The 5B11 monoclonal antibody specifically recognizes mouse CD123, the α chain subunit (IL-3Rα) of the mouse IL-3 receptor. The IL-3Rα chain is a 60-70 kD transmembrane glycoprotein that binds IL-3 with low affinity but cannot transduce signals by itself. The mouse IL-3Rα chain can complex with either of two homologous β chain subunits (βc and βIL-3) to form high-affinity heterodimeric IL-3 receptors. The βc chain is the common β chain subunit that can complex with the α subunits of the mouse IL-3R, IL-5R and GM-CSFR to form high-affinity receptors. The βIL-3 subunit can form high affinity IL-3 receptor complexes with only the IL-3Rα subunit. The βIL-3 subunit clone is specific for mouse IL-3 and binds with low affinity. The immunogen used to generate the 5B11 hybridoma was CTLL cells transfected with the mouse IL-3R alpha chain. The 5B11 antibody does not block the binding of IL-3 protein to the high affinity IL-3 receptor heterodimer.
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.