How are blood groups classified

Blood group system

1 definition

At a Blood group system is an antigen that is found in the blood, is polymorphic and is inherited independently. Antigen means that a recipient who does not express this trait may be sensitized by a transfusion or pregnancy and produce antibodies. According to the current definition, the coding gene for the corresponding protein or glycoprotein must also be known.

2 types of blood group systems

2.1 Erythrocytes

The blood group systems of the erythrocytes are best known. These are often referred to simply as "the blood group". Currently (2021) there are 36 recognized erythrocytic blood group systems, which are identified with a number in addition to the classic name.

The most important system, the ABO or AB0 system, is called 001 / ABO, the second most important system, Rhesus, is called 004 / RH and the third most important, the Kell system, is called 006 / KEL. The youngest member of the blood type systems is Augustine (036 / AUG). It describes a polymorphism that is unique to West Africa.

Polymorphisms that do not meet the entire definition of a blood group system are referred to as "collection".

The first 15 erythrocyte blood group systems according to ISBT nomenclature
No.symbolSurnamegeneCD no.
002 MNS MNS GYPA, GYPB CD235a, CD235b
004 RH rhesus RHD, RHCE CD240
005 LU Lutheran BCAM CD239
006 KEL Kell KEL CD238
007 LE Lewis FUT3 -
008 FY Duffy ACKR1 CD234
009 JK Kidd SLC14A1 -
010 DI Diego SLC4A1 CD233
011 YT Cartwright ACHE -
012 XG Xg XG CD99
013 SC Scianna ERMAP -
014 DO Dombrock ART4 CD297
015 CO Colton AQP1 -

2.2 platelets

The blood group systems of the platelets are classified today with the HPA system. These "human platelet antigens" have replaced older names. They are localized on the platelet glycoproteins. The most important system is HPA1, formerly PLA1, even earlier Zwehl (Zw).

2.3 Granulocytes

The HNA nomenclature (human neutrophil antigens) also exists for neutrophil granulocytes.

2.4 plasma proteins

There are also polymorphisms with plasma proteins that have blood group properties. One example is haptoglobin with the three phenotypes Hp 1-1, Hp 2-1 and Hp 2-2.

3 frequency distribution

The importance of blood group systems and the distribution of polymorphisms varies widely around the world. In certain populations, a trait cannot be polymorphic at all. Some indigenous peoples have 100% blood group 0, within this population the condition of a polymorphism is not met.

In Western Europe approx. 15% of the people are rhesus negative. In large parts of Asia, including Japan and Taiwan, the figure is only around 0.5%. As a result, a rhesus-negative visitor from Europe who needs a transfusion there cannot easily be supplied with rhesus-negative blood.

If the frequency distribution of the phenotypes in a blood group system is very one-sided, i.e. almost all individuals are "phenotype A positive" and only very few are "phenotype A negative", one speaks of high-frequency antigens. In the case of rare antigens, the distribution is reversed, meaning that "phenotype A negative" is the rule and "phenotype A positive" is the exception.

4 web links

The nomenclature of the blood group systems is maintained by a working group of the "International Society of Blood Transfusion".

Blood type frequencies by country