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™ BB515 which is part of the BD Horizon Brilliant™ Blue family of dyes. With an Ex Max near 490 nm and an Em Max near 515 nm, BD Horizon™ BB515 can be excited by the blue laser (488 nm) laser and detected with a 530/30 nm filter. This dye has been exclusively developed by BD Biosciences and is up to seven times brighter than FITC with less spillover into the PE channel. Due to similar excitation and emission properties, BB515, FITC, and Alexa Fluor™ 488 cannot be used simultaneously. It is not recommended to use BB515 in cocktails that include Streptavidin conjugates as it may cause high background.