Thread: Why would different types of blood reject each other

This does not make sense to me.
In class, we just learned about different types of blood (A,B,AB,O) the Rh negative/positive, and the antibodies they produce against each other according to the antigens that are present on the different white blood cell.

My question is: Why would red blood cells evolve to 'combat' each other?
Throughout the thousands of years, there was no blood transfusions and such back then, but even so, why would a body evolve to design itself to attack foreign blood? There would rarely, if never be a situation where blood from one primitive human enter the body of another primitive human. Its not like blood cells are invading microbes that actively seek out cells to destroy.

Why would red blood cells evolve to destroy different types of the same cell. There does not seem to be any advantage; by today's standard, it would be an advantage if red blood cells didn't attack each other.

Any thoughts/facts/reasons?

Thanks!

You don't develop specifically anti-A or anti-B antibodies, but people pick up antibodies against structurally similar antigens in food or from bacteria/viruses.

Originally Posted by TPhaoimnaes

This does not make sense to me.
In class, we just learned about different types of blood (A,B,AB,O) the Rh negative/positive, and the antibodies they produce against each other according to the antigens that are present on the different white blood cell.

My question is: Why would red blood cells evolve to 'combat' each other?
Throughout the thousands of years, there was no blood transfusions and such back then, but even so, why would a body evolve to design itself to attack foreign blood?

You don't inherit immune specificity- it is not, in itself, something that comes from evolution. Instead we have evolved an immune system which generates many random specificities (I think it's something like 1,000,000,000,000 possible unique specificities for T cells). Each new T and B cell has a unique random specificity. Before those cells are released into our circulation, our body filters out any cells which recognise elements of our own bodies, leaving only cells which will recognise a wide panel of potential foreign things.

This is called central tolerance.

Originally Posted by TPhaoimnaes

There would rarely, if never be a situation where blood from one primitive human enter the body of another primitive human. Its not like blood cells are invading microbes that actively seek out cells to destroy.

They don't have to be, they just have to be something our bodies did not use as a "filter" during T and B cell generation.

Originally Posted by TPhaoimnaes

Why would red blood cells evolve to destroy different types of the same cell.

Red blood cells don't kill anything at all. That's all done by white blood cells, and only a subpopulation of those too.

Originally Posted by TPhaoimnaes

There does not seem to be any advantage; by today's standard, it would be an advantage if red blood cells didn't attack each other.

As I said, they don't. You are broadly correct though, it would be an advantage if we could tolerate foreign blood. Induction of tolerance is an idea with very broad applications so I have no doubt that there are immunologists researching that very idea with respect to blood transfusion.

Alright, thanks a lot
So if I understand correctly...
the answer to my question is that the reason there are different types of antigens on blood cells is because the immune system randomly generated a specific one, so the body could recognize it as part of itself.

Thanks

Originally Posted by TPhaoimnaes

Alright, thanks a lot
So if I understand correctly...
the answer to my question is that the reason there are different types of antigens on blood cells is because the immune system randomly generated a specific one, so the body could recognize it as part of itself.

Thanks

Not quite, say you're type A, this is hereditary. The surface antigen is determined by your genetics.

Now, your body produces white blood cells with a wide range of antigen specificity, this is random. However, during the process of making those T and B cells, your body filters out the cells that recognize self-antigens. This is to stop your white blood cells from attacking yourself.

So, if you have type A antigens on your red blood cells, you will not make any mature white blood cells that recognize A as "other" and attack it.

You will produce white blood cells that recognize B antigens, and antigens close to B antigens.

As a side note, the reason why most people are seropositive for antibodies against other blood types is because of structural similarities with bacterial and viral proteins.

Originally Posted by i_feel_tiredsleepy

Originally Posted by TPhaoimnaes

Alright, thanks a lot
So if I understand correctly...
the answer to my question is that the reason there are different types of antigens on blood cells is because the immune system randomly generated a specific one, so the body could recognize it as part of itself.

Thanks

Not quite, say you're type A, this is hereditary. The surface antigen is determined by your genetics.

Now, your body produces white blood cells with a wide range of antigen specificity, this is random. However, during the process of making those T and B cells, your body filters out the cells that recognize self-antigens. This is to stop your white blood cells from attacking yourself.

So, if you have type A antigens on your red blood cells, you will not make any mature white blood cells that recognize A as "other" and attack it.

Or more precisely, you will make them but your body will test and then deactivate them before letting them into your circulation.

Originally Posted by i_feel_tiredsleepy

You will produce white blood cells that recognize B antigens, and antigens close to B antigens.

As a side note, the reason why most people are seropositive for antibodies against other blood types is because of structural similarities with bacterial and viral proteins.

Interesting. That would be a good explanation for why we have circulating antibodies and, presumably, memory lymphocyte pools in place prior to transfusion. Otherwise we'd be able to tolerate one random transfusion, as the adaptive response would need time to ramp up if we were relying on the naive lymphocyte pool for recognition. It would act as a prime. The second transfusion would go very badly

Okay, THERE"S the answer I'm looking for XD

As a side note, the reason why most people are seropositive for antibodies against other blood types is because of structural similarities with bacterial and viral proteins.

I suspected it some, but I thought that the red blood cells and foreign microbes would be more different.

Thank you very much.

Originally Posted by TPhaoimnaes

Okay, THERE"S the answer I'm looking for XD

Both answers are part of the what you're looking for. Tiredsleepy's answer neatly explains why we react to foreign blood immediately, not why we react to it at all, which is for the reasons I previously gave.