In vivo administration of RAPA impairs DC T-cell stimulatory activity. (A) Allostimulatory activity of freshly isolated, immunomagnetic bead—purified B10 (H2K^b,IA^b) DCs from animals (3/group) injected with RAPA (10 days) or drug vehicle (“vehicle DC”). Mean proliferative activity of fully allogeneic C3H (H2K^k, IA^k) responder T cells in 72-hour MLRs is shown (± SD). (B-E) Adoptive transfer of freshly isolated splenic B10 DCs from animals (panel C, normal; panels D and E, Flt3L-treated) that were injected with RAPA (7 days) or vehicle into fully allogeneic C3H recipients. C3H mice received 5 × 10⁵ magnetic bead—purified B10 DCs (intravenously). Ten days later, the mice were killed and splenic T cells restimulated with graded numbers of γ-irradiated donor splenocytes. (C-D) Mean proliferation of C3H responder T cells (3 animals/group) in 72-hour MLRs is shown (± SD). T cells from nonimmunized animals (“naive”), from animals given DCs from drug vehicle-injected controls, as well as syngeneic splenocytes (“syngeneic control”) were used as controls. (E) Effect of adoptive transfer of DCs on IFN-γ, IL-2, IL-4, and IL-10 production by recipient T cells after restimulation with donor alloantigen (splenocytes). Mean cytokine production of C3H responder T cells (3 animals/group) in a 72-hour MLR is shown (± SD). *P < .05 versus vehicle (2-tailed Student t test).