The E3 monoclonal antibody specifically recognizes CD307a which is also known as Fc receptor-like protein 1 (FCRL1), Fc receptor homolog 1 (FCRH1), or Immune receptor translocation-associated protein 5 (IRTA5). CD307a (FCRL1) is a type I transmembrane glycoprotein that belongs to the IRTA gene family within the Ig gene superfamily. It has three extracellular Ig-like domains, a glutamic acid residue in its transmembrane region, and two consensus immunoreceptor tyrosine-based activation motifs (ITAMs) in its cytoplasmic domain. CD307a (FCRL1) bears sequence homology to classical Fc receptors. CD307a (FCRL1) is first expressed on pre-B cells and increases with maturation being expressed on naïve and memory B cells. It is downregulated by activated germinal center (GC) B cells. It may also be expressed by B cell-derived leukemia and lymphoma cells. CD307a may play key roles in B cell activation, differentiation and effector functions.
The antibody was conjugated to BD Horizon™ BUV496 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 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.