In vitro experiments further confirmed that periodontitis gingival fibroblasts secreted higher levels of C3 protein at 30 ng/ml compared to healthy fibroblasts at about 20 ng/ml (Figure 5F), and Pg-LPS stimulation could enhance C3 secretion by gingival fibroblasts from baseline at 10 to about 20 ng/ml (Figure 5G). This evidence concerns the gene C3 and periodontitis.