Predominant role of the Fab fragment in delaying hyperacute rejection in guinea pig-to-rat xenotransplantation

Small animal models of xenotransplantation

Organ transplantation has become a successful and acceptable treatment for end-stage organ failure. Such success has allowed transplant patients to resume a normal lifestyle. The demands for transplantation have been steadily increasing, as more patients and new diseases are being deemed eligible for treatment via transplantation. However, it is clear that human organs will never meet the increasing demand of transplantation. Therefore, scientists must continue to pursue alternative therapies and explore new treatments to meet the growing demand for the limited number of organs available. Transplanting organs from animals into humans (xenotransplantation) is one such therapy. The observed enthusiasm for xenotransplantation, irrespective of the severe shortage of human organs and tissues available for transplantation, can be said to stem from at least two factors. First, there is the possibility that animal organs and tissues might be less susceptible than those of humans to the recurrence of disease processes. Second, a xenograft might be used as a vehicle for introducing novel genes or biochemical processes which could be of therapeutic value for the transplant recipient.To date, millions of lives have been saved by organ transplantation. These remarkable achievements would have been impossible without experimental transplantation research in animal models. Presently, more than 95% of organ transplantation research projects are carried out using rodents, such as rats and mice. The key factor to ensure the success of these experiments lies in state-of-the art experimental surgery. Small animal models offer unique advantages for the mechanistic study of xenotransplantation rejection. Currently, multiple models have been developed for investigating the different stages of immunological barriers in xenotransplantation. In this chapter, we describe six valuable small animal models that have been used in xenotransplantation research. The methodology for the small animal model establishment includes animal selection, preoperative care, anesthesia, postoperative care, and detailed procedures.

The role of immunomodulation in ABO-incompatible adult liver transplant recipients

BACKGROUND

ABO-incompatible (ABO-i) liver transplantation (LT) is a high-risk procedure due to the potential for antibody-mediated rejection (AMR) and cell-mediated rejection. The aim of the current report is to illustrate the results of a retrospective comparison study on the use of immunomodulation with therapeutic plasma exchange (TPE) associated to high-dose immunoglobulins (IVIg) and extracorporeal photopheresis (ECP) in ABO-i adult LT patients.

PATIENTS AND METHODS

Between January 1996 and December 2005, 19 patients underwent ABO-i LT. The study was designed for a comparison between two groups of ABO-i LT. Group 1 (control group) consisted of 11 patients treated with TPE only. Group 2 (study group) included eight patients treated with TPE and IVIg. Moreover, all Group 2 patients received acute rejection prophylaxis with ECP.

RESULTS

The graft survival at 6, 12, and 18 months was 63.6, 54.4, and 45.5% for Group 1 vs. 87.5, 87.5, and 87.5% for Group 2 (P < or = 0.001). In Group 1 there were 3(27.3%) cases of AMR; 5 (45.4%) biopsy-proven acute rejections (BPAR); 1 (9.1%) chronic rejection and 3 (27.3%) ischemic-type biliary lesions (ITBL). In Group 2 there were no cases of AMR, BPAR, chronic rejection, or ITBL (P = 0.013).

CONCLUSION

At median follow-up of 568 days, TPE in combination with IVIg and ECP appears to protect the graft from AMR in ABO-i liver transplantation. Continued patient enrollment will allow validation of these preliminary observations or the opportunity to devise newer AMR-avoidance policies.

Treatment of antibody-mediated rejection with high-dose immunoglobulins in ABO-incompatible liver transplant recipient

ABO-incompatible liver transplantation (LT) entails high risk of antibody-mediated rejection (AMR) and poor graft survival. Different treatment modalities have been reported, but none with use of a 2-week course of high-dose polyclonal i.v. immunoglobulins (IVIg) associated with plasmapheresis without the use of steroid pulses or monoclonal antibody. A 60-year-old male patient with blood-group O, Caucasian, underwent urgent LT for acute liver failure after hepatectomy for HCV-related hepatocellular carcinoma. He was grafted with a 66-year-old, blood-group A, HCV-positive liver graft. Pretransplant conditioning consisted of plasmapheresis and immunosuppression was triple with tacrolimus (TAC), steroids, and mycophenolate mofetil with anti-IL2-R monoclonal antibodies, plasmapheresis if hemagglutinin level >1:8, and extracorporeal photopheresis. After reduction of liver function tests to baseline, the patient presented a tenfold increase in alanine aminotransferases (ALT) levels 7 days post-transplantation. AMR was confirmed on histology. Treatment consisted of IVIg (1.5 g/Kg/daily for the first 7 days, and 1 g/Kg/daily from day 8 to 14) with a 14-day course of plasmapheresis. No side effect was observed and daily blood IgG levels ranged between 24.4 and 36.4 g/l. At the end of the scheduled course ALT returned to baseline. A control liver biopsy 55 days after LT showed no rejection and replacement of necrosis with fibrous strands. This case may support the role of high-dose IVIg for treatment and/or prophylaxis of severe AMR.