Phenotypically, PB Treg cells showed similar expression levels of CD4, CD25, CD127, CD39, and CD161 in RA patients and healthy controls, with a slight, but significantly, increased expression of FoxP3 in RA patients, both in CD45RO+ Treg cells and in CD45RO− Treg cells. Here, FOXP3 is linked to rheumatoid arthritis.