Fig. 4.
The inhibition of interleukin-1β(IL-1β) (A), IL-6 (B), and IL-8 (C) degradation by a Porphyromonas gingivalis triple gingipain-deficient mutant was detected by enzyme-linked immunosorbent assay. Human gingival epithelial cells were challenged with heat-killed P. gingivalis 33277 for 24 h and the supernatant was subsequently incubated with the live RgpA/RgpB/Kgp mutant KDP128. The negative control was 24-h supernatant alone. The positive control was supernatant incubated with live wild-type P. gingivalis 33277. The data are expressed as percentages of the initial cytokine concentration of the negative control. Values represent the mean ± SD of at least two experiments. Statistical comparisons are to the negative control (**P < 0.01, ***P < 0.001).