The 9A1.5 monoclonal antibody specifically binds to an extracellular domain of Delta-Like Protein 4 that is encoded by the Dll4 gene. Delta-Like Protein 4 is a type 1 transmembrane glycoprotein that is also known as Delta-like 4, Delta-like Ligand 4, Delta4 and DL4. It is a member of the Delta/Serrate/Jagged Family of Notch ligands. Notch ligands are classified by the presence of specific structural motifs including an N-terminal Delta-Serrate-LAG-2 (DSL) domain necessary for Notch binding, EGF repeats, and the DOS domain (a specialized EGF repeat). The Notch family of transmembrane receptors and their ligands control cell-fate "decisions" during the development of many organs in a wide variety of animal species. Delta-Like Protein 4 activates cellular signaling pathways by binding to Notch1 and Notch4 receptors. It is involved in embryonic vascular development and tumor angiogenesis, and is induced by vascular endothelial growth factor (VEGF)-A and hypoxia. Delta-Like Protein 4 and Notch receptor signaling are also intimately involved in the regulation of innate and adaptive immunity. Delta-Like Protein 4 is highly expressed by cortical thymic epithelial cells (TEC). Interaction between Delta-Like Protein 4-positive TEC and Notch1 expressed by T cell precursors drives T cell lineage commitment, expansion and maturation within the thymus. Delta-Like Protein 4 is also expressed by dendritic cells and plays a role in peripheral T helper cell differentiation. Blocking of Delta-Like Protein 4 and Notch receptor interactions serves to diminish autoimmune diseases in mouse model systems.
The antibody was conjugated to BD Horizon™ BUV496 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.