Tattoo Keepers
Tattoos stay on the skin thanks to immunity
Kirill Stasevich, "Science and Life" based on LiveScience: Tattoos Last Forever Because Your Immune Cells Are Hungry for Dead Skin
Our skin is regularly updated, and this applies not only to the epidermis, in which the replacement of old cells with new ones takes only a month, but also to a deeper layer – the dermis. But if the skin is renewed, then why do tattoos remain on it for so long?
To understand why the tattoo pigment does not "fade" when the skin is renewed, researchers from the French INSERM Institute tattooed the tails of mice and traced how the skin cells behave.
When ink gets into the skin during tattooing, it attracts the attention of immune cells of macrophages. Their function is to eat everything alien and potentially dangerous. Macrophages also perceive pigment particles as something that should neutralize, and absorb them. But macrophages themselves don't live very long either. It would seem that after the death of the macrophage, the paint that was in it can now come off together with the dying skin particles.
However, as stated in an article in the Journal of Experimental Medicine, this "orphan" paint is picked up by other macrophages that have replaced the deceased.
In the experiment, mice were given an injection a few weeks after tattooing, which killed all macrophages in the skin (without harm to animal health) – however, the tattoo remained in place: new cells came to where it was and absorbed the paint that was found in the intercellular space of the dermis.
In another experiment, a piece of tattooed skin was transplanted from one mouse to another, and after six weeks, all the paint that was in the transplanted skin was transferred from the cells of one mouse (donor mouse) to the cells of another. According to the authors of the work, immune macrophages are the only cells in the skin that can absorb tattoo pigment, and tattoos remain on the skin for so long precisely because of this ability, as well as due to the fact that macrophages pick up the paint left after dead cells.
It is known that many people would like to reduce their tattoos, but now it takes quite a long time to erase a tattoo. It may be possible to speed up the process if you purposefully destroy macrophages on the tattooed area of the skin for a while – of course, doing this in such a way as not to damage the immune system as a whole.
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