NCIt synonyms : Anti B4-BR; Anti-B4-bR; Anti-B4 Blocked Ricin; Anti B4bR; Monoclonal Antibody Anti-B4 Blocked Ricin;
NCIt definition : An immunotoxin comprised of an anti-B4 (anti-CD19) murine monoclonal antibody linked
to the modified plant-derived toxin blocked ricin. The antibody moiety of anti-B4
blocked ricin immunotoxin binds to B lymphocytes that express B4; after internalization
of the immunotoxin by the B4-expressing B cell, the ricin moiety cleaves the N-glycosidic
bond between the ribose and adenine base at position 4324 in the B lymphocyte 28S
ribosomal RNA, resulting in ribosome inactivation, inhibition of protein synthesis,
and cell death. Blocked ricin is ricin which has been chemically modified such that
the lectin binding sites of the B chain (galactose-binding sites) have been blocked
by covalent attachment of affinity ligands, leaving the ribosome-inactivating activity
of the ricin A chain intact.;