\n <\/p>\n
Hidden Guests: Migrating Cells and How the New Science of Microchimerism is Redefining Human Identity Lise Barn\u00e9oud, transl. Bronwyn Haslam Greystone Books (2025)<\/p>\n
The chimaera of Greek mythology was \u201can evil creature with a lion\u2019s head, a goat\u2019s body, and a serpent\u2019s tail\u201d, notes journalist Lise Barn\u00e9oud in Hidden Guests. Humans are also chimaeras \u2014 thanks to the presence of cells that are not our own inside our bodies.<\/p>\n
Could baby\u2019s first bacteria take root before birth?<\/p>\n<\/p>\n
Mothers carry cells that came from their biological children, passed across the placenta when the baby was in the womb. Likewise, children carry cells that were transferred to them in utero from their mothers \u2014 some of which might even be from the child\u2019s maternal grandmothers, older siblings or twin.<\/p>\n
These \u2018microchimeric\u2019 cells have been found in every organ that has been studied so far. But they are also rare \u2014 much rarer, for example, than the trillions of microorganisms that reside in our guts, on our skin and in many other organs. We carry only one microchimeric cell for every 10,000 to 1 million of our own cells.<\/p>\n
In Hidden Guests, the author invites readers to learn about the pioneering \u201cmicrochimerists\u201d \u2014 scientists who discovered these fascinating shared cells. She also challenges us to consider the broader implications for health and science, and the philosophy of the fact that we are all chimaeras.<\/p>\n
Microchimeric cells were, we learn, discovered through a series of accidental observations. In the late 1800s, pathologist Georg Schmorl described \u2018giant cells\u2019 in the lungs of people who had died from eclampsia \u2014 a life-threatening inflammatory condition that can occur during pregnancy. These giant cells resembled the cells of the placenta, leading Schmorl to suggest that fetal cells passing into the bloodstream of mothers was the norm, rather than the exception.<\/p>\n
The probiotic home: where microbes are welcome guests<\/p>\n<\/p>\n
Then, in 1969, a team studying immunity in pregnant people detected white blood cells that contained the Y chromosome in the blood of individuals who would eventually give birth to boys1. For more than two decades, it was presumed that these microchimeric cells were a temporary feature of pregnancy. It wasn\u2019t until 1993 that geneticist Diana Bianchi found cells with Y chromosomes in women who had given birth to sons between one and 27 years earlier2.<\/p>\n
This finding overturned the dogma that children inherit genes from their parents and never the other way around \u2014 these transferred fetal cells move through the family tree, travelling \u2018backwards in time\u2019 from children to their mothers. Bianchi and others would go on to show that these cells have remarkable regenerative properties \u2014 promoting wound healing in mothers by transforming into blood vessels or skin cells.<\/p>\n
Microchimerism also calls into question a central tenet of immunology: that the immune system works by classifying cells in a binary fashion, as \u2018self\u2019 or \u2018non-self\u2019. Under this simplistic model, microchimeric cells should trigger an immune response and be rejected by the body \u2014 but they do not. Barn\u00e9oud challenges readers to consider whether forcing microchimerism-related discrepancies to fit into existing immunological rules is appropriate, instead of allowing these cells to influence new immunological rules.<\/p>\n
At around the same time that Bianchi was making her groundbreaking discovery, rheumatologist Lee Nelson also found Y-chromosome-containing cells in people who had previously given birth to sons3. Nelson was studying autoimmune diseases, which disproportionately affect middle-aged women, and at the time were thought to be caused by hormone imbalances.<\/p>\n
Cells pass from mother to baby, and vice versa, across the placenta.<\/span>Credit: Jeffrey Davis\/Getty<\/span><\/p>\n","protected":false},"excerpt":{"rendered":" Hidden Guests: Migrating Cells and How the New Science of Microchimerism is Redefining Human Identity Lise Barn\u00e9oud, transl. Bronwyn Haslam Greystone Books (2025) The chimaera of Greek mythology was \u201can evil creature with a lion\u2019s head, a goat\u2019s body, and a serpent\u2019s tail\u201d, notes journalist Lise Barn\u00e9oud in Hidden Guests. Humans are also chimaeras \u2014<\/p>\n","protected":false},"author":1,"featured_media":39974,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[10185,376,6401,337],"class_list":{"0":"post-39973","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-cells","9":"tag-death","10":"tag-genetically","11":"tag-life"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/39973","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=39973"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/39973\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/39974"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=39973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=39973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=39973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}