Aim: To investigate the effect of the collagenase gene (prtC) product of Porphyromonas gingivalis on inducing host cells to secrete inflammatory cytokines, and to discuss the correlation between the PrtC level in subgingival plaque samples and clinical parameters. Methods: A prokaryotic expression sys-tem pET32a-prtC-Escheria coli BL21DE3 was constructed. Antigenicity and im-munoreactivity of the recombinant PrtC protein (rPrtC) was identified by Weste blotting. ELISA was applied to detect interleukin (IL)-1α, IL-8, and TNF-α levels in supeatants from rPrtC-induced human umbilical vein endothelial cells (HUVEC) originated ECV304 cells. Clinical parameters recorded at baseline and after treat-ment included bleeding on probing (BOP), probing depth (PD), and attachment loss (AL). ELISA was established to measure the PrtC level in 196 subgingival plaque samples from 49 patients with chronic periodontitis. Results: After co-incubation with 1 μg/Ml rPrtC for 24 h and with 5 or 10 μg/Ml rPrtC for 12 h, the levels of IL-1α, IL-8, and TNF-α secreted by the ECV304 cells increased signifi-candy (P6 mm PD sites was higher than that in the BOP-negative or the ≤2 mm AL or ≤6 mm PD sites (P0.05). Conclusion: rPrtC is able to directly induce host cells to synthe-size and secrete IL-1α, IL-8, and TNF-α. The PrtC level in subgingival samples is correlated with BOP, AL, and PD.