Although, that FOXP3 is highly specific to Tregs,54 studies suggest that FOXP3+CD4+ T cells are functionally and phenotypically heterogeneous, and consist of suppressive and non-suppressive T cells.35 42 55 56 For example, FOXP3+CD4+ T cells in colorectal cancer can be classified into three subsets based on their expression levels of CD45RA and FOXP3: Fraction I (Fr-I, FOXP3lowCD45RA+), Fraction II (Fr-II, FOXP3highCD45RA-), and Fraction III (Fr-III, FOXP3lowCD45RA−). Here, CD4 is linked to colorectal cancer.