CD33 is a member of the SIGLEC (Sialic Acid-Binding Ig-Like Lectin) family of receptors, and the gene comprises seven coding exons. Exon 2 encodes the canonical IgV domain, exon 4 encodes the IgC structural domain, and exons 6 and 7 encode cytosolic ITIMs (Immunotyrosine Inhibitory Motifs). CD33 acts as a cell surface antigen which is expressed on normal myeloid cells and CD34+ blasts in AML (Acute Myeloid Leukemia). The antigen serves as a target of GO (Gemtuzumab/Ozogamicin), which exerts anti-leukemic effects in refractory AML.
