The C7 monoclonal antibody specifically binds to the low-density lipoprotein (LDL) receptor, a type I membrane protein that is encoded by the LDLR gene. LDL is the major cholesterol-carrying lipoprotein in plasma. Cell surface LDLR controls the level of cholesterol in plasma by binding to and internalizing LDL and transporting it to lysosomes where LDL is degraded, cholesterol is released into the cell, and LDLR is recycled back to the cell surface. Hence LDLR is found in cell-surface and intracellular membranes (eg, clathrin-coated pits, golgi, endosomes, and lysosomes). Expression of LDLR is a marker for in vitro differentiation of hepatocytes from human embryonic stem cells. LDLR is suspected to mediate infections by viruses that associate with lipoprotein in the blood. Mutations in LDLR are largely responsible for Familial Hypercholesterolemia (FH). The C7 monoclonal antibody has been reported to react with bovine and human LDLR, but not LDLRs of mouse, rat, Chinese hamster, rabbit or dog.
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.