A recent study published in the Journal of Experimental Medicine described how immune cells can be used to improve tattoo removal procedures. The study was done at the Immunology Center of Marseille-Luminy in France and led by researchers Sandrine Henri and Bernard Malissen.
By studying mice that had been tattooed, Henri and Malissen found that macrophages, a type of immune cell that can consume foreign unhealthy debris, may help to make tattoos less permanent.
Henri said that the group studied a mouse in which macrophages were eliminated. Using these mice, the team identified the identity of skin cells that are responsible for the maintenance of tattooed skin.
“By characterizing their phenotype, origin, and dynamics, we showed that they corresponded to dermal macrophages that have ingested melanin granules,” Henri, Malissen and co-authors wrote in the study. “Benefiting from the knowledge gained on melanophage dynamics, we further elucidated the identity, origin, and dynamics of the myeloid cells that are found in the mouse skin and capable of capturing and retaining tattoo pigment particles.”
The study was actually an accident as neither Henri nor Malissen was initially looking to study tattoos. Instead, they noticed that macrophages bound to melanin granules in black mice and were led to consider how immune cells might affect tattoos.
The researchers tattooed green stripes on the tails of albino mice and using a microscope, found out that macrophages did indeed attach to the ink particles. Killing off the ink-bound macrophages did not do anything to the tattoo because new macrophages replaced the dead ones.
Most people think that tattoos are permanent because the ink sits deep in the skin. This belief has been backed by previous scientific trials that stated tattoos work by permanently staining fibroblasts, or cells that synthesize collagen.
However, the researchers in this study said that tattoos are maintained by macrophages continuously engulfing and regurgitating ink crystals.
Most of the time, when foreign substances enter the body, macrophages descend to consume the toxin. However, because ink gradules are too bulky for breakdown by macrophages, the macrophages instead simply hold on to the granules.
When the granule bound macrophage dies, the remains of the immune cell, along with the ink granules, are consumed by a new macrophage, completing the ink recycling process.
The idea that macrophages bind tattoo ink particles may be important in future techniques used to remove tattoos. According to the New York Times, tattoo laser removal can take as many as 20 treatments.
In the United States alone, one in five people have a tattoo somewhere on their body, and there are tens of thousands of laser removals annually. Researchers are now working to see if anti-inflammatory ointment that suppresses macrophages can help to reduce the number of treatments for tattoo removal.
Some dermatologists have attempted this ointment technique with successful results. For example, according to the New York Times, Jared Jagdeo, a dermatologist at the University of California, Davis, has been using this technique since 2014 and can now remove tattoos in 10 or fewer treatments.
