Daclizumab is a humanized monoclonal antibody to CD25, the alpha subunit of the IL2 receptor on T lymphocytes, which was used in the past to treat and prevent acute cellular rejection after solid organ transplantation and is currently approved as a second line therapy of refactory relapsing multiple sclerosis. Daclizumab has been linked to occasional mild-to-moderate serum enzyme elevations during therapy, and to rare but potentially severe and fatal instances of immune mediated, clinically apparent liver injury.