On the other hand, the scant IDO-peripheral cells frequency in inactive IBD patients is consistent with the findings of our group in rheumatoid arthritis and systemic lupus erythematosus patients and in human primary biliary cirrhosis [27, 41], and it might be related to the recruitment of blood derived-DC at the tissue in order to induce tolerance [42]. Here, IDO1 is linked to primary biliary cholangitis.