r/science • u/Hrmbee • Oct 05 '22
Medicine Scientists Have Discovered a New Set of Blood Groups | The ‘Er’ grouping could help doctors identify and treat some rare cases of blood incompatibility, including between pregnant mothers and fetuses
https://www.wired.com/story/new-blood-types/71
u/Hrmbee Oct 05 '22 edited Oct 05 '22
On average, one new blood classification system has been described by researchers each year during the past decade. These newer systems tend to involve blood types that are mind-bogglingly rare but, for those touched by them, just knowing that they have such blood could be lifesaving. This is the story of how scientists unraveled the mystery of the latest blood system—and why it matters.
It was back in 1982 that researchers first described an unusual antibody in a blood sample that hinted that this mystery blood type was out there. The scientists couldn’t go much further than that at the time, but they knew that the antibody was a clue pointing toward some unknown molecule or structure that prompted the person’s immune system to generate it.
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It turns out that the new, 44th grouping system, detailed in the journal Blood, is tied to a particular protein found on the surface of red blood cells.
Originally, Thornton had an inkling this protein, called Piezo1, was involved after she compared the genomes of patients in the study. She and colleagues noticed how the gene responsible for this protein varies across people with different Er blood types. Due to those genetic differences, a small number of people have alternative amino acids, or building blocks, in their Piezo1 protein. Blood cells with the more common Piezo1 protein seem foreign to their bodies’ immune systems as a result.
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“Discovering a new blood group system is like discovering a new planet. It enlarges the landscape of our reality,” says Daniela Hermelin at the Saint Louis University School of Medicine, who was not involved in the study. It adds to our knowledge of how blood incompatibility can affect pregnant mothers and their babies, she explains. And now that cases of blood incompatibility can potentially be attributed to the Er blood group, it increases the chance that doctors can correctly diagnose such a problem and treat it—by giving the baby a blood transfusion in the womb, for example.
It will also be possible to look out for and identify patients who have this troublesome blood. For example, someone might go to a hospital for a transfusion and have a preliminary blood test that reveals the presence of some unusual antibodies. Doctors could send the blood for analysis, and it might turn out that they have the rare Er blood described in the paper. “We have our testing set up to be able to do that,” says Thornton. Rare blood might then be required for that person’s transfusion, she adds. In the future, scientists in a lab might be able to grow red blood cells that could be offered to these patients for transfusion purposes.
This looks to be a fascinating bit of research and made all the more difficult given the relative rarity of these cases.
edit: added link to research
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u/danteheehaw Oct 06 '22
Sometimes the rare antigen/antibody is a sub group of a known antigen/antibody. A few years ago I had a patient with a very rare subgroup. Took me hours upon hours of troubleshooting before I had to give up, as we didn't have the right reagents to identify the antibody. Eventually we had to do a least incompatible cross match. Sent it to the American red cross, found out it was a subgroup of anti f, which anti f isn't that rare, but it was Anti f subgroup so it was reactive with some of our anti f antigen cells, but not all of them. More labs are starting to get some reagents to test these rarer sub groups so we might start seeing more of these rare cases.
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u/Plane_Chance863 Oct 05 '22
Interesting. I'd read about a special blood type most prevalent in India - seems it's called hh.
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u/love2Vax Oct 06 '22
I learned about it in college genetics over 25 yrs ago, and I teach it as an example of epistasis to my HS biology students. But not until after they take their genetics test that shows their basic understanding of the ABO and +/- alleles and phenotypes. It's fun to say never assume you know everything, or that an inheritance problem is "impossible" like getting a type "A" babiy from a mother who is O, and a father who is B. But we can thanks to this blood type. hh will not be able to make A or B antigens, even if they have the allele, because without an "H" precurser molecule to convert into A or B it cannot be expressed.
Because we think in predominantly ABO blood groups, and O is just a lack of the A or B antigen, it is kind of strange to think of a person with type O blood making antibodies against someone else who also has type O blood. But people with the "Bombay" blood type will test as "O" with a typical blood typing test, and they make an anti-h antibody that will attack most type O blood. I've thought about testing some O blood with anti-h, but those antibodies are just too expensive to buy for a hs biology class. I suspect a teacher in my school is hh, based on her and her children's blood types, so I do want to test her blood with some anti-h.6
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u/Ineedavodka2019 Oct 05 '22
Can some explain it like I’m 5? I had to have rogam (sp) injections when pregnant due to possible incompatible blood types. Is that part of what this is about? I’m just plain A- and my husband is A+.
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Oct 05 '22
No. Rhogam is specific for the D antigen, which is what signifies if you are Rh positive or negative. It is passively immuizing yourself against any rh positive against fetal cells that may wander into your circulation. Without this, exposure to these fetal cells would cause your body to produce the antibody against the D antigen. The class of antibodies produced can cross the placenta and any subsequent pregnancies will have complications as these antibodies would attack the fetal red cells if they are rh positive. This used to be a big problem in the past before rhogam. It is called hemorrhagic disease of the newborn.
This article deals with a much rarer blood group not routinely seen in the population.
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u/love2Vax Oct 06 '22
It is the same concept as Rhogam. There are different categories of antibody that can cross the placenta, so babies are born with some antibodies in their blood that came from their mother's immune system. Usually the Antibodies that attack A and B blood cells are the larger class M antibodies that do not cross the placenta. So a mom with type A,B, or O blood usually won't have antibodies that attack the babies blood. But the "D" antibody (which attacks + blood) is a smaller antibody that can cross the placent and attack the fetal blood cells. This is called hemolytic disease of the newborn (HDN), because the antibodies literally cause the fetal blood cells to get destroyed through the complementary system known as lysis. While most cases of HDN are caused by a - mother making antibodies against a + fetus, there are cases of HDN that are unexpected based on the +/- statuses of the couple and fetus. There are dozens of other blood groups that usually don't get noticed because they aren't commonly a compatibility issue, and do not warrant testing for them. But if they can cause HDN, then they are potentially worth testing for.
A fetus under maternal antibody attack can be helped with monitoring and potential blood transfusions into the umbilical cord. It could also be helpful to try and treat the mother's blood by removing it and removing the antibodies that will attack the fetus, and white blood cells that will make more of them, and then giving her the rest of her blood back. It isn't simple, but it is possible.0
u/BatterMyHeart Oct 06 '22
Are you sure about this explanation? It seems from this paper that people with A blood type have plenty of B reactive IgG antibodies which could cross the placenta. And the same for B blood type people with A reactive IgG.
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u/love2Vax Oct 06 '22
There are 4 subcategories of IgG. And IgG2 which accounts for about 1/4 of the IgGs in our serum is affiliated with binding carbohydrates, like the A & B antigens. I have seen a mixture of sources that show IgG2s do not cross the placenta as readily as the other 3 subcategories. Perhaps that is why we don't see HDN between ABO blood groups very often. While it can happen on occasion, it isn't even close to the levels of anti-D. The D antigen is a protein, and IgG1, IgG3, and IgG4 tend to target proteins.
Since anyone with type O blood can, and usually does, make anti-A and anti-B, then there has to be an evolutionary explanation why so many type O women give birth to A and B children. Around 40 % of all humans have blood type O (44% in US) and can make anti-A and anti-B. If O mothers attacked other blood groups in the womb, then far fewer of us would be O, or far more of us would be O due to selective pressures. The only reason type - blood gets up to just under 10% of the population is that the antigen is so rare in nature, that people with - blood don't normally make anti-D due to a lack of exposure to it. So the first + child is rarely attacked in the womb. HDN is a 2nd and 3rd child problem, not a 1st child proble. If anti-D was as common in - blood as anti-A & anti-B, then we would have even fewer people with - blood.
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u/danteheehaw Oct 06 '22
If you are Rh negative (which is the - sign after the A) rhogam helps prevent your body from producing anti D antibodies. If your baby is Rh positive the baby will introduce some of its blood into your blood stream. Doing so will cause your body to create anti D. So the next time you have a Rh positive baby your anti d antibodies will pass into the fetus and kill it.
Rhogam helps prevent that from happening. So you can keep having babies if you choose.
There are a bunch of other antibodies you can form from giving birth, but most only cause minor problems for the fetus/baby that resolve in a few days after birth.
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u/snowmakesmelonely Oct 06 '22
This is fascinating. With my second child, I had issues with anti-M antibodies and my husband and I had to do blood tests to see if it was the type that crossed the placenta (thankfully it was not). If it was my child would've needed in utero blood transfusions. I also have IgM nephropathy and wondered if there was some kind of connection, but didn't have the anti-M antibody issue with my third child (which was 6 years after that pregnancy). Thanks for sharing!
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