blood grouping
The categorizing of blood according to the presence or lack of particular antigens on red blood cells (RBCs) and matching antibodies in the plasma is known as blood grouping. Pregnancy care, organ transplants, safe blood transfusions, and medical diagnosis all depend on it.
Basis of Blood Grouping
Blood groups are determined by:
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Antigens (Agglutinogens) – proteins or carbohydrates present on the surface of RBCs
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Antibodies (Agglutinins) – proteins present in blood plasma that react against foreign antigens
If incompatible blood is mixed, agglutination (clumping of RBCs) occurs, which can be life-threatening.
MAJOR BLOOD GROUPING SYSTEMS
1. ABO Blood Grouping System
Discovered by Karl Landsteiner (1901).
This system is based on two antigens (A and B) and two antibodies (anti-A and anti-B).
Types of ABO Blood Groups
| Blood Group | Antigen on RBC | Antibody in Plasma |
|---|---|---|
| A | A antigen | Anti-B |
| B | B antigen | Anti-A |
| AB | A and B antigens | None |
| O | No antigen | Anti-A and Anti-B |
Transfusion Rules (ABO)
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A → receives from A, O
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B → receives from B, O
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AB → receives from all (universal recipient)
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O → donates to all (universal donor)
Wrong transfusion → agglutination → hemolysis → shock or death
2. Rh (Rhesus) Blood Grouping System
Discovered by Landsteiner and Wiener (1940).
This system depends on the Rh (D) antigen.
| Rh Type | D Antigen |
|---|---|
| Rh positive (Rh⁺) | Present |
| Rh negative (Rh⁻) | Absent |
-
Rh⁻ individuals do not naturally have anti-Rh antibodies
-
Antibodies form only after exposure (transfusion or pregnancy)
Rh Incompatibility and Pregnancy
Occurs when:
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Mother: Rh⁻
-
Fetus: Rh⁺
Effects
-
Mother forms anti-Rh antibodies
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In next pregnancy, antibodies can destroy fetal RBCs
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Causes Hemolytic Disease of the Newborn (Erythroblastosis fetalis)
Prevention
-
Injection of Anti-D (RhoGAM) to Rh⁻ mother after first delivery
OTHER BLOOD GROUP SYSTEMS
There are 30+ minor blood group systems, such as:
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MN system
-
Kell system
-
Duffy system
They are important in:
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Repeated transfusions
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Organ transplantation
-
Forensic medicine
BLOOD GROUP DETERMINATION
Method
-
Blood is mixed with:
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Anti-A serum
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Anti-B serum
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Anti-D serum
-
-
Agglutination indicates presence of corresponding antigen
IMPORTANCE OF BLOOD GROUPING
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Safe blood transfusion
-
Organ and tissue transplantation
-
Management of pregnancy
-
Forensic science and paternity testing
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Genetic and population studies
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