It has never been easy to explain how tattoos work. While the tattoos are 'forever', but the cells of the dermis do not: change many times throughout life. Why don't they disappear? The key seems to be in the macrophages.
Macrophages are cells with hunger. A central element of the immune system that specializes in recognizing, swallowing and destroying damaged, dead cells or different types of infections. They are to put it in some way, the thugs of the immune system, those who do "dirty work". And, for adjusting to the cinematic cliché, as good bullies they are, they love tattoos.
Ink, skin and macrophages
For years, it was thought that tattoos worked by staining fibroblast cells in the dermal layer of the skin. More recently, researchers have suggested that macrophages are attracted to the wound produced by the needle and devour the pigment as if it were an aggressive pathogen.
However, none of these explanations solved the problem. Now a group of French researchers has discovered that these cells can pass the pigment to the new cells when they die.
To unravel the problem, two researchers Sandrine Henri and Bernard Malissen of the Immunology Center of Marseille-Luminy developed genetically modified mice thanks to which they were able to eliminate macrophages from the dermis and some other tissues. After eliminating them, the cells end up being replaced by new macrophages.
The funny thing is that, although they confirmed that the dermal macrophages were the only type of cell that acquired the pigment when they tattooed the tails of the mice. However, when they removed these macrophages, the tattoo remained. The only conclusion is that macrophages release the pigment at death and weeks later it is absorbed by the new macrophages that take its place.
The weak point of tattoos
This cycle of capture, release, and recapture of the pigment occurs continuously in the tattooed skin. "We believe that when macrophages laden with tattoo pigment die during the course of adult life, neighboring macrophages recover the released pigments and dynamically ensure the stable appearance and long-term persistence of tattoos," explains Henri.
It is true that tattoos can be removed by laser pulses that cause skin cells to die and release their pigment. There, as we now know, a dialectic begins between neighboring macrophages that struggle to maintain the pigment and the lymphatic system of the body that tries to keep it away from the skin.
"The elimination of the tattoo can be improved if we combine laser surgery with the transient elimination of the macrophages present in the tattoo area," the researchers say. "As a result, the pigment released by laser pulses would not be recaptured immediately, which increases the likelihood of them draining through the lymphatic vessels."