Why is blood type O able to donate blood to all blood groups even though it contains anti-a and anti-b?

Answer 1

It is at least what i Have been told but it is because if somebody needs blood and they are not type O, type blood O would work for them. So if you have type A for an example and need blood type O would work.

Answer 2

Your question is somewhat misinterpreted. Type 0 blood does not have "anti-a or anti-b", type O blood simply does not respond to an anti-A or B test. The reason that type O blood can be universally donated is because of the agglutinogens (a type of antigen) present on the surface of the red blood cells. Type A and B blood cells have different markers on their surface, type AB has both markers. Type O blood however has none of these markers. When a foreign marker is introduced the body will naturally recognize it as foreign and rally its antibodies to fight the foreign bodies. Since type O blood has none of these markers (type O genetically codes for a marker, but it is not a viable protein), it won't trigger an antibody reaction.

That being said, RH factor must be considered too. Either you have the RH factor or you don't, which leads to being RH+ or RH-. Just like with ABO type, it is a marker on the surface of the cell. If you have it, you will recognize its presence as normal. If not, it will trigger an antibody response. The interesting thing though is that RH+ individuals will recognize RH- cells as normal too. This means that O- really is the universal donor, they can donate blood to anyone. O+ individuals can only donate to people that are RH+.