ObjectiveNeutrophils are prominent components of solid tumours and exhibit distinct phenotypes in different tumour microenvironments. However, the nature, regulation, function and clinical relevance of neutrophils in human gastric cancer (GC) are presently unknown.DesignFlow cytometry analyses were performed to examine levels and phenotype of neutrophils in samples from 105 patients with GC. Kaplan-Meier plots for overall survival were performed using the log-rank test. Neutrophils and T cells were isolated, stimulated and/or cultured for in vitro and in vivo regulation and function assays.ResultsPatients with GC showed a significantly higher neutrophil infiltration in tumours. These tumour-infiltrating neutrophils showed an activated CD54+ phenotype and expressed high level immunosuppressive molecule programmed death-ligand 1 (PD-L1). Neutrophils activated by tumours prolonged their lifespan and strongly expressed PD-L1 proteins with similar phenotype to their status in GC, and significant correlations were found between the levels of PD-L1 and CD54 on tumour-infiltrating neutrophils. Moreover, these PD-L1+ neutrophils in tumours were associated with disease progression and reduced GC patient survival. Tumour-derived GM-CSF activated neutrophils and induced neutrophil PD-L1 expression via Janus kinase (JAK)-signal transducer and activator of transcription 3 (STAT3) signalling pathway. The activated PD-L1+ neutrophils effectively suppressed normal T-cell immunity in vitro and contributed to the growth and progression of human GC in vivo; the effect could be reversed by blocking PD-L1 on these neutrophils.ConclusionsOur results illuminate a novel mechanism of PD-L1 expression on tumour-activated neutrophils in GC, and also provide functional evidence for these novel GM-CSF-PD-L1 pathways to prevent, and to treat this immune tolerance feature of GC.

CD4+ T cell responses are critical for the pathogenesis of Helicobacter pylori infection. The present study evaluated the role of the Th17 subset in H. pylori infection. H. pylori infection induced significant expression of IL-17 and IFN-g in mouse gastric tissue. IL-23 and IL-12 were increased in the gastric tissue and in H. pylori-stimulated macrophages. Cell responses were examined by intracellular staining for IFN-g, IL-4, and IL-17. Mice infected with H. pylori developed a mixed Th17/Th1 response; Th17 responses preceded Th1 responses. Treatment of mice with an anti-IL-17 Ab but not a control Ab significantly reduced the H. pylori burden and inflammation in the stomach. H. pylori colonization and gastric inflammation were also lower in IL-17 2/2 mice. Furthermore, administration of recombinant adenovirus encoding mouse IL-17 increased both H. pylori load and inflammation. Further analysis showed that the Th1 cell responses to H. pylori were downregulated when IL-17 is deficient. These results together suggest that H. pylori infection induces a mixed Th17/Th1 cell response and the Th17/IL-17 pathway modulates Th1 cell responses and contributes to pathology. The Journal of Immunology, 2010, 184: 5121-5129. H elicobacter pylori is a Gram-negative, microaerophilic bacterium that resides extracellularly in the gastric mucosa and infects .50% of the population worldwide. H. pyloriinduced chronic inflammation is the cause of gastritis and peptic ulcers and a risk factor for gastric cancer (1, 2). H. pylori infection causes severe local inflammation in the gastric mucosa. CD3 + CD4 + T cells are increased in infected gastric lamina propria and play important roles in the pathogenesis of persistent H. pylori infection (3). Traditionally, CD4 + T cells are classified into two main classes: Th1 and Th2, on the basis of their cytokine secretion and immune regulatory function. Th1 cells secrete IFN-g, IL-2, and IL-12 and regulate cellular immunity, whereas Th2 cells produce IL-4, IL-5, and IL-13 and mediate humoral responses. To date, studies of immune responses to H. pylori have largely focused on Th1 and Th2 cells, and it is generally accepted that H. pylori infection results in a Th1-dominant response and that gastric inflammation largely depends on Th1 cell responses (3-6); however, IFN-g secretion alone is insufficient to induce gastritis (3). Thus, the detailed mechanism of pathogenesis is not clear. A novel subset of effector T cells, identified by secretion of IL-17, has been defined as Th17 cells. Th17 cells are distinct from Th1 and Th2 cells in their differentiation and function (7,8). TGF-b and IL-6 from activated macrophages/dendritic cells are required for Th17 cell differentiation in murine systems (9), whereas IL-12 and IFN-g promote Th1 cell development and IL-4 primes Th2 cell differentiation. The expansion and survival of Th17 cells are promoted by IL-23 (9), a heterodimeric cytokine composed of a unique p19 subunit and a p40 subunit shared with IL-12 (10). The identification of Th17 cells necessit...

Edited by Tamas DalmayKeywords: MiR-155 MyD88 Inflammation Helicobacter pylori a b s t r a c t has been implicated as a central regulator of the immune system. We have previously reported that miR-155 negatively regulates Helicobacter pylori (H. pylori)-induced inflammation, but the molecular mechanism of miR-155 regulating the inflammation is not fully clear. Here, we identified myeloid differentiation protein 88 (MyD88) as a target gene of miR-155, and found that miR-155 decreased MyD88 expression at the protein but not the mRNA message level, suggesting that the miR-155-mediated inhibition is a post-transcriptional event. Furthermore, the overexpression of miR-155 led to significantly reduced IL-8 production induced by H. pylori infection. Thus, we have demonstrated that miR-155 can negatively regulate inflammation by targeting a key adaptor molecule MyD88 in inflammatory pathways.

ObjectiveHelper T (Th) cell responses are critical for the pathogenesis of Helicobacter pylori-induced gastritis. Th22 cells represent a newly discovered Th cell subset, but their relevance to H. pylori-induced gastritis is unknown.DesignFlow cytometry, real-time PCR and ELISA analyses were performed to examine cell, protein and transcript levels in gastric samples from patients and mice infected with H. pylori. Gastric tissues from interleukin (IL)-22-deficient and wild-type (control) mice were also examined. Tissue inflammation was determined for pro-inflammatory cell infiltration and pro-inflammatory protein production. Gastric epithelial cells and myeloid-derived suppressor cells (MDSC) were isolated, stimulated and/or cultured for Th22 cell function assays.ResultsTh22 cells accumulated in gastric mucosa of both patients and mice infected with H. pylori. Th22 cell polarisation was promoted via the production of IL-23 by dendritic cells (DC) during H. pylori infection, and resulted in increased inflammation within the gastric mucosa. This inflammation was characterised by the CXCR2-dependent influx of MDSCs, whose migration was induced via the IL-22-dependent production of CXCL2 by gastric epithelial cells. Under the influence of IL-22, MDSCs, in turn, produced pro-inflammatory proteins, such as S100A8 and S100A9, and suppressed Th1 cell responses, thereby contributing to the development of H. pylori-associated gastritis.ConclusionsThis study, therefore, identifies a novel regulatory network involving H. pylori, DCs, Th22 cells, gastric epithelial cells and MDSCs, which collectively exert a pro-inflammatory effect within the gastric microenvironment. Efforts to inhibit this Th22-dependent pathway may therefore prove a valuable strategy in the therapy of H. pylori-associated gastritis.

No abstract