CD21 is a 145 kDa transmembrane glycoprotein that is expressed on mature B cells, follicular dendritic cells, a subset of immature thymocytes and on some epithelial cells. CD21 is also known as the C3d Receptor, Complement Receptor 2 (CR2), and the Epstein-Barr Virus receptor, (EBV-R). CD21 is part of a large signal-transduction complex that also includes CD19, CD81 and Leu13. CR2 serves as a receptor for the activation fragments of complement component C3, i.e. C3d, iC3d, and C3dg and C3d-bound antigens and plays a central role in the immune response by amplifying B-cell activation and proliferation. CR2 is also the receptor for EBV by binding its surface glycoprotein gp350/220. Anti-human CR2 hybridomas were generated from Cr2-/-mice (lacking the cr2 gene, that encodes CR2 and CR1 in mice) immunized with the recombinant protein representing the first two amino-terminal short consensus repeats (SRC) of human CR2, SCR1-2. Both the C3d and EBV binding sites of hu CR2 were localized to these sites. Clone 1048 has been reported to specifically react with CR2-expressing cells and to inhibit CR2 interactions with C3 fragments or the EBV surface protein, gp350/220.
The antibody was conjugated to BD Horizon™ BV786 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 786-nm. BD Horizon BV786 can be excited by the violet laser and detected in a filter used to detect Cy™7-like dyes (eg, 780/60-nm filter).