الفهرس 
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Abstract
The first human orthotopic liver transplantation (LT) in Europe was performed by Sir Roy Calne in Cambridge in 1968, only one year after the first successful human liver transplantation reported by Thomas Starzl in the United States.
Since then LT has evolved rapidly, becoming the standard therapy for acute and chronic liver failure of all aetiologies, with more than 80,000 procedures performed to date. Survival rates have improved significantly in the last 25 years, achieving rates of 96% and 71% at 1 and 10 years after LT respectively.
The incidence of acute and chronic rejection has declined with improvement of immunosuppression regimens in liver transplant recipients. Acute cellular rejection (ACR) occurs in 15–25% of liver transplant recipients on Tacrolimus based immunosuppression regimens and generally improves with steroids in majority. ACR does not affect long term graft or patient survival in most of cases,As acute rejection usually responds well to treatment.
The CD44 protein belongs to a large family of type I transmembrane glycoproteins. CD44, first described in 1983, is expressed on the surface of most vertebrate cells and is an important receptor for the components of extracellular matrix (ECM) such as: fibronectin, osteopontin, collagen and, most notably, hyaluronic acid (HA). CD44 and its interaction with hyaluronan have been found to be involved in a wide variety of physiological processes, among which are cell adhesion and migration, cell signaling, lymphocyte activation or tumor metastasis.
All members of the CD44 family areencoded by one single gene containing 19 exons in humans. Exons1 to 16 encode the extracellular part of CD44. The first 5 exons are expressed in all isoforms. The next 10 exons, exon 6 to exon 15, are designated as variant exons (v1-v10) as they are included in various combinations or excluded (in the CD44 standard (CD44s) isoform) by alternative splicing in the CD44 ectodomain. Exon 17 encodes the hydrophobic transmembrane domain and exons 18 or 19 give rise to the intracellular part of CD44, these three exons are common to all CD44 isoforms. The heterogeneityof the CD44 family is further increased by several posttranslational modifications, such as N- and O-glycosylations, or palmitoylation.
The study was conducted on patient all were recruited from ASCOT from May 2017 till December 2018. It included 20 adult patients with Post LDLT with elevated liver function tests and they were reviewed to determine if the serum level of CD44 had a value in diagnosis of acute rejection depending on proving the rejection by liver biopsy. They were distributed as 14 males and 6 females with age ranging 16 - 59 years. After obtaining the results of liver biopsy we had 14 patients with rejection, 4 patients with cholangitis with biliary obstruction and 2 patient with rejection with vascular insult.
The control group was with irrelevant past medical history and normal liver functions, normal liver biopsy and underwent measurement of CD44 serum level. They were distributed as 14 males and 6 females with age ranging 26 – 41 years.
In conclusion, there was correlation between different pathological findings in liver biopsy and Serum level of CD44 that the low levels being with rejection and higher levels being with control group, that the CD44 may be used as a marker for rejection.