The H5 monoclonal antibody specifically binds to CD307c which is also known as Fc receptor-like 3 (FCRL3), Immune receptor translocation-associated protein 3 (IRTA3), IFGP family protein 3 (IFGP3), and SH2 domain-containing phosphatase anchor protein 2 (SPAP2). The FCRL3 gene is present in humans but not in mice. CD307c is a type I transmembrane glycoprotein that belongs to the FCRL family within the Ig gene superfamily. CD307c shares sequence homology with classical the Fc receptors. CD307c is expressed on subsets of B cells, plasma cells, NK cells, CD8+ T cells, and CD4+ natural T regulatory cells. CD307c isoforms contain multiple extracellular Ig domains and immunoreceptor-tyrosine activation (ITAM) and inhibitory (ITIM) motifs in their intracellular domains. CD307c may be involved in the regulation of immune responses. Genetic variation in FCRL3 has been associated with susceptibility to certain autoimmune diseases.
The antibody was conjugated to BD Horizon™ BUV661 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 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.