ABO Blood Grouping System Overview

RH blood Grouping and ABO blood grouping. While some people are very used to the Rh- Blood grouping system, it is important to know that the ABO blood grouping system is well recognized and they both work hand in hand. Please do not mistake blood grouping for genotypes, they are not the same in any way. - My previous post.

I discussed the Rh Blood Grouping method in my previous post, but it is good that we know that there isn't only the Rh blood grouping system, there is also the ABO blood grouping system, and today, we are doing the ABO type of grouping.

When a person is said to have a blood group A, it means that the red blood cells of the person have A-antigens. When a person is said to have a B blood group, it means that the red blood cells of the person should have the B-antigens, people who A and B antigens present in the Red blood cells are known to fall under the blood group AB, and people who do not have any of the antigens (either A or B) are said to be O blood group. While the O blood group does not have A and B antigens, they possess the H substance or you can call it the H-antigen. The antigens of the Red Blood Cells are found at the surface of erythropoietic precursor cells because why the red blood cells are anucleated cells, and the precursor cells possess a nucleus. All red blood cells possess numerous oligosaccharides precursor molecules, and they are modified with the help of the 19th chromosome which expresses a gene that produces an enzyme known as the Fucose transferase which is attached to the oligosaccharide chain. When there is a fucose transferase on the Oligosaccharide, it is referred to as H-substance/H-antigen. Everyone has the H-substance expressed in their blood during erythropoiesis.

In Blood group-A, there is a step further during erythropoiesis. After the fucose transferase has been attached to the oligosaccharide. Chromosome 9 in the erythrocyte precursor cell, from both parents, makes a transferase enzyme known as the N-acetylGalactosamine (NAGA) which will be added to the H-substance, creating the A-antigen. People with blood group A initially had the H-substance before the N-acetylGalactosamine (NAGA) transferase was added to it. The N-acetylGalactosamine (NAGA) transferase can also be called transferase-A. With Blood Group-B, There is a precursor red blood cell with the 19 chromosome which makes the fucose transferase on the oligosaccharide to make the H-substance. In chromosome 9 there is a gene that does not create N-acetylGalactosamine (NAGA) transferase but rather creates Galactose. The galactose then heads to the H-substance, thereby creating the B-antigen. It is important to know that people with both A-antigen and B-antigens have the H-substance initially before the attachment of their transferase. It is important to know that people with Blood groups A and B can get their transferase from either of their parents or both, they can be homozygous or heterozygous. There can be an inactive gene in one of the parents or they might both have active genes from both parents, whereas the offspring can have genes AA or AO, and BB or BO.

In people with the AB blood group, we will start with chromosome 19 which creates fucose transferase that attaches to oligosaccharides to become the H-antigen/H-substance. In the precursor cells of the parent, one can make the transferase-A while the other will be making the Transferase-B, with both being active, converting the H-substances into A-antigens and B-antigens, allowing the person to possess both molecules causing the blood group to be AB. At one Locus, there can be only one gene where the other gene is not functional making the Alleles, which are variants of one gene from a locus.

For ease, it is important to know which blood can donate to one another, so I will make a tabular illustration.

With the Rh factor which I talked about in the post before this, a person with a negative Rh factor can give to both Negative and Positive, while a positive Rh factor can only give to positive and not negative. These cause a lot of confusion and it is important that you know them and know your blood group.

https://www.ncbi.nlm.nih.gov/books/NBK2267/

http://nbtc.naco.gov.in/assets/resources/training/5.pdf

https://www.nhs.uk/conditions/blood-groups/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260296/

https://microbiologynote.com/blood-grouping-principle-and-procedure/

https://www.nature.com/articles/nature02399

https://emedicine.medscape.com/article/1731198-overview