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 BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).