The TU66 monoclonal antibody specifically recognizes human CD39 which is also known as Ectonucleoside triphosphate diphosphohydrolase 1 (NTPDase 1), Ecto-ATP diphosphohydrolase 1 (Ecto-ATPDase 1), or Ecto-apyrase. CD39 is an integral membrane glycoprotein with two transmembrane domains, N- and C-terminal cytoplasmic tails, and an extracellular region that contains the NTPDase 1 active site. CD39 is encoded by ENTPD1 which belongs to the ectoenzyme family. CD39 is variably expressed on activated T cells and B cells, regulatory T cells (Treg), dendritic cells, Langerhans cells, NK cells, monocytes, macrophages, endothelial cells, and granulocytes. CD39 acts on extracellular nucleoside triphosphates and diphosphates including ATP and ADP that are hydrolyzed into AMP. Through cell surface CD73 (Ecto-5'-nucleotidase), regulatory T cells can act on extracellular AMP to generate immunosuppressive adenosine. CD39 is involved in the control of the extracellular pool of phosphorylated nucleosides, the suppression of inflammation and immunity, and the regulation of platelet 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.