ACP5 and periodontitis: The synthetic (+)-terrein-treated periodontitis mice showed reduced neutrophil infiltration compared to that in the PBS-treated periodontitis mice (Figure 5a); TRAP staining showed no osteoclasts in both the PBS-treated and synthetic (+)-terrein-treated control mice (Figure 5a,b), and the PBS-treated periodontitis mice showed a significant increase in the number of osteoclasts compared to that in the PBS-treated and synthetic (+)-terrein-treated control mice (both p < 0.001, Figure 5a,b).