The 6H6 monoclonal antibody specifically recognizes the Interleukin-3 receptor alpha chain (IL-3Ra) which is also known as CD123. IL-3Ra (CD123) is a ~70 kDa type I transmembrane glycoprotein that is encoded by IL3RA (interleukin 3 receptor subunit alpha) which belongs to the type I cytokine receptor family within the immunoglobulin gene superfamily. This receptor chain consists of an extracellular region that contains an immunoglobulin-like N-terminal domain (NTD) with a fibronectin type III (FnIII) fold followed by two more FnIII domains that form the cytokine receptor module (CRM), a transmembrane region, and an intracellular tail. IL-3Ra (CD123) binds IL-3 specifically and with low affinity. IL-3Ra (CD123) forms a high-affinity signaling receptor for IL-3 (IL-3R) with the ß common chain (ßc; also known as, CD131) that is shared with the heterodimeric IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors. IL-3Ra (CD123) is variably expressed on certain hematopoietic progenitor cells, basophils, eosinophils, mast cells, monocytes, macrophages, dendritic cells, megakaryocytes, and on some B cells, endothelial cells, and leukemia cells. Bound IL-3 can signal through IL-3R to promote the activation, proliferation, differentiation, and viability of these cells. Amongst monoclonal antibodies specific for human IL-3Ra (CD123), the 6H6 and 9F5 antibodies do not block IL-3 binding to the IL-3R whereas the 7G3 antibody does block IL-3 binding to its receptor in a dose-dependent manner.
The antibody was conjugated to BD Horizon BV750 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 750-nm. BD Horizon Brilliant BV750 can be excited by the violet laser (405 nm) and detected with a 750/30 nm filter with a 740 nm long pass. Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BV750 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended.