Tolerance of Lung Allografts Achieved in Nonhuman Primates via Mixed Hematopoietic Chimerism.

While the induction of transient mixed chimerism has tolerized MHC-mismatched renal grafts in nonhuman primates and patients, this approach has not been successful for more immunogenic organs. Here, we describe a modified delayed-tolerance-induction protocol resulting in three out of four monkeys achieving long-term lung allograft survival without ongoing immunosuppression. Two of the tolerant monkeys displayed stable mixed lymphoid chimerism, and the other showed transient chimerism. Serial biopsies and post-mortem specimens from the tolerant monkeys revealed no signs of chronic rejection. The tolerant recipients also exhibited T cell unresponsiveness and a lack of alloantibody. This is the first report of durable mixed chimerism and successful tolerance induction of MHC-mismatched lungs in primates.

Long-term lung transplantation in nonhuman primates.

Despite advances in surgical technique and clinical care, lung transplantation still remains a short-term solution for the treatment of end-stage lung disease. To date, there has been limited experience in experimental lung transplantation using nonhuman primate models. Therefore, we have endeavored to develop a long-term, nonhuman primate model of orthotopic lung transplantation for the ultimate purpose of designing protocols to induce tolerance of lung grafts. Here, we report our initial results in developing this model and our observation that the nonhuman primate lung is particularly prone to rejection. This propensity toward rejection may be a consequence of 1) upregulated nonspecific inflammation, and 2) a larger number of pre-existing alloreactive memory T cells, leading to augmented deleterious immune responses. Our data show that triple-drug immunosuppression mimicking clinical practice is not sufficient to prevent acute rejection in nonhuman primate lung transplantation. The addition of horse-derived anti-thymocyte globulin and a monoclonal antibody to the IL-6 receptor allowed six out of six lung recipients to be free of rejection for over 120 days.

Alefacept promotes immunosuppression-free renal allograft survival in nonhuman primates via depletion of recipient memory T cells.

Renal allograft tolerance has been achieved in MHC-mismatched primates via nonmyeloablative conditioning beginning 6 days prior to planned kidney and donor bone marrow transplantation (DBMT). To extend the applicability of this approach to deceased donor transplantation, we recently developed a novel-conditioning regimen, the "delayed protocol" in which donor bone marrow (DBM) is transplanted several months after kidney transplantation. However, activation/expansion of donor-reactive CD8(+) memory T cells (TMEM) occurring during the interval between kidney and DBM transplantation impaired tolerance induction using this strategy. In the current study, we tested whether, Alefacept, a fusion protein which targets LFA-3/CD2 interactions and selectively depletes CD2(high) CD8(+) effector memory T cells (TEM) could similarly induce long-term immunosuppression-free renal allograft survival but avoid the deleterious effects of anti-CD8 mAb treatment. We found that Alefacept significantly delayed the expansion of CD2(high) cells including CD8(+) TEM while sparing naïve CD8(+) T and NK cells and achieved mixed chimerism and long-term immunosuppression-free renal allograft survival. In conclusion, elimination of CD2(high) T cells represents a promising approach to prevent electively the expansion/activation of donor-reactive TEM and promotes tolerance induction via the delayed protocol mixed chimerism approach.

Hand-assisted laparoscopic splenectomy in ABO-incompatible kidney transplant recipients.

OBJECTIVE: We perform living-related ABO-incompatible kidney transplantations to alleviate the organ shortage in our country. Splenectomy has been performed routinely in these recipients, although its clinical significance remains controversial. In this study, we have reported our experience with a hand-assisted laparoscopic splenectomy (HALS) technique. METHODS: Between April 2000 and December 2006, 50 patients (23 males) underwent ABO-incompatible kidney transplantation with HALS. The mean age and weight of the recipients were 44 +/- 13 years and 56 +/- 12 kg, respectively. All patients underwent preoperative plasmapheresis to reduce isoagglutinin (A and/or B antibody). In 6/50 patients, a hand-assisted device was placed through a peritoneal window in the right lower abdominal skin incision for kidney engraftment. In the remaining 44 patients, a 6-cm upper midline or periumbilical midline incision was made for the hand-assisted device in the lateral position. RESULTS: An ABO-incompatible procedure was completed successfully in all cases. The average HALS time was 118 +/- 42 minutes, with an average pneumoperitoneum time of 79 +/- 40 minutes and average blood loss of 48 +/- 81 g. There were two conversions to open splenectomy because of intraoperative bleeding and suspected pneumothorax. Two other cases required relaparotomy because of hematoma and perforation of the ileum. Successfully operations were achieved through the previous periumbilical incision. CONCLUSIONS: Although meticulous, rigorous surgical technique is essential, HALS is safe and feasible for recipients of ABO-incompatible grafts with tissue weakness and a bleeding tendency because of renal failure and preoperative plasmapheresis.