Have you ever heard of microchimerism? It is the harboring of small numbers of cells that originated in a genetically different individual. This happens naturally during pregnancies, when the cells of the mother are transported to the fetus and vice versa. Such cells can be found in different regions of body. Currently it is still not clear, whether they are harmful or helpful for the women’s organism.
The broadest research in microchimerism(MC) is dedicated to finding a link between autoimmune diseases and MC. So far, there are 200 papers published on MC-autoimmune disease coincidence. Nearly half of them, as seen on the figure below, are from USA. Studies suggests that the number of male cell DNA in women with autoimmune diseases such as rheumatoid arthritis, scleroderma, thyroiditis, etc., are higher than in women without these conditions. The most cited research paper on relationship between MC and autoimmune disease is “Microchimerism and HLA-compatible relationships of pregnancy in scleroderma.” with 55 citations.