Indoleamine 2,3-dioxygenase (IDO) Expression in Chronic Periodontitis

Indoleamine 2,3-dioxygenase (IDO) is an intracellular tryptophan-oxidizing enzyme with antimicrobial and immunosuppressive characteristics. The expression of IDO is inducible by several inflammatory cytokines. Its expression and role in the pathogenesis of periodontal diseases has not been explored. Objective: To evaluate the IDO expression within healthy gingiva and periodontitis gingiva. Methods: Twelve human gingival tissue samples were obtained from patients who underwent periodontal treatment. The expression of IDO in frozen tissue sections was detected by immunohistochemistry. Results: IDO expression was observed in all gingival tissue samples. IDO was expressed by gingival epithelial cells, fibroblasts, endothelial cells and inflammatory mononuclear cells. Distinct nuclear staining was detected in epithelial cells. Periodontitis gingiva had higher proportion of cells expressing IDO than that of healthy gingiva. Conclusions: IDO expression is upregulated in chronic periodontitis. Increased expression of IDO may exert an immnosuppressive role in the pathogenesis of periodontitis.