The A1/CD307d monoclonal antibody specifically recognizes CD307d which is also known as Fc receptor-like protein 4 (FCRL4), Fc receptor homolog 4 (FCRH4), or Immune receptor translocation-associated protein 1 (IRTA1). CD307d (FCRL4) is a type I transmembrane glycoprotein that belongs to the IRTA gene family within the Ig gene superfamily. It has four extracellular Ig-like domains, a helical transmembrane region, and two consensus immunoreceptor tyrosine-based inhibition motifs (ITIMs) and one immunoreceptor tyrosine-based switch motif (ITSM) in its cytoplasmic domain. CD307d (FCRL4) binds to aggregated IgA and IgG, and its highest level of expression is on memory B cells in mucosa-associated lymphoid tissues (MALT). Chromosomal abnormalities in the region of the FCRL4 gene are associated with non-Hodgkin lymphoma and multiple myeloma, and CD307d (FCRL4) may play a role in HIV-induced memory B cell dysfunction.
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.