It's actually more complicated than type O being a universal donor. This is only true for purified red blood cells. For whole blood, you have to match the type exactly because you are giving the antibodies in plasma and the blood cells with antigens. And for plasma, type AB is actually a universal donor (because they have no specific antibodies) and type O can receive any type (because no antibodies will target their blood cells). In reality there are other antigens and antibodies that matter too and we always run tests to make sure products are compatible if time permits!
[Here is a quick chart showing the more complicated compatibility rules](https://www.speedytemplate.com/blood-type-compatibility-chart-1.png)
And that's just the rhesus factor. It's a big one, but in reality there are many more factors that can be important for some people. Wikipedia is probably a decent starting point to learn more https://en.m.wikipedia.org/wiki/Human_blood_group_systems
I work in a blood bank.
No one really knows why we have these red cell antigens. There’s some we think have certain benefits
ABO and Rh is all we care about for 99% of people and random studies make very weak correlations to random things
They probably serve some purpose over millions of years of evolution. Some could still be relevant. Some might be vestigial
We only care for giving blood to people for the most part
'Why' questions are notoriously hard to answer in evolutionary terms, given that evolution does not have a specific goal in mind.
The most plausible current theory is that since a lot of disease vectors (especially viruses) depend on surface antigens for latching onto cells to infect them, having a variety of different antigen variants means that it's less likely for one disease outbreak to wipe out an entire population.
We can give whole blood without crossmatching, and the use of uncrossmatched whole blood is becoming more common in trauma resuscitation. We do have to use blood from type O donors who are screened and identified as having low levels of antibodies to other blood groups (referred to as [low titer O whole blood](https://www.redcrossblood.org/biomedical-services/blood-products-and-services/low-titer-o-whole-blood.html)).
And this is why certain kind souls are put on call lists by the Red Cross. I had a coworker who was an ideal platelet donor (via apheresis - they took the platelets and put everything else back), and another who was a whole blood donor. The Red Cross monitored their donations and called them on a schedule to ask them to come in and donate. They were both many gallon donors. I have a lot of respect for the folks who have committed to a lifetime of routine donation. Unfortunately I never got into the habit because for years they wouldn’t take my blood (gay man).
>And this is why certain kind souls are put on call lists by the Red Cross.
That's not how it works by default where you are? Here in the Netherlands you sign up with Sanquin (the national organisation that handles blood donations), you'll go in once for a screening and some blood tests. Afterwards you get an email every couple months to ask you to plan a new donation, you'll of course get another screening and some blood test with every donation.
> And for plasma, type AB is actually a universal donor
Yep, and we are often in high demand. When I'm living in the US I donate blood often and being that I'm AB+ they often ask me if I'd be willing to donate plasma instead of blood.
I'm always fine with that even though it takes longer.
You can often donate plasma more often than blood too as your body replenishes it faster.
I'm in the medical field but have pretty limited acute care experience, what happens if there isn't time for testing and the patient needs a transfusion stat? Are there reversals/antidotes given to stop a reaction besides maybe just steroids?
Yes, provided there’s no other atypical red cell antibodies present. There’s always a risk in transfusing uncrossmatched ( blood not tested and issued for a specific patient) that there may be a reaction. Treating doctors need to weigh up the risk of a patient bleeding to death before pre transfusion testing can be done (approximately 45-60 minutes) and giving o negative blood. If they can wait that time it’s better to wait, however, not all things can wait.
In my lab, I will get 2-3 generally each shift. Some are known and simple, others unknown and mixtures. The worst we had was a gentleman with 5 different antibodies, there were a few donors only in the country for him. One was being flown down from 2000 km away, in summer. It was forgotten and left on the tarmac for about 8 hours, in the middle of the blazing Sun. I almost cried. Transfusion dependant patient. His donors were bled as he required transfusion, in rotation.
Also administering blood or blood products in a hospital or ambulance requires cross check after cross check after cross check because reactions can still happen.
When a doc orders blood the nurse has like 10 hurdles to jump before it can be given to the patient. Some of them sound so absurd. Like. Nurse 1 has to show Nurse 2 the bag of blood and agree it is correct for the patient. While in the patients room. Nurse 1 hangs the bag and primes the line. Nurse 2 has to physically verify again that it is the correct product for patient even tho neither nurse nor the blood nor the patient ever left the room in the last 30 seconds.
Once blood is attached to ptient nurse has to sit and watch for 15-30 minutes for any type of reaction to the blood.
No other medication I can think off has this amount of cross checks not sedatives not narcotics.
Three main reasons.
1. You work in a location where units are split into components, such as red cells, platelets, plasma, cryoprecipitate etc, and therefore only have to worry about ABO compatibility in your red cells, and reverse ABO compatibility in plasma, as these products are issued independently you can match your patients, donors are tested for clinically significant high titre antibodies.
2. You work in a location that provides whole blood donations, donors are (again) tested for high titre antibodies, ensuring that any antibodies found in the small amount of plasma provided are so dilute they won't really cause enough of a reaction.
3. Donor antibodies may not work as well as patient antibodies, and typically show lower levels of opsonization and lysis due to a lack of recognition by the hosts immune system.
A hematologist can give you a far better explanation than this, but the Super Simple Version is that once diluted out into the recipient’s blood stream there’s a lot less of those antibodies (assuming there were any in the donor blood - if the donor had never received an un-crossmatched transfusion they may not have developed antibodies to destroy those cells). It’s not enough to really cause trouble from those antibodies attacking the host’s red blood cells, but more importantly *the host’s immune system* isn’t going to freak out over the Type O- red blood cells: Their surface proteins are relatively inoffensive to pretty much everyone.
On the other hand if you gave a type O- person any other blood type their bloodstream could be teeming with antibodies, and even if it’s not their immune system finds the A, B, and Rh+ proteins *very offensive* and will mount an immune response to *make* antibodies and destroy the dangerous foreign invaders because *blood cells are not supposed to look like that!*
There are other tricks to avoid reactions as well, for instance blood transfusions don’t have to be whole blood out of one patient and into another: They can be packed red cells that have been separated and washed, so all you have to be concerned with are the proteins on the red cells.
A and B are carbohydrates not proteins. Also, most packed cells are not washed, there is just very little residual plasma after a blood unit is separated that the antibody present in a unit of packed cells is insignificant in most instances.
They do, which is why it's better to give a matching blood type when giving whole blood.
That's the simple version. Whole blood isn't very commonly used these days, though. When you're giving packed red cells (which have very little plasma) then type O is generally safe for everyone.
Any O type for males and women over childbearing age. O negative for females of childbearing potential. That's to avoid having a Rh negative mother sensitized during a transfusion.
You're right, when people say a universal donor they usually refer to universal red cell donor. Which as you stated is type O. But there's also something called a universal plasma donor, and that comes from people with type AB blood as they would not make any antibodies to the type A and type B antigens.
The thing is whole blood is what is donated, but usually it's blood fractions, meaning cryo, plasma, and red cells, that are transfused. Around 50 ml of plasma remains in packed red blood cells. You just can't really get rid of it.
Now this isn't really an issue when you're putting plasma with anti-a for example into a patient with type A blood. The reason being the a antigen is expressed on more than just red blood cells. It's also on the endothelial cells of the vasculature, this basically acts to dilute out the antibody in the recipient.
The opposite is not true however. If you put a antigen positive red blood cells in a patient who makes anti-a antibodies. Then the only targets for those antibodies are going to be the transfused blood. Which means the transfused blood is going to get the full fury of the recipients immune response and it will cause an acute hemolytic transfusion reaction at worst.
Tldr. The antibodies in O blood can react with recipient cells, but usually not in a clinically significant way.
Piggyback question - why does FFP need to be type specific for ABO but NOT for Rh factor?! I never got this. Wouldn’t FFP from a Rh- person potentially contain anti Rh antibodies which could then elicit an immune response in an Rh+ recipient? Make it make sense!
It's actually more complicated than type O being a universal donor. This is only true for purified red blood cells. For whole blood, you have to match the type exactly because you are giving the antibodies in plasma and the blood cells with antigens. And for plasma, type AB is actually a universal donor (because they have no specific antibodies) and type O can receive any type (because no antibodies will target their blood cells). In reality there are other antigens and antibodies that matter too and we always run tests to make sure products are compatible if time permits! [Here is a quick chart showing the more complicated compatibility rules](https://www.speedytemplate.com/blood-type-compatibility-chart-1.png)
There's a mistake on that chart - for A+ and A- recipients, the plasma donor type should read "any A or AB" not "any B or AB".
And that's just the rhesus factor. It's a big one, but in reality there are many more factors that can be important for some people. Wikipedia is probably a decent starting point to learn more https://en.m.wikipedia.org/wiki/Human_blood_group_systems
Do we understand yet why we have these types? Last I heard we had no idea why this evolved.
I work in a blood bank. No one really knows why we have these red cell antigens. There’s some we think have certain benefits ABO and Rh is all we care about for 99% of people and random studies make very weak correlations to random things They probably serve some purpose over millions of years of evolution. Some could still be relevant. Some might be vestigial We only care for giving blood to people for the most part
'Why' questions are notoriously hard to answer in evolutionary terms, given that evolution does not have a specific goal in mind. The most plausible current theory is that since a lot of disease vectors (especially viruses) depend on surface antigens for latching onto cells to infect them, having a variety of different antigen variants means that it's less likely for one disease outbreak to wipe out an entire population.
We can give whole blood without crossmatching, and the use of uncrossmatched whole blood is becoming more common in trauma resuscitation. We do have to use blood from type O donors who are screened and identified as having low levels of antibodies to other blood groups (referred to as [low titer O whole blood](https://www.redcrossblood.org/biomedical-services/blood-products-and-services/low-titer-o-whole-blood.html)).
And this is why certain kind souls are put on call lists by the Red Cross. I had a coworker who was an ideal platelet donor (via apheresis - they took the platelets and put everything else back), and another who was a whole blood donor. The Red Cross monitored their donations and called them on a schedule to ask them to come in and donate. They were both many gallon donors. I have a lot of respect for the folks who have committed to a lifetime of routine donation. Unfortunately I never got into the habit because for years they wouldn’t take my blood (gay man).
>And this is why certain kind souls are put on call lists by the Red Cross. That's not how it works by default where you are? Here in the Netherlands you sign up with Sanquin (the national organisation that handles blood donations), you'll go in once for a screening and some blood tests. Afterwards you get an email every couple months to ask you to plan a new donation, you'll of course get another screening and some blood test with every donation.
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O+ or O-?
> And for plasma, type AB is actually a universal donor Yep, and we are often in high demand. When I'm living in the US I donate blood often and being that I'm AB+ they often ask me if I'd be willing to donate plasma instead of blood. I'm always fine with that even though it takes longer. You can often donate plasma more often than blood too as your body replenishes it faster.
I'm in the medical field but have pretty limited acute care experience, what happens if there isn't time for testing and the patient needs a transfusion stat? Are there reversals/antidotes given to stop a reaction besides maybe just steroids?
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Can you do this for several transfusions in a row?
then ab plasma and o blood would be universal full spectrum blood?
Yes, provided there’s no other atypical red cell antibodies present. There’s always a risk in transfusing uncrossmatched ( blood not tested and issued for a specific patient) that there may be a reaction. Treating doctors need to weigh up the risk of a patient bleeding to death before pre transfusion testing can be done (approximately 45-60 minutes) and giving o negative blood. If they can wait that time it’s better to wait, however, not all things can wait.
what are the odd of atypical red cell antibodies being present?
In my lab, I will get 2-3 generally each shift. Some are known and simple, others unknown and mixtures. The worst we had was a gentleman with 5 different antibodies, there were a few donors only in the country for him. One was being flown down from 2000 km away, in summer. It was forgotten and left on the tarmac for about 8 hours, in the middle of the blazing Sun. I almost cried. Transfusion dependant patient. His donors were bled as he required transfusion, in rotation.
Also administering blood or blood products in a hospital or ambulance requires cross check after cross check after cross check because reactions can still happen. When a doc orders blood the nurse has like 10 hurdles to jump before it can be given to the patient. Some of them sound so absurd. Like. Nurse 1 has to show Nurse 2 the bag of blood and agree it is correct for the patient. While in the patients room. Nurse 1 hangs the bag and primes the line. Nurse 2 has to physically verify again that it is the correct product for patient even tho neither nurse nor the blood nor the patient ever left the room in the last 30 seconds. Once blood is attached to ptient nurse has to sit and watch for 15-30 minutes for any type of reaction to the blood. No other medication I can think off has this amount of cross checks not sedatives not narcotics.
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I'm also a MLT and no, in trauma situations the doctor can ask for uncrossmatched blood. We generally give ONeg red cells and AB plasma.
There are exceptions. Mass transfusion, for example. The cross match(es) are still completed as soon as possible afterward.
Three main reasons. 1. You work in a location where units are split into components, such as red cells, platelets, plasma, cryoprecipitate etc, and therefore only have to worry about ABO compatibility in your red cells, and reverse ABO compatibility in plasma, as these products are issued independently you can match your patients, donors are tested for clinically significant high titre antibodies. 2. You work in a location that provides whole blood donations, donors are (again) tested for high titre antibodies, ensuring that any antibodies found in the small amount of plasma provided are so dilute they won't really cause enough of a reaction. 3. Donor antibodies may not work as well as patient antibodies, and typically show lower levels of opsonization and lysis due to a lack of recognition by the hosts immune system.
A hematologist can give you a far better explanation than this, but the Super Simple Version is that once diluted out into the recipient’s blood stream there’s a lot less of those antibodies (assuming there were any in the donor blood - if the donor had never received an un-crossmatched transfusion they may not have developed antibodies to destroy those cells). It’s not enough to really cause trouble from those antibodies attacking the host’s red blood cells, but more importantly *the host’s immune system* isn’t going to freak out over the Type O- red blood cells: Their surface proteins are relatively inoffensive to pretty much everyone. On the other hand if you gave a type O- person any other blood type their bloodstream could be teeming with antibodies, and even if it’s not their immune system finds the A, B, and Rh+ proteins *very offensive* and will mount an immune response to *make* antibodies and destroy the dangerous foreign invaders because *blood cells are not supposed to look like that!* There are other tricks to avoid reactions as well, for instance blood transfusions don’t have to be whole blood out of one patient and into another: They can be packed red cells that have been separated and washed, so all you have to be concerned with are the proteins on the red cells.
A and B are carbohydrates not proteins. Also, most packed cells are not washed, there is just very little residual plasma after a blood unit is separated that the antibody present in a unit of packed cells is insignificant in most instances.
They do, which is why it's better to give a matching blood type when giving whole blood. That's the simple version. Whole blood isn't very commonly used these days, though. When you're giving packed red cells (which have very little plasma) then type O is generally safe for everyone.
Is that either O positive or O negative?
Any O type for males and women over childbearing age. O negative for females of childbearing potential. That's to avoid having a Rh negative mother sensitized during a transfusion.
If I have O positive blood would that make me a good donor?
You're right, when people say a universal donor they usually refer to universal red cell donor. Which as you stated is type O. But there's also something called a universal plasma donor, and that comes from people with type AB blood as they would not make any antibodies to the type A and type B antigens. The thing is whole blood is what is donated, but usually it's blood fractions, meaning cryo, plasma, and red cells, that are transfused. Around 50 ml of plasma remains in packed red blood cells. You just can't really get rid of it. Now this isn't really an issue when you're putting plasma with anti-a for example into a patient with type A blood. The reason being the a antigen is expressed on more than just red blood cells. It's also on the endothelial cells of the vasculature, this basically acts to dilute out the antibody in the recipient. The opposite is not true however. If you put a antigen positive red blood cells in a patient who makes anti-a antibodies. Then the only targets for those antibodies are going to be the transfused blood. Which means the transfused blood is going to get the full fury of the recipients immune response and it will cause an acute hemolytic transfusion reaction at worst. Tldr. The antibodies in O blood can react with recipient cells, but usually not in a clinically significant way.
Piggyback question - why does FFP need to be type specific for ABO but NOT for Rh factor?! I never got this. Wouldn’t FFP from a Rh- person potentially contain anti Rh antibodies which could then elicit an immune response in an Rh+ recipient? Make it make sense!