Additional Study Information: The purpose of this study is to evaluate the safety of siplizumab when used as induction immunosuppression in patients with primary sclerosing cholangitis or autoimmune hepatitis undergoing liver transplantation. Induction immunosuppression drugs are very potent anti-rejection drugs that are given immediately after transplantation to prevent rejection. Siplizumab is investigational, meaning it has not yet been approved for market use for this disease condition by the United States Food and Drug Administration (FDA). Participants will receive two doses of siplizumab: on the day of transplant and on post-transplant day 4. The duration of participation is one year post-transplant. If you have any questions regarding this study, please contact the Transplant Clinical Research Center (TCRC).