TABLE 2.

PAO-I-induced apoptosis requires adhesion of live bacteria expressing a functional type III secretion system^a

Preparations used for infection	% Annexin-positive cells
No bacteria	11.5 ± 2.9
PAO-I wild type	33.2 ± 4.9
PAO-I supernatant	11.4 ± 3.2
PAO-I wild type, heat inactivated	13.5 ± 4.7
CFTR peptide-pretreated PAO-I wild type	26.7 ± 2.9
Type III secretion system-deficient PAO-I	17.2 ± 5.6

^aChang cells were left uninfected or infected for 3 h with PAO-I, PAO-I supernatants (from 3 × 10⁹ PAO-I; 3 h), heat-inactivated PAO-I (20 min; 80°C), PAO-I pretreated with CFTR peptide (15 min; 1 μM), or a type III secretion system-defective PAO-I mutant, respectively. Apoptotic cell death was then determined by FACS analysis of FITC-annexin-stained cells. Cell debris and bacteria were excluded from the analysis by means of size gates (values are means ± SD; n = 3).