Questions and Answers
What are the two main blood group systems?
ABO and Rh systems
Why is the ABO system the most important for transfusion therapy?
It can cause strong fatal reactions if incompatible blood is transfused.
What is the pathogenesis of haemolytic disease of the foetus & newborn (HDFN)?
It occurs when antibodies from the mother attack the baby's red blood cells.
List three essential steps in blood compatibility testing.
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Define antigen.
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Define antibody.
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What is agglutination?
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What is alloimmunization?
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Which of the following blood group systems are considered major? (Select all that apply)
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Which antibodies are considered clinically significant in the ABO system?
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The ABO phenotype for blood group O is represented by the genotype ______.
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The RhD gene can be either present (RhD positive) or absent (RhD ______).
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Match the blood group phenotypes with their corresponding antigens and antibodies.
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Study Notes
Blood Group Systems and Typing
- Two main blood group systems: ABO and Rh.
- ABO system is vital for transfusion therapy due to the presence of naturally occurring antibodies which can lead to severe transfusion reactions if mismatched.
- Haemolytic disease of the foetus and newborn (HDFN) occurs when maternal antibodies cross the placenta and attack fetal red blood cells.
Key Concepts
- Antigens: Substances recognized as foreign; induce immune response.
- Antibodies: Immune response products specifically reacting with antigens.
- Agglutination: Clumping of red blood cells when antibodies bind to antigens on multiple cells.
- Alloimmunization: Immune response to non-self antigens in the same species, often from transfusions.
- Immunogenicity: Potential to provoke an antibody response, influenced by the antigen’s size and complexity.
Blood Group Systems and Antigens
- Over 29 known blood group systems; 9 major systems identified: ABO, Rh, MNS, P, Kell, Duffy, Kidd, Lewis, and Lutheran.
- Approximately 400 distinct blood group antigens described in these systems.
- Significant in transfusion as individuals without certain antigens may develop antibodies leading to transfusion reactions.
Clinical Significance of Blood Groups
- ABO and Rh groups are the most clinically significant due to their strong immunogenic properties.
- Some blood groups (e.g., Lewis) have reduced clinical importance, reacting at lower temperatures and presenting less frequently.
- Patients needing repeated transfusions (e.g., Sickle Cell Disease, Thalassaemia) may be at risk for delayed hemolytic reactions due to these less common antigens.
Types of Blood Group Antibodies
- Natural Antibodies: Develop early in life post-exposure to similar antigens, mainly IgM. Clinically significant examples: anti-A and anti-B from the ABO system.
- Immune Antibodies: Form in response to transfusions or during pregnancy, primarily IgG, with anti-D from the Rh system being a notable example.
The ABO System
- Considered the most critical blood group system for transfusions.
- ABO genes are located on chromosome 9, controlled by alleles A, B, and O (O is recessive).
- ABO blood types based on antigens and corresponding antibodies:
- Type O: Genotype OO, no antigens, has anti-A and anti-B antibodies (50% frequency in Malawi).
- Type A: Genotype AA or AO, A antigen, has anti-B antibodies (24% frequency).
- Type B: Genotype BB or BO, B antigen, has anti-A antibodies (22% frequency).
- Type AB: Genotype AB, AB antigens, no antibodies (4% frequency).
The Rh System
- Composed of RhD and RhCE genes, featuring five antigens: D, C, c, E, e.
- RhD is the most significant; presence indicates RhD positive, absence indicates RhD negative.
- Rh antibodies develop from previous transfusions or pregnancies.
Compatibility Testing Steps
- Performed in the laboratory to ensure safe transfusions:
- Grouping of ABO and RhD for the patient.
- Screening for antibodies in patient serum.
- Cross-matching between patient serum and donor red blood cells to verify compatibility.
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Description
This quiz focuses on blood group systems, emphasizing the significance of the ABO system in transfusion therapy. It covers the pathogenesis of haemolytic disease of the fetus and newborn, as well as essential steps in blood compatibility testing. Ideal for MBBS and BDS first-year students.
