The AFS98 monoclonal antibody specifically recognizes CD115 which is also known as Colony stimulating factor 1 Receptor (CSF-1R), Macrophage colony-stimulating factor 1 receptor (M-CSFR), or c-fms. This type I transmembrane glycoprotein is a receptor tyrosine kinase (RTK) that is encoded by Csf1r which belongs to the Ig superfamily. CD115 (CSF-1R) is comprised of an extracellular ligand-binding domain that is followed by a single transmembrane segment and a split intracellular tyrosine kinase domain. This receptor is expressed on monocytes, macrophages, dendritic cells, osteoclasts, and their precursors. Colony-stimulating factor 1 (CSF-1), also known as Macrophage colony-stimulating factor (M-CSF), binds to and signals through CD115 (CSF-1R) homodimers which undergo tyrosine autophosphorylation. The activated receptors transduce intracellular signals resulting in cytoskeletal reorganization and gene expression involved in the proliferation, differentiation, and survival of CSF-1-responding cells. Through CD115 (CSF-1R), CSF-1 regulates the release of proinflammatory cytokines and other mediators from macrophages and plays a role in the bone resorption activity of osteoclasts. Interleukin-34 (IL-34) is another ligand for CD115 (CSF-1R) that can induce similar, as well as, some different biological responses by target cells that express this receptor.
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.