CD4⁺CD25⁺ T cells isolated from HIV-infected patients constitutively express Foxp3 mRNAs. RNA was extracted from purified CD4⁺CD25^– (lanes 1) and CD4⁺CD25⁺ (lanes 2) T cells immediately after cell isolation from 3 patients. Foxp3 expression was analyzed using 2 steps of RT-PCR (see “Analysis of TGF-β1 and FoxP3 expression”). An expected 152-bp PCR product was detectable in CD4⁺CD25⁺ but not in CD4⁺CD25^– T cells (except a faint detectable band in patient 1).