Rh Grouping: Rh blood group system was discovered by Karl Landsteiner and Weiner in the 1940s. ‘Rh’ is derived from Rhesus Monkey. Rh blood group antigens are proteins in chemical nature. There are 49 Rh antigens. D antigen is the most important antigen neurologically. Rh factor is coded by a dominant gene ‘D’. Hence, the individual with DD/Dd is the code for Rh antigen (Rh+), the individual with dd does not code for Rh antigen (Rh-). Rh factor present on the surface of red blood cells (RBCs) is an antigenic protein.
The antigenic protein Rh factor is found on the surface of erythrocytes. It was first found in a rhesus monkey.
Rh antigen is present in Red blood cells of the body. In around 85% of the human population, Rh grouping is present but is absent among the rest of the 15% population.
Human beings in whom there is a presence of Rh antigen on the surface of red blood cells (RBCs), are the Rh positive (Rh +ve) individuals.
Human beings in whom there is an absence of the Rh antigen on the surface of red blood cells (RBCs) are the Rh negative (Rh –ve) individuals.
If Rh negative (Rh –ve) is exposed to Rh positive (Rh +ve) type, then Rh negative will form antibodies. Rh –ve treats Rh +ve as a foreign substance and fights against it and protects itself against further exposure.
Rh group should be matched before blood transfusion because if Rh –ve person is exposed to Rh +ve blood then person with Rh –ve blood starts forming antibodies against Rh antigens.
What is Rh Grouping Antibodies?
Our immune system forms antibodies against the missing ABO Blood Group Antigens. In the ABO blood group system, antibodies in the serum of an individual will against the missing antigen on the red blood cells but this does not happen in the case of Rh blood group system, no natural anti-Rh antibodies are found in the serum of the Rh negative (-ve) individuals.
But if Rh negative (Rh –ve) individuals are exposed to Rh antigens, and then their immune system can be sensitized to produce Rh antibodies. This exposure of Rh negative (Rh-ve) individuals to Rh antigen can happen in two cases:
- During Blood Transfusion
- When Rh negative (Rh-ve) mother encounters Rh antigens on fetal red blood cells (RBCs)
If pregnant mother has Rh negative (Rh –ve) blood and fetus has the Rh positive (Rh +ve), then there is no major problem in the first delivery but during first delivery but during first delivery the fetus blood intermingle with mother’s blood and the mother’s blood start forming antibodies against Rh factor in her blood.
In the subsequent delivery there is a possibility that Rh antibodies from the mother leaks into the blood of the fetus and destroy the RBCs of the fetus. This is called erythroblastosis foetalis. This can be avoided by treating the mother after the delivery of the first child.
Rh antigen or D antigen is highly immunogenic, therefore, determination of Rh antigen’s presence or absence on an individual’s red blood cells (RBCs) is very important, especially in blood donor’s transfusion recipients and mothers.
Blood Group Types
On the basis of the Rh blood group system, there are eight different blood groups. These are -:
Designation A, B, AB and O reflects the presence or absence of ABO blood type antigens. Antibodies in the serum will be against the missing ABO Blood type antigens. They can be -:
- Anti – A antibodies
- Anti – B antibodies
The ‘+’ or ‘-’ after a blood type reflects the presence and absence of Rh antigen respectively.
- A+ and A– : In both these blood groups, antigens are present on RBCs. Since, the missing antigen is B antigen, therefore anti – B antibodies will be found in the serum.
Rh antigens are present in A positive (A+) individuals and absent in A negative (A-) individuals.
- B+ and B– : In these individuals, positive and negative antigens present on RBCs are B antigens. Since the missing antigen in this case is A antigen, therefore anti – A antibodies will be formed in the serum.
Rh antigens are present in B positive (B+) individuals and absent in B negative (B-) individuals.
- AB+ and AB– : In this case, antigens present on the RBCs are both antigen A and antigen B. Since, none of the antigens are missing, therefore no antibodies are found in the serum.
Rh antigens are present in AB positive (AB+) individuals and absent in AB negative (AB-) individuals.
- O+ and O– : ‘O’ is derived from the German word ‘Ohne’ which means ‘without’.
This blood group lacks the properties of both the other blood groups. In both O+ and O- blood types, neither A nor B antigens are present in the red blood cells (RBCs). Since, both the antigens are absent; therefore, antibodies in the serum are anti – A antibodies and anti – B antibodies.
Rh antigens are present in O positive (O+) individuals and absent in O negative (O-) individuals.
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