The L178 monoclonal antibody specifically binds to CD44 which is also known as Homing-associated cell adhesion molecule (H-CAM) or Phagocytic glycoprotein 1 (Pgp-1). CD44 is a single-pass type I transmembrane glycoprotein that exists in a variety of isoforms also known as variant CD44 (CD44v) or CD44R forms. CD44 is synthesized as a 37 kDa polypeptide that is converted to an 80-95 kDa form by glycosylation via N- and O-linkages, or to a 180-200 kDa form by the addition of chondroitin sulfate. It is expressed on leucocytes, erythrocytes, epithelial cells and weakly on platelets. Depending on the cell type, CD44 may participate in a variety of functions including cell adhesion, motility and cell activation.
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.