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™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.