Long-term immunosuppression carries potential adverse effects such as risk of infection, malignancy, renal insufficiency, diabetes and hypertension. In clinical liver transplantation, some liver transplant recipients maintain allograft function without immunosuppressive drugs. This is called as "operational tolerance". Many attempts have been made to identify immunological biomarkers predicting operational tolerant patients. Therefore, the investigators aimed to identify patients who have the potential to be operationally tolerant using biomarkers, withdraw immunosuppressant gradually and stop ultimately with monitoring of biomarkers.

Among long term stable liver transplant recipients, we will select some proportion of patients who have the high potential for obtaining operational tolerance using biomarkers.

Then, we will gradually reduce immunosuppressants and monitor biomarkers as well as biochemical tests. The course of tapering off immunosuppressant will take about 1 year.

During withdrawal of immunosuppression, participants will be closely monitored for liver enzyme, immunological profile.

If there are some signs of rejection, liver biopsy will be undertaken and participants will be treated using immunosuppressant.

After complete withdrawal of immunosuppressant, participants will be followed for at least of 1 year.

Inclusion Criteria:

• long term stable liver transplant recipients

Exclusion Criteria:

• liver transplant due to autoimmune disease
• liver transplant due to hepatitis C virus (HCV)
• history of graft rejection
• history of biliary infection or stricture