Red blood cell blood group antigens: structure and function.
For example, the antigens of the ABO blood group are sugars. They are produced by a series of reactions in which enzymes catalyze the transfer of sugar units. One large role carbohydrates play in cells is in cell-cell recognition. boxes at left, click on a blood type to see the structure of the ABO blood type antigens. Six patients in each group were secretors of blood group antigens in the saliva and Le genes and their relationship to the structure of the blood group antigens.Blood Types: ABO and Rh (with donuts and sprinkles!)
Click on the blood groups to find out more about the antigens that define it. Red blood cell antigens determine your blood group The antigens expressed on the red blood cell determine an individual's blood group. The functions of many of the blood group antigens are not known, and if they are missing from the red blood cell membrane, there is no ill effect. This suggests that if the blood group antigens used to have a function, e. But the presence or absence of red blood cell antigens becomes extremely important when blood from different people mixes, e.
This also happens when a mother becomes pregnant because during labor, a small amount of fetal blood enters her circulation. In these circumstances, exposure to the foreign antigens on the red blood cells can trigger immune reactions.
It is not possible to completely remove the danger of adverse reactions when blood from two people mix, but the danger can be minimized. Before a blood transfusion takes place, the blood to be donated must be "typed and cross matched" with the patient's blood to ensure immune compatibility see Chapter 3.
In pregnancy, the risk of the mother's immune system attacking the foreign antigens present on her fetus' red blood cells is prevented by giving the mother antibodies to cover fetal red blood cell antigens and removing them from the mother's circulation before her immune cells find them see Chapter 4. It is determined by the frequency of the three alleles of the ABO gene in different populations. Blood type O is the most common worldwide, followed by group A. Group B is less common, and group AB is the least common.
The frequencies of ABO and Rh type in the United States were recently examined by collecting data from blood donors over a 10 year period 1. The charts below summarize the findings for blood type and race: The highest percentage of RhD- was found in white donors It is also the most common blood type in populations around the world, including the USA 1 and Western Europe 2, 3.
It is also high among Australian aborigines.
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The highest frequencies are found in small, unrelated populations. It is also the rarest of the blood groups. The classification of blood cell antigens Traditionally, newly discovered red blood cell antigens were named alphabetically e.
Under this terminology, each blood group antigen has a number, and it belongs to a blood group system, a collection, or a series 4.
Blood groups A blood group system contains antigens controlled by a single gene or by multiple closely linked lociand the system is genetically distinct. At the time of writing, there are 22 blood group systems, including the ABO, Rh, and Kell blood groups which contain antigens that can provoke the most severe transfusion reactions.
Each blood group antigen is assigned a six-digit number by the ISBT. The first three digits represent the blood group e. For example, for ABO, the A antigen was the first to be discovered and has the number The most basic oligosaccharide attached is called the O antigen also referred to as the H antigen.
Blood type O only has the O antigen attached to the red blood cells. Blood type A is formed through the addition of the A antigen, which has N-acetylgalactosamine GalNAc glycosidically bonded to the O antigen. Similarly for blood type B, the B antigen has an additional galactose forming a glycosidic bond to the O antigen.
GalNAc transferase adds the extra N-acetylgalactosamine for the A antigen while Gal transferase adds the extra galactose for the B antigen. The genes that code for GalNAc and Gal transferases are exact, but for three amino acids. This strong similarity between the two enzymes shows they are related through divergent evolution.
Functionality[ edit ] The importance of glycosyltransferases is most prominent when a person needs a blood transfusion.
Type O blood can be given to anyone because everyone has the ability to recognize the O antigen. However, a person with type A or type O blood cannot recognize the B antigen while another with type B or O blood cannot recognize the A antigen.
The ABO Blood Type System
It is because of this process that people with type AB blood can accept transfusions of any blood type, since they have all three antigens already present in their bodies.
It should be noted that in reality, transfusions are complicated by the Rhesus factor. These four phenotypes can produce six different genotypes that each person can be: On the surface of red blood cells, there are 2 types of antigen: Type AB contains both antigens on the surface and has neither antibodies. Blood type O has no antigens and thus have both A and B antibodies in its system. In this regard, blood type O may be the universal donor and blood type AB is the universal recipient. We can also look at the property of Rh protein whether it's absence or presence in our blood.
- Variations on a Theme
- Structural Biochemistry/Carbohydrates/Blood Type
- Blood Types and Carbohydrate Chemistry
The RH factor is more important if the mother is to have a second child. This will not affect the first child since the mother will only produce this antibody after the child is born.
This is because the antibodies for the RH protein are specific proteins called memory cells that are small enough to pass the placenta.
This will result in a miscarriage. One way around this is to give the mother Rhogam after birth. This is a synthetic protein antibody that will destroy the left over fetal cells before it has a chance to interact with the mother's immune system.
Mixing Different Blood Types[ edit ] Our body generates antigens or antibodies to protect us from the unfamiliar molecules. They will then recognize this difference and clash with the molecules to get rid of them.
Red blood cell blood group antigens: structure and function.
For blood transfusion, it is very important to make sure that both the recipient and the donor match in blood type. Universal Donors and Universal Recipients Blood type O is the universal donors due to its versatility of having no molecules on the red blood cell surfaces, which will not trigger any immune response. Therefore type O blood can be donated to any of the other four blood types earning its name.
Blood type AB is the universal recipients due to its lack of antibodies that recognize type A or B surface molecules.