The 165903 monoclonal antibody specifically recognizes UL16-binding protein 2, 5, and 6 (ULBP-2/5/6). UL16 is a human cytomegalovirus (HCMV) glycoprotein that can bind to human ULBP proteins which share homology with MHC class I proteins. ULBP-2 is also known as RAET1H (retinoic acid early transcript), NKG2DL2 (NKG2D ligand 2), and ALCAN-alpha. ULBP-5 is likewise known as RAET1G whereas ULBP-6 is also referred to as RAET1L. The ULBP-2/5/6 proteins possess only the alpha 1 and alpha 2 Ig-like domains and have no capacity to bind peptides or interact with beta 2 microglobulin. All three proteins can be expressed on the cell surface as glycophosphatidylinositol (GPI)-linked forms whereas ULBP2 and ULBP5 also exist as transmembrane-anchored forms. These proteins may be expressed on various cells types during development or cells experiencing stress caused by high proliferative activity, infection, transformation, or exposure to mediators in inflammatory or autoimmune diseases. The ULBP-2/5/6 proteins can bind to NKG2D and thereby transduce activating signals into NK cells and costimulatory signals into activated CD8+ T cells resulting in enhanced cell-mediated cytotoxicity or cytokine production. The expression of ULBP-2/5/6 proteins on infected or tumor cells can play an important role in immune surveillance and homeostasis.
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.