The A59 monoclonal antibody specifically recognizes CD89. CD89 is the Fc receptor for IgA (FcαR), a 55-75 kDa glycoprotein expressed exclusively on cells of granulocytic and monocyte/macrophage lineages in peripheral blood, but not on lymphocytes. It is also expressed on promyelocytes in bone marrow and in the cytoplasm of fixed monocytes. This mAb does not block IgA binding and is more efficient than native IgA ligands in the isolation of FcαR molecules. FcαR plays a role in triggering phagocytosis and respiratory burst.
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.