THE BLOOD GROUPS
grouping was discovered by Karl Landsteiner, an Austrian physiologist in 1901. He
received the Nobel Prize of Medicine in 1930 for this. The blood groups
of most people in the world are:
- A+ (ca 37% of the population)
- O+ (32%)
- B+ (10%)
- A- (7%)
- O- (6%)
- A+ (5%)
- B- (2%)
- AB- (1%)
There are over 600 other factors, but
the four groups above (A, B, O and AB) are the ones mostly used.
You will know which group you belong to if your blood is tested. The surfaces of the red blood cells contain special proteins called antigens. The blood plasma or serum also contains natural antibodies which are always present in the blood, unlike the antibodies produced by lymphocytes. It is these antibodies that react with the antigens from another blood group to cause clumping. Different blood groups contain different types of antigens and they are classified according to the antigens and natural antibodies present. For example, group A has antigen A, and group B has
antigen B, group AB possesses both antigens A and B. Group 0 does not possess any antigen at all.
Antibodies may be represented by small letters a and b. For example, antibody a reacts with antigen A and clumping occurs. If you belong to blood group A, your red blood cells possess antigen A and your serum contains antibody b. Your serum could not contain antibody a, or your own red blood cells would
agglutinate. Similarly, a person with group B will have antigen B and antibody a. Group AB contains both
antigens A and B but no antibodies. Group 0 has no antigens but contains both antibodies a and b.
This fact is summarised in the table below.
on red blood cell
A & B
a & b
The genes in your
cells control the blood group that you process. Thus blood group are determined hereditarily. The child gets
a blood group gene from the mother, and one from the father.
- If the mother and father have O-genes, the child becomes blood group O.
- If one of the parents has A-genes, and the other has O-genes, the child will be blood group A. The child will have one A- and one O-.
- If the child gets A genes from both of the parents, it will be blood group A, but it will have two A-genes.
- If the one of the parents has A-genes, and the other parent has B-genes, the child will have blood group AB.
- Parents with blood group A, can get children with blood group O. That is because the parents can have both A-genes, and
donors can give to these recipients:
- O can give to O, A, B and AB
- A can give to A and AB
- B can give to B and AB
- AB can give to AB only
Then there is the Rhesus system witch was discovered by Karl Landsteiner and A.S. Wiener in 1941.
The Rhesus factor (D) is attached to the red blood cells on people that are Rhesus-positive. People that are Rhesus-negative (about 15%)
do not have the D-factor. They can transport oxygen to all parts of the body. If a
woman who is Rhesus-negative gets pregnant with a Rhesus-positive child, her blood can start making antibodies against the babies blood so that it clots. The risk is not very high when
she is having her first baby. During her second pregnancy, there
will be more the antibodies and thus it more and dangerous to the baby. To prevent the baby from getting hurt,
she can take Rhesus-prophylaxis. The Rhesus-prophylaxis is developed from people that are immune to the Rhesus-factor. Rhesus-prophylaxis
hinders the antibodies, and we often do not have to do a blood transfusion on the baby (change the babies blood).
Nowadays we can carry out a transfusion inside the womb.
The Rhesus blood group works as same as the ABO-group..
- Two Rhesus-positive parents have a Rhesus-positive child, and a Rhesus-negative child, if the parents have Rhesus-negative genes.
- If one of the parents is Rhesus-negative, and the other positive, they have one Rhesus-positive child, and one Rhesus-negative child.
- Both parents have Rhesus-negative blood, and their child will be Rhesus-negative.
ęCopyright TQ Team 25896, 1999. The Circulatory System- Online Learning.