The 1A5 monoclonal antibody specifically recognizes Sialic acid binding Ig-like lectin 5 (Siglec-5) which is also known as CD170, CD33 antigen-like 2 (CD33L2) and Obesity binding protein-2 (OBBP2). CD170 is a type I transmembrane glycoprotein that forms a ~140 kDa dimer on the cell surface. CD170 is encoded by SIGLEC5 which belongs to the SIGLEC (sialic acid binding Ig-like lectin) family within the immunoglobulin superfamily. The extracellular region of CD170 consists of an N-terminal V-set Ig-like domain, which contains the sialic acid binding site, followed by 3 C2-set Ig like domains, a transmembrane region and a cytoplasmic tail containing 2 immunoreceptor tyrosine-based inhibitory motifs (ITIMs) which regulate cellular signaling. CD170 bind to alpha-2,3- and alpha-2,6-linked sialic acid glycoproteins and glycolipids and to glycophorin A. It is highly expressed on neutrophils and expressed at lower levels on monocytes, macrophages, dendritic cells, and some lymphocytes. CD170 is an adhesion molecule that may function in regulating cellular activation and in sialic-acid dependent binding to cells.
The antibody was conjugated to BD Horizon™ BV650 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 650-nm. BD Horizon BV650 can be excited by the violet laser and detected in a filter used to detect APC-like dyes (eg, 660/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there will be spillover into the APC and Alexa Fluor® 700 detectors. However, the spillover can be corrected through compensation as with any other dye combination.