Precisely where sensitization occurs after transplantation is uncertain, but it has been immunological dogma that sensitization to skin grafts occurs “centrally” in the draining lymph nodes. On the other hand, sensitization to fully-vascularized organs (kidney, heart, etc.) has been thought to occur “peripherally” within the graft itself. We have previously shown that mature dendritic cells migrate from the blood into the spleens of normal mice in a T cell-dependent manner, raising the possibility that circulating host dendritic leukocytes might be recruited from the blood into allografts where T cells had accumulated. This would provide a precedent for peripheral sensitization after transplantation.