Peripheral tolerance during and after pregnancy. The effect of pregnancy on percentages of CD4⁺CD25⁺CD127^lowFOXP3⁺ Tregs (A), and CD4⁺CD38⁺HLA-DR⁺ cells (B), and on plasma level of TGF-β (C) in 20 HIV-infected and 16 HIV-negative women. Measurements were performed at 3 time points during pregnancy (in the first, second, and third trimesters) and 2 to 6 months postpartum. (A) Statistical analysis of percentage Tregs showed a significant interaction with time. In HIV-negative women, percentage Tregs were significantly expanded during the second trimester to levels significantly higher than in HIV-negative women (P = .02). (B) Percentages of CD4⁺CD38⁺HLA-DR⁺ cells were significantly higher in HIV-infected women than in controls (P = .0024) and decreased significantly during pregnancy (P = .032). (C) TGF-β was significantly lower in HIV-infected women at all time points, and a significant interaction with time was demonstrated (P = .035). Data are mean (± SEM). P values for time, group, and time × group effect in the mixed repeated models are shown. NS indicates not significant.