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What Red and Black Tattoos Do to Your Immune System
What Red and Black Tattoos Do to Your Immune System
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0:00
Whether it’s biker gangs or bachelorette parties, a lot of people love to get tattoos.
0:04
Nearly a third of people in the US and a quarter
0:07
of people in the UK have at least one tattoo. That’s a lot of people.
0:11
And getting that sweet body art involves injecting foreign material into the body,
0:16
not to mention the teeny puncture wounds from tiny needles as the ink is injected.
0:21
This process can cause inflammation,
0:23
and inflammation means the immune system is getting involved.
0:26
But even after the tattoo-induced inflammation subsides,
0:29
it looks like that sick dragon on your back is still affecting your immune cells.
0:34
Which could teach us something about – of all things – vaccination.
0:38
[♪ INTRO]
0:41
To know why your immune system is on the alert when you get a tattoo,
0:45
we have to talk a little bit about what tattoos are.
0:47
The inks are insoluble pigments suspended in alcohol or water.
0:52
Those pigments can be natural or synthetic chemicals.
0:55
Sometimes, metal oxides are present.
0:57
Some of the components in tattoo ink have been
0:59
known to cause allergic contact dermatitis.
1:02
In poorly regulated inks, there can be high levels of
1:05
certain metals or additives that aren’t great for you.
1:08
Also, tattoos are made of many tiny injection sites
1:12
and these can get infected, if not looked after properly.
1:15
But let’s go with the best-case scenario:
1:17
high-quality tattoo ink, injected under sterile conditions.
1:21
When you get a tattoo, ink is microinjected into your dermis,
1:25
the middle layer of your skin, below the sheddable skin cells of the epidermis.
1:30
Some of that ink gets washed away to the nearest lymph node,
1:33
but most of the pigment sticks around.
1:35
Your body’s “foreign object alert” goes off,
1:38
recruiting immune cells called dermal macrophages to check it out.
1:42
This is your immune system’s job.
1:44
There’s no way to say “don’t worry boys,
1:46
I’m doing this on purpose, so you can hang back for now.”
1:50
Besides, given the risks we mentioned earlier,
1:52
it’s probably good for your immune cells to get involved just in case.
1:56
The skin gets inflamed, because immune system signalling can cause swelling
2:00
and redness as blood vessels dilate and immune cells arrive on the scene.
2:04
But ideally, when those macrophages show up,
2:07
tattoo ink is the only foreign object around.
2:10
These cells swallow the pigment, but don’t digest it.
2:13
They stick around, keeping the ink in place.
2:15
A macrophage doesn’t live forever,
2:17
but when it dies another macrophage comes along and re-swallows the ink,
2:22
so the tattoo stays put.
2:24
Unfortunately, tattoo ink isn’t a healthy diet:
2:27
these macrophages have shorter lifespans than those that don’t eat ink.
2:31
So… maintaining a tattoo involves cycling through dermal macrophages.
2:36
But how does that affect the immune system overall?
2:39
To test this, in a 2025 study, researchers tattooed
2:43
mouse footpads with red, black, or green ink.
2:46
As we’ve mentioned, tattoo inks are not equal:
2:49
setting aside the lack of standardization in additives,
2:52
different colors have different pigments, hence the team testing three different inks.
2:57
What they found was that pigments accumulated in nearby lymph nodes,
3:01
causing a color-dependent increase in node size,
3:05
which was still significantly different two months post-tattoo.
3:09
There was also an uptick in the production of
3:11
immune signalling molecules immediately post-tattoo,
3:14
as well as recruitment of various types of immune cells
3:17
to the dye-laden lymph node.
3:19
Basically, the immune system was being vigilant.
3:22
The immune signals varied in timing and intensity between dye colors,
3:26
but all had some long-term effects.
3:29
All this got the researchers interested in how tattooing
3:32
would affect the immune system’s responsiveness to vaccination.
3:35
Vaccines work by giving your body a piece of
3:38
an infectious agent in advance of infection.
3:41
Or a dead version, or a genetic recipe,
3:43
depending on what kind you’re talking about.
3:45
In general, though, think of it like showing your immune cells
3:48
a mugshot so they can do a drill of their response.
3:51
This way, the body can get itself primed and ready to fight the real invader.
3:55
Vaccines are often delivered by injection.
3:58
And while we already know that it’s a bad idea to inject a vaccine
4:01
into a fresh tattoo, or to get a tattoo at the injection site just after vaccination,
4:07
it wasn’t clear how vaccines and tattoos interact more generally.
4:11
And if you didn’t know that, yeah, wait at least a month between
4:15
getting a vaccination and getting a new shoulder piece.
4:17
We’ll come back to the new study, but before that,
4:20
all science needs funding, so here’s a quick break.
4:23
This SciShow video is supported by Brilliant:
4:25
the online learning platform offering a new way to learn math.
4:28
And science and programming and data and a range of topics.
4:32
We all know the old strategy of cramming a bunch of formulas into your head
4:36
for a quiz coming up way too soon doesn’t lead to lifelong knowledge.
4:40
So Brilliant lets you play around with concepts until they make sense.
4:44
Like in their course on the Coordinate Plane
4:46
that shows you how to plot points and visualize the mathematical world.
4:50
To learn for free with Brilliant for a full 30 days, go to brilliant.org/scishow,
4:54
scan the QR code onscreen, or click on the link in the description.
4:58
They’re also giving you unlimited daily access to
5:00
everything on Brilliant with 20% off an annual Premium subscription.
5:05
So in this 2025 study, mice were given a COVID-19
5:09
mRNA vaccine 2 days or 2 months after tattooing.
5:13
And there was an effect: tattooed mice had
5:16
lower spike presentation on macrophages.
5:18
mRNA vaccines for COVID-19 deliver blueprints for a harmless piece of the virus.
5:25
In order to work, immune cells like macrophages have to take up the mRNA,
5:30
and translate it into the virus’s so-called spike protein.
5:34
Then they bring it to some B cells and go “Yo, get a load of this.”
5:37
Then the B cells go “Oooooh, so that’s what it looks like.
5:40
Cool, I’ve been warned and will be ready to
5:42
make a bunch of antibodies for next time it shows up.”
5:45
But in the mice with tattoos, the “get a load of this” part was happening less.
5:50
Tattooed mice also had reduced production of the type of antibody known as IgG,
5:55
and IgG is one of B cells’ go-to weapons.
5:59
Since their macrophages were already busy,
6:01
they weren’t expressing the spike protein as well.
6:04
So they weren’t presenting B cells with example spike protein,
6:08
which basically means the vaccine didn’t work as well in tattooed mice.
6:13
And they found that human immune cells cultured in a dish
6:16
that were given the mRNA vaccine behaved similarly
6:19
to the mouse model in the presence of different tattoo inks.
6:23
But it’s not all bad news.
6:24
A different set of mice were given a UV-inactivated flu virus,
6:29
a type of vaccine that doesn’t require
6:31
macrophages to take it up and make the antigens itself.
6:34
In this case, the mice with tattoos had more robust responses
6:38
to the vaccine than the control group, especially those tattooed in red or black.
6:43
In a way, the tattoo ink had primed the immune system.
6:47
We call ingredients that do this adjuvants,
6:49
and they’re often administered with vaccines to enhance their effects.
6:53
So it looks like the heightened immune surveillance caused by
6:55
tattoos could be a good or bad thing for vaccines, depending on the type.
7:00
Also, the effects varied depending on how recent the vaccine was.
7:03
But that’s not where the how-has-tattooing-affected-vaccination story ends.
7:07
A 2008 study showed that injecting vaccines using
7:10
a tattoo gun was more effective than your typical intramuscular injection.
7:15
Subsequent studies have shown similar results,
7:17
when it was a DNA-based vaccine being injected.
7:20
So even if it turns out tattoos don’t boost some vaccines in humans
7:23
the way they do in mice, one day your immune system
7:26
may still benefit from tattoo technology.
7:29
In theory, anyway.
7:30
Obviously, vaccination wasn’t ever the intended use of tattoo guns,
7:33
so researchers have been tweaking the system to enhance vaccine delivery.
7:37
Having tattoos could influence how your body responds to vaccination.
7:41
The type of ink and the timing could make a difference,
7:44
as could the type of vaccine.
7:46
Or at least, they do in mouse models, which are famously not people.
7:50
More work needs to be done, especially human studies,
7:53
to see what the pros and cons are.
7:55
Obviously, there’s nowhere near enough
7:57
evidence to make a recommendation about tattoos here.
8:00
But what does seem clear that tattoos are in a long-term relationship
8:04
with your immune cells, so it makes sense they’d affect immune responses.
8:08
Might not be something you think about when you’re in the artist’s chair,
8:11
but it goes to show just how complicated our bodies are.
8:14
[♪ OUTRO]
What Red and Black Tattoos Do to Your Immune System - Video học tiếng Anh
