Anti-CD33 molecule antibodies are directed against the protein encoded by the gene CD33 in humans. The gene may also be known as gp67, SIGLEC3, SIGLEC-3, myeloid cell surface antigen CD33, and CD33 antigen (gp67). Structurally, the protein is reported to be 39.8 kilodaltons in mass. Based on gene name, canine, monkey, mouse and rat orthologs may also be found.