B7-DC is also called programmed death ligand 2 (PDL2). It has recently been clustered as CD273. This ligand is a 42 kD member of the immunoglobulin receptor superfamily 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. The TY25 antibody has been reported to be useful for blocking PD-1 mediated interactions.