Apoptotic Activated T Cells Inhibit HIV in DCs Figure 4. TNF-areleased in co-cultures of DC and ApoAct mediate partial reduction in HIV infection and an increase in the percentage of CD86+ cells. (A) Conditioned medium (CM) was collected from co-cultures of DCs and ApoAct after 24 hours. Immature DCs were exposed to the supernatants in increasing concentrations (final volume, 1 ml) in the presence of HIVBaL. The percentage of intracellular p24+ cells was measured by flow cytometry after 7 days. One representative experiment out of two is shown. Two replicates were used to generate mean 6 SD. No statistical analyses were performed for the CM dose-response analyses. (B) DCs were exposed to HIVBaL (HIV); conditioned medium (CM) from DC and ApoAct co-cultures; or blocking mAbs to RANTES, MIP-1a, MIP-1b, and IFN-cmAb mixor to TNF-aa-TNF-a). The percentage of HIV-infected DCs was measured by flow cytometry in cells from eight donors. Significant differences were assessed by the non-parametric Wilcoxon matched-pairs test and are indicated by *p,0.05. (C) DCs were exposed to HIV, and CM was added at the same time as HIV (0 hours) or after 2 or 16 hours of incubation before assessment of intracellular p24 by flow cytometry after 7 days in five donors. Significant differences were assessed by the non-parametric Mann-Whitney U-test and are indicated as **p,0.01. (D) DCs were exposed to HIV and co-cultured with ApoAct added at the same time (0 hours) or after 2 or 16 hours after HIV infection in six donors. Significant differences were assessed by the non-parametric Mann-Whitney U-test and are indicated as ***p,0.001. The experiments were carried out in the presence or absence of blocking TNF-a mAbs in three donors and no statistical analyses were performed. Assessments of intracellular p24 by flow cytometry were performed 7 days after HIV exposure. (E) DCs were exposed to CM with or without simultaneous HIV exposure in the presence or absence of blocking TNF-a mAb, and the percentage of CD86+ cells was measured by flow cytometry after 7 days in five donors. Significant differences were assessed by the non-parametric Mann-Whitney U-test and are indicated as *p,0.05. (F) DCs were exposed to HIV in the presence of decreasing concentrations of rTNF-a (iii = 25 ng/ml, ii = 2500 pg/ml, i = 250 pg/ml) with or without simultaneous addition of TNF-a mAb. Assessments of intracellular p24 by flow cytometry were performed 7 days after HIV exposure. Data represent mean+SD from two donors obtained from one representative experiment out of three. doi:10.1371/journal.pone.0021171.g004 such as for example APOBEC3F [25]. These findings have implications for viral transmission as DCs are likely to be one of the first target cells upon transmission when encountering infected cells and/or free virus. We found significantly reduced HIV infection in DCs that had been co-cultured with ApoAct but not in DCs co-cultured with ApoRest. It was previously suggested that alloantigen-induced immune responses may reduce HIV susceptibility in CD4+ T cells [47,49]. In the present study, we show that both allogeneic and autologous ApoAct are able to provide DCs with a maturation signal; however, a prerequisite for the induction of DC maturation and anti-viral activity was that both the allogeneic and autologous PLoS ONE | www.plosone.org 9 June 2011 | Volume 6 | Issue 6 | e21171