However, we cannot rule out that this kidney is a unique organ with respect to its ability to induce tolerance with this protocol, and that the liver lacks an important cell or factor that is present only in the kidney. The results of this study are limited by the small number of animals that survived until rejection and the small group sizes of animals that received identical induction therapy. duration of chimerism in liver recipients was comparable to that previously reported in renal transplant recipients. However, unlike in the kidney model, the liver was rejected soon after immunosuppression withdrawal. Rejection was associated with proliferation of recipient CD8 T effector cells in the periphery and liver, increased serum IL-6 and IL-2, but peripheral Treg numbers did not increase. Anti-donor antibody was also detected. Conclusions These data show the transient chimerism protocol does not induce tolerance to livers, likely due to greater CD8 T cell responses than in the kidney model. Successful tolerance induction may depend on greater control or deletion of CD8 T cells in this model. Introduction Advances in surgical technique and immunosuppression have led to great improvements in short-term liver allograft survival.1,2 However, long-term sequelae of immunosuppression Cincluding contamination, graft failure and malignancy C are still the leading causes of patient death. 2C5 Side effects of immunosuppression such as diabetes, hypertension, hypercholesterolemia and renal failure also decrease quality of life.3C6 The induction of tolerance early after liver transplantation (LT) would therefore be expected to improve outcomes. Induction of mixed hematopoietic chimerism (MC) at the time of solid organ transplant consistently induces tolerance in rodents, nonhuman primates (NHP) and humans.7 In cynomolgus monkeys, simultaneous kidney and bone marrow transplantation (SKBMT) with a nonmyeloablative conditioning regimen resulted in transient MC and tolerance across MHC barriers in up to 70% of recipients.8C10 This strategy was translated to humans, where immunosuppression was discontinued successfully in 70% of SKBMT recipients.11,12 Studies in primates and humans have shown that tolerance is mediated by regulatory T cells (Tregs) in the early post-transplant period, with deletion of donor-reactive T cell clones observed later after immunosuppression withdrawal.13C15 On the other Tricaprilin hand, rejection was associated with high numbers of pre-transplant donor-reactive memory T cells in the NHP model.16 This suggests a complex interaction between Tregs, clonal deletion and pre-existing alloreactivity determines whether tolerance is induced after transient donor chimerism. In NHPs, the nonmyeloablative conditioning regimen does not induce tolerance to organs considered to be less tolerogenic than the kidney (e.g. islets and heart).17,18 Thus, the organ plays a critical role in the induction of tolerance with this protocol. In some animal models the liver is the most tolerogenic organ. For example, in pigs and rodents, a liver can be accepted in the absence of immunosuppression19,20 and can reverse donor-specific sensitization.21 Therefore, we hypothesized that this liver could Tricaprilin facilitate the induction of tolerance with a nonmyeloablative transient MC protocol. Here, we report the results this strategy with LT in a preclinical cynomolgus monkey model. 22 We demonstrate that despite developing donor chimerism at comparable levels and duration as in the SKBMT model, liver recipients rapidly rejected their graft following withdrawal of immunosuppression. This rejection was characterized Rabbit Polyclonal to AN30A by proliferation of CD8 effector T cells in the periphery and the graft, suggesting that, with the transient MC protocol, these cells prevent tolerance induction early after LT. Materials and Methods Animals Fourteen cynomolgus macaques (7 donor-recipient pairs) weighing 6.1C10.2 kg were used (Charles River Primates, Wilmington, MA). Recipients and donors were selected for ABO compatibility and mismatching of Tricaprilin MHC (Physique 1) as determined by the Genetic Services Unit of the Wisconsin National Primate Research Center at the University of Wisconsin-Madison (see supplemental details).23 Donors and recipients had differential binding of anti-Bw6 antibody (H38, One Lambda Canoga Park, CA) to peripheral blood mononuclear cells to allow tracking of chimerism. All macaques were housed at the Institute of Comparative Medicine (Columbia University Medical Center, New York, NY). This facility holds a current OLAW Assurance, USDA registration and is AAALAC.
