Your blood type depends on which ANTIGEN is sitting on your red blood cells (RBCs). For example, people with type A blood have an A antigen sitting on their RBCs (type B people have a B antigen,etc...people with type O blood have neither an A nor a B antigen on their RBCs.) Which antigen you have is determined by genetics, and you've inherited that from your biological parents.
The reason people with type A blood cannot receive blood transfusions from someone with type B blood is because the person with type A blood not only has A antigen, but likely has what we call ANTIBODIES against the B type blood.
When the blood of a person with A antigen is exposed to B antigen, as it would be if they were to receive blood from a donor with type B blood, their blood would be shocked! What is this foreign substance the B antigen? It would manufacture a defence against this foreign substance, and that defence is ANTIBODY. In this case, it would produce anti-B antibody.
As the picture above suggests, when antibody mixes with antigen, the RBC, in this case, would not survive. That is why people with type A blood cannot receive a transfusion from someone with type B blood.
To take it just one step further...people with type O blood have NEITHER A antigen NOR B antigen. However, they DO have both anti-A and anti-B antibody. Therefore, they can GIVE blood to anyone and any type, but can only receive type O blood.
As for the positive and negative type, it's pretty much the same idea. The + or - simply refers to whether or not the RBC has or does not have what's known as the rho antigen on it. The simple rule to remember:
That's enough detail for now.
- Back to giving and receiving blood chart
- Blood type and having children
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