The W5C5 monoclonal antibody specifically reacts with SUSD2 (sushi domain containing 2), which is expressed on mesenchymal stem cells (MSC) and on some cancers and neoplastic cell lines. It is not detected on hematopoietic cells of the peripheral blood and bone marrow. SUSD2 is a type I transmembrane protein that may interact with galectin-1 and the potential cytokine C10orf99, through which it may affect cell growth and immune responsiveness. It has a large extracellular region that contains a sushi domain (a conserved sequence that is often associated with proteins of the complement system). SUSD2 is a marker that is useful for identifying and isolating MSC from bone marrow and endometrial tissue, and those MSC may be induced to differentiate into a wide variety of cell types. Varying levels of SUSD2 expression may correlate with either suppression or enhancement of the growth of different types of neoplastic cells, presumably via a variety of direct and indirect mechanisms.
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.