The fas and fas ligand pathways in liver allograft tolerance.
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The Fas and Fas ligand (Fas/FasL) pathways may play a central role in cytotoxicity or immunoregulation in liver transplantation. Here, in an attempt to examine the role of Fas/FasL on drug-free tolerance, we measured mRNA levels of Fas/FasL in livers by reverse transcriptase-polymerase chain reaction (RT-PCR), and also protein levels of Fas/FasL in livers by immunohistochemistry and in serum by dot blot assay. PVG recipients bearing DA livers showed serious rejection between post-operative (POD) days 7 and 14, but this rejection was naturally overcome without any immunosuppression. Fas gene and protein products were expressed on almost every cell in livers taken from naive rats, and at any time point in both syngeneic and allogeneic orthotopic liver transplantation (OLT) rats. In contrast, FasL mRNA in DA livers was detectable at POD 2, peaked at POD 14, and declined at POD 63 in allogeneic OLT (DA-PVG). Although the FasL gene was detectable in isografts at POD 14, its expression was much lower than in allografts. The time course and localization of FasL expression indicated that the expression of FasL gradually switched from infiltrating cells to hepatocytes when the rejection was naturally overcome and tolerance was induced in this OLT model. Soluble Fas could constitutively be detected at any time point in the serum of the tolerogenic OLT (DA-PVG) rats and was not diminished during the rejection phase. Soluble FasL peaked at POD 14 in allogeneic OLT, while sFasL was significantly lower in the serum of normal and syngeneic OLT rats. These findings suggest that the Fas and FasL pathways, including soluble forms, may contribute to the control of the immune response in this drug-free tolerance OLT model. (+info)
Immunogenicity and safety of hepatitis A vaccine in liver and renal transplant recipients.
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Organ transplant recipients with chronic hepatitis B or hepatitis C virus infection may be at increased risk of fulminant hepatitis A. Liver transplant (LTX) recipients, renal transplant (RTX) recipients, and healthy controls received 2 doses of hepatitis A vaccine 6 months apart. Anti-hepatitis A virus (anti-HAV) seroconversion after the primary dose occurred in 41% of the LTX patients, 24% of the RTX patients, and 90% of the controls. After the booster dose, the respective rates were 97%, 72%, and 100% (P<.001). RTX patients also had significantly lower geometric mean titers (GMTs) of anti-HAV than LTX patients and controls. In the RTX group, the seroconversion rate and GMT were inversely associated with the number of immunosuppressive drugs received by the patients. The vaccine was well tolerated. Hepatitis A vaccine can be recommended to LTX and RTX patients, but the patients should receive a full course of 2 doses before imminent exposure. (+info)
The predictive value of transabdominal ultrasonography in the diagnosis of biliary tract complications after orthotopic liver transplantation.
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BACKGROUND: In transplant recipients with choledococholedocostomy (CDCD), endoscopic retrograde cholangiopancreatography (ERCP) remains the gold standard for the diagnosis of biliary leak or strictures. Transabdominal ultrasonography (TAUS) has been used to screen patients with suspected biliary tract complications, prior to ERCP, although the clinical effectiveness remains unclear. AIMS: To assess the predictive value of TAUS in the diagnosis of biliary tract complications after liver transplantation. METHODS: 144 consecutive ERCP and corresponding ultrasonogram reports performed over a 67 month period in 79 patients after liver transplantation were analysed retrospectively. RESULTS: 77 ERCP patients had both a TAUS and a successful ERCP. Biliary tract abnormalities were found at TAUS in 49 (64%) of the 77 patients. TAUS had an overall sensitivity of 77%, and specificity of 67%, with positive and negative predictive values of 26% and 95% respectively, when adjusted for the prevalence rate of biliary complications after liver transplantation of 12.8% in our population. The use of bile duct calibre as sole criterion for an abnormal scan improved the specificity (76%) and with a corresponding reduction in sensitivity (66%). The risk of false negative TAUS was similar in both the early and late post-transplant periods. CONCLUSIONS: A normal TAUS after liver transplantation with CDCD makes the presence of biliary complications unlikely. (+info)
An optimization model for sequential decision-making applied to risk prediction after liver resection and transplantation.
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The paper demonstrates a sequential decision procedure, which allows for optimal cost-effective or early decision-making while maintaining given error constraints. As a specific example the construction of a sequential decision procedure to determine if a patient was a high risk patient or not is used. The advantages of the procedure are demonstrated by a surgical problem of risk prediction from a clinical study on liver resection and transplantation. Data are available pre, peri- and postoperative, and form the basis of three clinical scores. The quality of the procedure is measured in terms of sensitivity and specificity, and the procedure will be optimized in a way, that a priori given error constraints will be maintained. A decision theoretic model is introduced and a robust procedure is developed. The approach is feasible for any fixed number of continuous clinical test scores obtained in a time sequence. Two sets of scores derived form linear discriminant analysis and artificial neural networks are compared. (+info)
Upregulation of heme oxygenase-1 protects genetically fat Zucker rat livers from ischemia/reperfusion injury.
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We examined the effects of upregulation of heme oxygenase-1 (HO-1) in steatotic rat liver models of ex vivo cold ischemia/reperfusion (I/R) injury. In the model of ischemia/isolated perfusion, treatment of genetically obese Zucker rats with the HO-1 inducer cobalt protoporphyrin (CoPP) or with adenoviral HO-1 (Ad-HO-1) significantly improved portal venous blood flow, increased bile production, and decreased hepatocyte injury. Unlike in untreated rats or those pretreated with the HO-1 inhibitor zinc protoporphyrin (ZnPP), upregulation of HO-1 by Western blots correlated with amelioration of histologic features of I/R injury. Adjunctive infusion of ZnPP abrogated the beneficial effects of Ad-HO-1 gene transfer, documenting the direct involvement of HO-1 in protection against I/R injury. Following cold ischemia/isotransplantation, HO-1 overexpression extended animal survival from 40% in untreated controls to about 80% after CoPP or Ad-HO-1 therapy. This effect correlated with preserved hepatic architecture, improved liver function, and depressed infiltration by T cells and macrophages. Hence, CoPP- or gene therapy-induced HO-1 prevented I/R injury in steatotic rat livers. These findings provide the rationale for refined new treatments that should increase the supply of usable donor livers and ultimately improve the overall success of liver transplantation. (+info)
Randomized trial of weekly sulfadoxine/pyrimethamine vs. daily low-dose trimethoprim-sulfamethoxazole for the prophylaxis of Pneumocystis carinii pneumonia after liver transplantation.
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We conducted a prospective, randomized clinical trial among liver transplant patients to assess the efficacy and safety of weekly sulfadoxine/pyrimethamine compared with daily trimethoprim-sulfamethoxazole in the prevention of Pneumocystis carinii pneumonia. The studied drugs were given during 6 months after transplantation. One hundred twenty patients were included. None of the 60 patients receiving weekly sulfadoxine/pyrimethamine developed Pneumocystis carinii pneumonia, whereas two cases (3%) developed among the 60 patients who received trimethoprim-sulfamethoxazole. For both patients, the studied medication had been discontinued several weeks earlier because of adverse effects. No differences were observed in the incidence of adverse effects. We conclude that weekly sulfadoxine/pyrimethamine is as effective and safe as is daily trimethoprim-sulfamethoxazole in the prophylaxis of Pneumocystis carinii pneumonia after liver transplantation. (+info)
Cross-Canada spread of methicillin-resistant Staphylococcus aureus via transplant organs.
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We report our investigation of the transmission of methicillin-resistant Staphylococcus aureus (MRSA) through transplantation. The kidneys, liver, and corneas were harvested from a child who died in Nova Scotia. Several days postmortem it was learned that culture of a premortem endotracheal tube aspirate from the donor yielded MRSA. Both kidneys were transplanted into a child in Nova Scotia and the liver into a child in Alberta. Both recipients subsequently became blood culture-positive for MRSA. One corneal ring from the donor was MRSA-positive. All four MRSA isolates were mecA-positive by polymerase chain reaction (PCR). The relatedness of the MRSA isolates was examined by restriction fragment length polymorphism (RFLP) analysis, a 16S-23S ribosomal PCR typing method, and comparison of antibiograms. Results were identical for all four MRSA isolates. These findings indicate that MRSA from the donor was transferred to recipients during implantation of harvested organs in Alberta and Nova Scotia, a cross-Canada spread. (+info)
Lessons From Genetically Engineered Animal Models VI. Liver repopulation systems and study of pathophysiological mechanisms in animals.
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The ability to localize transplanted hepatocytes in the liver offers exciting new opportunities. Transplanted hepatocytes enter liver plates, form hybrid plasma membrane structures with adjacent hepatocytes, express liver genes correctly, and survive indefinitely. The transplanted cell mass is regulated, such that cell proliferation is limited in the normal adult liver, whereas the liver is repopulated extensively when proliferation rates in transplanted and host hepatocytes become dissociated or host hepatocytes are ablated selectively. Transplanted hepatocytes are susceptible to hepatitis viruses. These aspects of transplanted hepatocyte biology indicate that liver repopulation systems can help address questions concerning pathophysiological mechanisms. (+info)