FIG. 3.

Apoptosis of J774A.1 cells infected with type III secretion mutants of PA103. J774A.1 cells were infected for 6 h at an MOI of approximately 160 and then tested for apoptosis by using the quantitative ELISA for apoptosis. Bacterial mutants with type III secretion pathway defects were associated with significantly less apoptosis than wild-type PA103. Interestingly, PA103exoU::Tn5, which has an intact secretion pathway but does not secrete the effector protein ExoU, was associated with wild-type levels of apoptosis, indicating that this factor is not necessary for induction of programmed cell death. Error bars represent standard errors of the means for experiments performed in triplicate.