What tattoos really do to our bodies' immune systems

(CNN)I lay on the mat of the open-air bungalow in Apia, Samoa, looking up at a gecko. As its tail quivered, I felt a sympathetic twitch in my leg. Su'a Sulu'ape Paulo III, the sixth-generation Samoan hand-tap tattoo master leaning over me, paused to see if my movement was due to pain.

I'd been in Samoa for a month, studying Samoan tattooing culture and the impact of the big traditional pieces called pe'a and malu -- tatau in general -- on the immune system. Now I was getting my own hand-tapped leg tattoo, albeit considerably smaller.
This field season was the fourth of my research on the relationship between tattooing and immune response. My first study had focused on a small sample, mostly women, in Alabama. What I'd observed among that group suggested that tattooing could help beef up one's immune response.
But one small study in the United States wasn't proof of anything -- despite headlines blaring that tattoos could cure the common cold. Good science means finding the same results multiple times and then interpreting them to understand something about the world.
    That's why I traveled in 2018 with fellow anthropologist Michaela Howells to the Samoan Islands. Samoans have a long, continuous history of extensive tattooing. Working with contemporary machine and hand-tap tattooists in American Samoa, we wanted to see if we'd find the same link to enhanced immune response.

    Immune defenders rush to tattoo's tiny wounds

    More than 30% of Americans are tattooed today. Yet, few studies have focused on the biological impact beyond risks of cancer or infection.
    Tattooing creates a permanent image by inserting ink into tiny 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. So 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 immunologists call adaptive responses. Proteins in the blood will try to fight and disable specific invaders that they recognize as problems. There are several classes of these proteins -- called antibodies or immunoglobulins -- and they continue to circulate in the bloodstream, on the lookout lest that same invader is encountered again. They're at the 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.
    In American Samoa, Howells and I worked at the Historic Preservation Office to recruit study participants with help from tattoo artists Joe Ioane of Off Da Rock Tattoos, Duffy Hudson of Tatau Manaia and traditional hand-tap tattooist Su'a Tupuola Uilisone Fitiao. Our sample of 25 tattoo recipients included both Samoans and