Biological therapy stimulates the body’s immune system to help kill cancer cells. Rituxan, which depletes certain B cells, is used for patients with non-Hodgkin’s lymphoma as well as rheumatoid arthritis. It is one of the early successful biological agents, a monoclonal antibody, approved by the FDA. A newer monoclonal antibody, Avastin, recognizes and blocks creation of new blood vessels that might feed tumors, thus depriving them of nutrition. Other biological agents include interferon, interleukin, colony stimulating factors and vaccines.