Indoleamine 2,3-dioxygenase expression is associated with chronic rhinosinusitis: review of the evidence.

PURPOSE OF REVIEW: Indoleamine 2,3 dioxygenase (IDO), the key metabolic enzyme implicated in tryptophan catabolism has been studied extensively during the past years in cancer, infections and autoimmunity. This review summarizes the findings of the immunomodulatory effects of IDO. In addition, the possible role of IDO in chronic rhinosinusitis (CRS) is discussed.

RECENT FINDINGS: Epithelial and leukocyte IDO expression is pronounced in CRS with nasal polyps and antrochoanal polyps. Although IDO associates with atopic disorders of the lower respiratory tract, we were not able to find an association between IDO and allergic rhinitis in the sinonasal mucosa.

SUMMARY: IDO might have a distinct role in the upper and lower respiratory tract. Future studies need to identify whether the IDO found in sinonasal mucosa is active and if it is a cause or a reason in the development of CRS with nasal polyps.