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.