PROJECT SUMMARY/ABSTRACT Our parent grant focuses on the disruptions caused by trauma, infection, and sepsis that compromise immune function. We have uncovered exciting new mechanisms that are essential for immune cell function and we found that these important mechanisms are impaired in critically ill patients. We discovered that the functions of immune cells depend on ATP release and autocrine feedback via purinergic receptors. We could show that mitochondria deliver the ATP that drives these autocrine feedback mechanisms. For that purpose, mitochondria are trafficked to specific regions within immune cells where they deliver their ATP in a spatiotemporally highly organized manner. Our work has provided strong evidence that trauma, infection, and sepsis impair these delicate signaling processes. In order to study the rapid and complex signaling mechanisms associated with mitochondria and purinergic receptor signaling, we must use live-cell imaging with a highly sophisticated microscope system. However, our current microscope system is not fast and versatile enough to study the connections between the trafficking of mitochondria, their activation, cellular ATP release, stimulation of purinergic receptors, and the function of immune cells isolated from healthy subjects and critical care patients. Here, we request supplemental funds that would allow addition of certain components to our existing microscope system. These key components would greatly increase scanning speed and acquisition of confocal images. The upgraded system would provide multi-dimensional data that would help to elucidate the central roles of mitochondrial dynamics in the function of immune cells in health and disease.