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Helicobacter pylori (H. pylori) is a bacterial pathogen that exclusively colonizes the human gastric mucosa and can cause persistent infection. In this process, H. pylori employs various strategies to avoid recognition by the human immune system. These range from passive defense strategies (e.g., altered LPS or flagellin structures) that prevent recognition by pattern recognition receptors (PRRs) to more active approaches, such as inhibition of IL-2 secretion and proliferation of T cells via VacA. Despite the growing evidence that H. pylori actively manipulates the human immune system for its own benefit, the direct interaction of H. pylori with immune cells in situ is poorly studied. Here, we present a novel intravital imaging model of the murine stomach gastric mucosa and show for the first time the in situ recruitment of neutrophils during infection and a direct H. pylori-macrophage interaction. For this purpose, we applied multiphoton intravital microscopy adapted with live drift correction software (VivoFollow) on LysM-eGFP and CX3CR1-eGFP reporter mice strains in which specific subsets of leukocytes are fluorescently labeled. Multiphoton microscopy is proving to be an excellent tool for characterizing interactions between immune cells and pathogens in vivo. Author summary: This study focuses on the dynamics of H. pylori infection and its interaction with myeloid immune cells, using an innovative in vivo multiphoton imaging approach to observe real-time events in the infected gastric mucosa. In contrast to conventional methods, this novel technique allows us to dynamically investigate the host immune response. Our results show the spatio-temporal distribution of neutrophils and the internalization of H. pylori by macrophages over time. Using intravital multiphoton microscopy enhanced with live drift correction software and utilizing LysM-eGFP and CX3CR1-eGFP reporter mice, we established an intravital imaging model for the gastric mucosa of mice. Notably, we observe a significant increase in neutrophil infiltration into the gastric submucosa during early infection, indicating a rapid response of the innate immune system within the gastric crypts. However, in the chronic infection phase, a contrasting decrease in neutrophil influx is seen, indicating an adaptive innate immune response with fewer neutrophils infiltrating the tissue at an increased rate. Importantly, our data suggest that H. pylori is dependent on macrophages to proliferate and colonize the gastric mucosa during chronic infection. [ABSTRACT FROM AUTHOR]

Macrophages are crucial effector cells of the innate immune system and have important roles in the initiation and resolution of inflammation as well as in tissue homeostasis. To fulfill these diverse roles, macrophages exhibit metabolic flexibility to quickly adapt to the needs of the effector functions required, as well as to the microenvironment. This metabolic flexibility is exemplified by proinflammatory macrophages, which upregulate glycolysis to both initiate and sustain the process of inflammation. Upregulation of glycolysis does not only represent a fast means of ATP generation. It also fuels glycolytic side pathways that are crucial for an effective inflammatory response by influencing the cell's redox balance as well as by providing building blocks and substrates for epigenetic reprogramming. The aim of this short review is to explore how three of these pathways - the pentose phosphate pathway, the glycerol phosphate shuttle, and the serine synthesis pathway - help macrophages sustain their proinflammatory phenotype and functions.