The 9-4D2-1E4 monoclonal antibody specifically binds to CD115 which is also known as Colony stimulating factor 1 receptor (CSF-1R) or Macrophage colony-stimulating factor 1 receptor (M-CSFR). This type I transmembrane glycoprotein is a receptor tyrosine kinase (RTK) that belongs to the Ig superfamily. It is expressed on a variety of cells including those committed to the mononuclear phagocyte lineage, such as, monocytes, macrophages, and osteoclasts. CSF-1 binds to and signals through CSF-1R homodimers which undergo tyrosine autophosphorylation and transduce downstream signaling pathways resulting in cytoskeletal reorganization and gene expression. CSF-1R activation stimulates the proliferation, differentiation, and survival of cells within the mononuclear phagocyte system. Acting through CD115, CSF-1 induces macrophage spreading and motility, and in combination with RANKL, CSF-1 drives the differentiation of mononuclear phagocytes to become osteoclasts. Interleukin-34 (IL-34) is another ligand for CD115 that can induce similar, as well as, some different biological responses by CD115-positive target cells.
The antibody was conjugated to BD Horizon™ BUV737 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 737-nm. BD Horizon Brilliant BUV737 can be excited by the ultraviolet laser (355 nm) and detected with a 740/35 filter. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into channels detecting Alexa Fluor® 700-like dyes (eg, 712/20-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 BUV737 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV737 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.