Fascinating Aspects of Glycobiology—Part 3 (ABO Blood Types)

Larry A. Law

Discovering the power of glycobiology sugars on the ABO blood typing system represented my biggest aha moment.  Our blood is classified into four different groups: A, B, O, and AB. This classification is done based upon the different sugars surrounding the red blood cell (RBC). The medical community calls the effect of these sugars antigens because of how the immune system reacts to them. 

Blood

The ABO blood typing system is the most common method for differentiating types of blood.  Like 11% of the world's population, I have type B blood. Angie has type A (40%). Our son, Logan, is in the rarest blood group (4%): AB. Many of our sons-in-law belong to the most common and versatile blood type—type O (45% of the population). Each of the blood types have RBCs surrounded by sugar antennas (glycolipids). There are approximately 800,000 antennas (strands of cell-surface, sugar structures) on each RBC. Picture a man's beard. The face of the RBC is covered with nearly a million strands of whiskers! 

Sugar Strands

Each of the nearly one million strands has several sugars linked together. Human cells can have a forest of strands of sugar that can branch out in long chains in many different directions. An individual's RBCs are all coded with the same particular strands of sugar, this accounts for their blood type. The image at the top of this blog post depicts the particular arrangement of sugars for each blood type. Type O has 4 sugars and they are in the exact same order as the first four sugars on the other blood types. But type A and type B have an extra, fifth sugar added to the chain. Type B has a molecule of galactose added and type A has a molecule of N-acetyl galactosamine added. Type AB has both type A and type B chains on its glycocalyx. What is extremely interesting is that there is no difference between the various types of blood except for the last (terminal) sugar on the end of the strand. Everything else is identical. However, a blood transfusion of the wrong blood type could lead to serious side-effects including death. Does the body pay attention to these sugars? This observation dramatically answers that question and indicates how precisely the body pays attention to these sugars. One sugar in the wrong place could cause death—wow!!  

Transfusions of Blood

Type O blood is the coveted blood type. It is called the universal donor because it can be transfused into anyone and there is never a problem. Type AB is called the universal receiver because recipients can receive blood from any of the other three blood types and they never have a problem with that blood. However, type A, B, and O get more complicated. Type A cannot receive from type B or AB. Type B cannot receive from type A or type AB. Type O cannot receive from type A, B, or AB. The reason is that each of the blood types have no problem with the first four sugars because that is the standard pattern in all four types of blood. But add a fifth sugar and the immune system reacts. It will wage a war against all RBCs that do not have just the first four sugars (Type O) or their fifth type of sugar unique to their blood type. A foreign fifth sugar will cause the immune system to kill every stranger RBC, because it views them as not native (foreign) and therefore an enemy to the body.

The immune system pays very close attention to the sugars on the surface of our cells receptors. In fact, this is at the crux of how the immune system cells patrol our borders and keep us safe from foreign invasion. The immune system identifies bacteria, viruses, pathogens, and toxic substances by assessing the pattern of their sugar profiles. If something is identified as not belonging to the body, then it is destroyed. In this way, disease is prevented. If the glycocalyx on cells becomes compromised, then the immune system cannot communicate correctly and autoimmune or degenerative disease results. This represents the incredible power inherent in nutritional glycobiology.