Comparative study of regulatory T cell function of human CD25(+) CD4(+) T cells from thymocytes, cord blood, and adult peripheral blood

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 human CD25(+) CD4(+) T cells at various stages of maturity, we investigated in detail the functional differences of CD25(+) CD4(+) T cells from thymocytes, cord blood (CB), and adult peripheral blood (APB). CB CD25(+) 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 CB CD25(+) 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 the CD45RA(+) to the CD45RA(-) phenotype. These functional differences in CD25(+) CD4(+) T cells from Thy, CB, and APB hence suggest a pathway of maturation for Treg in the peripheral immune system. Copyright (C) 2008 Wakae Fujimaki et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.