By Billie Rubin, reporting from the labs of Stanford Blood Center
The antigens on the surface of red blood cells can be made out of proteins, carbohydrates, glycoproteins or glycolipids. The A and B antigens that we commonly hear about belong to the ABO system. You can think of the systems as family members determined by your genes.
In addition to the ABO system, there are another 28 systems of antigens that are currently recognized, like the Rh system, and the Duffy system. Altogether there are 29 blood group systems that contain about 600 antigens between them.
Some antibodies to those antigens (about 14 of them) are more common than others and are clinically significant. They can cause serious reactions if transfused to an incompatible patient and therefore need to be identified beforehand so the hospital can find compatible blood that lacks the corresponding antigens.
The RBC surface is a very busy world!