The B4B6 monoclonal antibody specifically binds to CD172b, which is also known as Signal regulatory protein β (SIRPβ), or SIRP-beta-1 (SIRPB1/SIRPβ1). CD172b is a 50 kDa, type I transmembrane glycoprotein that belongs to the SIRP family within the Ig gene superfamily. CD172b has a transmembrane domain that contains a positively-charged lysine residue. This allows CD172b to interact with a transmembrane signaling adaptor protein, DAP12/KARAP, and transduce stimulatory signals into cells. CD172b is expressed on monocytes, macrophages, dendritic cells, and granulocytes. It is not expressed on CD34+ cells. CD172b/SIRPβ and its counterpart, CD172a/SIRPα, appear to have complementary roles in signal regulation and may work together in tuning cellular responses to certain ligands. This clone has been reported not to cross-react with CD172a.
The antibody was conjugated to BD Horizon™ BUV737 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 737-nm. BD Horizon Brilliant BUV737 can be excited by the ultraviolet laser (355 nm) and detected with a 740/35 filter. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into channels detecting Alexa Fluor® 700-like dyes (eg, 712/20-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 BUV737 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV737 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.