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Despite their obvious clinical importance for blood transfusion and organ transplants, the day-to-day purpose served by the ABO glycoproteins remains a mystery.

ABO mysteries and myths – Genetics may hold the key to finding the answers

The physiological functions of ABO blood types remain a mystery

Despite their obvious clinical importance for blood transfusion and organ transplants, the day-to-day purpose served by the ABO glycoproteins remains a mystery. Numerous associations have been made between ABO blood types and other traits, including increased susceptibility to disease. However, none of these can be described as the role of ABO glycoproteins.

ABO blood types and infectious diseases

Associations have been found between various infectious diseases and the ABO blood types. For example, people of blood type A appear to be more susceptible to smallpox, type B individuals may be more susceptible to infantile diarrhea, and type O individuals more susceptible to bubonic plague. Some research suggests that blood of type O is especially tasty to mosquitoes, which could be a significant factor in the contraction of malaria.

In this way, the frequency of ABO glycoproteins and their underlying alleles in human populations may have been influenced to a greater or lesser extent by infectious diseases in different parts of the world. For example, the highest frequency of blood type B is found in India. This may be partly due to selection against people with blood type A because of smallpox and people with blood type O because of plague.

ABO blood types and non-infectious diseases

The ABO phenotype has also been linked with non-infectious diseases, such as stomach ulcers (more common in type O individuals) and gastric cancer (more common in type A individuals – read more here). Some stomach ulcers are however infectious in nature (caused by the helicobacter pylori bacteria, and therefore related to antibodies).

Another observation is that individuals with blood type O tend to have lower levels of the von Willebrand Factor (vWF), which is a protein involved in blood clotting (read more here). Obviously there is much still to be learned about the basic physiological functions of the ABO blood types.

Myths associated with ABO blood types

There are numerous popular myths surrounding ABO blood groups. These beliefs have existed since the ABO blood groups were first discovered and can be found in different cultures throughout the world.

For example, during the 1930s, it became popular to connect blood groups and personality types.

Another myth involves special diets that suit different blood types. The abundance of books and websites on the topic indicate that this myth is persistant.

Yet other myths include the idea that blood type A causes severe hangovers, type O is associated with perfect teeth, and people with blood type A have the highest IQs.

Although fun and in some cases interesting, scientific evidence in support of these myths is scant or nonexistent.

More information

If you want to learn more about blood, ABO blood groups, transfusions or blood donations, talk to your doctor and visit the following websites:

• The ABO blood type game, from the Nobel Foundation
• All about blood from the American Red Cross
• The American Red Cross Article by Fumiichiro Yamamoto Ph.D., on the molecular genetic basis of the ABO system
• Ethnic and racial distribution of blood types
• Blood and its components
• Blood types, by The American Red Cross
• Distribution of ABO blood types
• The Human Blood Type Calculator, the University of Arizona´s Biology Project
• The Immune System: The National Institute on Allergies and Infectious Diseases
• Transfusion safety, from the National Institutes of Health
• What is blood?
• The World Health Organization on blood transfusion safety

This content was last reviewed on February 09, 2010.

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