Organ-derived dendritic cells activate naive allogeneic T cells in vitro, but liver-derived dendritic cells are less efficient. (A) Four days after coculture with different organ-derived host-type dendritic cells, absolute cell numbers of donor-type T cells are almost doubled with preferential stimulation of CD8⁺ cells (n = 15-17). CD4⁺ and CD8⁺ T cells express mostly an effector memory phenotype (CD44^hiCD62L^lo). (B) Liver-derived dendritic cells induce less proliferation of allogeneic T cells, as assessed by ³H-thymidine incorporation (1 representative of 4 experiments shown). (C) Determination of cytokines in cell culture supernatant shows comparable IFN-γ but significantly less IL-2 secretion by T cells stimulated with liver-derived dendritic cells (n = 6, *P < .05). (D) Expression of the activation marker CD25 is significantly lower in the liver group (n = 8-10, **P < .001), whereas CD69 is comparable. (E) Intracellular staining for IFN-γ and TNF-α shows similar expression in all 4 groups. (F) The induction of activated Foxp3⁺ regulatory T cells by all organ-derived dendritic cells is comparable. (G) The suppressive capacity of isolated CD4⁺CD25⁺ regulatory T cells is similar in a suppression assay using C57BL/6 responder and BALB/c stimulator. Panels D and F are gated on CD44^hiCD62L^lo T cells. Error bars represent SEM.