Demethylated CD8 gene in CD4+ T cells suggests that CD4+ cells develop from CD8+ precursors.
Carbone AM, Marrack P, Kappler JW. Demethylated CD8 gene in CD4+ T cells suggests that CD4+ cells develop from CD8+ precursors. Science. 1988 Nov 25; 242(4882):1174-6.