blood type O is said to be the universal do nor.It can be transfused to people with all blood types because red blood cells have glycoprotein antigens on their surfaces.Type A blood has A antigens type B has B antigens tpye AB has both and type O has neither. There are also antibodies in our blood but they are in the plasma -- not red cells. These protect the body from attack from germs.So the antibody in type A blood will attack cells with the B antigen while the antibody in type B blood will attack cells with the A antigen. Type O has no antigens so it can be give to any person