The release of CXCL8 from THP-1 cells stimulated with wild-type or gingipain mutants of P. gingivalis . THP-1 cells were stimulated with viable ATCC3277 (ATCC), W50, E8, K1A or heat-killed ATCC 33277 (ATCCHK) or W50 (W50HK) at MOI 100 for 24 hours. Values represent the mean ± SD. Statistically significant differences between the groups were determined using one-way ANOVA and Bonferroni post-hoc test. (*p < 0.05; **p < 0.01; ***p < 0.001; n = 4).