CD4 and melanoma: In addition, it is important to point out the differences in cellular markers used to define Treg populations: in most studies, Treg subset was defined as CD4+CD25+ (42), CD4+CD25highCD127low (9, 34, 35, 39), and even CD25highCD45RA− (7) or, instead, melanoma cell lines were used (37), while our study further dissects Treg population into three Treg subsets.