Characterizing ROS kinetics and role in Drosophila macrophages 4561

Abstract Description Although in mammalian macrophages, acidification and reactive nitrogen and oxygen species (ROS) are essential in phagosomal killing, it’s unknown whether they play a direct killing or regulatory role. The fruit fly Drosophila contains macrophages and has been used for important innate immunity discoveries. Since fly and mammalian macrophages can be infected by the same intracellular pathogens, including Mycobacteria and Salmonella, the killing mechanisms are assumed to be the same. However, our preliminary findings suggest that ROS play more of a regulatory than killing role in fly macrophages. Since fly macrophages are more ancient than mammalian macrophages, they have more fundamental roles pertaining to the macrophage killing mechanism, allowing us to more accurately determine the role and regulation of ROS in the mechanism. To further investigate the macrophage ROS role, we are using E. coli expressing the redox-sensitive GFP, roGFP2. Unlike the robust fluorescence of these bacteria in mammalian phagosomes, we have found that the fluorescence of roGFP2 is rapidly extinguished in fly phagosomes, suggesting differences in the chemical microenvironment. Moreover, we find these bacteria experience significant extracellular redox stress, including when bound to the surface of fly macrophages. Notably, this redox stress increases over time, and we are investigating whether this is due to a progressive “activation” of the fly macrophages, as is well-characterized in mammals. Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)