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Questions and Answers
What is the primary reason for using Rh-negative red blood cells in intrauterine transfusion?
What is the primary reason for using Rh-negative red blood cells in intrauterine transfusion?
What is the effect of administering 300 µg of IgG Rhogam at 28 weeks of gestation?
What is the effect of administering 300 µg of IgG Rhogam at 28 weeks of gestation?
What does a negative indirect Coombs test indicate in an Rh-negative pregnant woman?
What does a negative indirect Coombs test indicate in an Rh-negative pregnant woman?
If an Rh-negative woman's serum agglutinates Rh-positive cells in saline but shows a negative indirect Coombs test, what type of antibodies does she have?
If an Rh-negative woman's serum agglutinates Rh-positive cells in saline but shows a negative indirect Coombs test, what type of antibodies does she have?
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What is a potential next step for an Rh-negative woman tested for Rh antibodies who shows IgM reactions?
What is a potential next step for an Rh-negative woman tested for Rh antibodies who shows IgM reactions?
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Why is it important to monitor the indirect Coombs test in Rh-negative women with IgM antibodies?
Why is it important to monitor the indirect Coombs test in Rh-negative women with IgM antibodies?
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What is a key distinction between IgM and IgG anti-Rh antibodies in relation to pregnancy?
What is a key distinction between IgM and IgG anti-Rh antibodies in relation to pregnancy?
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What primary mechanism leads to the destruction of red blood cells coated with Rh antibodies?
What primary mechanism leads to the destruction of red blood cells coated with Rh antibodies?
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Which IgG subclasses are primarily responsible for binding to high-affinity Fcγ receptors?
Which IgG subclasses are primarily responsible for binding to high-affinity Fcγ receptors?
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What effect does the aggregation of antibodies have on their ability to bind to Fc receptors?
What effect does the aggregation of antibodies have on their ability to bind to Fc receptors?
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Why does the risk of Rh alloimmunization decrease when the mother and father are ABO incompatible?
Why does the risk of Rh alloimmunization decrease when the mother and father are ABO incompatible?
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What is a key distinction between bound and free immunoglobulin in the context of Fc receptor binding?
What is a key distinction between bound and free immunoglobulin in the context of Fc receptor binding?
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What condition enhances the likelihood of fetal red blood cells surviving in maternal circulation?
What condition enhances the likelihood of fetal red blood cells surviving in maternal circulation?
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What role do Kupffer cells play in the context of Rh antibody-coated red blood cells?
What role do Kupffer cells play in the context of Rh antibody-coated red blood cells?
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What is the consequence of fetal red blood cells entering the maternal circulation in an ABO incompatible scenario?
What is the consequence of fetal red blood cells entering the maternal circulation in an ABO incompatible scenario?
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Study Notes
Rh Alloimmunization and Hemolytic Disease of the Newborn
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Mechanism of Red Blood Cell Destruction:
- Rh antibodies coat red blood cells.
- Antibody-coated red cells adhere strongly to Fc receptors on macrophages (e.g., in the spleen and liver).
- IgG3 and IgG1 subclasses of antibodies bind most tightly to high-affinity Fcγ receptors (CD64).
- Macrophages engulf and destroy antibody-coated red blood cells, similar to how they destroy bacteria.
- Antigen binding and aggregation increase affinity for Fc receptors; free antibodies cannot bind.
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ABO Compatibility and Rh Alloimmunization Risk:
- ABO-compatible mothers have a higher risk (16%) of Rh alloimmunization compared to ABO-incompatible mothers (7%).
- If mother and fetus have the same ABO type, fetal blood persists longer in the mother.
- If mothers have ABO antibodies, fetal red blood cells are rapidly destroyed, hindering alloimmunization.
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Intrauterine Transfusion Cells:
- Rh-negative red blood cells are used in intrauterine transfusions to avoid hemolysis by maternal IgG Rh antibodies.
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RhoGAM Administration:
- Administering RhoGAM (300 µg IgG) at 28 weeks of gestation is safe as the amount is insufficient to harm the fetus.
- This amount of antibody does not harm the fetus and raises the maternal titer in the indirect Coombs test to 1:4 if the mother is already immunized by a previous fetus.
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Interpretation of Coombs Test Results:
- Negative indirect Coombs test in a pregnant Rh-negative woman indicates no IgG anti-Rh antibodies.
- Serum agglutination of Rh-positive cells in saline suggests IgM anti-Rh antibodies.
- IgM antibodies do not cross the placenta and pose no immediate risk.
- Repeated testing is required to rule out potential development of IgG antibodies.
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Description
Explore the mechanisms of Rh alloimmunization and the implications of hemolytic disease in newborns. This quiz covers topics such as the destruction of red blood cells by antibodies and the importance of ABO compatibility. Delve into the clinical aspects and risks associated with these conditions.
