Blood Typing Notes (Bio 11 Unit 3)

What Is Blood Typing?

  • Blood typing is the classification of human blood based on the presence or absence of specific antigens on the surface of red blood cells (RBCs) and antibodies in plasma.
  • Blood typing is essential for:
    • Safe blood transfusions
    • Organ transplants
    • Pregnancy compatibility
    • Forensic science

Key Terms to Know

  • Antigen: A protein or molecule on the surface of red blood cells that triggers an immune response.
  • Antibody: A protein in the plasma that attacks foreign antigens.
  • Agglutination: Clumping of blood cells due to incompatible antigens and antibodies.
  • Rh factor: An additional antigen that can be present (Rh⁺) or absent (Rh⁻) on RBCs.

ABO Blood Group System

  • There are four blood types in the ABO system: A, B, AB, and O.
  • This system is based on two antigens: A and B.
  • The following table summarizes ABO antigens and antibodies:
    • Blood Type A
      • Antigens on RBCs: A
      • Antibodies in Plasma: Anti-B
      • Can Receive From: A, O
      • Can Donate To: A, AB
    • Blood Type B
      • Antigens on RBCs: B
      • Antibodies in Plasma: Anti-A
      • Can Receive From: B, O
      • Can Donate To: B, AB
    • Blood Type AB
      • Antigens on RBCs: A and B
      • Antibodies in Plasma: None
      • Can Receive From: A, B, AB, O (Universal Recipient)
      • Can Donate To: AB
    • Blood Type O
      • Antigens on RBCs: None
      • Antibodies in Plasma: Anti-A and Anti-B
      • Can Receive From: O
      • Can Donate To: A, B, AB, O (Universal Donor)

Rh Factor

  • If you have the Rh antigen = Rh positive (Rh⁺).
  • If you don’t have the Rh antigen = Rh negative (Rh⁻).
  • Rh Compatibility in Transfusions
    • Rh Type: Rh⁺
      • Can Receive Rh⁺ Blood?: Yes
      • Can Donate to Rh⁺?: Yes
    • Rh Type: Rh⁻
      • Can Receive Rh⁺ Blood?: No (can only receive Rh⁻)
      • Can Donate to Rh⁺?: Yes
  • Rh⁻ people can’t receive Rh⁺ blood—they’ll form anti-Rh antibodies.
  • Rh⁺ people can receive both Rh⁺ and Rh⁻ blood safely.

Blood Typing Reactions (How It Works in a Lab)

  • A blood typing test uses anti-A, anti-B, and anti-Rh serums.
    1. A drop of blood is placed in three spots.
    2. Each spot is mixed with:
      • Anti-A antibodies
      • Anti-B antibodies
      • Anti-Rh antibodies
    3. Look for agglutination (clumping):
      • Clumping = that antigen is present.
      • No clumping = that antigen is absent.
  • Example:
    • Serum Added: Anti-A
      • Agglutination?: Yes
      • Meaning: A antigen present
    • Serum Added: Anti-B
      • Agglutination?: No
      • Meaning: No B antigen
    • Serum Added: Anti-Rh
      • Agglutination?: Yes
      • Meaning: Rh antigen present
      • → Blood type: A⁺

Inheritance of Blood Type

  • Blood type is determined by genes inherited from your parents.
  • ABO Gene Inheritance:
    • Alleles: A, B, O
    • A and B are dominant
    • O is recessive
    • Parent Genotype: AO x BO, Possible Child Blood Types: A, B, AB, O
    • Parent Genotype: AB x O, Possible Child Blood Types: A, B
    • Parent Genotype: OO x OO, Possible Child Blood Types: O
  • Rh Inheritance:
    • Rh⁺ is dominant over Rh⁻
    • Two Rh⁻ parents can’t produce an Rh⁺ child

Blood Transfusion Rules

  • Blood transfusions must match:
    • The ABO type
    • The Rh factor
  • Universal Donor/Recipient
    • Type O⁻: No A, B, or Rh antigens = universal donor
    • Type AB⁺: Has A, B, and Rh antigens = universal recipient

Clinical Importance

  • Blood Transfusion Reaction:
    • Happens when incompatible blood is transfused
    • Immune system attacks foreign RBCs
    • Can be fatal
  • Pregnancy & Rh Factor:
    • If an Rh⁻ mother carries an Rh⁺ fetus, she can develop anti-Rh antibodies
    • In future pregnancies, these antibodies can attack an Rh⁺ baby's blood (called Hemolytic Disease of the Newborn)
    • Prevented with Rhogam injection

Practice Blood Typing Scenarios

  • Scenario 1:
    • Anti-A: clumps
    • Anti-B: no clump
    • Anti-Rh: clumps
    • → Blood Type: A⁺
  • Scenario 2:
    • Anti-A: no clump
    • Anti-B: clumps
    • Anti-Rh: no clump
    • → Blood Type: B⁻

Summary Chart

  • Blood Type A⁺
    • RBC Antigens: A, Rh
    • Plasma Antibodies: Anti-B
    • Can Donate To: A⁺, AB⁺
    • Can Receive From: A⁺, A⁻, O⁺, O⁻
  • Blood Type A⁻
    • RBC Antigens: A
    • Plasma Antibodies: Anti-B, Anti-Rh
    • Can Donate To: A⁺, A⁻, AB⁺, AB⁻
    • Can Receive From: A⁻, O⁻
  • Blood Type B⁺
    • RBC Antigens: B, Rh
    • Plasma Antibodies: Anti-A
    • Can Donate To: B⁺, AB⁺
    • Can Receive From: B⁺, B⁻, O⁺, O⁻
  • Blood Type B⁻
    • RBC Antigens: B
    • Plasma Antibodies: Anti-A, Anti-Rh
    • Can Donate To: B⁺, B⁻, AB⁺, AB⁻
    • Can Receive From: B⁻, O⁻
  • Blood Type AB⁺
    • RBC Antigens: A, B, Rh
    • Plasma Antibodies: None
    • Can Donate To: AB⁺
    • Can Receive From: All types
  • Blood Type AB⁻
    • RBC Antigens: A, B
    • Plasma Antibodies: Anti-Rh
    • Can Donate To: AB⁺, AB⁻
    • Can Receive From: AB⁻, A⁻, B⁻, O⁻
  • Blood Type O⁺
    • RBC Antigens: Rh
    • Plasma Antibodies: Anti-A, Anti-B
    • Can Donate To: O⁺, A⁺, B⁺, AB⁺
    • Can Receive From: O⁺, O⁻
  • Blood Type O⁻
    • RBC Antigens: None
    • Plasma Antibodies: Anti-A, Anti-B, Anti-Rh
    • Can Donate To: All types
    • Can Receive From: O⁻

Key Points to Remember for Tests

  • A person cannot have antibodies against their own antigens.
  • Type O has no antigens, so it's the universal donor.
  • Type AB has no antibodies, so it's the universal recipient.
  • Rh⁻ blood should never receive Rh⁺ blood.
  • Agglutination = incompatible = clumping = dangerous.