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™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.