surgery, and then after a few years, your body’s like NOPE I DON’T LIKE THIS THING,

GET IT OUT and rejects that vital organ.

... heartbreaking, right?

Transplant rejection happens, and more often than you’d think.

About 50% of all transplanted organs are rejected within 10-12 years.

That’s a staggering number.

Organ rejection happens at the molecular level, something just isn’t compatible, and finally,

scientists think they’ve uncovered the basis of this response.

This is a-metaphorically-huge-but-literally microscopic-thing!

So we have to understand how the body deals with a foreign lung or liver or whatever.

And that relationship starts with the immune system.

So, let’s say you’re getting a new kidney … It’s a whole ecosystem of living things.

And it’s ALIEN.

The immune system knows this because the cells on the donor organ are different . But once

it knows, it’s definitely not going to ignore it.

As far as the immune system is concerned it could be a giant virus or poison!

So, it tries to get rid of it!

Your immune system is designed to attack anything it doesn’t recognize.

And there are two main parts within the human immune system that are responsible for this

1-2 punch: the innate immune system and the adaptive immune system.

The adaptive immune system response is what you think of, when you think “immune system.”

This is defcon 1.

White blood cells, are ready to attack the invader.

SHIT IS GETTIN’ REAL.

But, white bloods don’t just attack anything.

They need a snitch.

They need to be told what to attack.

That’s what’s been elusive for scientists, the triggers for the innate immune system

response.

How do the t-cells get fired up enough to attack your shiney new organ?

Bear with me, we’re about to get real molecular.

In a paper published in Science Immunology, they found that t-cells won't launch an offensive

unless another immune cell, called a Dendritic cell, yells, “intruder alert!”

Dendritic cells are on the lookout for a molecule called SIRP-alpha.

If your kidney is put in my body, the SIRP-alpha don’t match.

When they aren’t a match, a receptor on a monocyte called CD47 binds to that SIRP-alpha

protein…

The monocytes are another type of immune cells.

Once that binding happens, the dendritic cell rings the alarm and the big guns roll in...

and that’s what causes organ rejection.

Basically a protein interaction sets off a chain reaction that eventually leads to bye,

bye, kidney.

The exciting part of this nitty-gritty molecular discovery is that researchers think they can

block that interaction between the SIRP-alpha and CD47.

Basically, the monocytes never get bound up, so the immune system stays cool.

This could prevent organ rejection and lead to acceptance!

But more research is needed.

Plus, now that we know to look for it, we can match the SIRP-alpha from donors and recipients,

possibly causing lower organ rejection rates overall!

Being on a list for an organ for years, only to have it rejected is devastating for the

recipient, but think about it -- maybe that kidney could have worked in someone else!

The more we know about this process, the better we’ll be able to get organs to their forever

homes, and keep them safe inside the crazy neighborhood that is the human body.

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It’s hard enough to transplant a singular organ, but some scientists are actually trying

to transplant a human head..

Or I guess a whole human body?

Check out our video about it, here.

Do you guys have any burning science questions you want us to answer?

Let us know down in the comments, be sure to like this video, and subscribe so you never

miss an episode of Seeker.