The U23-56 monoclonal antibody specifically binds to Macrophage scavenger receptor 1 (MSR1) which is also known as CD204, Scavenger receptor A (SRA), Scavenger receptor class A member 1 (SCARA1), or Macrophage acetylated LDL receptor I and II. MSR1 is a trimeric type II transmembrane glycoprotein that belongs to the type 1 class A scavenger receptor family. MSR1 functions as a scavenger receptor that enables mononuclear phagocytes to take up and respond to a variety of negatively charged macromolecules including oxidized and acetylated low density lipoproteins. MSR1 also functions in innate immunity as a pattern recognition receptor. MSR1 allows macrophages to recognize and respond to microbial products, such as lipopolysaccharide and polyribonucleic acids, by the production of cytokines and inflammatory mediators. MSR1 also reportedly serves as a coreceptor that regulates the signaling of some Toll-like receptors including TLR-3, TLR-4, and TLR-9. MSR1 has been associated with several diseases including atherosclerosis, Alzheimer's disease, ischemic injury, and sepsis. The U23-56 antibody was tested by flow cytometric and Western blot analyses of MSR1-transfected and untransfected cells to verify its specificity.
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.