The C65-485 monoclonal antibody specifically recognizes the type II membrane protein known as 4-1BB Ligand (4-1BB-L) or CD137 Ligand (CD137L). This molecule belongs to the TNF superfamily and is encoded by TNFSF9 (Tumor necrosis factor superfamily member 9). CD137 Ligand has been reported to have costimulatory function on activated T cells. Reports suggest that stimulation of activated T cells via CD137 Ligand does not require the presence of other costimulatory molecules, including CD28. Some studies have reported human CD137 Ligand to be expressed preferentially on primary B cells and B-cell lines. The C65-485 antibody is able to react with recombinant human 4-1BB Ligand (rh4-1BB-L/CD137L) bound to CD137 (4-1BB receptor) expressed on phytohemagglutinin (PHA)-stimulated PBMC.
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.