[BLOG] Blood groups in feline: 8 facts about [AB]


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Last month, I had the opportunity to lecture at the World Cat Congress in Miami. Two reasons I was glad I could that: 1st/ I knew I would lecture to a group of passionate people, and nothings is better in order to have great discussions and 2nd/ it was in Miami, it was +27ºC while when I left Toronto it was -20… My topic: Colostrum and kitten’s immunity (you can see my slides here)

During the lecture, I obviously touched on feline neonatal erythrolysis. Indeed this is a typical situation feline breeders might encounter just after birth, when kittens from the [A] group suckle the milk from a [b] group female. If you need more info on this disease, please refer to the article we wrote on this topic few months ago here. And this is when it got interesting. At the break, I spoke with one of the breeders there. He asked me about my opinion: “When it comes to neonatal erythrolysis, how should we handle cats from the [AB] group?”. Mmm…


  • Three blood groups to consider in the feline species

Remember, there are 3 blood groups in cats: [A], [AB] and [b]. We usually speak a lot about [A] and [b]. But what about [AB]? Apart from the fact that “it is rare”, must admit this is not something I usually discuss. I have a slide I often use which shows that individuals from the [AB] group do not produce antibodies against [A] red cells nor [b]’s. But usually, again, because “it is rare”, that where the discussion ends.

I promised myself I would look into it. So when I got back home, I went back to the books (always a good thing to do when you question yourself!). Here is what I found on this [AB] group, might answer some questions feline breeders have!

Fact #1: The [AB] blood group is NOT a genetic mix between the alleles A and b. In fact it is a totally different allele (we might even have to change its name one day to avoid any confusion!). In terms of genetic determinism, we are therefore dealing here with 3 DIFFERENT alleles. The AB allele is recessive to the A allele, but dominant over b.


  • [AB]: not a common blood group in feline populations  

Fact #2: As you can see on the table below, it is indeed rare to find [AB] individuals. That explains why we tend to omit it when discussing feline blood groups.

from Knottenbelt, 2011 see here for reference

Fact #3: A blood group antigen is a protein that is carried by the red cells (that can eventually trigger an immune response). Red cells of cats from the [A] group carry type-A antigens, while red cells of cats from the [b] group carry type-b antigens. Red cells of [AB] individuals carry both type-A AND type-b antigens.

Fact #4: Tests we usually use in-house at the vet clinic generally detect those type-A and/or type-b antigens. As we said, [AB] individuals carry both: the cat is therefore [AB] when the test is positive for both antigens.

  • [AB]: about blood transfusion and neonatal erythrolysis

Fact #5:  [A] cats usually have low levels of anti-b antibodies, while [b] cats have high levels of anti-A antibodies. [AB] individuals have no antibodies neither against type-A or type-b antigens.

Fact #6: Since [AB] cats have no both express type-A and type-b antigens AND that they have no anti-A nor anti-b antibodies, these cats are in theory universal recipients when it comes to blood transfusion. In different studies, blood transfusion of [A] or [b] red cells in [AB] individuals did not lead to any adverse reaction. It has however been recently suggested that [AB] cats should only receive [A] or [AB] red cells. Indeed, the serum of [b] individuals still contains antibodies directed against type-A antigens (which [AB] red cells carry). In these cases, a immune reaction might still be triggered.

Fact #7:  Because [AB] red cells carry the type-A antigen, neonatal erythrolysis can also occur in [AB] kittens receiving the milk of a [b] queen.

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