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The persistence of Helicobacter pylori in the human gastric mucosa implies that the immune response fails to clear the infection. We found that H. pylori compromises the antigen presentation ability of macrophages, because of the decline of the presenting molecules HLA‐II. Here, we reveal that the main bacterial factor responsible for this effect is ADP‐heptose, an intermediate metabolite in the biosynthetic pathway of lipopolysaccharide (LPS) that elicits a pro‐inflammatory response in gastric epithelial cells. In macrophages, it upregulates the expression of miR146b which, in turn, would downmodulate CIITA, the master regulator for HLA‐II genes. Hence, H. pylori, utilizing ADP‐heptose, exploits a specific arm of macrophage response to establish its survival niche in the face of the immune defense elicited in the gastric mucosa. [ABSTRACT FROM AUTHOR]

Abstract: We have previously shown that DNA can be transferred to phagocytosing cells via the uptake of apoptotic cells. We report a model system that facilitates study of antigen presentation of genes transferred specifically via horizontal gene transfer. Constructs were generated encoding the LacZ gene or the influenza A nucleoprotein silenced by a STOP sequence flanked by two loxP sites. These reporter genes were demonstrated to be silent in donor cells and become activated after phagocytosis of Cre-expressing fibroblasts or macrophages. These results provide a model system for studying the influence of horizontally transferred antigens on activation of the immune system. [Copyright &y& Elsevier]

Abstract: Recognition of lipid antigens by T lymphocytes is well established. Lipids are recognized by T cells when presented in association with CD1 antigen-presenting molecules. Both microbial and self lipids stimulate specific T lymphocytes, thus participating in immune reactions during infections and autoimmune diseases. The immune system uses a variety of strategies to solubilise lipid antigens, to facilitate their internalization, processing, and loading on CD1 molecules. Recent studies in the field of lipid antigen presentation have revealed new mechanisms which allow the immune system to sense lipids as stimulatory antigens. [Copyright &y& Elsevier]