How does blood typing work?

Question

thomaster · Answer

Do you mean what the difference between the 4 blood groups is?
Or how they are determined?

thomaster · Answer

Group A has antigen-A in the red blood cell and antibody-B in the plasma.
Group B has antigen-B in the red blood cells and antibody-A in the plasma.
Group AB has antigen-A and B in the red blood cell and no antibodies in the plasma.
Group 0 has no antigens but has both antibody-A and B in the plasma.

Then you have antigen-D which determines the rhesus factor. If antigen-D is present the rhesus factor is positive and if antigen-D is absent, rhesus negative.

The blood group and the rhesus factor determines what donor blood a recipient can get.
Here is a table which shows the compatibility of the different blood types.

thomaster · Answer

For the type determination part:
You take 2 antibodies A and B
Then put 2 drops of blood on a microscope slide or something transparent.
Induce antibody A to the first drop and B to the second drop.
If only the blood in the first drop clots you have blood type A
If only the blood in the second drop clots you have blood type B
If the blood in both drops clots you have AB
And if the blood in neither of the 2 drops clots you have blood type 0

anonymous · Answer

Thanks man! That helped a lot :)