Abstract
Like most epithelial organs, the bladder and kidney can be directly accessed by bacteria evolved for invasion. Epithelia and immune cells attempt to stymie this infection with biophysical and chemical mechanisms. Goldspink et al. connected the Na(+) gradient in the kidney medulla with an immune defense mounted by dead cells (namely, the explosive death of neutrophils and macrophages), resulting in extracellular DNA traps. The pathway from Na(+) concentration to immune death is depicted.