Serum activity of indoleamine 2,3-dioxygenase predicts prognosis of community-acquired pneumonia.

Objectives: Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation in the kynurenine (Kyn) pathway. By depleting Trp, IDO plays a critical role in inducing immune suppression and tolerance. The aim of present study was to investigate serum IDO activity, determined by Kyn-to-Trp ratio (Kyn/Trp ratio), in community-acquired pneumonia (CAP) and to examine its clinical significance.

Increased serum kynurenine/tryptophan ratio correlates with disease progression in lung cancer.

Background: Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation along the kynurenine (Kyn) pathway. By depleting tryptophan, IDO is considered to be a fundamental immune escape mechanism for tumor cells. However, IDO expression in lung cancer has not been explored thoroughly.