expatiated that cathepsin S has a binding site for transcription factor interferon regulatory factor 1 (IRF1), and the association of IRF1 with IRF8 may promote the expression of cathepsin S. IRF8 has been demonstrated to be a regulator of osteoclast production in bone metabolism indicating that the interaction between cathepsin S and IRF8 might involve in periodontitis-associated bone loss (94). Here, IRF1 is linked to periodontitis.