BLOOD GROUPS
Blood is often called the “river of life.” It carries oxygen, nutrients, and hormones to every cell and removes waste products. But did you know that not all blood is the same? Human blood comes in different types, known as blood groups — and knowing your blood group can be a matter of life and death.
What is a Blood Group?
A blood group is determined by antigens — special proteins or carbohydrates found on the surface of red blood cells. If a certain antigen is present, your body accepts it. But if it is missing and enters through transfusion, your immune system attacks it, causing dangerous reactions.
There are two main systems for classifying blood:
1. ABO Blood Group System – Discovered by Karl Landsteiner in 1900.
Group A: A antigen on RBCs, Anti-B antibody in plasma.
Group B: B antigen, Anti-A antibody.
Group AB: Both antigens, no antibodies (universal recipient).
Group O: No antigens, both antibodies (universal donor).
2. Rh Factor – Discovered in 1940.
Rh-positive (Rh+) means D antigen present.
Rh-negative (Rh-) means D antigen absent.
Example: A+ means “A group with Rh antigen.”
The History Behind Blood Group Discovery
● Before 1900 – A Risky Practice
Before the discovery of blood groups, blood transfusions were a gamble. Some patients survived, but many died from unknown causes. Doctors had no idea that incompatibility between donor and recipient blood was to blame.
● 1900 – Karl Landsteiner’s Breakthrough
In Austria, Karl Landsteiner began mixing blood samples from different people. He noticed that in some cases, red blood cells clumped together — a reaction called agglutination. He concluded that this was caused by specific antigens and identified three groups: A, B, and C (later renamed O).
● In 1902, his colleagues Alfred von Decastello and Adriano Sturli found the AB group. These discoveries revolutionised medicine, making blood transfusions much safer.
● 1930 – Nobel Prize
Karl Landsteiner received the Nobel Prize in Physiology or Medicine for this life-saving discovery.
● 1940 – The Rh Factor
Landsteiner, working with Alexander S. Wiener, discovered another important antigen — the Rh factor, named after the rhesus monkeys used in experiments. This explained certain pregnancy complications and further improved transfusion safety.
● 1952 – Bombay Blood Group
In Mumbai, Dr. Y.M. Bhende discovered the Bombay blood group (hh), a rare type where even the O group antigen (H antigen) is missing. People with this blood group can donate only to others with the same rare type.
How is Blood Group determined?
The process of finding a person’s blood group is called blood typing or blood grouping. The most common method is the ABO and Rh typing by agglutination test.
Steps (Slide or Card Method):
1. Sample collection: A drop of blood is taken, usually from a finger prick.
2. Test surface: Three spots are prepared on a clean glass slide or special card.
3. Reagents added:
Anti-A serum on one spot.
Anti-B serum on another.
Anti-D serum (for Rh factor) on the third.
4. Mixing: A drop of the person’s blood is added to each spot and gently mixed.
5. Observation:
Clumping with Anti-A → Blood has A antigen.
Clumping with Anti-B → Blood has B antigen.
Clumping with both → Blood group AB.
No clumping with A or B → Blood group O.
Clumping with Anti-D → Rh positive; no clumping → Rh negative.
Why knowing Blood Groups is important
1. Safe transfusions – Matching prevents fatal immune reactions.
2. Pregnancy care – Avoids Rh incompatibility problems between mother and baby.
3. Organ transplants – Compatibility reduces rejection risk.
4. Forensics – Helps in identification in crime cases.
A quick compatability chart
In summary
The discovery of blood groups transformed medicine. From Karl Landsteiner’s careful experiments to the identification of rare types like the Bombay blood group, each step has saved countless lives.
Today, the simple agglutination test ensures that blood transfusions are safe and effective. Knowing your blood group is not just useful — it can be life-saving.
As Landsteiner’s work reminds us: “In the smallest drop of blood lies the greatest secret to saving life.”
