18 reported that reduced SLPI levels were found in inflamed gingival tissue and gingival crevicular fluid (GCF) of chronic periodontitis patients infected with P. gingivalis. The authors17–19 suggested that the degradation of SLPI by P. gingivalis gingipains might be responsible for reduced SLPI levels, decreased host protective capacity and periodontal tissue destruction in chronic periodontitis patients. This evidence concerns the gene SLPI and periodontitis.