The TY25 monoclonal antibody specifically binds to CD273, also known as B7-DC or PD-L2. CD273 is a 42-kDa type I membrane glycoprotein encoded by the Pdcd1lg2 gene of the B7 family of the Ig superfamily. Pdcd1lg2 mRNA is expressed selectively in dendritic cells (DC), liver, and a few transformed cell lines (hepatic, neuroblastoma, and myeloid), but not in lymphoid tissues or macrophages. The protein has not been detected on resting peripheral T and B lymphocytes, macrophages, or DC, but it is upregulated upon activation of T cells, macrophages, and DC by a variety of stimulatory factors. B7-DC's receptor, PD-1, contains an ITIM (Immunoreceptor Tyrosine-based Inhibitory Motif) on its intracytoplasmic region and is expressed on activated B and T lymphocytes, suggesting that B7-DC-PD-1 interaction may be involved in the negative regulation of immune responses. The second PD-1 ligand, B7-H1 (PD-L1), is also a member of the B7 family of the Ig superfamily. B7-DC may also participate in positive immunoregulation, or costimulation of T cells, through an additional receptor, which is not PD-1 and distinct from the alternate receptor for B7-H1. Moreover, B7-DC is the first B7 ligand that has been found to participate in bi-directional communication; ligation of B7-DC on DC stimulates those DC. The TY25 antibody blocks the binding of B7-DC to PD-1, but not to its alternate ligand.
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.