p38 MAPK is crucial for the induction and maintenance of T-cell anergy. IL-10DCs or mature DCs were cocultured with allogeneic CD4⁺ T cells to stimulate iTregs (R, □) and Teffs (E, ▪), and reactivated. The specific inhibitor SB203580 of MAPK p38 was added during the induction of the T-cell populations (middle panel) or during restimulation (bottom panel). Proliferation was detected 96 hours after restimulation as incorporation of [³H]-thymidine and demonstrated as cpm ± SEM (A). After 48 hours of culture, supernatants were collected and IL-2 production was measured by ELISA as described in “Materials and methods” (B). One of 5 independent experiments with similar results was shown. *Statistical significance according to the Student t test; P ≤ .05.