PDCD1 and cancer: In experimental cancer, inhibition of TREM-2 with anti-TREM-2 blocking monoclonal antibody (mAb) not only exhibits a robust antitumor effect when used as single-agent therapy, but also significantly improves the efficacy of immune checkpoint blockade (ICB) therapy when used in combination with anti-programmed cell death protein-1 (PD-1) treatment [81,83].