Background：CD273, known as B7-DC, is also called programmed death ligand 2 （PDL2）. This ligand is a 25 kD type I transmembrane protein and a member of B7 family within the immunoglobulin receptor superfamily and is expressed on a subset of dendritic cells, liver and a small subset of macrophages as well as a few transformed cell lines. CD273 has been reported to be stimulatory on dendritic cells when cross-linked and to inhibit T cell activation upon engaging the PD-1 receptor. CD273 has also been reported to bind to an alternative receptor and to mediate T cell activation through such non-PD1 mediated interactions.
