Activation of p38 and MAPKAP-K2/3 during the induction of iTregs. CD4⁺ T cells were cultured with allogeneic IL-10DCs or mDCs to induce the generation of iTregs (R) and Teffs (E). At days 0, 2, and 5 of culture, lysates of both T-cell populations were used for immunoprecipitation of p38 and MAPKAP-K2/3. Subsequently, in vitro kinase assays were performed using ATF-2 and HSP25 as specific substrates for p38 (panel A; top) and MAPKAP-K2/3 (panel B; top) to test the activation of the kinases. The incorporation of [³²P] was visualized after SDS-PAGE. Western blot analysis revealed equal expression of MAPK p38 and MAPKAP-K2/3 during primary culture in both iTregs and effector T cells (panels A-B; bottom). One of 5 representative experiments is shown.