TNF-α augments invasion of P. gingivalis in Ca9-22 cells. (A) Ca9-22 cells were treated with 10 ng/ml of TNF-α for 3 h. The cells were further incubated with P. gingivalis ATCC 33277 at an MOI of 100 for 1 h. Media in the cultures were then replaced with new media containing antibiotics for 1 h. Lysates of the cells with sterile water were then seeded on horse blood agar plates to determine the numbers of viable intracellular bacteria (means ± standard deviations [SD] [n = 3]). **, P < 0.01 versus TNF-α (-). CFU: colony forming units. (B) Ca9-22 cells were treated with 10 ng/ml of TNF-α for 3 h and were then incubated with P. gingivalis ATCC 33277 for 1 h. P.gingivalis was stained using antiserum for P. gingivalis whole cells. Then localization of P. gingivalis in the cells was observed by a confocal laser scanning microscope. Each molecule was visualized as follows: P. gingivalis (red). Bars in each panel are 10 μm.