Objective To evaluate the release of matrix metalloproteinase -8（MMP-8） and apoptosis rate of polymorphonuclear leukocytes（PMNs） after PMNs was triggered by Enterococcus faecalis（E.faecalis） in vitro. Methods The activated E.faecalis suspension was prepared and added to PMNs suspension as experiment group. As a positive control, phorbol myristate acetate（PMA） was used. As negative control, PMNs suspension was incubated with PBS. The release of MMP-8 was measured at 0, 20, 60, 120 min by ELISA method. E.faecalis lysate acted on PMNs as experiment group, PMNs suspension was incubated with PBS as negative control, samples in two groups were incubated at 37 ℃ for 2, 5, 10, 15 h. The apoptosis rate of PMNs was tested by Flow Cytometry. Results At 0 min, there was no significant difference of MMP-8 release in the experiment group and positive control（P＞0.01）；whereas at 60, 120 min, E.faecalis induced a significant lower MMP -8 release compared with the positive control（P ＜0.01）. The apoptosis rate of PMNs in both groups increased along with time, and apoptotic rate in experiment group was higher than that in the control group at 2, 5, 10, 15 h（P
