NUDT21 and acute respiratory distress syndrome: To further confirm the macrophage-specific role of NUDT21 in ARDS and minimize the confounding effects of neutrophils, we generated Nudt21f/fCx3cr1Cre mice, in which NUDT21 is selectively deleted in monocytes, macrophages, dendritic cells, and NK cells, but not in neutrophils31, 32.