The Scientist asks,
Diverse mammals, including humans, have been found to carry distinct genomes in their cells. What does such genetic chimerism mean for health and disease?
…
One common cause of such microchimerism is maternal-fetal trafficking of cells during pregnancy. The placenta is not an unbreachable barrier. Evidence of two-way cell transport across the placenta was reported as early as the 1950s and ’60s. While the mother’s immune system gets rid of most of her baby’s cells shortly after delivery, small numbers of fetal cells have been observed in mothers decades after they have given birth. In fact, because even spontaneous abortions cause fetal cells to be released into the mother’s body, women who become pregnant but never give birth can also display this form of microchimerism.7 Conversely, maternal cells have been found in the liver, lung, heart, thymus, spleen, adrenal, kidney, pancreas, brain, and gonads of healthy adults.8 Microchimerism could also originate from siblings’ cells, transferred from the mother during successive pregnancies. Regardless of the direction of transfer, the exogenous cells can migrate to a certain tissue, where they differentiate and proliferate, acting as if they were engrafted.
Likely critical to this integration of fetal cells in a mother’s tissues are the immune changes a woman undergoes during pregnancy to allow for tolerance of the fetus, which is genetically distinct from the mother and therefore potentially subject to immune attack. These changes could also explain why numerous autoimmune disorders seem to be associated with pregnancy. For example, the symptoms of rheumatoid arthritis sometimes improve during gestation but tend to return within three months of delivery. But could microchimerism also play a role in the etiology of these and other disorders?
So whatever did happen about the This is you CD?
You two?
Note: Most strange events in human life only come to attention if someone seeks modern medical treatment. The vast majority of human beings have lived and died without ever doing so. There may be more surprises yet.