• Question: Why can the blood type o be given to people with different blood types such as a, b and ab, and if this is so, can other blood types be given to people with the blood type o in return?

    Asked by anon-308588 on 27 Jan 2022.
    • Photo: Samuel Ellis

      Samuel Ellis answered on 27 Jan 2022:

      Blood types are a very cool bit of medical biology, and super important for safe transfusions, but also a little complicated. Short answer to your question is no, people with O type can only receive O blood.

      Detailed answer:
      It is all based on what kind of markers (called antigens) are present on the surface of your red-blood cells, because if you are given the wrong type of blood your antibodies will recognise it as foreign and cause a life-threatening reaction!

      The most important antigens are referred to as A and B, and you can have either both (so type AB), one (A or B), or neither (called type O). This is why O blood can be given to any other group, as it has no antigen to be recognised as foreign! However, people with type O can only receive O blood, as they would recognise any combination of A and B as bad.

      The other major typing system is Rhesus positive or negative, which is why a blood type can be A+ or A- for example. The rule here is that a negative blood type cannot receive positive blood as it would react to the Rhesus antigen.

      It is complicated, it is easiest to understand looking at a blood type compatibility table (google it!). Overall, O- blood can be given to all the other types, whereas AB+ could only go to another AB+ person

    • Photo: Valerie Vancollie

      Valerie Vancollie answered on 28 Jan 2022:

      They think the incompatibility listed above by Samuel may be responsible for some historical events as a woman who is Rhesus negative can have problems giving birth to a second child if the first was Rhesus positive (due to the father’s genes), as her immune system may react badly to the second baby if it too is Rhesus positive. They suspect this might have been the case with Anne Boleyn.

    • Photo: Melanie Krause

      Melanie Krause answered on 30 Jan 2022:

      Hi 🙂
      With blood types a special thing in genetics applies where we call something dominant or recessive. With blood type A you have specific Type A surface molecules on your red blood cells. With B you have the type B ones, with AB you have both and with 0 you have none.
      You have genetic information from both of your parents that is mixed within you. Your mother may have given you 0 so no surface molecules, but your dad may have given you A, so surface molecules of type A. As that means you definitely have these A molecules you are Type A (or genetically A0 to be exact). If you got A from both your parents you would be AA so you would have A molecules but more of them.
      But as people with 0 never have any A or B molecules they can not pass them on they are always 00.

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