The 17C9 monoclonal antibody specifically recognizes Complement receptor of the immunoglobulin superfamily (CRIg) which is encoded by the Vsig4 (V-set and immunoglobulin domain containing 4) gene. CRIg is a ~45 kDa single-pass type I transmembrane glycoprotein that contains a variable (V-type) immunoglobulin domain in its extracellular region which is required for binding complement components and promoting phagocytosis. CRIg is expressed on Kupffer cells and tissue resident macrophages, including a subset of resident peritoneal macrophages. CRIg binds complement fragments C3b and iC3b and plays important roles in innate and adaptive immunity. This complement receptor is involved in regulation of the complement cascade and serves as a phagocytic receptor in the clearance of pathogens, immune complexes, and apoptotic cells. CRIg-positive macrophages can reportedly function in the negative regulation of T-cell proliferation and IL-2 production.
The antibody was conjugated to BD Horizon BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).