ABO and Rh (blood types with donuts!) | Physiology 🐧🩸🩸🐧

>> Hello, and welcome to ThePenguinProf Channel!

Today's episode is going to be about understanding blood types,

the ABO and Rh groups.

There are so many misconceptions about blood typing.

Oh my gosh, you can eat based on your blood type.

Check this out - You can find your perfect match based

on your blood type.

It's really pretty ridiculous, but a lot of people are confused

because historically people had

to have blood tests before marriage.

In truth this really didn't have as much to do with blood types

as it had to do with disease,

especially diseases like syphilus.

But it accounts for a lot of the confusion that goes

on about blood groups and there are many blood groups.

Certainly the most important, and the focus of this video,

the ABO blood group and the Rh group.

Interestingly enough, we share the ABO

and Rh blood groups with our relatives.

Apes, chimpanzees, bonobos and gorillas.

Okay so students are totally plagued

by these donor recipient tables and they think

that they have to memorize all this.

For heavens sakes, don't do that!

That's what ThePenguinProf is for.

Okay we're going to go through what all of this stuff means

so that it makes sense to you

and then you don't have to memorize anything.

One quick request, if you can, please donate

and give the gift of life.

One blood donation can save several people.

Just a tiny bit of history here.

These blood groups were discovered

in around 1900 by Karl Landsteiner.

He wondered why some people were saved as a result

of blood transfusion but some patients died.

And boy, that's I think a really good question.

He received the nobel prize [ding] for his work in 1930.

Blood types are inherited genetic traits so they're just

like all the other things that we inherit,

which does again make me think about this date by type thing.

What if I can come up with a match by ear lobe type?

I mean that makes about as much sense.

Anyway, the thing that's confusing is that blood typing,

the ABO system, is not inherited in mendelian fashion.

So, it gets a little bit complicated

because we have 3 alleles.

And don't worry we're going to go through that.

I have an analogy here.

Red blood cells look a little bit like donuts.

Of course they don't have the hole

in the middle they have a little depression.

But my ABO analogy we're going to look

at donuts and sprinkles, okay?

And hopefully we'll make some sense of this.

Now, some people have donuts that have, on their surface,

little sprinkles that look like A's.

Okay just go with me on this.

We're going to call those people type A. Some people have donuts

that have sprinkles on them that are little B's and we're going

to call those people type B. Some people have donuts

and they're kind of greedy, they like it all, so they have both A

and B sprinkles on top, we're going to call those people AB.

And some people don't have any sprinkles at all,

they are sprinkle challenged, they are the plain donuts.

We call those people Type O. That causes some confusion

because some people think there are O sprinkles.

But their aren't.

And oh, by the way, different parts

of the world you may actually see this as type zero.

Which actually makes more sense.

Okay? No extra sprinkles.

These are the A B O phenotypes.

These are the traits that individuals can express.

So what this analogy means is that of course,

the donuts are the blood cells and the sprinkles are antigens.

Antigens on the cells surface,

and we designate the different antigens as either A or B.

So the A people have A antigens on the surface of their cells.

The B people have B antigens on the surface of their cells.

The A and B people of course have both.

And the plain donuts have neither A nor B.

But what do the antigens really look like?

Your textbooks in General Biology

and Introductory Physiology probably don't show you,

but this is ThePenguinProf channel so you're going

to get a little bit more out of me.

This is the idea.

I'm showing you only the carbohydrate portion

of the antigen so there's another section that kind

of anchors the thing into the cell membrane.

The plain donut has a sequence that looks like this.

That's the base unit.

For people with A sprinkles, A antigens,

at the end of the base you add one more unit.

It's called N-acetylgalactosamine

and that's what it really looks like.

People with B sprinkles, the B antigen, instead of adding that,

you add a galactose, which looks like this.

Now when you look at these you'll notice

that they're very similar in structure.

This is an acetomidogroup and this is a hydroxyl group.

Even though they look similar though,

chemically they are very different.

They have different properties.

This group is a hydrogen bond acceptor while the hydroxyl

group is a hydrogen bond donor.

So the point is that they do have different chemical

properties even though they do look rather similar.

Okay. So the alleles in the ABO system, they're encoded here

at the long arm on chromosome 9.

And this again is not an example of mendelian inheritance.

So it might be a little confusing.

There's actually three alleles that we worry about.

But don't worry we're going to go through it all.

We're going to use a lowercase i to code

for the base, that plain donut.

Okay? We're going to use a capital I

with a superscript a for the A antigen.

So that's the plain donut

and then add the N-acetylgalactosamine

and then finally the third allele we have is the B antigen.

SO we're going to take the base unit, the plain donut

and we are going to add galactose.

Those are the three alleles we have.

So when you combine the three alleles,

we're going to make all four blood group phenotypes.

I know you want to see how this works!

So, four different possibilities.

I'm reminding you again what this looks like.

We're talking about A people, they have the A sprinkles.

There are two ways that someone could inherit the A phenotype

or the A blood group.

You can be homozygous for A and this means

that both parents gave you this allele.

So you inherited two copies of the information

to make the A sprinkles.

But you could also inherit only one copy

so one parent gave you the information to make A sprinkles,

the other parent just gave you the plain donut information.

Either way, if you're homozygous or heterozygous you're going

to be blood type A. Same thing is true for people

who are blood type B. There are two ways

to be B. You can be homozygous for B

because both parents gave you the information

to make B sprinkles or you can be heterozygous

for B only one parent gave you the information.

If your blood type is AB there's only one genotype

that is possible.

One parent had to give the information to make A antigens,

A sprinkles, and the other parent had

to give information to make B sprinkles.

This by the way is a great example

of why the ABO inheritance is an example of co-dominance.

Why it's non-mendelian because A isn't dominant

over B or vice versa.

So that's a really cool thing to notice.

If you are blood type O there's only one genotype

that encodes the plain donuts.

You had to get two copies of that little i.

And that's how you inherit the four blood groups.

Now one more thing you need to understand before we talk

about transfusions and who's allowed to donate to whom.

And that has to do with antibodies.

So we've been talking about A and B antigens,

these are particles on the cell surface

and you have tons of them.

Not just the A or B. The body is full of antigens,

they help cells to identify each other

and many antigens are what we call self antigens.

They identify you as you!

The problem comes if you are exposed to foreign antigens.

Strangers.

If you're exposed to antigens that are not native to you,

your body is designed to make antibodies against them.

So you make antibodies against foreign antigens,

that's the key.

If you've never seen antibodies before,

this is what they look like.

There's this hyper variable region, this is the part here

as you can see that binds with the antigen.

It's very much like how a key fits a lock.

The idea is that if you are exposed to antigens

that are foreign to you, you'll make antibodies against them.

If antigens and antibodies come together you get a reaction

called agglutination.

And this is what normal blood should look

like on a microscope slide, you notice it looks very very nice

and all the cells are evenly spread out.

But in aggluntation the particles clump together.

And that nice fluid liquid blood can become more

like a solid and form clots.

And this is bad!

And this is why understanding blood types is essential

when you're talking about transfusions.

And why this table exists.

But, now we get to the point where you don't have

to memorize this anymore.

All you have to understand is

that no foreign antigens are allowed.

So what we're going to do is we're going

to take all four blood types.

We're going to mix them with the other blood types

and we're going to understand what happens

and why some mixes are allowed and some mixes are not.

So for a person that has antigen A, the B antigen is foreign

and they have antibodies against the B antigen.

So we're going to mix this blood with blood type A

and of course there's no problem,

that's their blood type.

But if that A person gets transfused with a blood sample

that contains B antigens, you've got a problem.

Because that B antigen will combine

with the anti B antibodies and the blood clumps

so that is not allowed.

If you transfuse with AB blood, that's also a problem.

The A is okay but remember they have B too.

So, that B is bad and causes the blood to clump.

Now why can you transfuse an A person with O blood?

The answer hopefully makes sense to you now.

This O is the plain donut.

It doesn't have any antigens

so you don't make antibodies against it.

So O blood is okay, perfectly fine.

What about B blood?

Now the person that has B antigens is sensitive to

and makes antibodies against A antigens.

So if you have a B patient and you transfuse A blood,

not good - - you're going to get clumping.

A B person with B blood obviously okay that's their

blood type.

AB is not okay because that A is foreign.

And O blood is fine, that's just a plain donut.

What about AB?

The AB person has antigens A and B.

And so they don't make antibodies against either.

So AB blood can be transfused with all four blood types.

Because they got it all.

What about O?

O individuals have antibodies against the A antigen,

because those are foreign, and the B antigen

because those are foreign too.

So you can't give an O person A blood

and you can't give an O person B blood or AB blood,

oh my gosh that's a double whammy.

You can only give O blood to an O person.

So, all that you have to remember is

that you can't give foreign antigens to someone.

And it should make sense now

that the type AB is the universal recipient

because you can't give them anything

that they don't already have!

And type O is the universal donor

because they are the plain donuts

and they don't excite anybody's immune system.

Okay, all we got left is the Rh antigen.

Sometimes called the D antigen.

This one's going to be really easy

because it's inherited in mendelian fashion.

And by the way named for the Rhesus macaque in which a lot

of the early studies were done.

The Rh antigen IS inherited

in mendelian fashion you'll be excited to know that.

If you're not excited I have a video on Mendelian Genetics:

Fun with Cats and Peas so if I run

through this a little bit fast and you're confused

with the vocabulary check that out I'll put the link

in the description bar below.

We're going to look

at the different options, there are only three.

As is typical for mendelian genetics.

Individuals who are homozygous dominant, capital R capital R,

they express the Rh antigen on their red blood cells.

Individuals who are heterozygous, right?

That dominant one will mask the recessive one.

Those individuals are also Rh positive the only way

to not express the Rh antigen is to be homozygous recessive.

These are the different possibilities

and I just wrote them out so you can see that only individuals

who are homozygous recessive will not express the Rh antigen

on their blood cells.

Everybody else will.

Now the medical importance of this is shown here.

If you have an Rh negative woman and an Rh positive man

and they conceive a child.

Oh look, she's so cut,e she's all like cuddling

against him, he's so positive.

Anyway. So, I made them both homozygous

for their respective Rh types.

So she's homozygous recessive, he's homozygous dominant.

Their fetus will be heterozygous.

So now look at what's happening you have an Rh negative woman

carrying an Rh positive fetus.

Antibodies flow in one direction from the mother's body

across the placenta to the fetus.

So it seems a little strange

that the Rh antigen being expressed

on the fetal red blood cells is not

in a sense seen by the mother's body.

So, usually that doesn't occur until the last trimester

or usually birth where there's usually hemorrhaging

and the mixing of blood.

And at that point the mother's body sees the Rh antigen

for the first time.

And you know what happens when you get a foreign antigen,

you make antibodies against it.

So from here on out the mother will make antibodies

against the Rh antigen.

For the rest of her life.

She is what we call sensitized.

Now up to this point there's actually no problem.

The problem comes in subsequent pregnancies.

If this Rh negative woman conceives another Rh positive

child now the situation is different,

because she is sensitized against Rh.

And the antibodies that she makes will flow

across the placenta to the fetus.

And will cause what is caused rhesus disease

or hemolytic disease of the newborn.

And that can be catastrophic.

Now there's good news.

The percent of individuals on the planet

who are Rh negative is relatively small.

These are data from the US, but it's similar around the world.

There's even more good news though,

there is a treatment called RhoGAM you can see here,

when it is administered.

And this will actually bind up

and block the mother's antibodies and prevent them

from binding to the blood cells of the fetus.

So that's really good news.

A lot of information as always I hope that was helpful.

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