P. gingivalis suppresses basal level CXCL8 accumulation. Primary dermal fibroblasts (50,000 cells/well) were stimulated with the indicated concentrations of viable or heat-killed P. gingivalis (HK Pg, MOI:1000) for 1 h (A), 6 h (B) and 24 h (C). CXCL8 expression was increased following short-term exposure (1 h), while long-term treatment (>6 h) suppressed CXCL8 accumulation. Heat-killed P. gingivalis treated fibroblasts resulted in elevated CXCL8 expression both after short- and long-term treatment. The asterisks indicate significant differences compared to the untreated negative control (C). *- p < 0.05; **- p < 0.01 (Student’s t-test).