HIV infection upregulated Foxp3 expression in TCR activated CD4+CD25- T cells. A. Purified CD4+CD25- T cells were infected with HIV1 (HIV NLA-3) and cultured with anti-CD3 and anti-CD28 antibodies in the absence (HIV-1) or presence of active TGF-β1 (2 ng/ml) (HIV-1+TGF-β) or anti-TGF-β1,2,3 antibody (HIV-1+anti-TGF-β) for 3 (data not shown) and 5 days. T cells were then stained for surface CD25 and intracellular Foxp3. A representative of two experiments is displayed. A parallel culture of TCR- and CD28-stimulated CD25- T cells without HIV infection (uninfected) was used as control. B. The supernatants from the same cultures in A were collected at the indicated time points and tested for HIV p24 with ELISA. The experiment was repeated twice with similar results.