Blood Types ??

In my keyword reports I often get queries about blood types. I would really like it if the person or persons making these keyword searches leave a comment on what their suspicions are or theories are with regards to this. The interesting thing about red blood cells is they do not have a nucleus or any DNA in it which would make it unidentifiable to the immune system entities (Angels). What is odd is some blood types have antigens that seem to have no function other then to render the cells useless if they are transfused in to a person that has blood type that is not compatible. What is odd is blood type O as it has no antigens and can be transfused in to anyone regardless of their blood type. I know there is likely a reason for this oddity one theory I have is it could stem from some sort of curse or battle between two tribes or tribe entities.