Could You Be a Human Chimera Without Knowing It?
Hey there! Welcome to Life Noggin! Did you know you could be a chimera and not even know it? I don’t mean a fire-breathing lion-goat-snake hybrid—that’s just a mythical creature, unfortunately. And I’m pretty sure you’d notice if you had body parts from other animals sticking out of your back. But you should probably turn around and check, just in case!
In reality, being a chimera means someone is comprised of at least two genetically distinct sets of cells, which means their body contains at least two different sets of DNA.
How Natural Chimerism Happens: Microchimerism, Twin Chimerism, and Fusion
Chimera cell populations come from multiple zygotes, or fertilized eggs. This can naturally happen in a few different ways. For instance, while a fetus is in the womb, cells can travel across the placenta, leading to the fetus absorbing a few of its parent’s cells—or vice versa. This is known as microchimerism.
Then there’s twin chimerism, which occurs when fraternal twins are conceived but one embryo dies in the womb. The surviving embryo could absorb some of the cells from the deceased embryo if their placentas are attached, with these cells often found in the bloodstream.
Finally, there’s fusion, or tetragametic chimerism, which can also happen when a fraternal twin embryo doesn’t survive. In this case, the two zygotes fuse together, forming one embryo. Individuals with this type of chimerism will have tissues made up of cells from one or both zygotes—meaning you could technically be your own twin.
What Are the Physical Signs of Being a Chimera?
In rare instances, people with tetragametic chimerism may have patches of different-colored skin, two different-colored eyes, or even both male and female genitalia. Those with microchimerism may experience autoimmune issues. However, most individuals with natural chimerism have no symptoms and can live their entire lives without knowing it.
Scientists don’t know how many people have natural chimerism, but some theorize it could be up to 10% of the population.
Artificial Chimerism: Blood Transfusions and Organ Transplants
Chimerism can also occur artificially. For example, a recipient of a transfusion or transplant can absorb some of their donor’s cells, which is a form of microchimerism. This can even happen if the donor isn’t human.
Xenotransplantation: Using Animal Organs in Human Bodies
Xenotransplantation involves transplanting organs, cells, or tissues across different species. Scientists have been experimenting in this field for over a century, and they believe the potential benefits are considerable, especially since the demand for transplants far exceeds the supply.
Xenotransplantation of animal organs and cells into human patients with life-threatening conditions began in the 1960s. These transplants most often come from pigs, which are now genetically modified to avoid rejection by the human body. However, pig cells contain porcine endogenous retroviruses in their genome, which can potentially infect human cells.
Because chimerism occurs during xenotransplantation, scientists are developing methods to detect infection rather than chimerism. This is one of the many things they’re working on to make xenotransplantation safer and more effective. Recent breakthroughs include the first patient to receive a pig heart and another to receive a pig kidney, both of whom lived for two months post-surgery—a huge step in this field.
Your Thoughts on Cloning and Future Topics
Question for you: If you could clone yourself, what would be the first thing you’d do? Let me know in the comments, or tell me what topic we should cover next!
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Sources for this video:
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