PDCD1 and cancer: More research is still needed to clarify the dual effects of PD-1/PD-L1 antibody blockade therapy on Tregs, which may depend on the regulation of multiple factors, such as differences in Treg subgroups, the effect of Tregs on different target cells (such as APCs) in chronic viral infections or cancer, and different downstream molecular mechanisms of regulation, etc. In the future, we should deeply explore the complex relationships between PD-1/PD-L1 and Tregs in tumor immunity and combination therapy to provide new strategies for improving the efficacy of immunotherapies for solid tumors.