The 515 monoclonal antibody specifically binds to CD44. CD44 is an 80-95 kDa type I transmembrane glycoprotein, also known as Phagocytic glycoprotein-1 (Pgp-1), or Extracellular matrix receptor type III (ECMR-III). CD44 is a member of the hyaladherin family of hyaluronan-binding proteins, with structural similarities to selectins. CD44 is the receptor for hyaluronic acid. CD44 is expressed on leucocytes, erythrocytes, epithelial cells and weakly on platelets. CD44 has functional roles in cell migration, lymphocyte homing and adhesion during hematopoiesis and lymphocyte activation. The 515 monoclonal antibody can reportedly block cellular adhesion to hyaluronic acid.
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.