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™ 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.