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🩸 Special Topic – Human Biology & Health

Blood Groups

Page 2: ABO & Rh Compatibility – Universal Donor & Recipient

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 1. What Is Blood Group Compatibility?

Blood group compatibility refers to whether a donor’s blood can be safely transfused into a recipient without causing immune reactions. Compatibility depends on antigen–antibody interaction.

If incompatible blood is transfused, antibodies in the recipient’s plasma attack donor red blood cells, leading to agglutination and hemolysis.

 2. ABO Compatibility Rules

Blood Group	Can Donate To	Can Receive From
A	A, AB	A, O
B	B, AB	B, O
AB	AB	A, B, AB, O
O	A, B, AB, O	O

➕➖ 3. Rh Factor Compatibility

Rh factor adds another layer of compatibility:

• Rh Positive (Rh+) can receive from Rh+ and Rh−
• Rh Negative (Rh−) should receive only from Rh−

Transfusing Rh+ blood to an Rh− person can lead to antibody formation, causing complications in future transfusions.

 4. Universal Donor & Universal Recipient

Based on antigen absence or presence:

• O− → Universal Donor (no A, B, or Rh antigens)
• AB+ → Universal Recipient (no anti-A, anti-B, or anti-Rh antibodies)

 5. Why Compatibility Testing Is Essential

• Prevents transfusion reactions
• Reduces risk of kidney failure and shock
• Ensures patient safety in surgeries and emergencies

 Exam Insight:
O− is the universal donor, while AB+ is the universal recipient — a frequently asked MCQ in competitive exams.

 Continue to Page 3: Medical Importance, Pregnancy & Rh Incompatibility

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