الفهرس 
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Abstract
Liver transplantation (LT) has emerged as an established and well-accepted therapeutic option for patients with acute and chronic liver failure and hepatocellular carcinoma. Hepatic allograft rejection is an inflammatory pathologic condition elicited by a genetic disparity between the donor and recipient and occurs due to T-cell mediated or antibody-mediated processes. It is classified into acute and chronic rejection based on timing, reversibility, and the histological features of the inflammatory infiltrate and the best diagnosis is through a percutaneous allograft biopsy based on Banff schema. Immunosuppression after LT requires a balance between prevention of graft rejection and minimization of the side effects of immunosuppressive drugs.
Regulatory T cells (Treg cells) constitute 1 to 2% of the human peripheral blood mononuclear cells (PBMC). They play an important role in T cell homeostasis and are critical regulators of immune tolerance. Quantitative and/or qualitative deficiencies of Treg cells have been suggested to contribute to the development of autoimmune diseases. Treg cells are defined by expression of the forkhead family transcription factor FOXP3 (forkhead box p3). In transplantation, FOXP3+ T cells play a role in the suppression of the donor-activated effector T cells and in tolerance induction
The FOXP3 gene is the main regulatory gene for the development and function of Treg cells and can convert naive T cells to Treg cells phenotype. The FOXP3 gene is polymorphic; the gene polymorphism has a significant role in allograft rejection episodes and posttransplant graft function after organ transplantation.
The aim of this study was to count the Treg cells (CD4+CD25+ FOXP3+) in the peripheral blood and to study the FOXP3 rs3761548 gene polymorphisms in living donor liver recipients, to analyze the relation between the circulating Treg cells, the gene polymorphism and the occurrence and degree of severity of acute cellular rejection (ACR) and to study the relation between the circulating Tregs, the gene polymorphism and the occurrence of different infectious complications, and finally to analyze the relation between the immunosuppressive regimens received by the transplant recipients, the circulating Treg cells and the gene polymorphisms.
The present study included 100 subjects who were classified into four groups. The first group included 30 transplant recipients with ACR and the degree of rejection was classified into (mild, moderate and severe) according to Banff Schema, the second group included 30 transplant recipients without ACR, the third group included 20 chronic hepatitis C patients, and the fourth group included 20 age- and gender-matched healthy volunteers as control group.
All participants in this study were subjected to full history taking and their laboratory investigations were collected from their files. All the transplant recipients received immunosuppressive drugs based on the National Liver Institute policy.
Culture, isolation and identification of microorganisms from the different clinical samples (collected from all the transplant recipients under aseptic technique up to one month post-surgery) were performed according