VISUALIZING HOST MACROPHAGES-MICROBIAL PATHOGENS INTERACTIONS IN THE AMPHIBIAN XENOPUS
Jacques Robert, University of Rochester Medical Center
Jacques Robert and Rhoo, Kun Hyoe
Department of Immunology & Microbiology, University of Rochester Medical Center, Rochester, NY
Cells of the monocytic lineage play a central role in host defenses, development and homoeostasis. However, the heterogeneity and plasticity of macrophages, depending on their developmental stage, tissue residence and types of activation, challenge the functional characterization of these cells. One way to gather more direct insights into their immunological role is to develop intravital animal models to visualize macrophage activity in real time. Using transgenesis to express fluorescent reporter genes under the control of cell type-specific promoters, we have characterized several transgenic lines, which label different subsets of myeloid lineages in tadpoles. These transgenic lines include xlurp:GFP (myeloid cells), xmpeg:GFP (mononuclear phagocytes), and double xlurp:GFP/xmpeg:mCherry (green myeloid cells such as granulocytes and yellow to orange macrophages). Beside to assessing the involvement of myeloid cells during infection with ranavirus FV3, we are currently adapting these transgenic lines for characterizing the role of macrophages in host immune defenses against Mycobacteria marinum (Mm). Notably, in combination with fluorescently labeled recombinant Mm, we have been able to visualize Mm-infected macrophages intravitally at the site of infection in the muscle tail, as well as to follow Mm dissemination to other organs such as liver and lung. We anticipate that our system will provide novel insights into the complex interactions of mycobacterial pathogens and host macrophages.