NCIt definition : A radioimmunoconjugate comprised of rituximab, a recombinant chimeric monoclonal antibody
directed against the CD20 antigen, and labeled with iodine I 131 with potential antineoplastic
activity. The antibody moiety of iodine I 131 rituximab binds to the CD20 antigen
thereby delivering cytotoxic iodine I 131 specifically to cancer cells expressing
CD20. The CD20 antigen, a hydrophobic transmembrane protein, is expressed on normal
pre-B and mature B lymphocytes.;