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™ BUV496 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 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.