How do tattoos remain for decades on the skin, while the cells that “contain” them (which hold the colored pigments) have a much shorter life and die? Researchers have been searching for an explanation for years, but now a possible response comes from a team of immunologists from Aix-Marseille Université (France). While performing a study on other topics, in fact, they have “come across” a mechanism that could of explain how pigments stay in the skin such a long time.
Basically, the researchers have seen that, when the cells die and degrade, the tattoo pigments (present in them) are captured and eaten, literally, by macrophages, fundamental cells of the immune system. When the macrophages die, they release the color in the surrounding microenvironment and in this way recall the response of other macrophages, which in turn eat the pigments and perpetuate the reaction, keeping the color in place. The pigments remain on site also because they are too big and can not be carried by the cells of the immune system, through the lymphatic vessels, in the lymph nodes. A detailed explanation of these complex mechanisms is available on the journal Scientific American, which resumed the study published by French researchers on the Journal of Experimental Medicine.
The conclusions of the scholars of Marseilles also reveal an important practical application: the possibility, that is, to facilitate the removal of tattoos by laser (an operation that currently does not often lead to satisfactory results), modulating the immune response temporarily. Furthermore, on the opposite side, the mechanism identified by the immunologists of the Aix-Marseille Université could be exploited in the future to absorb different types of molecules through the skin for therapeutic purposes.