Immunosuppressive effect of IDO on T cells in patients with chronic hepatitis B *

Aim:  Recently indoleamine 2,3‐dioxygenase (IDO) has drawn considerable attention as a mechanism of immune regulation. Our study was to observe the role of IDO in immune tolerance of chronic hepatitis B (CHB), so as to provide a novel approach for reestablishment of active immunity. Methods:  Peripheral venous blood samples were taken from 50 CHB patients and HBV viral load, T lymphocyte subsets as well as the mRNA, protein and activity of IDO were detected. The correlations between HBV viral load, T lymphocyte subsets and IDO were statistically analyzed. Blood samples from 50 healthy people were tested as a control group. Results:  In CHB patients, the mRNA, protein and activity of IDO were all significantly more than those in control group (mRNA:[2.11 ± 0.615] × 10 3 vs. [0.143 ± 0.026] × 10 3 ; protein: 0.22 ± 0.06 vs. 0.02 ± 0.0017; activity: 26.07 ± 8.12 vs. 4.98 ± 1.65; P  < 0.05) and IDO mRNA was positively correlated with HBV viral load ( r  = 0.502, P  < 0.001) and alanine aminotransferase (ALT) ( r  = 0.65, P  < 0.01). Furthermore, IDO mRNA, protein and activity were negatively correlated with CD4(+) T cells ( r  = −0.622, −0.682, −0.549 respectively, P  < 0.05), CD8 (+) T cells ( r  = −0.487, −367, −294 respectively, P  < 0.05) and the ratio of CD4/CD8 ( r  = −0.426, −0.533, −0.397 respectively, P  < 0.05). Conclusion:  IDO closely correlates with HBV viral load and is responsible for immunotolerance against HBV. Suppression of IDO could be a novel approach to break tolerance in CHB.