The Prize:

The 1930 Nobel Prize in Medicine or Physiology to Karl Landsteiner “for his discovery of human blood groups.”

The Science:

Modern surgery, emergency medicine, and the treatment of blood disorders are all dependent on blood and blood products. Transfusions between two people turn treatments requiring blood into simple procedures, but it hasn’t always been this way.

During the 17th century, scientists began experimenting with blood transfusion both between animals and from animals to humans. Not surprisingly, most patients died from the procedure as a result of immune reactions to the transfused blood which causes red blood cell death, kidney failure, and shock. The low success rate of these early attempts led to banning the practice.

An adverse reaction to transfused blood is a result of a healthy immune system. The immune system is how the body recognizes “self” vs. “non-self” to protect against bacteria, viruses, or allergens. In the case of a blood transfusion between two individuals of a different blood type—or two species—the patient’s immune system recognizes the incoming blood to be non-self and mounts an immune reaction to protect the body.

In 1875 it was discovered that an animal-to-human blood transfusion resulted in the clumping (agglutination) and a breaking up (lysis) of the incoming red blood cells (RBCs). Karl Landsteiner realized that the same process may occur in blood transfusions between two humans as well.

In 1900, Landsteiner discovered and described three blood types now known as A, B, and O. Decastrello and Sturli added AB to the list in 1902. By mixing two blood types in a test tube, one of a known blood group and one unknown, everyone’s blood type can be classified. Blood samples of the same type will have no effect on each other, but mixing different blood types will cause visible clumping. It was subsequently discovered that the ABO blood types follow classical Mendelian genetics.

Thus every individual inherits a genetic copy of A, B, or O from each of their parents. Blood types A and B are dominant over O, such that having one copy of either A or B masks O, so an individual with one copy of A and one copy of O has blood type A. To have the blood type O, one must have two copies of the O gene. In contrast, individuals with a copy of each of A and B have blood type AB (an example of genetic co-dominance).

We now know that the ABO gene encodes a protein that adds sugar molecules to the surface of RBCs. The A and B copies encode proteins that add two different types of sugars, whereas the O protein is not active and adds no sugar at all. It is the identity of this sugar that alerts the host immune system that non-self RBCs are present in the body.

Blood types A and B are incompatible because they have different sugars on the surface of RBCs, but A and B blood type individuals can accept type O blood (the universal donors) because type O RBCs do not carry an immunogenic sugar. Blood type O individuals can only accept type O, and blood type AB individuals are tolerant of all blood types (the universal acceptors).

For his discovery of the ABO system, Landsteiner was awarded the Nobel in 1930. After his initial discovery of the ABO blood groups, Landsteiner continued to work in the field and in 1939, in collaboration with others, discovered the Rh blood group. They found that in addition to the ABO types, one can either be (+) or (-) for the Rh antigen, thus one’s blood type is described by a letter and the Rh factor (i.e. A+, O-, etc.).

There are now 30 known blood groups that describe every individual’s exact blood type. The other blood groups are usually important only in matching individuals who have had multiple transfusions and may have developed an allergy to other blood types in the process.

The Significance:

It has been estimated that over one billon lives have been saved as a result of timely blood transfusion made possible by the discovery of the major blood groups. Unfortunately, many transfusion recipients have received contaminated blood and contracted diseases such as HIV/AIDS, hepatitis, and syphilis. As a result, today blood is thoroughly screened before processing and transfusion.

The ABO blood system has also inspired pseudo-scientific theories of personality types associated with each blood type (very popular in Japan and South Korea) and a diet fad based on dietary rules unique to one’s blood type. Although fun to think about, these theories have never been scientifically researched.