[Gestational microchimerism in human diseases]. / Microchimérisme postgestationnel en pathologie humaine.

Microchimerism is defined as the persistence within an individual of a low level of cells or DNA derived from another individual. The most common source of microchimerism is pregnancy. Bidirectional transplacental materno-fetal cell trafficking occurs during most pregnancies and chimeric cells can persist in blood or tissues for decades after childbirth. It can leads to fetal (fetal-maternal transfer) or maternal (maternal-fetal transfer) microchimerism. Characterization of cells implied in microchimerism is incompletely known: it could be at least partly, fetal progenitors cells with ability of self renewal and specific differentiation according to the surrounding tissue. The transferred fetal cells can be recruited in various injured maternal tissues (auto-immune diseases, stroma of various tumours associated with pregnancy) but their precise biological role is uncertain. Microchimerism has been implicated in the pathogenesis of autoimmune diseases (especially systemic sclerosis) but current data suggest that fetal microchimeric cells may participate in maternal physiological response and injured tissue repair. Similar observations were made with maternal microchimerism (excepted with juvenile idiopathic inflammatory myopathies whose immunopathogenesis is probably related with transfer of maternal immune cells).