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™ BUV661 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 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.