Figure 8

ECP-DL induced hypo-responsiveness is donor-specific and is associated with increased frequency of circulating T-regulatory cells. Lewis rats received orthotopic liver grafts from ACI donors 7 days after injection of ECP-DL without additional IS. Skin grafts from both donor (ACI) and third party (BN) rats were applied to the same recipient 100 days post-liver transplant to determine whether the tolerance is donor specific. Animals were monitored, and serial blood samples were analyzed by flow cytometry for the frequency of Tregs. (a) Representative gross images showing the donor-type skin grafts at post-operative (POD) 130 versus third-party skin grafts. By POD 180, the donor-type skin grafts further improved in appearance, while third-party skin grafts ulcerated, indicating rejection; the liver graft appears normal in situ. (b) Representative dot-plot showing % of Tregs, and a bar graph of the number of Tregs in the blood at POD7 showing higher percentage and absolute numbers of Tregs in ECP-DL treated recipients than the untreated or those receiving short-course tacrolimus (TAC). (c) The percentage of Tregs over the course of the experiment; animals receiving either ECP-DL or ECP-DL/ECP-RL had significantly higher percentages of Tregs than isograft controls at all time points.