When you decide to get a tattoo, your mind runs to the design, the artist, perhaps the pain. But perhaps we should be more concerned with what happens to the immune system.
The spread that lasts for years
Researchers analyzed the three most popular colors in tattoos: black, red and green. After application, the ink passes through lymphatic vessels and accumulates in lymph nodes, organs that filter and monitor lymph and play a key role in the immune response.
Acting on this process are macrophages, stationary immune cells that specialize in capturing and neutralizing foreign agents. Ink represents an unusual target: macrophages engulf it but fail to degrade it. This accumulation of pigment in the lymph nodes can persist for years or even the entire life of the tattooed subject, keeping the cells in a constant state of stress.
Cellular stress
Pigment uptake causes cellular damage by inducing apoptosis, i.e., programmed death, in macrophages. Red and black inks have been found to be particularly toxic in vitro, increasing the number of dead cells. This continuous process leaves the ink trapped and gradually impairs the immune system’s ability to defend itself, reducing the effectiveness of cells deputed to fight foreign agents.
The body’s reaction to ink develops in two phases. An initial acute phase occurs locally in the first few hours after the tattoo, followed by a chronic phase that can continue for months. Researchers have detected signs of inflammation in draining lymph nodes up to two months after tattooing.
This condition of persistent inflammation can contribute to a progressive weakening of the immune system and increase vulnerability to more serious diseases.
Vaccines and impaired immune response
One of the questions raised by the study concerns the impact of tattoos on vaccine response. Experimental data indicate that ink accumulated in the lymph nodes can modulate the immune response in a vaccine-specific manner. A reduced IgG antibody response to the anti-SARS-CoV-2 mRNA vaccine was observed in tattooed mice. Similar results were also found in human immune cells.
In contrast, the response to UV-inactivated influenza vaccines was enhanced, probably because the ink-induced inflammation acts as a natural “adjuvant,” strengthening the response of some vaccines but interfering with more complex mechanisms, such as those of mRNA vaccines.
Understanding the mechanisms by which ink interacts with the immune system is a key step in making this practice safer, without necessarily having to give up the artistic expression that, for many, makes tattooing a form of personal identity.
