Which various blood groups exist

Why are blood groups important?

Is the donor’s blood compatible with that of the patient? This is the essential question in modern transfusion medicine. Because what is life-saving for one person can be life-threatening for another. Blood groups were discovered by Austrian physician and Nobel Prize winner Karl Landsteiner. In 1901, he established that blood from different people can only be mixed if certain characteristics match. To this end, he established the AB0 system, which still plays an important role in blood donation today. Added to this comes the rhesus system, also established by Landsteiner at a later date.

Which blood groups exist?

• A
• B
• AB
• 0

Every person belongs to one of these four blood groups. The distribution varies worldwide. In Switzerland, blood group A is the most common (at around 45%), followed by blood group 0 (41%). The rarest blood groups are B (around 9%) and AB (around 5%).

Which blood group can donate to whom?

Blood groups are identified by the genetically-determined characteristics of the surface of the red blood cells. Located on these surfaces are proteins which act as antigens. With these antigens the immune system can form antibodies against foreign blood: blood group A has antigen A, blood group B has antigen B. A tolerates blood groups A and 0; and B tolerates blood groups B and 0.

Universal donor

Blood group 0 (especially with the rhesus factor negative) contains no antigens, which is why these people can donate blood to anyone, but as recipients they can only tolerate their own blood group.

Universal recipient

In the AB group, both antigens A and B are present, which means that: AB tolerates all blood groups.

Donating blood is important

The notion of donating blood may seem outdated. But without voluntary «bloodletting», the lives of many seriously ill and injured people could not be saved. Every day, around 760 blood donations are needed in Switzerland. Because blood can only be kept for a limited period and cannot be produced artificially, it needs to be constantly replenished. But only 2.5% of the population is willing to donate blood regularly, even though little stands in their way: anyone who weighs more than 50 kilograms and is between 18 and 75 years old is eligible to donate. For a first donation, the age limit is 60.

Young men wanted

Everyone knows that you can donate blood. What is less well-known is the practice of donating blood stem cells, yet for children and adults with life-threatening diseases such as leukaemia, it is often the only possible way to save their lives. Volunteers are therefore being sought who – online and anonymously – are ready to register as blood stem cell donors.

Men under 30 years of age are particularly called upon. So far, they are under-represented in the donor registry although, from a medical point of view, their stem cells are ideal for transplantation. The older the donor, the higher the risk that the foreign cells will be rejected by the patient's immune system. Those registered will only be approached for a donation if their own tissue characteristics match those of the diseased person, the probability of which tends to be rather low.

What does the rhesus factor mean?

In the case of a blood transfusion, it’s not only the blood group that is taken into account. Also important is the rhesus factor, i.e. other antigens found on the red blood cells. The most important antigen in medical terms is antigen D. This antigen is present in people with a positive rhesus factor and absent in people with a negative rhesus factor. This results in a total of eight blood group combinations: A+, A-, B+, B-, AB+, AB-, 0+, 0-. Determining the rhesus factor is also important during pregnancy. If a foetus is rhesus-positive but the expectant mother is rhesus-negative, complications can arise. Today action can be taken to prevent this.

Why is «golden blood» the rarest blood group?

Worldwide, there aren't even 50 people with «golden blood» flowing through their veins. It is the rare blood group Rh-zero, in which all antigens from the Rhesus system are missing. In principle, people with this blood group are the absolutely perfect donors. But because «golden blood» is so rare, it plays only a minor role in everyday medicine.