To determine whether the phenotype of CD4+CD25−Foxp3+ T cells resembled that of CD4+CD25+Foxp3+ Treg cells or CD4+CD25+Foxp3− effector T cells, we investigated molecules associated with regulation of Treg suppressive function, including CTLA-4, GITR, Helios, and ICOS, in untreated RA patients and HCs. This evidence concerns the gene TNFRSF18 and rheumatoid arthritis.