The human gastrointestinal tract harbors about a thousand of species of commensal microorganisms that interact in a constant, homeostatic relationship with the immune system of the host. The disruption of this balance is implicated in a variety of diseases. Thus, the establishment of cause-effect relationship between the gut microbiota, the intestinal epithelium and the immune system is a crucial step in the development of successful microbiome-related strategies for maintaining human health. For this purpose, we have developed a microfluidics-based co-culture device, termed HuMiX that allows proximal co-culture of human epithelial cells and microbes, mimics physiologically relevant spatial dimensions and establishes extracellular matrix conditions that guarantee stable growth conditions for both cell contingents. HuMiX is already supported by CORE, PoC, AFR and INTER Mobility schemes from the FNR. This FNR Inter-mobility application is meant to foster the development of the HuMiX2.0 model by inclusion of representative immune cells, expand and foster a long term collaboration between Wilmes lab and Honda lab in RIKEN, publish at least two joint publications and to result in new joint IP after the completion of this grant. The aim of this study is to expand the HuMiX platform to analyze the interactions between the immune system and intestinal microbiota in the human gut. In the ImmunoHuMiX we will co-culture gastrointestinal microbes, epithelial and immune cells (peripheral blood mononuclear cells – PBMC), in three distinct chambers. Immune function will be assessed using cytometry by time-of-flight – CyToF panel to allow comprehensive analysis of innate and adaptive immune cells within PBMCs and will provide us with a system-wide view of immune signaling. We are currently investigating the influence of Klebsiella pneumoniae on human immune populations of PBMCs. Interestingly, colonization with microbes of oral origin can be seen in the intestine of patients with several diseases such as Inflammatory Bowel Disease (IBD) and colon cancer. In this study we will use strains of K.pneumoniae. These have been isolated in Honda’s lab from oral cavities of patients suffering of Crohn’s Disease and an Ulcerative Colitis – the principal types of IBD, specifically inducing the Th1 lymphocyte population. The CD4+Th1 T-cells are critical for adequate responses to intracellular bacteria and viruses. The applicant is currently working on experiments in order to describe the effect of K.pneumoniae on different immune subsets such of CD4+ cells Dendritic Cells, CD8+ Cells and B cells. To strengthen the already ongoing collaboration and to benefit from Dr. Honda’s internationally recognized knowledge in the field of immunology he applicant is eager to visit, Dr. Honda’s lab in RIKEN institute. To foster the development of ImmunoHuMiX, the applicant will learn several unique techniques, such as: isolation of lamina propria mononuclear cells from colonic tissue, transmission electron microscopy, both currently not mastered in LCSB, and thus will exchange the key scientific knowledge during her stay in Honda’s lab. Dr. Honda, a team leader of the Laboratory for Gut Homeostasis at the RIKEN Center for Integrative Medical Sciences is an internationally recognized expert in innate immune signaling and mucosal immunology. Dr. Honda is one of the pioneers and has an extensive experience in investigating influences of the gut microbiota on the host immune system, identification of gut unique immune cell subsets and development of new therapeutic ways to treat IBD and cancer by means of manipulation of the gut microbiota. Hence, it is absolutely pertinent for the ImmunoHuMiX development to be able to profit from Dr. Honda experience and this exchange will help advance the progress of Humix 2.0, will be an important learning experience for the applicant and will lead to the generation of new joint IP.