Live imaging innate immune cell behavior during normal development, wound healing and infection

Cells of the innate immune system perform a number for functions that range from clearing apoptotic cell corpses during normal organ development to removing invading pathogens and helping regulate the immune response to infection. Traditional approaches to assessment of these immune cell behaviors have relied upon histological analysis of fixed tissue samples complemented by in vitro functional data. Despite providing significant insights, translating the results from such studies into a multicellular whole animal context is difficult. Recent advances in cell labeling techniques and imaging technologies has given researchers unprecedented ability to directly observe immune cell activities within a live whole animal context. Such live imaging approaches are essential to completely appreciate these activities within their intact normal physiological setting. The zebrafish embryo, with its optical transparency and fully functional innate and adaptive immune systems, represents an ideal system in which to live image innate immune cells. When this is coupled with the relative ease with which specific immune cells can be fluorescently labeled within transgenic reporter lines and the ability to both genetically and chemically interfere with genetic pathways, the zebrafish is emerging as a strong vertebrate platform in which to make novel contributions to understanding immune cell biology. This chapter will discuss how our group and others use live imaging to assess the behavior of myeloid leukocytes during normal development and in response to different inflammatory stimuli, including wounding and pathogenic challenge.