K. pneumoniae ompA attenuates IL-1β-induced IL-8 expression. A, ELISA of IL-8 released by A549 left untreated (CON) or infected for 1 h with Kp52145 or 52OmpA2 and then stimulated with IL-1β (50 ng/ml) for 2 h (n = 3). *, p < 0.05 (for the indicated comparisons; one-way ANOVA). B, immunoblot analysis of CYLD, MKP-1, and tubulin levels in A549 cells left uninfected (CON) or infected with Kp52145 or 52OmpA2 for 3 h. Data are representative of three independent experiments. C, immunoblot analysis of CYLD, MKP-1, and tubulin levels in A549 cells transfected with either control or NOD1 siRNA, which were left uninfected (CON) or infected with Kp52145 or 52OmpA2 for 3 h. Data are representative of three independent experiments.