PDCD1 and neoplasm: When the PD1/PD-L1 pathway blockade is combined with stimulatory anti-OX40 [140], or with anti-CTLA-4 and anti-CD137 [139,148], ID8-tumor bearing mice achieve a prolonged survival, and exhibit an increased CD8+ and Foxp3-CD4+ T-cell-to-Treg ratio, as well as a reduction of MDSC.