The programmed death-1 receptor (PD-1, CD279) with its ligands PD-L1 (CD274, B7-H1) and PD-L2 (CD273, B7-DC) constitutes a inhibitory pathway in cancer immunity. Therapeutic antibodies for blocking PD-1 and PD-L1 have been developed and are undergoing human clinical testing. Negating the PD-1/PD-L1 interaction is of particular interest as PD-L1 is upregulated by many human cancers. On the other hand, the role of PD-L2 in modulating immune responses is less clear, and its expression is more restricted compared to PD-L1, thus making it a less obvious target in cancer immunotherapy. However, in this context, several aspects of PD-L2 biology deserve attention, including a partial contextual dependency of PD-L2 expression.
Rozali EN, Hato SV, Robinson BW, Lake RA, Lesterhuis WJ. Programmed Death Ligand 2 in Cancer-Induced Immune Suppression. Clinical and Developmental Immunology. 2012;2012:656340.