4 ms·

There are three components that can cause problems with transfusions: "A", "B" and "Rhesus". A person can have any combination of those three (8 combinations).

There are three components that can cause problems with transfusions: "A", "B" and "Rhesus". A person can have any combination of those three (8 combinations). The A/B/AB/O is basically having only A, only B, both, or neither. And the +/- is whether you have the "Rhesus" component. The basic rule is that you can't introduce new components to a person who doesn't have them in their system, and will be treated as foreign contaminants. So someone with all three components already (AB+) can take any blood because their system already is used to all three components. A person with none of the components in their system (O-) would have an allergic reaction to any of the three components being introduced. On the other hand their blood is safe to donate to anyone else as it won't introduce any "unexpected components" to a recipient. EDIT: ah, I see - article doesn't mention Rhesus. I guess it can convert AB- to O-, or AB+ to O+.

wbl 3y ago
Oh there are more. I think hundreds are known, but only a few populations have each one.
smegger001 3y ago
there is also the HH blood group that will react negatively to O type blood as well as A and B.
- Terr_ 3y ago
  That naming is a little confusing, because if you say "blood group "A" or "B", that indicates the presence of A and B antigen structures, however "blood group H" means a lack of H. (Since almost everybody has H, it was discovered much later.) Since H is also a building-block needed for A and B to show up, it makes for fun medical-mystery plots, where a child's blood-type seems to be O and doesn't match their parents, but in reality they did get parental A/B/AB genes that just aren't able to express because each parent contributed a nonfunctional H-allele. https://www.ncbi.nlm.nih.gov/books/NBK2268/ https://www.ncbi.nlm.nih.gov/books/NBK2268/
  - Terr_ 3y ago
    P.S. IANAPhlebotomist, but if I could wave a wand to change the nomenclature, I'd make it stop relying on an implicit "nothing" state that keeps changing under us as we discover new features that are either usually-present or usually-absent. Instead patients would have a "blood code" that indicates the tested presence or absence of phenotype cellular features, and any feature not listed would be considered "not yet known, do a test if it might be important." For example, today's AB- would become +HAB-R for "has H,A,B lacks Rhesus factor." Similarly, O+ would become +HR-AB, and the super rare mutation we were just talking about would be either +R-HAB or -HABR. Then when we eventually discover a yet-another factor X... Well, yes, your code wouldn't be constant throughout your life, because after an X-test it would gain either a +X or -X... However the upshot is that it eliminates weird implicit guessing games, and medical professionals will "know what they don't know".
    - thaumasiotes 3y ago
      > For example, today's AB- would become +HAB-R for "has H,A,B lacks Rhesus factor." That's already the way A, B, and Rhesus factor work. The abbreviation for Rhesus factor is "+", but the formal terminology is "Rh+". I would have expected "H-" by analogy.
      - Terr_ 3y ago
        > That's already the way A, B, and Rhesus factor work. No, it isn't: The current ABO system is incapable of expressing "null" data (e.g. "we don't know if B antigens are present or not") and relies on implicit "no marking means false" assumption, which becomes a problem if a new/newly-important antigen feature is discovered, or if a new variation of an existing antigen is found. For example, suppose we discover a new type Z, which is a membrane-sugar just like A and B, and logically ought to be encoded the same way. It exists in a 50/50 ratio in every existing blood-group, and it finally explains some rare but fatal transfusion problems. Now some unconscious patient arrives at the emergency room with a wristband saying "AB+". Does that string mean they were tested for Z already, and it was absent, or does it mean there no data about whether Z is present or not? Nobody knows! Worse, if you do a test and discover no Z, then you write the same thing and have the same problem later, all because of the mistake of encoding "false" as an empty string. Now you might say "Forget the ABO crap, require Z+ or Z- to appear as a separate item", I'll say: "I totally agree, but let's remove the ABO crap and encode all the antigens the same way to make it logically consistent and clear." > I would have expected "H-" by analogy. If you're thinking of another section like "A Rh+ H-", then that's close to what I'm proposing, except that it hasn't fixed the historical ambiguities of O/A/AB. If you fix it to make things explicit and consistent, it becomes "A+ B- Rh+ H- ", and if you shorten Rh to R and group similar things together... that leads to codes like +R-HAB or -ABH+R, which are (ordering aside) what I just proposed.
Buttons840 3y ago
I think O is recessive (if I remember from high school correctly). A is really AO (if we're being verbose). B is BO, AB is AB, O is OO. Each parent passes one of them on. So, a A dad and O mom would mix (being verbose again) AO and OO, and thus the child might be AO or OO, A or O. The + or - is for an independent "Rhesus" component, as you say. Not sure how this passes through the genes. This is all like high school level knowledge, so maybe someone can share more if they want. My dad had surgery and some paperwork we received said that he had AB blood. It became a family joke because me and my siblings are all O blood type. If my dad really did have AB blood then we are not his children. The hospital later confirmed it was a mistake.
- deleted 3y ago
  [deleted]
- blendergeek 3y ago
  You mostly remember correctly. One small nitpicko on the genetics (based on my high school biology) A can be either AA or AO and B can be either BB or BO. AB is always AB like you said and O is always OO.
- linooma_ 3y ago
  > I think O is recessive Strangely, O is very common.
  - riffraff 3y ago
    I seem to remember the explanation is that A and B are somewhat recent mutations in evolutionary terms, they simply have not had time to cancel out 0 yet. Of course there's crackpot theories (aliens!) too.
  - thaumasiotes 3y ago
    What's the strange part? "Recessive" and "common" are different concerns. Having five fingers per hand is recessive too.
    - 3y ago
jorvi 3y ago
Also important to note that blood plasma is the reverse. So AB+ is universal plasma donor, and O- universal plasma receiver!

wbl 3y ago

Oh there are more. I think hundreds are known, but only a few populations have each one.

smegger001 3y ago

there is also the HH blood group that will react negatively to O type blood as well as A and B.

Terr_ 3y ago
That naming is a little confusing, because if you say "blood group "A" or "B", that indicates the presence of A and B antigen structures, however "blood group H" means a lack of H. (Since almost everybody has H, it was discovered much later.) Since H is also a building-block needed for A and B to show up, it makes for fun medical-mystery plots, where a child's blood-type seems to be O and doesn't match their parents, but in reality they did get parental A/B/AB genes that just aren't able to express because each parent contributed a nonfunctional H-allele. https://www.ncbi.nlm.nih.gov/books/NBK2268/ https://www.ncbi.nlm.nih.gov/books/NBK2268/
- Terr_ 3y ago
  P.S. IANAPhlebotomist, but if I could wave a wand to change the nomenclature, I'd make it stop relying on an implicit "nothing" state that keeps changing under us as we discover new features that are either usually-present or usually-absent. Instead patients would have a "blood code" that indicates the tested presence or absence of phenotype cellular features, and any feature not listed would be considered "not yet known, do a test if it might be important." For example, today's AB- would become +HAB-R for "has H,A,B lacks Rhesus factor." Similarly, O+ would become +HR-AB, and the super rare mutation we were just talking about would be either +R-HAB or -HABR. Then when we eventually discover a yet-another factor X... Well, yes, your code wouldn't be constant throughout your life, because after an X-test it would gain either a +X or -X... However the upshot is that it eliminates weird implicit guessing games, and medical professionals will "know what they don't know".
  - thaumasiotes 3y ago
    > For example, today's AB- would become +HAB-R for "has H,A,B lacks Rhesus factor." That's already the way A, B, and Rhesus factor work. The abbreviation for Rhesus factor is "+", but the formal terminology is "Rh+". I would have expected "H-" by analogy.
    - Terr_ 3y ago
      > That's already the way A, B, and Rhesus factor work. No, it isn't: The current ABO system is incapable of expressing "null" data (e.g. "we don't know if B antigens are present or not") and relies on implicit "no marking means false" assumption, which becomes a problem if a new/newly-important antigen feature is discovered, or if a new variation of an existing antigen is found. For example, suppose we discover a new type Z, which is a membrane-sugar just like A and B, and logically ought to be encoded the same way. It exists in a 50/50 ratio in every existing blood-group, and it finally explains some rare but fatal transfusion problems. Now some unconscious patient arrives at the emergency room with a wristband saying "AB+". Does that string mean they were tested for Z already, and it was absent, or does it mean there no data about whether Z is present or not? Nobody knows! Worse, if you do a test and discover no Z, then you write the same thing and have the same problem later, all because of the mistake of encoding "false" as an empty string. Now you might say "Forget the ABO crap, require Z+ or Z- to appear as a separate item", I'll say: "I totally agree, but let's remove the ABO crap and encode all the antigens the same way to make it logically consistent and clear." > I would have expected "H-" by analogy. If you're thinking of another section like "A Rh+ H-", then that's close to what I'm proposing, except that it hasn't fixed the historical ambiguities of O/A/AB. If you fix it to make things explicit and consistent, it becomes "A+ B- Rh+ H- ", and if you shorten Rh to R and group similar things together... that leads to codes like +R-HAB or -ABH+R, which are (ordering aside) what I just proposed.

Buttons840 3y ago

I think O is recessive (if I remember from high school correctly). A is really AO (if we're being verbose). B is BO, AB is AB, O is OO. Each parent passes one of them on. So, a A dad and O mom would mix (being verbose again) AO and OO, and thus the child might be AO or OO, A or O. The + or - is for an independent "Rhesus" component, as you say. Not sure how this passes through the genes. This is all like high school level knowledge, so maybe someone can share more if they want. My dad had surgery and some paperwork we received said that he had AB blood. It became a family joke because me and my siblings are all O blood type. If my dad really did have AB blood then we are not his children. The hospital later confirmed it was a mistake.

deleted 3y ago
[deleted]
blendergeek 3y ago
You mostly remember correctly. One small nitpicko on the genetics (based on my high school biology) A can be either AA or AO and B can be either BB or BO. AB is always AB like you said and O is always OO.
linooma_ 3y ago
> I think O is recessive Strangely, O is very common.
- riffraff 3y ago
  I seem to remember the explanation is that A and B are somewhat recent mutations in evolutionary terms, they simply have not had time to cancel out 0 yet. Of course there's crackpot theories (aliens!) too.
- thaumasiotes 3y ago
  What's the strange part? "Recessive" and "common" are different concerns. Having five fingers per hand is recessive too.
  - 3y ago

jorvi 3y ago

Also important to note that blood plasma is the reverse. So AB+ is universal plasma donor, and O- universal plasma receiver!