Detection of naïve and effector CD4+ cells in peripheral blood mononuclear cells. According to Ref. , naïve Tcon cells (fraction I), effector Tcon cells (II), naïve Treg cells (III), and effector Treg cells (IV) were CD4+ by flow cytometry. CD25 expression in each subpopulation is shown in the histogram. Representative data from a healthy donor, a patient with chronic GVHD (cGVHD), and our thymectomized patient are shown.