A recent study revealed that tattoo pigments do not stay in the skin; instead, they migrate and accumulate in lymph nodes, potentially leading to lifelong alterations in the immune system. Current findings do not yet permit a conclusion regarding whether these changes are beneficial or detrimental. Scientists merely suggest that pigment retention in the lymph nodes might persistently affect local immunity.
The complex mixture of the ink, which is insoluble in bodily fluids, provides tattoos with their longevity. Although prior research has linked tattoo ink ingredients to various health concerns, there is insufficient investigation into how ink components interact with the immune response.
To assess how tattooing impacts the immune response, the study’s first author, Santiago F. Gonzalez, and his associates developed a mouse model.
They applied a tattoo measuring 25 square millimeters on the paw pads of mice using three widely used commercial inks (black, red, and green). Employing advanced microscopy, the research team tracked ink transfer in real time immediately following the tattooing procedure.
The results demonstrated that the pigments do not remain solely in the skin but also enter the lymph nodes. Within the lymph nodes, macrophages—immune cells that eliminate microbes and damaged cells—engulf these pigments and trigger an inflammatory response.
Within 24 hours, the researchers observed a “significant reduction” in the total macrophage count, indicating that tattoo ink causes macrophage death. Traces of the pigment persisted in the lymph node even after two months.
The paper hypothesizes that the persistence of the ink and the demise of macrophages may impact these cells’ capacity to manage the spread of pathogenic viruses and bacteria. The research is published in the Proceedings of the National Academy of Sciences.
Since macrophages are crucial for generating a sustained immune response following vaccination, the team was interested in testing vaccines. They administered an mRNA-based COVID-19 vaccine or an ultraviolet-inactivated influenza shot directly into the tattooed footpad.
Regarding the COVID vaccine, the antibody response against the protein was weakened. Conversely, with the flu vaccine, the opposite occurred: the ink likely bolstered the immune reaction.
Santiago explains that mRNA-based vaccines require macrophages to capture the vaccine and express the antigens that ensure the mRNA vaccine’s efficacy.
“In tattooed individuals, these macrophages are full of ink, so the ink essentially prevents [the vaccine] from functioning properly,” stated Santiago.
In the case of the influenza vaccine, the response is steered by dendritic cells rather than macrophages.
“These dendritic cells perceive the inflammation caused by macrophage demise as a sort of adjuvant,” says Santiago, explaining why tattoo ink might enhance the immune response.
Ultimately, Santiago suggested that individuals should generally refrain from injecting vaccines directly into tattooed skin. Moreover, he recommends that people exercise caution when getting tattoos overall. Much remains unknown that warrants further exploration.
Humans began creating tattoos a very long time ago. An international consortium of anthropologists, cultural heritage specialists, and lab technicians discovered tattoos on the face and arm of an 800-year-old Andean mummy that had never been previously encountered.
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