Infected cells resist apoptosis induction via the extrinsic pathway. Uninfected and wildtype-infected cells analyzed in the apoptosis assay treated with TRAIL. Top: DAPI stain of uninfected (left) and infected (center) cells treated with TRAIL. Note the uninfected cells have characteristic apoptotic nuclei while the infected cell, in which the bacteria are also stained with the DAPI, has a healthy nucleus. An uninfected cell without TRAIL treatment appears on the right. Bottom: Phase contrast view of the cells. The infected cell, in which the bacteria are visible in the cytoplasm, has a healthy, round appearance while the uninfected cells are apoptotic. Images are representative of three repeated experiments, and cell counts of at least 300 cells demonstrated that infected cells consistently appeared healthy (data not shown).