Defective DC maturation is likely due to impaired CD154 induction on AT-2 HIV-exposed CD4⁺ T cells. (A) Exposure to AT-2 HIV and neutralizing anti-CD154 Ab mediates similar defective DC maturation. Three different culture conditions were established: DCs were cultured with either untreated T cells, AT-2 HIV exposed T cells, or untreated T cells, and the cocultures were performed in the presence of blocking anti-CD154 Ab (10 μg/mL). Functional inhibition in AT-2 HIV exposed T cells or untreated T cells was defined by comparison with untreated T cells. Results are shown as the mean percentage of inhibition ± SE for each parameter (3 donors). (B) Decreased IL-12 p40 induction because of exposure of T cells to AT-2 HIV is corrected by exogenous rCD154. DCs were cocultured with AT-2 HIV-exposed T cells and rCD154 (+ +), AT-2 HIV-exposed T cells (+ -), untreated T cells and rCD154 (- +), and untreated T cells (- -). Results are shown as the mean ± SE IL-12 p40 production (4 donors). ^*Significant difference (P < .03, paired t test); NS indicates a nonsignificant difference (P > .5).