Figure 6.

Phagocytosis assay. Polymorphonuclear neutrophil (PMN) phagocytosis of the clinically separated P. gingivalis strain M5-1-2, after preincubation with complement-inactivated serum, pretreated, and not pretreated with gingipain K. The periodontitis patient serum used contained high titers of opsonizing antibodies against the bacterium. PMNs were mixed with bacteria at a 1:20 ratio for the indicated times, and remaining bacteria in the supernatants were counted. Bacteria mixed with gingipain K-treated serum (solid bars) resulted in a lower degree of phagocytosis by PMNs after 5 min as compared to the control (open bars).