Muromonab-CD3 is a mouse monoclonal antibody to CD3, often referred to as OKT3, which was withdrawn from use in 2010 but was previously used to treat acute cellular rejection after solid organ transplantation. Muromonab has been linked to mild and transient serum enzyme elevations during therapy, but has not been linked to cases of clinically apparent liver injury. Muromonab is a potent immunosuppressive agent and might result in reactivation of hepatitis B in susceptible patients.