Portal venous (pv) transfusion before transplant with large numbers (100 x 10(6)) of irradiated multiple minor histoincompatible spleen cells (B10.Br) augments allogeneic skin graft survival in C3H mice. We have shown in earlier studies that this is correlated with preferential activation for production of type 2 cytokines (interleukin [IL]-4 and IL-10) and decreased production of type 1 cytokines (IL-2 and interferon [IFN] gamma). We have also shown that recombinant (r)IL-12, in association with anti-IL-10 monoclonal antibody, can reverse in vivo the graft prolongation afforded by pv immunization and the altered cytokine production that follows. Adoptive transfer of inhibition of graft rejection is possible at early times after pv immunization, using plastic adherent cells obtained from the liver of treated mice. We show below that within 4 days of pv immunization, dendritic cells (NLDC-145+) isolated from the thymus, mesenteric lymph node (MLN), and.