Effect of supernatants from ATP-treated DCs on naive T CD4⁺ cells. Naive T CD4⁺ cells were partially activated (A) with coated anti-CD3 or (C) fully activated with coated anti-CD3 and soluble anti-CD28 in the presence of supernatant from nontreated DCs (CTRL) or ATP-treated DCs (ATP) for 48 hours. Cell suspensions were then additionally incubated for 16 hours in the presence of [³H]-thymidine (0.037 MBq/well [1 μCi/well]). The effect of human recombinant TSP-1 (7 μg/mL) was also tested on thymidine incorporation of partially activated (B) or fully activated (D) naive T CD4⁺ cells in fresh medium. (E) Supernatants from nontreated DCs (left) or ATP-treated DCs (right) were previously incubated for 2 hours at room temperature in the presence (▪) or the absence (□) of neutralizing anti–TSP-1 mAb at 25 μg/mL (clone C6.7, which selectively interferes with TSP-1/CD47 interaction). Fully activated T CD4⁺ cells were incubated in the presence of these DC supernatants for thymidine incorporation experiments. (F-G) Fully activated T CD4⁺ cells were incubated in the presence of supernatants from nontreated or ATP-treated DCs. After 48 hours, IFN-γ (F) or IL-10 (G) levels were measured by ELISA. Data represent the mean ± SD of triplicate experimental points obtained in 1 representative experiment out of 5 (A-D) or 2 (E-G).