice. These observations suggest that CD4⁺ T cells may play an important role in regulating or suppressing gastric CD8⁺ T cells which, in the absence of CD4⁺ T cells, may mediate more-severe disease. These studies have revealed a potentially important role for CD8⁺ T cells in the gastric disease resulting from H. pylori infection.     

Role of vacuolating cytotoxin in gastritis due to Helicobacter pylori in gnotobiotic piglets.

To investigate the role of the Helicobacter pylori cytotoxin in the pathogenesis of gastritis, gnotobiotic piglets were colonized with either toxigenic H. pylori or a nontoxigenic isogenic mutant. Only piglets given the toxigenic strain developed toxin-neutralizing antibodies (indicating that toxin is expressed in vivo), but there was no difference in bacterial colonization, epithelial vacuolation, or gastritis between the two groups of piglets.     

Role of tumor necrosis factor alpha in Helicobacter pylori gastritis in tumor necrosis factor receptor 1-deficient mice

Increased gastric production of interleukin 8 and tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathogenesis of Helicobacter pylori-associated gastroduodenal disease. In the present study we used a mouse model to demonstrate whether loss of the tumor necrosis factor receptor 1 (TNF-R1) function leads to differences in gastric inflammation or the systemic immune response in H. pylori infection. Six different clinical isolates of H. pylori (three cytotoxin-positive and three cytotoxin-negative strains) were adapted to C57BL/6 mice. TNF-R1-deficient (TNF-R1(-/-)) mice (n = 19) and isogenetic controls (n = 24) were infected and sacrificed after 4 weeks of infection. Inflammation of the stomach and the humoral immune response to H. pylori were evaluated by histological, immunohistochemical, and serological methods. There was no detectable difference in the grade or activity of gastritis in TNF-R1(-/-) mice when they were compared with wild-type mice, but the number of lymphoid aggregates was slightly reduced in the gastric mucosa of TNF-R1(-/-) mice. Interestingly, total immunoglobulin G (IgG), as well as IgG1, IgG2b, and IgG3, H. pylori-specific antibody titers were significantly higher in wild-type mice. As revealed by immunoblot analysis, the difference in reactivity against H. pylori antigens was not based on a failure to recognize single H. pylori antigens in TNF-R1(-/-) mice. We therefore suggest that TNF-R1-mediated TNF-alpha signals might support a systemic humoral immune response against H. pylori and that the gastric inflammatory response to H. pylori infection seems to be independent of TNF-R1-mediated signals.     

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.     

转录因子T-bet/GATA-3在致敏大鼠脾CD4+T细胞中失衡表达和调节的研究

目的 探讨转录因子T-bet/GATA-3在卵白蛋白(OVA)致敏大鼠脾CD4+T细胞中失衡表达,及地塞米松和咪喹莫特对其的调节作用.方法 从SD大鼠脾脏中分离获得CD4+T细胞,ELISA法测定细胞上清液中细胞因子IL-4、IL-5和IFN-γ含量;Western blot检测CD4+T细胞中T-bet和GATA-3表达.结果 在4个时间点培养细胞上清液中,空白对照组检测到低水平IFN-γ;随着培养时间延长,阳性对照组IL-4和IL-5持续增加,IFN-γ保持在低水平.地塞米松干预组IL-4、IL-5和IFN-γ低表达,均低于空白对照组(P＜0.01);咪喹莫特干预组IL-4和IL-5表达降低,IFN-γ表达增强.此作用从培养6 h开始,12 h达高峰,持续至24 h.在4个时间点培养细胞中,空白对照组检测到转录因子T-bet和GATA-3蛋白表达;随着细胞培养时间延长,阳性对照组T-bet表达降低,GATA-3表达增加.地塞米松干预组T-bet低表达,GATA-3在24 h内表达水平无明显变化;咪喹莫特干预组与阳性对照组比较,GATA-3表达降低,T-bet表达增强.此作用从细胞培养6 h开始,12 h达高峰,持续至24 h.结论 OVA致敏大鼠脾CD4+T细胞中,转录因子T-bet/GATA-3失衡表达,即T-bet低表达,GATA-3异常高表达;地塞米松抑制CD4+T细胞中T-bet表达,对GATA-3表达无明显作用;咪喹莫特通过调节CD4+T细胞中T-bet和GATA-3平衡表达,纠正TH1和TH2细胞的失衡,提示咪喹莫特可能在由TH2细胞介导免疫异常的哮喘中发挥作用.     

Mast cells in Helicobacter pylori associated antral gastritis

Mast cells are known to be effector cells in various inflammatory reactions, but their role in gastritis is unclear. The present study was undertaken to investigate the extent of mast cell involvement in antral gastritis with and without Helicobacter pylori (H. pylori) infection and thus evaluate the possible role of mast cells in the pathogenesis of H. pylori-associated gastritis. Antral mucosal biopsies were taken from 212 subjects with symptoms suggestive of acid peptic disease. Sections were assessed for inflammation. Modified Giemsa stain was used to detect H. pylori infection and 1% toluidine blue to count mast cells. Mast cell counts were significantly higher in the antral mucosa even in H. pylori-negative gastritis (68.4 +/- 6.7/mm2), as compared to normal non-inflamed mucosa (45.7 +/- 5.8/mm2) (P < 0.05). However, with H. pylori infection, the mucosal mast cell count were markedly increased (123.8 +/- 4.7/mm2) as compared to normal mucosa (P < 0.01). and H. pylori-negative gastritis (P < 0.01) this increase was noticed uniformly in patients with H. pylori-positivity, irrespective of the presence or absence of a peptic ulcer. After cure of H. pylori infection, the mast cell density decreased significantly (44.9 +/- 4.6/mm2) to reach levels that were similar to those in normal mucosa. There was a positive correlation between the antral mucosal mast cell density and polymorphonuclear and mononuclear cell infiltration (rs = 0.61). H. pylori infection, and 0.73 respy. It was concluded that could be responsible for increasing the mast cell density in the gastric antrum. Probably by inducing castain mucosal cytokine.     

Intraepithelial infiltration by mast cells in human Helicobacter pylori active gastritis

Recent observations suggest an involvement of mast cells in Helicobacter pylori gastritis, but the mechanism of intraepithelial mast cell activation in H. pylori-infected patients remains to be clarified. Intraepithelial mast cells, identified by immunohistochemistry for CD117, were quantified in antral biopsies from 6 patients with H. pylori "active" chronic gastritis, 7 patients with H. pylori "nonactive" gastritis, and 9 controls. Antral biopsies from patients with H. pylori "active" gastritis showed higher intraepithelial mast cell counts than those from patients with H. pylori "nonactive" gastritis and from controls. Electron microscopy, selectively performed in 6 cases of H. pylori "active" gastritis, confirmed the presence of intraepithelial mast cells and allowed their subdivision into mature cells with intact electron-dense granules or degranulated cells. Other mast cells appeared to migrate through defects in the basement membrane into the epithelial layer. Mast cells in these areas often showed piecemeal degranulation or were characterized by large canaliculi, expanded Golgi areas, and a few granules, a process similar to the phase of recovery from anaphylactic degranulation of isolated human mast cells. The possible significance of these unusual ultrastructural findings is discussed.     

Role of gastric epithelial cell-derived transforming growth factor beta in reduced CD4+ T cell proliferation and development of regulatory T cells during Helicobacter pylori infection

Gastric epithelial cells (GECs) express the class II major histocompatibility complex (MHC) and costimulatory molecules, enabling them to act as antigen-presenting cells (APCs) and affect local T cell responses. During Helicobacter pylori infection, GECs respond by releasing proinflammatory cytokines and by increasing the surface expression of immunologically relevant receptors, including class II MHC. The CD4⁺ T cell response during H. pylori infection is skewed toward a Th1 response, but these cells remain hyporesponsive. Activated T cells show decreased proliferation during H. pylori infection, and CD4⁺ CD25⁺ FoxP3⁺ regulatory T cells (Tregs) are present at the site of infection. In this study, we examined the mechanisms surrounding the CD4⁺ T cell responses during H. pylori infection and found that transforming growth factor β (TGF-β) plays a major role in these responses. GECs produced TGF-β1 and TGF-β2 in response to infection. Activated CD4⁺ T cells in culture with H. pylori-treated GECs were decreased in proliferation but increased upon neutralization of TGF-β. Naïve CD4⁺ T cell development into Tregs was also enhanced in the presence of GEC-derived TGF-β. Herein, we demonstrate a role for GEC-produced TGF-β in the inhibition of CD4⁺ T cell responses seen during H. pylori infection.     

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.     

Association of Helicobacter pylori with HLA-DR antigen expression in gastritis.

AIMS: To assess the association between Helicobacter pylori-associated gastritis and HLA-DR antigen (class II antigen) expression. METHODS: Fifty endoscopic gastric biopsy specimens were studied for the presence of H pylori, degree and type of inflammation, and for HLA-DR antigen expression in the epithelium. The cases were chosen to represent different categories: inflamed gastric mucosa with (n = 13) and without (n = 20) H pylori, and non-inflamed mucosa (n = 17). RESULTS: The antigen was aberrantly expressed in the antral mucosal epithelium in 11 of 12 cases (92%) with acute-on-chronic gastritis when H pylori was also present. It was present in the antrum in only seven of 18 H pylori negative cases (39%) with acute-on-chronic/chronic gastritis. One of three cases of acute gastritis and three of seven cases of chronic gastric erosions (non-inflamed category) showed positive staining. Generally, there was more staining in the antral than body mucosa and in the surface/foveolar epithelium than in the glands. No aberrant HLA-DR antigen expression was found in the 10 cases of normal gastric mucosa examined. CONCLUSIONS: These findings suggest that H pylori may have a role in the induction of class II HLA antigen expression in chronic gastritis and lend support to the view that these organisms may be responsible for part of the inflammatory response.     

Helicobacter pylori induces chronic active gastritis in p53-knockout mice

Gastritis and peptic ulcers result from Helicobacter pylori (H. pylori) infection. To analyze the influence of Helicobacter on inflammatory responses and cell proliferation, we used an animal model of H. pylori-induced gastritis in p53-knockout mice. H. pylori were introduced by gastric intubation into p53-knockout C57BL/6 mice. The animals were then followed-up for 1 year and compared with uninfected controls of the same genotype. Serum levels of anti-H. pylori antibody and histopathological changes were analyzed according to the updated Sydney System. Immunohistochemistry for proliferating cell nuclear antigen (PCNA) and TUNEL staining were also performed. The infected mice showed significantly increased levels of anti-H. pylori antibody in serum. Histologically, p53-knockout mice exhibited increased scores of chronic and active inflammation compared with uninfected controls. The PCNA and TUNEL indices were 25.5% and 10/mm, respectively, in the inflammatory foci of infected mice, and were increased compared with the controls. In the p53-knockout mice, H. pylori infection caused severe inflammatory reactions. The p53 gene may play an important role in inflammatory responses including cell proliferation and apoptosis.     

Role of corpus gastritis and cagA-positive Helicobacter pylori infection in reflux esophagitis

Considering that the role of Helicobacter pylori infection in gastroesophageal reflux and reflux esophagitis (GERD) is still controversial and that the role of virulence markers of the bacterium has not been evaluated in most studies of GERD, we investigated the association among H. pylori infection with cagA-positive and -negative strains, corpus gastritis, and GERD in a large group of patients by controlling for confounding factors. We studied prospectively 281 consecutive adult patients: 93 with GERD and 188 controls. H. pylori infection status was diagnosed by culture, by the preformed urease test, with a carbolfuchsin-stained smear, and by histology. The cagA status was determined by PCR of H. pylori isolates and gastric biopsy specimens. H. pylori infection was diagnosed in 191 (68.0%) of 281 patients. Among the 93 patients with GERD, 84 presented with mild or moderate esophagitis and 9 presented with severe esophagitis. In the multivariate analysis, the age of the patients and the degree of oxyntic gastritis were associated with GERD. Among the strains isolated from patients with GERD and from the control group, 24.4 and 66.9%, respectively, were positive for cagA (P < 0.001). Compared to infection with cagA-negative strains, infection with cagA-positive H. pylori strains was associated with a more intense gastritis in the corpus (P = 0.001). cagA status (odds ratio [OR] = 0.16, 95% confidence interval [CI] = 0.07 to 0.40), gastritis of the corpus (OR = 0.69, 95% CI = 0.48 to 0.99), and age (OR = 1.04, 95% CI = 1.01 to 1.07) were associated with GERD. In conclusion, the study provides evidence supporting the independent protective roles of cagA-positive H. pylori strains and the degree of corpus gastritis against GERD.     

Cytokine expression in CD4+ cells exposed to the monocyte locomotion inhibitory factor produced by Entamoeba histolytica

Entamoeba histolytica produces monocyte locomotion inhibitory factor (MLIF), a pentapeptide with in vitro and in vivo anti-inflammatory properties. MLIF may interfere with leukocyte migration, disturbing the balance of pro- and anti-inflammatory cytokines secreted by CD4⁺ T lymphocytes. We evaluated the effect of MLIF on expression of pro- and anti-inflammatory cytokines in human CD4⁺ T lymphocytes. Regulatory cytokines [interleukin-1 beta (IL-1β), IL-2, interferon gamma (IFN-γ), IL-5, IL-6, and IL-10] were studied by enzyme-linked immunosorbent assay method in CD4⁺-cell supernatant fluids. Proinflammatory cytokines were produced per se by MLIF (IL-1β, IL-2, and IFN-γ) and also anti-inflammatory cytokines (IL-5, IL-6, and IL-10) with 1-phorbol-12 myristate-13 acetate + MLIF; the IL-1β, IFN-γ, IL-5 and IL-6 production was inhibited but not that of IL-10 which disclosed increase in its expression. MLIF disturbs the pro- and anti-inflammatory balance, and it induces inhibition of IL-1β (principal proinflammatory cytokine) and increases IL-10 (prototype of an anti-inflammatory cytokine).