The U21-1283 monoclonal antibody specifically recognizes Neuropilin-1 (NRP1), also known as CD304, Blood dendritic cell antigen 4 (BDCA4), and Vascular endothelial cell growth factor 165 receptor (VEGF165R). CD304 is a type I transmembrane glycoprotein involved in the development of the nervous and cardiovascular systems. It mediates the interaction, growth, survival, and migration of a variety of normal and tumor cells. CD304 is expressed on neurons, thymocytes, regulatory T cells, a subset of T follicular helper cells, dendritic cells, endothelial cells, and certain tumor cells. Neuropilin-1 has a very short cytoplasmic domain and interacts with various coreceptors to form ligand-binding, signal-transducing receptor complexes. CD304 complexes with Plexin-A family members to bind chemorepellent Class 3 Semaphorins and guide neuronal axon growth. It also functions as a coreceptor with VEGFR2/CD309 to stimulate angiogenesis in response to VEGF165. CD304 mediates the interactions between some T cells and dendritic cells.
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.