Macrophage cytokine response to P. gulae. RAW 264.7 macrophages were incubated with no bacteria (▩), P. gulae ATCC 51700 (□), P. gingivalis ATCC 33277 (), or P. gingivalis W50 (■) for 90 min before the cells were centrifuged and the bacterium-containing supernatant was removed. The cytokine responses were measured after 24 h of incubation. Data are expressed as pg/ml. Means ± the SEM are shown (*, P < 0.05; **, P < 0.005; ***, P < 0.0005; ****, P < 0.00005 [P. gulae and P. gingivalis ATCC 33277 versus P. gingivalis; n = 3]).