Comparative Study of Regulatory T Cell Function of HumanCD25+CD4+T Cells from Thymocytes, Cord Blood, and Adult Peripheral Blood

Abstract

CD25+CD4+regulatory T cells suppress T cell activation and regulate multiple immune reactions in in vitro and in vivo studies. To define the regulatory function of humanCD25+CD4+T cells at various stages of maturity, we investigated in detail the functional differences ofCD25+CD4+T cells from thymocytes, cord blood (CB), and adult peripheral blood (APB). CBCD25+CD4+T cells displayed low-FOXP3 protein expression level and had no suppressive activity. In contrast,CD25+CD4+T cells from thymocytes or APB expressed high expression level of FOXP3 protein associated with significant suppressive activity. Although CBCD25+CD4+T cells exhibited no suppressive activity, striking suppressive activity was observed following expansion in culture associated with increased FOXP3 expression and a shift from theCD45RA+to theCD45RA−phenotype. These functional differences inCD25+CD4+T cells from Thy, CB, and APB hence suggest a pathway of maturation for Treg in the peripheral immune system.