Is Foxp3 a good marker for regulatory T cells?

ABSTRACT

To track the changes in the tested Treg markers especially Foxp3 following activation to determine whether data of human studies using Foxp3 in evaluation of Tregs are reliable or not. Four-colour flow cytometry analysis was carried out to calculate the percentages of Tregs before and after lymphocyte activation. Foxp3 expression by CD4(+)CD25(+)* and CD4(+)CD25(high) T cells increased after T cell activation. A moderate negative correlation was observed between the percentage of each of CD4(+)CD25(+)Foxp3(+)IL10(+) or CD4(+)CD25(high) Foxp3(+)IL10(+) T cells and the percentage of CD4(+)CD25(+) T cells "after activation" and a weak negative correlation was similarly observed between the percentage of CD4(+)CD25(-)Foxp3(+)IL10(+) T cells and the percentage of CD4(+)CD25(+) T cells "after activation". A moderate negative correlation was observed between the percentage of each of CD4(+)CD25(+)Foxp3(+)IL10(+), CD4(+)CD25(high)Foxp3(+)IL10(+) or CD4(+)CD25(-) Foxp3(+)lL10(+) T cells and the percentage of CD4(+)CD25(high) T cells "after activation". CD4(+)CD25(high) T cell subpopulation expressed a significantly higher level of intracellular Foxp3 compared with CD4(+)CD25(low) and CD4(+)CD25(-) T cells subpopulations. In conclusions, Foxp3 is a good marker of Tregs especially if panels of markers were used for their identification. CD4(+)CD25(high) Foxp3(+) T cell subpopulation mostly represents Tregs and thus should be the one targeted in Treg studies.