“Tattooing creates a permanent image by inserting ink into punctures under the topmost layer of skin. Your body interprets a new tattoo as a wound and responds accordingly in two general ways.
Innate Immune responses involve general reactions to foreign material.
Getting a new tattoo triggers your immune system to send white blood cells called macrophages to eat invaders and sacrifice themselves to protect against infection.
Your body also launches what immunologist call adaptive responses. Proteins in the blood will try fight and disable specific invaders that they recognize as problems.
Several classes of proteins such as
1. Antibodies
2. Immunoglobulins
Proteins continue to circulate in the bloodstream, on the lookout lest that same invader is encountered again.
Proteins are at ready to quickly launch an immune response the next time around.
This adaptive capacity of the immune system means that we could measure immunoglobulins in saliva as approximations of previous stress caused by tattooing.”
https://edition.cnn.com/2019/10/03/health/tattoo-immune-system-conversation-wellness/index.html
“A recent study by the American Journal of Human Biology claims that tattoos may stimulate immune system responses in individuals who receive them over time.
Researchers measured the immune function of participants by collecting a sample of their saliva and analyzing their levels of immunoglobulin A (IgA, an antibody in mucus membranes) before and after tattoo sessions.
Results showed that immune system response was greater in subjects with more tattoo experience than in those with less. Participants who had the least amount of tattoo experience had the greatest decrease in the IgA than those who had the most experience.”
https://www.ctpost.com/living/article/Study-Tattoos-stimulate-immune-system-response-6891004.php
“Study revealed that those with no pre-existing tattoos experienced a greater strain on their immune system (a larger dip in their IgA levels) possibly due to greater feelings of stress.
Those on their second, third (or twelfth) tattoo instead experienced a surge in their IgA immediately following their inking session. Their bodies appeared to be less stressed by the experience having gone through the process at least once before.”
https://www.scientificamerican.com/article/do-tattoos-boost-your-immune-system/