Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: EvaH on 23/09/2020 16:58:09
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Carlo asks:
Why is it that our body produces B-Antibodies when I have the blood-group A? I can't find an answer anywhere. Is it just because our bodies produces millions of different antibodies and then by coincidence one fits?
Can you help?
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Is it just because our bodies produces millions of different antibodies and then by coincidence one fits?
That's pretty much it...
Your body produces very many antibodies, based on some hyper-variable parts of the chromosomes.
- Some of these come from the Major Histocompatibility Complex (MHC)
- Inbreeding reduces the range of MHCs available to an individual
- With more variation in MHC, you can generate a greater range of antibodies, and potentially detect more pathogens, more precisely
Many of these antibodies will react to your own body; an auto-immune disease with potentially lethal effects
- So part of maturation of the immune system is to "weed out" those antibodies that will attack your own body
- What is left is a whole range of antibodies, some of which will recognize a foreign blood group, if you have a transfusion without proper blood group matching
- So a person with blood group A will develop antibodies against blood group B. They were always there (at a low level), but now they will multiply, and this person will have an immediate and significant reaction to future blood group B exposure.
- or, more commonly, a women with blood type Rh- bearing a baby with blood type Rh+ will develop antibodies to Rh+, which will cross the placenta and kill subsequent Rh+ babies. These days, this is treated by an injection of Rh+ antibodies immediately after birth, so the woman does not multiply up her own Rh+ antibodies.
See: https://en.wikipedia.org/wiki/Rh_disease
https://en.wikipedia.org/wiki/Major_histocompatibility_complex
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A specific set of proteins (antigens) is expressed on the membranes of erythrocytes - non-nuclear red blood cells that are responsible for transporting oxygen. These proteins are capable of triggering immune responses aimed at recognizing foreign proteins and eliminating them (elimination). Each antigen has its own antibody in the blood plasma. Therefore, the blood group is determined by the presence of one or another antigen protein on the surface of erythrocytes and an antibody protein in the plasma. Some antigens are expressed to a lesser extent and cause immune responses much less frequently, therefore they are not of high clinical significance, and some to a greater extent, and neglect of them can lead to death for the recipient.
In the AB0 system, antigens A and B can be contained on the surface of erythrocytes, and antibodies anti-A and anti-B in the blood plasma. In cases where antigen A and antibody anti-A intersect, destruction of red blood cells occurs. So if a person has antigen A, then they have anti-B antibody. There are four possible combinations (groups):
0 (I) - there are no antigens A and B on erythrocytes, but the corresponding antibodies are in the plasma;
A (II) - antigen A on erythrocytes, anti-B antibody in plasma;
B (III) - antigen B on erythrocytes, anti-A antibody in plasma;
AB (IV) - antigens A and B on erythrocytes, no antibodies in plasma.
Different subgroups can exist within the same blood group. Antigens A and B are encoded by several different genes, and depending on which gene encodes a particular antigen, their immunogenicity will differ. For example, the A1 antigen is slightly less immunogenic than the A2 antigen.
All this is important both in blood transfusion and in organ transplantation, because antigens A and B can be expressed not only on the surface of erythrocytes, but also in many other places: on the membrane of liver cells, on the surface of the endothelium - the cell layer lining the vessels from the inside ... And if the blood groups of the organ donor and the recipient do not match, then, most likely, such a transplant will not be able to take place.
The Rh factor system consists of blood groups determined by 59 antigens. The most important are antigens D, C, c, E, e, which have immunogenic properties. The commonly used terms "Rh positive" (Rh +) and "Rh negative" (Rh-) refer only to the presence or absence of the most immunogenic Rho (D) antigen.
The Kell system includes 25 antigens, including antigen K - the most immunogenic after A, B and D. As in the case of the Rh factor, people are divided into two groups (Kell-negative and Kell-positive) based on the presence of the K antigen in erythrocytes or lack thereof. This antigen is not counted in plasma transfusion, but is counted in red blood cell transfusion.
Blood groups are determined by a set of genes that do not affect either the character or the color of the hair and eyes, or the rate of absorption of food, or the predisposition to certain diseases. Not a single study in the world, conducted on large reliable statistical samples, found links between blood groups and other functions or characteristics of the body. There is no scientific background or evidence that blood type diets and other similar methods work.
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part of maturation of the immune system is to "weed out"...
PS: The place where much of this immune system training occurs is the Thymus.
And the selection process operates on T-Cells.
https://en.wikipedia.org/wiki/Thymus#Positive_selection