Blood Group of Humans

10.5

Blood Groups of Humans

Introduction

Human blood is classified into A, B, AB and O groups.
Donation and transfusion of blood is based on the compatibility of the blood group of the donor and the recipient.
This is because the recipient has antibodies in the blood serum that can act against the antigen on the red blood cells of the donor.
Blood transfusion from a donor to a recipient must take into consideration the blood group type of the donor and the recipient.
If the blood group of both the donor and receiver is not compatible, the red blood cells of the recipient will experience agglutination (coagulation).

Blood Groups

Blood Group A

Blood Group B

Blood Group AB

Blood Group O

Rhesus Factor

Another antigen found on the surface of the red blood cells is the Rhesus factor (Rh factor).
The red blood cells of an individual with the Rh factor or antigen D are known as Rh-positive.
An individual who does not possess the Rh factor or antigen D is known as Rh-negative.
If the blood of a Rh-positive donor mixes with the blood of a Rh-negative recipient, the blood of the recipient will react by producing the Rhesus antibody or anti-D antibody.
When the recipient receives another dose of Rh-positive blood, the Rhesus antibody will cause the agglutination of the donor blood cells.
This situation could result in the death of the recipient.

Pregnancy and Rhesus Factor

Usually, problems will arise when an Rh-negative mother marries an Rh-positive father and conceives an Rh-positive foetus.
During the last month of pregnancy, fragments of foetal blood cells containing antigen D cross the placenta and enter the blood circulation of the mother.
As a result, the white blood cells in the mother’s blood will react and produce anti-D antibodies that will flow back through the placenta into the foetal blood circulatory system.
The antibodies will destroy the red blood cells of the Rh-positive baby before or immediately after birth.
However, the concentration of antibodies produced is not enough to affect the first child. But the anti-D antibodies will last in the blood circulatory system of the mother.
The problem arises when the second child is also Rh-positive.
The anti-D antibodies that are present in the mother’s blood cross the placenta and destroy the red blood cells of that foetus.
The symptoms of this disease are called erythroblastosis fetalis.
The second foetus dies if the blood is not replaced with Rh-negative blood through blood transfusion.
In a less serious situation, the baby may suffer from anaemia and mental retardation.
However, this problem can now be addressed by treating the affected mother with anti-Rhesus globulins after the first pregnancy to stop the formation of anti-D antibodies.

10.5

Blood Groups of Humans

Introduction

Human blood is classified into A, B, AB and O groups.
Donation and transfusion of blood is based on the compatibility of the blood group of the donor and the recipient.
This is because the recipient has antibodies in the blood serum that can act against the antigen on the red blood cells of the donor.
Blood transfusion from a donor to a recipient must take into consideration the blood group type of the donor and the recipient.
If the blood group of both the donor and receiver is not compatible, the red blood cells of the recipient will experience agglutination (coagulation).

Blood Groups

Blood Group A

Blood Group B

Blood Group AB

Blood Group O

Rhesus Factor

Another antigen found on the surface of the red blood cells is the Rhesus factor (Rh factor).
The red blood cells of an individual with the Rh factor or antigen D are known as Rh-positive.
An individual who does not possess the Rh factor or antigen D is known as Rh-negative.
If the blood of a Rh-positive donor mixes with the blood of a Rh-negative recipient, the blood of the recipient will react by producing the Rhesus antibody or anti-D antibody.
When the recipient receives another dose of Rh-positive blood, the Rhesus antibody will cause the agglutination of the donor blood cells.
This situation could result in the death of the recipient.

Pregnancy and Rhesus Factor

Usually, problems will arise when an Rh-negative mother marries an Rh-positive father and conceives an Rh-positive foetus.
During the last month of pregnancy, fragments of foetal blood cells containing antigen D cross the placenta and enter the blood circulation of the mother.
As a result, the white blood cells in the mother’s blood will react and produce anti-D antibodies that will flow back through the placenta into the foetal blood circulatory system.
The antibodies will destroy the red blood cells of the Rh-positive baby before or immediately after birth.
However, the concentration of antibodies produced is not enough to affect the first child. But the anti-D antibodies will last in the blood circulatory system of the mother.
The problem arises when the second child is also Rh-positive.
The anti-D antibodies that are present in the mother’s blood cross the placenta and destroy the red blood cells of that foetus.
The symptoms of this disease are called erythroblastosis fetalis.
The second foetus dies if the blood is not replaced with Rh-negative blood through blood transfusion.
In a less serious situation, the baby may suffer from anaemia and mental retardation.
However, this problem can now be addressed by treating the affected mother with anti-Rhesus globulins after the first pregnancy to stop the formation of anti-D antibodies.