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™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.