Rituxan is an antibody made from human and mouse protein. It reacts with a certain antigen on lymphoma cells and causes the body's immune system to destroy the lymphoma cells. 90Y Zevalin and 111In Zevalin are murine-based antibodies combined with a radioactive agent that can also destroy lymphoma cells. Unlike Rituxan, 90Y Zevalin cannot be traced by regular scanning and requires indium to determine its distribution through the body.