PDCD1 and breast cancer: In this study, we aimed to examine the effect of breast cancer cells on the expression level of ICs on CD4+ T cell subsets, including CD4+CD25−, CD4+CD25+, and CD4+CD25+FoxP3+Helios+ Tregs, in the absence and presence of anti-PD-1 mAb, anti-PD-L1 mAb or both mAbs.