The immunopathogenic and immunomodulatory effects of interleukin‐12 in periodontal disease

Interleukin 12 (IL‐12) is an inflammatory cytokine that promotes the response of the immune system. This cytokine has been implicated as a potent stimulator of several diseases characterized by inflammatory‐induced bone destruction, such as rheumatoid arthritis and periodontitis. Yet, the exact role of IL‐12 in the development and progress of periodontitis has not been clarified. Several studies have demonstrated a positive correlation between the level of IL‐12 and the severity of periodontal destruction. Deletion of IL‐12 in mice with periodontitis significantly suppressed the level of bone destruction. Interestingly, next to a role in modulating the pathogenesis, IL‐12 also has immunological‐regulatory properties. This cytokine induces expression of immunosuppressive molecules, such as indoleamine‐pyrrole 2,3‐dioxygenase (IDO). Thus, these findings suggest both negative and positive influences of IL‐12 in periodontal disease. It is currently proposed that the diversity of action of cytokines is a molecular key which regulates biological development and homeostasis. Accordingly, the actions of IL‐12 might be one of the mechanisms that regulate homeostasis of periodontal tissue during and following inflammation. Therefore, this article aims to review both destructive and protective functionalities of IL‐12 with an emphasis on periodontal disease.