Give Blood England and Wales

The purpose of blood groups in evolutionary terms is not known. Animals have blood groups which are not the same as human blood groups but are species specific. So blood from one species is not effective when transfused to another species and indeed could be harmful or even lethal.

The term ‘blood groups’ refers to the proteins and sugars on the surface of our red cells and the ability to form these substances is inherited. For humans there are many blood group systems and each human has a unique spectrum of blood groups with the exception of identical twins or triplets whose blood groups are exactly the same.

The most important blood group system for humans is the one we call the ABO system. All human beings are either of blood group O, A, B or AB or one of the minor variants of these four groups. In terms of the evolution of human beings, we do not know which blood group came first, but the compounds which make up the ABO system differ only in minor ways. The percentage of each of the four blood groups present in the population varies in different parts of the world. It may be that originally, all human beings were of blood group O since, in communities which have been isolated for hundreds of years such as some South American Indian tribes, all the members of that community are of group O.

It is also known that the A, B, O and AB blood groups may be differentially associated with various diseases. There is a theory that people of blood group A were more likely to die from plague. So, when the plague which originated in the Far East swept towards Europe, people of group A died more often that people of other groups. This could possibly explain why group A is less common in the Far East than it is in Europe and why in Scandinavian countries where people were not effected much by plague, there is a high proportion of group A within the population.

In countries where there is a more equal proportion of group A and group B, there tends to be a higher proportion of people of group AB as would be expected. There are small differences in the percentages of group O, A, B and AB, even between the English, Welsh, Scots and Irish. Some of these differences in blood groups are illustrated in the attached charts. The four blood groups A, B, O and AB are most important because very early in life all human beings develop antibodies against the A and B substances associated with the other blood groups. So, group O people develop anti-A and anti-B, group A develops anti-B, and group B develops anti-A in the plasma. Thus, for example group A blood is dangerous if given to a group O person because the anti-A in the plasma of the group O person will react with the transfused group A red cells.

The second most important blood group system used to be called the ‘Rhesus Group’ because of its similarity to blood groups in rhesus monkeys. The most important part of this rhesus system is the D substance and humans are categorised as D positive or D negative. In the UK 15% of people are D negative and 85% are D positive. This becomes important in pregnancy because a D negative woman can carry a D positive baby and develop antibodies which can affect future pregnancies. In the Far East the D negative group is less common and so there are fewer problems associated with pregnancy and the D blood group.

There are many other blood group systems designated by all the letters of the alphabet. Because blood groups are inherited, some blood group systems are particularly prominent in people of one race or ethnic background. People of Afro-Caribbean ethnic origin are more likely to suffer from an inherited disease known as sickle cell anaemia than people of other ethnic groups. Such people may require regular blood transfusions and, as a result of transfusions in the UK, the sickle cell anaemia sufferer may develop antibodies to various blood groups which are common in people of Northern European origin. If this happens then the patient may need to receive blood only from people of Afro -Caribbean origin in the future.

There are other conditions such as thalassemia, where regular transfusion is essential. This is more common in people of Greek origin and people from the Indian subcontinent than in Northern Europeans. It is therefore very important that we collect blood from people of all the various ethnic minority communities in the UK, so that sufficient blood is available for the treatment of patients from those ethnic minority communities who require regular transfusions and have developed blood group antibodies.

> Components of Blood