Decreased IgA antibody production in the stomach of gastric adenocarcinoma patients.

Gastric adenocarcinoma is closely associated with Helicobacter pylori infection. It is also much more frequent in patients with common variable immunodeficiency or selective IgA-deficiency than in the general population. To investigate a possible link between local antibody production and gastric tumors, we studied gastric B cell infiltration and local IgA production in patients with H. pylori induced gastric adenocarcinomas. These studies showed that total and H. pylori-specific IgA antibody levels were substantially lower in gastric tissue from the cancer patients compared to those from asymptomatic H. pylori carriers. However, serum IgA levels were similar in the cancer patients and asymptomatic carriers. As could be expected, H. pylori infected asymptomatic carriers had considerably increased IgA antibody levels compared to uninfected subjects. We conclude that patients suffering from gastric adenocarcinoma have a dramatically decreased local IgA production in the stomach compared to asymptomatic H. pylori infected individuals.

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.

CD4+ CD25high regulatory T cells reduce T cell transendothelial migration in cancer patients.

Cell-mediated immunity is thought to be the main mechanism of anti-tumour responses of the host, but it is not known if cancer disease affects T cell recruitment from blood to tissues. Therefore, we compared Heliobacter pylori-induced T cell transendothelial migration (TEM) in H. pylori-infected gastric carcinoma patients, colon and lung carcinoma patients and healthy volunteers. H. pylori induced significant T cell migration from all groups. However, there was a dramatic reduction of T cell TEM in gastric carcinoma patients (80%) compared to healthy individuals. A similarly reduced transmigration was also seen in colon and lung carcinoma patients. We found significantly increased frequencies of T(reg) cells in the blood of gastric carcinoma patients compared to healthy individuals, and depletion of T(reg) cells from the blood of these patients prior to TEM restored T cell migration. The effect of T(reg) cells was largely dependent on cell-cell contact, but not on IL-10 or TGF-beta. In addition, the presence of T(reg) cells led to reduced T cell attachment to endothelium and decreased production of T cell-recruiting chemokines during TEM. In conclusion, T(reg) cell-mediated reduction of T cell TEM may reduce T cell recruitment in patients with epithelial malignancies, thereby hampering anti-tumour responses.

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.

Helicobacter pylori induce neutrophil transendothelial migration: role of the bacterial HP-NAP.

Continuous recruitment of neutrophils into the inflamed gastric mucosal tissue is a hallmark of Helicobacter pylori infection in humans. In this study, we examined the ability of H. pylori to induce transendothelial migration of neutrophils using a transwell system consisting of a cultured monolayer of human endothelial cells as barrier between two chambers. We showed for the first time that live H. pylori, but not formalin-killed bacteria, induced a significantly increased transendothelial migration of neutrophils. H. pylori conditioned culture medium also induced significantly increased transendothelial migration, whereas heat-inactivated culture filtrates had no effect, suggesting that the chemotactic factor was proteinaceous. Depletion of H. pylori-neutrophil activating protein (HP-NAP) from the culture filtrates resulted in significant reduction of the transmigration. Culture filtrates from isogenic HP-NAP deficient mutant bacteria also induced significantly less neutrophil migration than culture filtrates obtained from wild-type bacteria. HP-NAP did not induce endothelial cell activation, suggesting that HP-NAP acts directly on the neutrophils. In conclusion, our results demonstrate that secreted HP-NAP is one of the factors resulting in H. pylori induced neutrophil transendothelial migration. We propose that HP-NAP contributes to the continuous recruitment of neutrophils to the gastric mucosa of H. pylori infected individuals.

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.

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.

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.