Why A, B or O can donate blood to AB?

[jaumzaum]

AB people don't have agglutinins anti A or anti B so it might seem they can receive any type of blood. But if the donator is A for example, it's own blood will have agglutinins anti B that will agglutinate the AB blood. So why can AB people receive blood from non AB people?

 

[Wrichik Basu]

I had the same question, and spoke to a doctor last year. He said that although it's written in books that O is an universal donor and AB is an universal receiver (considering same Rhesus factor), inter-group blood transfusion is discouraged, because of the reason you've mentioned. If large quantities of blood are transfused, there are chances of agglutination, leading to haemorrhage. Unless it's very urgent, doctors don't support inter-group blood transfusion.

 

[Laroxe]

In the ABO blood types the important thing is which antibodies are present in the plasma of the recipient, the antibodies in the plasma of the donor are not at a level that would cause the recipients cells to be damaged. The main transfusion reaction is caused by the cells in the donor blood being destroyed and as group AB don't have antibodies in their plasma the transfusions should be safe. Remember the cells of group AB have both antigens, if there were antibodies they wouldn't survive.
However Wrichik is right, there are lots of antigenic groupings and blood is full of all sorts of other antigens they always try to specifically match the donor blood to each recipient.