A comparative study on changes in hemostasis in orthotopic and auxiliary liver transplantation in pigs

Adoptive Immunotherapy for EBV-associated Malignancies

Latent Epstein-Barr virus (EBV) infection is associated with a diverse group of malignancies including Burkitt's lymphoma, Hodgkin's disease, nasopharyngeal carcinoma (NPC), and lymphoproliferative disease (LPD). EBV proteins expressed in these malignancies provide targets for the adoptive immunotherapy with antigen-specific cytotoxic T cells (CTL) and EBV-specific CTL have been used successfully for the prophylaxis and treatment of EBV-LPD post hematopoietic stem cell transplantation (HSCT). The clinical experience with EBV-specific CTL for other EBV-associated malignancies such as Hodgkin's disease and NPC is limited and the results obtained so far indicate that EBV-specific CTL are less effective than for EBV-LPD post HSCT. Decreased CTL efficacy most likely reflect immune evasion strategies by tumor cells such as down regulation of immunodominant EBV proteins and secretion of inhibitory cytokines. To overcome these immune evasion strategies a number of approaches have been developed including targeting CTL to subdominant EBV antigens and genetically modifying CTL to increase their potency.

T cell therapies

T cell therapies are increasingly used for the treatment of malignancies and viral-associated diseases. Initial studies focused on the use of unmanipulated T cell populations after allogeneic stem cell transplantation. More recently, the use of antigen-specific T cells has been explored. This chapter reviews the clinical experience with polyclonal Epstein-Barr virus (EBV)-specific cytotoxic T cells (CTL) for the treatment of EBV-associated malignancies. Strategies on how to improve the antitumor activity of EBV-specific CTL are being discussed. If effective, these strategies will have broad implications for T cell therapies for a range of human tumors with defined antigens.

Role of the donor liver in the origin of platelet disorders and hyperfibrinolysis in liver transplantation

We investigated the role of the donor liver in the origin of platelet disorders and hemostatic defects in liver transplantation. Eighteen pigs received an orthotopic or a heterotopic, auxiliary liver graft. Liver biopsies were taken for electron microscopic studies 5-10 min after reperfusion in nine animals. Blood samples were taken from the first hepatic outflow and from the systemic circulation before and 5 min after graft recirculation. Electron microscopy did not show any evidence of microthrombi or platelet aggregation in the graft, either after orthotopic liver transplantation or after heterotopic liver transplantation. Most blood platelets, which were lying free in the sinusoids, showed cell processes and many seemed to have lost their granulae, suggesting a degree of platelet activation. There were also signs of phagocytosis of platelets by the Kupffer cells. In the hepatic outflow, platelet count was significantly lower (p < 0.05) and fibrinolytic activity significantly higher (p < 0.01), than systemic post-reperfusion values. There were no important changes in the coagulation parameters. No significant changes were found between the effects on hemostasis of orthotopic and auxiliary graft reperfusion. In the second part of the study evidence for platelet activation was found after graft reperfusion in human liver transplantation. Plasma levels of platelet factor-4 and beta-thromboglobulin increased significantly after graft reperfusion. These studies suggest that platelet disorders and increased fibrinolytic activity are the major components of the hemostatic defect after graft recirculation in liver transplantation. Sequestration of platelets in the graft is probably due to the accumulation of (activated and degranulated) platelets in the sinusoids and phagocytosis by Kupffer cells.

New aspects of heterotopic liver transplantation

In this report the history and clinical results of heterotopic liver transplantation (HLT) are reviewed and some special aspects of current research on HLT are high-lighted. The first laboratory experiments on liver transplantation were performed with auxiliary heterotopic grafts. The initial clinical results of HLT, however, were disappointing and orthotopic liver transplantation (OLT) evolved to be the procedure of choice. Of all the patients who received a heterotopic graft before 1980, only two survived. Since 1980, 50 HLTs are known to have been performed on 48 patients. Results of HLTs after 1986 are clearly better than earlier ones, and survival rates come within the range of those reported for OLT. Intraoperative fibrinolysis is found in the anhepatic phase of OLT, something which is absent in HLT. Tissue-type plasminogen activator (t-PA) is said to be responsible for this phenomenon, as well as for the postreperfusion hyperfibrinolysis. Parallel to the hemostatic changes, the intraoperative hemodynamic stability may be impaired by deleterious substances that arise during liver transplantation. Furthermore, the interaction between the two livers, the effect of HLT on portal pressure and hypersplenism, and the possible role of HLT in inborn errors of hepatic metabolism are described. Special attention is given to the treatment of acute hepatic failure. OLT, in an early phase of the disease, negates the possibility of spontaneous recovery, while delay of the decision to transplant may lead to further deterioration of the patient's clinical condition. As the procedure of HLT is reversible, the decision to transplant can be made more quickly. The clinical experience with HLT for acute liver failure is reported in detail.