It is important to note that reports from cancer studies suggest that PD-1 engagement with PD-L1 does not cause dephosphorylation, but leads to phosphorylation and activation of AKT and ERK, which increases chemo resistance of the cancer cells (102, 103), implying a difference in PD-1 signaling between chronic infection and cancer that requires further investigation. The gene discussed is PDCD1; the disease is cancer.