The GIR-208 antibody recognizes the extracellular region of CD119 which is also known as the alpha chain subunit (80-95 kDa glycoprotein) of the human interferon-γ receptor (IFN-γRα). The functionally active-form of the human IFN-γ receptor consists of two (or more) subunits, with IFN-γRα responsible for IFN-γ binding and both the IFN-γRα and β chains required for the transduction of biologic responses. The IFN-γ receptor α chain (CD119) is expressed on the surface of most human cells (except mature erythrocytes) including monocytes, macrophages, T cells, B cells, NK cells, neutrophils, fibroblasts, epithelial cells, and endothelium. Binding of 125I-labeled GIR-208 antibody to IFN-γRα+ cells is reported to be specifically inhibited in the presence of excess IFN-γ. GIR-208 does not cross react with IFN-γ as tested by ELISA. The ability of this antibody to bind to IFN-γ receptors of species other than human has not been determined. The immunogen used to generate this hybridoma was human IFN-γRα purified from human placenta. The GIR- 208 has been reported to block the binding of 125I-human IFN-γ to IFN-γRα+ cells as well as purified, soluble human IFN-γRα. GIR-208 is a neutralizing antibody that has been shown to neutralize the anti-viral activity of IFN-γ on WISH cells in a dose-dependent fashion.
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.