The monoclonal antibody specifically recognizes CD33, a human myelomonocytic antigen which is also known as Sialic acid-binding Ig-like lectin 3 (Siglec-3 or SIGLEC3). CD33 is a 67 kDa type I transmembrane glycoprotein that belongs to the Ig supergene family. The CD33 antigen is present on monocytes (bright) and granulocytes (dim). Granulocytes can be further subdivided into neutrophil, eosinophil, and basophil populations based on CD33 staining in combination with other cell-surface antigens. The CD33 antigen is also found on CFU-Mix, CFU-GM, CFU-Meg, a portion of BFU-E, myeloblasts, promyelocytes, myelocytes, and metamyelocytes, but not on earlier precursors. The CD33 antigen is expressed on blast cells in greater than 85% of acute myeloid leukemias (AML), and it can be aberrantly expressed in acute lymphoblastic leukemias (ALL). Normal lymphocytes, platelets, and erythrocytes do not express the CD33 antigen. CD33 can reportedly function as a sialic acid-dependent cell adhesion molecule and this function can be modulated by endogenous sialoglycoconjugates when CD33 is expressed on the membrane.
The antibody was conjugated to BD Horizon Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.