The A2MR-α2 monoclonal antibody specifically reacts with a 600 kDa, type I membrane single protein, also known as the α2 Macroglobulin (α2M) receptor/low density lipoprotein receptor-related protein 1 (LRP-1). Reported to be an endocytic receptor involved with intracellular signalling, lipid homeostasis, clearance of apoptotic cells, and α2 Macroglobulin mediated clearance of secreted amyloid precursor protein found in Alzheimer patients. The single chain receptor undergoes cleavage, shortly after synthesis, into the 85 kDa transmembrane β chain that non-covalently binds to the extracellular 500-515 kDa a chain. It has a broad cellular distribution, but in the hematopoietic system it is expressed on monocyte lineage cells. α2M/LRP-1 mediates endocytosis of a variety of ligands including α2M-proteinase complexes, plasminogen activators in complex with plasminogen activator inhibitor, or Pseudomonas Exotoxin A. Ligand binding to α2M/LRP-1 is followed by rapid transport of the ligand to lysosomes for degradation.
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.