The ALMA.16 monoclonal antibody specifically recognizes CD42a. CD42a is a 17-22 kDa type I transmembrane glycoprotein that is also known as Platelet glycoprotein IX (GPIX), or Glycoprotein 9 (GP9). CD42a forms a noncovalently linked complex (GPIb/GPIX/GPV) with CD42b, CD42c and CD42d that may serve as a receptor for von Willebrand factor. It is expressed on platelets and megakaryocytes and is absent on the platelets of patients with Bernadr-Soulier Syndrome (BSS). Although the CD42a function is not fully understood, GPIX glycoprotein is important for the assembly and membrane expression of the CD42 complex and for the maintenance of the functional conformation of CD42b (GPIb).
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.