An IRES-EGFP-SV40 poly A sequence was inserted immediately downstream of the endogenous Foxp3 translational stop codon, but upstream of the endogenous polyA signal, generating a bicistronic locus encoding both Foxp3 and EGFP. Expression of EGFP is restricted to the T cell lineage, primarily to the CD4+ T cell population. (J:120713)