Stories tagged antigens


Blood donation.: Image courtesy size8jeans.
Blood donation.: Image courtesy size8jeans.
I am a blood donor – and if you are not, and are able to, I would encourage you to be a donor too. The process of blood donation is relatively simple, and sort of painless. And although all blood looks the same, and is made of the same basic elements, there are actually eight different common blood types: A(+/-), B(+/-), AB(+/-), and O(+/-). The letters A and B stand for two antigens that can be present on the surface of a red blood cell. Someone with the A antigen can’t donate to someone with the B antigen, and vice versa. For example, I have type A blood, meaning the A antigen is present on my blood cells. My blood can be donated to persons who have types A or AB blood and I can get blood from donors who are also type A or who are type O. If I received type B blood I would suffer a serious, possibly fatal, hemolytic reaction. It is therefore very important that the blood type of a donor and a recipient be properly identified.

To further complicate matters, blood types are also either positive or negative for the presence of another antigen, Rh. If you have the Rh antigen on the surface of your red blood cells you have Rh+ blood, if you do not have the Rh antigen, you are Rh-. So, if you have Rh- blood you can only receive blood from others of the same blood type (A, B, AB, or O) who also have Rh- blood. But, if you are Rh+ you can receive from both Rh+ and Rh- blood types.

Now, type O blood (called type zero in some countries) has neither the A or B antigen and therefore, type O negative blood can be given to anyone. Persons with type O negative blood are referred to as “universal donors”. If everyone had type O negative, blood transfusions would be less risky – unfortunately, only about 7% of Americans have type O negative blood.

Recently a company called ZymeQuest in Massachusetts announced that it had discovered two enzymes, called glycosidases and derived from bacteria, that could be used to strip A or B antigens from the surface of the red blood cells, essentially enzyme-converting them to type O cells. By converting all A-negative, B-negative and AB-negative blood into O-negative blood would increase the availability of “universal donor blood” from 7% to 16%. While we’re likely far away from this blood conversion being used in patients, it is currently being tested in the U.S. and in Europe.

Learn more about donating blood here and here.

Play a game to see if you can match the right blood donor to the right recipient here.