Indoleamine 2,3-Dioxygenase 1 as an Adjunctive Histopathological Marker of Cholangitis Activity in Primary Biliary Cholangitis.

IDO-1 was expressed in 64 of 83 cases (77.1%).

IDO-1 positivity was significantly reduced in ursodeoxycholic acid-treated patients (50.0%) compared with untreated patients (95.9%, p < 0.0001).

In the ursodeoxycholic acid subgroup, unlike other histological features, IDO-1 expression remained significantly associated with higher cholangitis activity scores.