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  • Back in the 19th century, if you needed a blood transfusion, it was a risky proposition.

  • 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 typesthe well known ABO blood groups youve 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 were 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 cellin 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 speciesbest 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 youre 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 youre unhappy with the blood type you have, just blame your parents.

  • But here’s what’s so cool!

  • Were 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 theyre 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 were 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 weve come a long way.

  • That is, until we can just make synthetic blood, which is being worked on, but were

  • 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, well see you

  • next time on Seeker.

Back in the 19th century, if you needed a blood transfusion, it was a risky proposition.

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なぜ血液型があるのか? (Why Do We Have Blood Types?)

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    林宜悉 に公開 2021 年 01 月 14 日
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