The MIH37 monoclonal antibody specifically recognizes Programmed cell death 1 ligand 2 (PD-L2) which is also known as CD273 and Butyrophilin B7-DC (B7-DC). This regulatory molecule is a 42-kDa type I membrane glycoprotein encoded by Pdcd1lg2 which belongs to the B7 family of the Ig superfamily. CD273 (PD-L2) is comprised of an extracellular region with an N-terminal IgV-like domain followed by an IgC2-type domain, a transmembrane sequence, and a cytoplasmic tail. Although not detected on resting leucocytes, its expression is upregulated upon activation of macrophages and dendritic cells (DC) by a variety of stimulatory factors including IL-4, IL-13, or GM-CSF. CD273 (PD-L2) serves as a ligand for the coinhibitory receptor, CD279 (PD-1), a receptor that likewise binds to the CD274 (PD-L1) ligand. CD273 (PD-L2) also binds to Repulsive guidance molecule b (RGMb) that is expressed by T cells, macrophages, neutrophils, and DC. RGMb may associate with other receptors that transduce costimulatory or coinhibitory signals. The MIH37 antibody reportedly blocks the binding of CD273 (PB-L2) to its receptors, CD279 (PD-1) or RGMb and can inhibit antigen-specific T cell responses and hapten-induced contact hypersensitivity reactions. The TY25 monoclonal antibody reportedly binds with lower affinity near or at the same mouse CD273 (PD-L2) epitope recognized by the MIH37 antibody.
The antibody was conjugated to BD Horizon™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.