What are the four different blood types?

The four different blood types are A, B, AB and O. People with the A blood type have the A antigen in their red blood cells and the B antibody in their plasma.

People with the B blood type have the B antigen in their red blood cells and the A antibody in their plasma. People with the AB blood type have both types of antigens in their red blood cells, but they lack any antibody in their plasma. People with the O blood type have no antigens in their red blood cells, but their plasma contains both A and B antibodies. They are universal donors, meaning they can donate their blood to people of any blood type.