Blood type is determined by the presence or absence of specific antigens named A and B, molecules that are attached to red blood cells.
- Type A: individuals with Type A have an A antigen on red blood cells and B antibodies in their plasma (the almost transparent liquid that is part of the blood).
- B: individuals with Type B have
the B antigen on red blood cells and A antibodies in their plasma.
- Type AB: individuals with Type AB have both A and B antigens on red blood cells but neither A nor B antibodies in their plasma.
dies in their plasma.