Acute respiratory distress syndrome (ARDS) is a common deadly illness often seen in the intensive care unit. Macrophages, the first responders of our immune system, are always found in lungs of patients with ARDS. However, it is unclear if there is a subset of cells that act as the main propagators of the disease. I believe we can find a subset of these cells that when targeted, may help us stop or even reverse ARDS.