PDCD1 and Autoimmunity: Dysfunctionsof the regulatory effect of the PD-1/PD-L1 checkpointtoward the immune system can lead to several diseases related to autoimmunity,infections, and cancer.3,4 In cancer cells, overexpressionof PD-L1 leads to the progression of T cells into an exhausted stateand decreased tumor cell apoptosis.