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Author Topic: Why do we have blood groups?  (Read 616 times)

Offline thedoc

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Why do we have blood groups?
« on: 29/03/2016 16:50:01 »
Narelle Bowern asked the Naked Scientists:
First question of two:
1. What is the point of blood groups i.e. what is the biological reason for having different blood groups?
What do you think?

Question split into two threads - mod
« Last Edit: 29/03/2016 21:22:19 by evan_au »


 

Offline evan_au

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Re: Why do we have blood groups?
« Reply #1 on: 29/03/2016 21:50:03 »
Blood groups must be managed in blood transfusions because of our immune systems.

The immune system is always on the lookout for "foreign bodies" like bacteria, viruses and parasites. Once identified, the immune system attacks and destroys the invader.

Humans are not identical - we all have a slightly different mix of proteins and sugars produced from instructions in our DNA. If someone is exposed to a chemical which does not naturally occur in their body (eg due to an incorrect blood transfusion), the immune system will go into attack mode and destroy it.

Three of the chemicals commonly seen on the surface of red blood cells are labelled A and B (sugars) and Rh (a protein). You may inherit none of them, all three, or somewhere in between.
  • If you have A visible, your blood type is labeled with A
  • If you have B visible, your blood type is labeled with B
  • If you have both A and B visible, your blood type is labeled with AB
  • If you have neither A nor B visible, your blood type is labeled with O
  • If you have Rh visible, your blood type is labeled with +
  • If you don't have Rh visible, your blood type is labeled with -

So problems occur if someone is suddenly exposed to a protein they don't naturally carry.
  • For example, a person with O- blood does not display any of these three markers.
  • If they are transfused with blood from an AB+ person (who displays all 3 markers), their immune system will go into overdrive, and attack these foreign blood cells.

See: http://en.wikipedia.org/wiki/Human_blood_group_systems

The same thing happens with organ transplants, only there are far more chemical markers displayed on complex tissues like a kidney. So tissue type matching is more complex than blood type matching, and will usually require an organ recipient to spend the rest of their lives on anti-rejection drugs.
 

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Re: Why do we have blood groups?
« Reply #1 on: 29/03/2016 21:50:03 »

 

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