When doctors tried to remove one person’s blood and put it in someone else, sometimes

it was a success.

But sometimes the blood would clump together, which could result in death.

And this is the kind of procedure you want to get right every time.

It wasn’t until the early 1900s that this guy, Austrian doctor Karl Landsteiner, developed

a system of categorizing blood types — the well known ABO blood groups you’ve probably

heard of.

Dr. Landsteiner traced transfusion complications...namely, death... back to two things; antigens and

antibodies.

Understanding this has made blood transfusions much more successful.

And using this information today, plus a century of more research, scientists are developing

a method to advance blood transfusions success rates even more by transforming all donated

blood to the universal donor type.

Antibodies are proteins produced by the immune system that can recognize, investigate and

if needed, destroy an antigen, which is anything that triggers an immune response.

A lot of the time, antigens are viral or bacterial invaders that can cause sickness or infections.

Usually your immune system will recognize them and label them as something to attack

with antibodies and get rid of in the future.

But other times these antigens are produced by our own bodies, called self-antigens, which

our immune system will leave alone.

The whole ABO blood system is built upon on these sugar-based self-antigens and corresponding

antibodies.

And the type of blood you have tells you which type of antigens and antibodies we’re talking

about: Type A means you have A antigens on the outside

of the red blood cells and B antibodies in the plasma.

Type B reverses this, B antigens on the outside of the red blood cell with A antibodies floating

around.

People with AB blood have both A and B antigens, but no antibodies in their plasma while type

O blood has no antigens, but have A and B antibodies.

For the most part everyone in the world has one of these four blood types.

And it’s these combinations that create those botched transfusions that Dr. Landsteiner

noticed.

Basically if your blood has A antigens and all of a sudden you get blood with B antigens,

your body will see them as foreign invaders and attack.

These attacks can cause clumps of red blood cells and antibodies to form.

If these clumps get too large, blood clots can spark severe symptoms and even death.

So, when you receive blood it has to match with your type, or be type O, also known as

the universal donor type.

Wait, but what about those positive and negative symbols?

Great question!

That positive or negative symbol that comes after your ABO blood type is based on something

called the Rhesus Blood Group System.

Rhesus blood grouping is similar to the ABO system because it too has to do with the presence

or absence of an antigen on the outside of the red blood cell — in this case the protein-based

Rh antigen.

This becomes important again when it comes to blood transfusions, a body with Rh negative

blood will reject Rh positive blood.

Now, the big question is why is our blood like this?

Well, this question takes us down two different paths.

First off, we don’t know why we evolved to have different blood types.

In the age of transfusions, it would be a lot easier if we all had the same blood type,

but somewhere along the way, it was in the human species’ best interest to develop

different blood types.

Many experts hypothesize that they developed to help fend off disease, but since this all

happened millions of years ago, it remains a hypothesis.

But even though we don’t know a hundred percent why our blood is like this evolutionarily,

we know much more about its heritability, or why you have the blood type you do.

It all comes down to our genes.

The genetic information your parents pass down to you help determine things like what

color your hair is, how susceptible you are for a disease or how tall or short you are.

This is the same for blood type and it all comes down to the ABO gene, which has three

different versions, or alleles: A, B and O. Each parent has two of these alleles, because

they each got one from their parents and passed one down to their child.

This all comes together and gets encoded in our DNA to create the blueprint that our body

will use to make our blood.

If you’re curious, here’s a handy chart to tell you what allele combinations will

create certain blood types.

When new blood is made, our DNA will instruct the enzymes to either build A antigens, B

antigens, both or none depending on the inherited allele combination.

So, if you’re unhappy with the blood type you have, just blame your parents.

But here’s what’s so cool!

We’re getting closer to technology that bypasses the need for matching blood types

entirely.

Scientists recently discovered that enzymes found in our gut, when added to blood, could

strip away the sugar-based antigens on the cell’s surface.

That would effectively change type A or B to type O, which again, is known as the universal

donor type since it can be given to A, B, AB or O patients.

Hello, my name is Peter Rahfed, I’m a postdoc at the University of British Columbia.

I’m working in the lab of Stephen G Withers and we are doing metagenomics screenings trying

to find new enzymes capable of converting red blood cells.

And they have succeeded at finding an enzyme in some human gut bacteria that has been able

to convert blood.

But of course, it’s more complicated than that.

That there are enzymes available which can cleave sugars.

You can think, okay we can find the right one that can cleave off this sugar, and can

convert A or B into O, that’s the general idea.

The big question for us was where could we find those kinds of enzymes?

Because they are not everywhere.

IN the human gut, there are so called, mucins, which are covering your intestines.

And they’re there to protect you.

But at the same time, our microbiome, like our bacteria, also evolved to cooperate, to

live together with us, and learned to stick to the mucins and chew the sugars away and

use them for their own nutrition.

And interestingly, on those mucins there are the same sugar structures you would find on

red blood cells.

So the idea is in our gut, there are already bacteria living which have the right enzymes

to cleave those kinds of structures we’re looking into.

But it’s not as simple as taking this bacteria’s enzyme and adding it to the donated blood.

Peter’s team isolated the DNA from the bacteria responsible for telling the enzymes to cleave

the sugars off the mucins and put that DNA into lab bacteria.

Now, this new lab bacteria produces the enzymes that are programmed to cleave the sugars off

the red blood cells, which will create O type blood.

Then what we can do is we can draw blood, take the red blood cells out of the blood,

incubate it with the enzyme, leave it for a while then we can wash the enzymes away

and then those red blood cells are modified.

Making more O blood will be huge, since more blood can be given to more patients in need

with less complications.

In just over 100 years we’ve come a long way.

That is, until we can just make synthetic blood, which is being worked on, but we’re

not quite there yet.

Did you know the first human blood transfusions didn’t even use human blood?

In the late 1660s, French physician Jean-Baptiste Denys used the blood of a sheep and then a

calf on his patients.

The first recipient did survive, but subsequent failures caused any human blood transfusions

to be banned for over a hundred years...at least until we discovered blood types.

Probably not a bad idea.

Thanks for watching this episode of Seeker Human, I’m Patrick Kelly, we’ll see you

next time on Seeker.