PDCD1 and cancer: Recent reports have also shown that OX40 agonists can inhibit both Treg function and the generation of transforming growth factor-β-inducible Treg.19, 26 However, there have also been two reports that OX40 agonists can enhance Treg proliferation.27, 28 The percentage of Tregs and/or their expression of the proteins studied herein may change following administration of anti-OX40, anti-PD-1 or anti-CTLA-4 to cancer patients, potentially leading to clues for the timing of co-therapies.