start here

You are running a private army

Right now, without asking you, millions of cells are patrolling your body. You have never met them and they have never had a day off.

This is what they do all day, and the one mistake that turns them against you.

the day job

Most of it you never notice

A nick from a bread knife. A dodgy prawn. Whatever the office has been coughing round all week. It gets dealt with while you get on with your evening.

When people talk about having a good immune system, this is it. A night shift you never see the invoice for.

the only rule

Is this me, or is this not me?

Every immune cell is basically a bouncer with one question on the clipboard. Not me gets thrown out. Me gets waved through.

Miss a real germ and you get an infection. Mistake yourself for a germ and you get an autoimmune disease. Same question, two ways to get it wrong.

ONLY ME, THANKS

boot camp

Almost nobody graduates

Recruits train in the thymus, a gland behind your breastbone. Anything that reacts to your own body gets binned on the spot.

0still standing

›››

drag to run the cull

👈

nobody is squeaky clean

A few sneak out anyway

The cull is brutal, but it is not perfect. You are walking around right now with cells that could turn on you.

So is everybody else. Your mates, your gran, your dog. Which raises the obvious question: why isn't everyone ill?

the answer

Because someone holds the lead

A second set of cells spends your entire life keeping the twitchy ones calm. Think of the sensible friend who quietly takes your car keys off you.

For most people that arrangement holds for life. Autoimmune disease is what happens when it stops holding.

SAME SHAPE. OOPS.

how it goes wrong

A germ turns up wearing your face

Your army memorises an invader's shape. If a piece of that shape looks like a piece of you, it has just memorised you as well.

0shape match

›››

drag the virus in

👈

and then it doesn't stop

The germ leaves. The army stays.

Normally a fight ends because the enemy is gone. Your own joints, thyroid or gut cannot exactly move out.

That is the whole disease in one line: a battle with no way to finish, inside a building you happen to live in.

what it feels like

It comes in waves, not a straight line

Flares, then quiet spells. Swelling, stiffness first thing, and a bone deep tiredness that a good night's sleep does nothing for.

Which is why it often takes years to name. On a decent week you look completely fine to everyone around you.

same mistake, different address

Where it happens decides what it's called

Around 80 named autoimmune diseases. Largely the same error, just at a different address.

0under attack

›››

drag through the body

👈

the unfair bit

Four in five patients are women

Nobody has fully cracked why. The leading suspect is the X chromosome: women have two, and the machinery that quietens the spare one seems to leave tempting targets lying around.

Hormones and the immune rewiring of pregnancy are the other suspects. This one is still an open question, not a solved one.

EVERY DIAL IS A TRADE

so what do you do

You can't retrain it, so you turn it down

Anti-inflammatories, then steroids, then drugs like methotrexate, then biologics that block one signal instead of the whole system.

0immune volume down

›››

drag the volume down

👈

the whole thing

Six things you now know

1 questionIs this me? Every immune cell is trained on that, and nothing else.
2 to 5%Of recruits survive thymus boot camp. The rest reacted to you.
mimicryA germ that looks a bit like you gets you attacked by mistake.
80+Named autoimmune diseases. Same error, different address.
4 in 5Patients are women, and the X chromosome is the best guess why.
the tradeTreatment turns your army down, so infections get an easier run at you.

Not a body breaking down. A body working exactly as designed, aimed at the wrong thing.