Compared with normal conditions, the exosomes of periodontal ligament stem cells isolated from Porphyromonas gingivalis lipopolysaccharide (LPS) induced periodontitis environment transfer less miR-155-5p and increased Sirtuin-1 (SIRT1) protein into CD4+ T cells, and then led to the up-regulation of Th17 and the relaxation of Tregs, thus exacerbating the inflammatory microenvironment of periodontitis (76). The gene discussed is CD4; the disease is periodontitis.