الفهرس 
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Abstract
Microchimerism is the presence of a small population of cells or DNA in one individual that derives from another genetically distinct person. This process of cell traffic can occur between mother and fetus during pregnancy bidirectionally from fetus to mother and vice versa.
Due to the association between pregnancy and autoimmune disease, and the preponderance of these diseases in women, laboratory studies have for years attempted to link microchimeric fetal cells with the onset of auto immune diseases after pregnancy.
Studies demonstrated that within maternal tissues the fetal microchimeric progenitor cells are capable of self-renewal, proliferation, differentiation and activation.It have been demonstrated that this activation of progenitor cells can result in the production of paracrine and autocrine inflammatory cytokines and chemokines that are involved in autoimmune diseases. It was demonstrated that clones of these types of hibernating cells are involved in a form of graft-vs-host reactions seen in some autoimmune diseases.
Overall there appears to be evidence of increased fetal cell presence in diseased tissues than healthy tissues. For example, fetal microchimerism has been demonstrated in Hashimoto’s thyroiditis and Graves’s Disease but found to be absent in normal thyroids.Microchimerism is suggested to be implicated in the pathogenesis of the autoimmune diseases specially systemic sclerosis.
It is debatable whether microchimerism plays a role in triggering autoimmune disease perhaps by three mechanisms: Stimulating graft versus-host disease, host versus-graft disease or contribute to tissue repair.
Maternal microchimerism has been also found increased in association with some autoimmune diseases. As long term maternal microchimerism was first discovered in the peripheral blood of SSc patients and healthy subjects, and has been identified in the target organs and blood in NLS and myositis, so a role of maternal microchimerism in autoimmune diseases has been suggested.