B43-PAP Immunotoxin

**Semantic type:** Amino Acid, Peptide, or Protein|Immunologic Factor|Pharmacologic Substance

**Definition:** A mouse-derived anti-human CD19 monoclonal antibody linked to pokeweed (Phytolacca americana) antiviral protein (PAP) with antileukemic activity. The monoclonal antibody portion specifically binds to the CD19 antigen, a cell surface molecule normally expressed only by B lymphocytes and follicular dendritic cells, while over-expressed in B-lineage lymphocytic leukemia cells. Following internalization, PAP, a plant hemitoxin and a ribosome-inactivating protein, is cleaved from the immunoconjugate and released into the cytoplasm where it enzymatically removes a single adenine base from a conserved, surface exposed loop sequence of rRNA leading to inhibition of protein synthesis and cell growth, but not necessarily cell death.

**Synonyms:** - B43 Immunotoxin - B43-PAP - B43-PAP immunotoxin - B43-Pokeweed Antiviral Protein Immunotoxin