The 175128 monoclonal antibody specifically recognizes Axl which is also known as Adhesion related kinase (Ark), Tyro7, or Ufo. Tyro-3, Axl, and Mer constitute the TAM subfamily of receptor tyrosine kinases (RTK). Axl is a single-pass type I transmembrane glycoprotein comprised of an extracellular region with two immunoglobulin (Ig)-like domains and two fibronectin type III (FNIII) domains, a transmembrane segment and a conserved intracellular tyrosine kinase domain. Axl is variably expressed by multiple cell types including monocytes, macrophages, dendritic cells, platelets, endothelial cells, vascular smooth muscle cells, and fibroblasts. Axl binds to the vitamin K-dependent Growth arrest-specific protein 6 (Gas6) through its extracellular Ig-like domains. Ligand binding leads to receptor dimerization, and autophosphorylation of tyrosine residues within the cytoplasmic Axl domains. This results in the activation of downstream signaling pathways that control cellular adhesion, aggregation, phagocytosis/efferocytosis, proliferation, survival, and migration. Through these activities, Axl plays major roles including development, the regulation of hematopoiesis and immunity, and ensuring the integrity of the vascular system. Abnormal expression of Axl has been observed in various cancers and by tumor cell lines.
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.