Production of cytokines by DCs and T cells. (A) Production of cytokines at different time points during the differentiation process of DCs grown in different cytokine combinations. CD34⁺ cells were cultured in the presence of SCF (▴), IL-16 (♦), TPO (•), or IL-16 plus TPO (▪), and the released cytokines were measured in the supernatants by ELISA. The concomitant presence of IL-16 and TPO induced the production of higher levels of TGF-β, IL-10, and IFN-α, and lower levels of IL-12p70, which became increasingly evident during the second week of culture. The mean ± SEM from 2 independent experiments is shown. (B) Production of cytokines by DCs. Unfractionated CD34⁺ cells, CD34⁺/CD4⁺, and CD34⁺/CD4^- sorted cells were grown in the presence of the indicated cytokine combinations for 14 days, and the released cytokines were measured in the supernatants by ELISA. IL-16/TPO-DCs obtained either from unfractionated CD34⁺ cells or from CD34⁺/CD4⁺ or CD34⁺/CD4^- cells produced higher levels of TGF-β, IL-10, and IFN-α, and lower levels of IL-12p70, than the other types of DCs. Mean ± SEM from 4 independent experiments. IL-16-DCs, TPO-DCs, and IL-16/TPO-DCs compared with SCF-DCs with the paired Wilcoxon signed rank test; ^*P < .05. (C) Production of cytokines by T cells cocultured with IL-16/TPO-DCs compared with SCF-DCs. Monocyte-depleted PBMCs were cultures alone (left columns), or with SCF-DCs (central columns), or with IL-16/TPO-DCs (right columns). After the indicated days of DC/T coculture, T cells were reactivated with PMA and ionomycin for 5 hours, and their intracellular expression of cytokines detected by flow cytometry. Gated on CD4⁺ T cells, density plots show the expression of IFN-γ and IL-2 (upper row) or IL-10 (lower row). Quadrants were set according to the fluorescence intensities of isotype-matched controls. T cells cocultured with IL-16/TPO-DCs failed to express IL-2 and IFN-γ. IL-10 was not expressed in any condition. One representative of 3 independent experiments is shown.