The WTH1 monoclonal antibody specifically binds to rat CD1d and crossreacts with mouse CD1d (with stronger reactivity against mouse CD1d1 than CD1d2). CD1d is a type I transmembrane glycoprotein that is noncovalently associated with β2-microglobulin. CD1d is expressed on various cell types including subsets of thymocytes, T cells, B cells, monocytes, macrophages, dendritic cells, endothelial cells and epithelial cells. Although structurally similar to MHC Class I antigens, CD1d molecules are rather non-polymorphic and serve to present non-peptide antigens such as endogenous or microbial glycolipids to T lymphocytes (NKT cells). The WTH2 monoclonal antibody reportedly binds to a non-overlapping epitope on rat CD1d and also crossreacts with mouse CD1d when compared with WTH1. Both WTH1 and WTH2 reportedly interfere with antigen recognition by CD1d-restricted T cells.
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.