الفهرس 
FETAL MICROCHIMERISM (FMOnly 14 pages are availabe for public view
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Abstract
Chimerism in an individual refers to the coexistence of cells arising from two distinct organisms. It can arise iatrogenically via transplant or blood transfusion, and physiologically via twin to twin transfer, or from trafficking between mother and fetus during pregnancy ( Rust & Bianchi , 2009). The fetal cells persist in the mother for decades and colonize a variety of maternal organs. It has been associated with disorders of pregnancy, autoimmune disease and the clinical outcome of allogeneic hematopoietic stem cell transplantation (Lapaire et al., 2007). Fetal microchimerism has been implicated as a factor in the longer lifespan of women (Johnson & Bianchi, 2004). Microchimeric fetal cells may include stem cells capable of prolonging natural tissue repair and regeneration (Mikhail et al., 2008). They are also capable of differentiation into tissue lineages and express appropriate phenotypic markers and genes for differentiation into liver, heart, pancreatic and vascular endothelial cells (Gordon et al., 2006).
Many of the diseases associated with microchimerism affect the endocrine system. Studies of feto-maternal microchimerism in the thyroid have documented the presence of fetal cells in association with Hashimoto thyroiditis, Graves’ disease, thyroid adenoma, and papillary thyroid carcinoma. Studies of materno-fetal microchimerism have documented the presence of maternal cells in juvenile diabetes and other pediatric conditions ( Rust & Bianchi , 2009).
Fetal cell microchimerism has potential implications for every female who has been pregnant (Lapaire et al., 2007). Cells of fetal origin have been found within maternal hematopoietic and immune cell populations (Khosrotehrani & Bianchi, 2005), mesenchymal cells from the marrow (O’Donoghue et al., 2003) and tissues and organs such as heart, liver, spleen and thyroid (Bayes-Genis et al., 2005).
During pregnancy, fetal microchimerism has been exploited for prenatal gender determination and potentially for prenatal diagnosis of karyotypic abnormalities (Bianchi, 2007). Assays for fetal microchimeric cells are being actively pursued. In particular, cell-based assays are considered to be especially desirable because it then becomes possible to identify single cells of fetal origin and to perform prenatal diagnosis as well as gender assignment in the same cell (Bianchi & Hanson, 2006). Nucleated red blood cells in the maternal circulation are unique in having an exclusively fetal origin and have been used as a target cell population for fetal gender identification (Cha et al., 2005). Cells of fetal origin have been detected among other mature cell types in maternal blood, including lymphocytes, monocytes and natural killer cells (Loubiere et al., 2006), but these cell types are less likely than stem cells to persist in the long-term or to explain the observations of fetal cell microchimerism in diverse tissues. Many studies have demonstrated that fetal DNA can be detected in maternal blood using more sensitive methodology such as PCR (Bianchi, 2004). PCR is a biochemistry and molecular biology technique for enzymatically replicating DNA without using a living organism, such as E.coli or yeast. Q-PCR is used to measure the quantity of a PCR product. It is the method of choice to quantitatively measure small amounts of DNA (Podzorski, 2003). Application of the Q-PCR assays range from microchimerism determination to viral / proviral load characterization (Wilhelm & Pingoud, 2003).
In our study, the presence of Y- chromosome specific sequence in maternal peripheral blood was examined in an attempt to detect feto-maternal microchimerism using real time quantitative polymerase chain reaction-based assay with fluorogenic Y - chromosome specific Probes (SRY). The study was performed on a total of 50 out-patient women, without prior blood transfusion history, divided into 2 groups: The first group comprised 35 parous women who had given birth to at least one male offspring as a test group. The second group comprised 15 women with no prior history of male pregnancies.
Our results revealed that the quantity of the Y- chromosome present in the maternal blood was significantly higher among the test group compared to the control group. Of the women who had one male offspring, 87.5% exhibited the presence of Y- chromosome. On the other hand all the women who had more than one male offspring exhibited the presence of the Y- chromosome. In addition there was a significantly higher quantity of Y- chromosome detected among the group of females who had more than one male offspring. Thereby a significant positive correlation was established between number of male offspring and quantity of Y- chromosome detected in the maternal circulation. No significant correlation was established between the age of the male offspring and the presence of Y – chromosome in the maternal blood. from our previous findings we conclude that fetomaternal microchimerism does in fact exist among this cohort of parous women and the degree of which is affected by the number of male pregnancies regardless the time that has elapsed since the last pregnancy. Detection of fetal microchimerism has tremendous impact on an array of medical aspects that can make use of such a phenomenon.