Macrophages and epithelial cells respond differently to the Pseudomonas aeruginosa type III secretion system

The multiple effects of Pseudomonas aeruginosa type III secretion have larg ely been attributed to variations in cytotoxin expression between strains. Here we show that the target cell type is also important. While lung epithe lial cells showed significant changes in morphology but not viability when infected with P. aeruginosa, macrophages were efficiently killed by P. aeru ginosa. Both responses were dependent on the type III secretion system.