ABO Blood Group System

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Questions and Answers

What is the primary significance of the ABO blood group system?

It identifies individuals for blood donation eligibility.

It plays a crucial role in transfusion and transplantation. (correct)

It helps in diagnosing blood-related diseases.

It is used mainly for determining genetic inheritance.

Why is the ABO blood group system considered the most important blood group system?

It is universally applicable across all countries.

It is the only blood group system that determines blood type.

It has the most complex genetic variation compared to others.

It is crucial for patient safety in medical procedures. (correct)

Which of the following statements accurately reflects the role of the ABO blood group system?

It is essential for compatibility in transplantation. (correct)

It has no impact on organ transplantation.

It can be disregarded in emergency medical situations.

It is primarily used for research purposes in hematology.

How does the ABO blood group system differ from other blood group systems?

It is the most widely recognized and utilized in clinical settings. Signup and view all the answers

What aspect of the ABO blood group system contributes to its complexity in transfusion medicine?

The variations in blood types across different populations. Signup and view all the answers

What is the role of the H gene in the context of A-specific immunodominant sugar?

It links A-specific sugars to the H substance. Signup and view all the answers

Which of the following best describes the precursor substance mentioned in the context of A-specific immunodominant sugar?

It is a type 2 precursor substance linked to H substance. Signup and view all the answers

What characteristic does the A-specific immunodominant sugar possess?

It confers specificity on a biological level. Signup and view all the answers

In the relationship between the immunodominant sugar and the H substance, what action is primarily involved?

Linkage facilitated by the action of the H gene. Signup and view all the answers

Which statement accurately reflects the specificity of the mentioned sugar?

It confers A specificity to the immune response. Signup and view all the answers

At what age is the expression of antigens considered fully developed in individuals?

Between 2 to 4 years of age Signup and view all the answers

What percentage of antigenic sites do newborn RBCs carry at most?

25% to 50% Signup and view all the answers

How is the strength of reaction of newborn RBC with reagent antisera compared to adult RBC?

Weaker than adult RBC Signup and view all the answers

What factor may influence the phenotypic expression of ABH antigens?

Race and genetic interaction Signup and view all the answers

What is the secretory status of ABH soluble antigens?

Can be found in all body secretions Signup and view all the answers

What is the consequence of transfusing incompatible blood due to naturally occurring antibodies in the ABO blood group system?

Immediate lysis of recipient's RBCs Signup and view all the answers

Which statement is true about the performance of serum grouping in ABO blood group system?

It is unique to the ABO blood group system Signup and view all the answers

What is the peak age for the production of ABO antibodies?

Between 5-10 years Signup and view all the answers

Why is it illogical to perform reverse grouping in newborn infants?

Maternal antibodies may interfere with results Signup and view all the answers

What characterizes the antibodies produced in the ABO blood group system?

They activate complement and are mainly IgM Signup and view all the answers

What relationship exists between the forward and reverse typing in the ABO blood group system?

There is an inverse reciprocal relationship Signup and view all the answers

Which subgroup of type A blood is rarely found in the Asian population?

A2 Signup and view all the answers

What typically happens to anti-A and anti-B antibody levels in elderly individuals?

They decline and may become undetectable Signup and view all the answers

What role does the FUT2 gene play in the secretory phenotype of antigens?

It codes for fucosyltransferase that modifies precursor substances in secretions. Signup and view all the answers

Which mutation in the ABO gene directly results in the inactive form of the A transferase enzyme?

Deletion within the 5' region of the catalytic domain. Signup and view all the answers

A2 RBC exhibit specific characteristics compared to A1 RBC. Which statement accurately reflects this difference?

A2 RBC react only with anti-A, not anti-A1. Signup and view all the answers

In the case of weak A subgroups, which characteristic is typical for these individuals?

Decreased number of A antigen sites per RBC. Signup and view all the answers

How do Bombay phenotype individuals react to anti-H sera, and what does this imply?

They fail to react, revealing the absence of H antigen. Signup and view all the answers

Which genetic condition results in the inability to produce H antigens, as seen in the Bombay phenotype?

Double dose recessive hh genotype. Signup and view all the answers

Which of the following tests is utilized to differentiate weak A subgroups through their reactions with specific antibodies?

Forward grouping with anti-A and anti-H. Signup and view all the answers

Para-Bombay phenotypes are characterized by which of the following genetic conditions?

Reduced H antigen production or presence of small amounts. Signup and view all the answers

What allows for the distinction between A1 and A2 RBC during serological testing?

Reacting differently with anti-A1 sera. Signup and view all the answers

For ABO subgroups, which aspect is primarily responsible for differences in the transfer of immunodominant sugars to H substance?

Amino acid substitutions stemming from genetic alterations. Signup and view all the answers

What type of antibodies are typically present in the serum of individuals with the Bombay phenotype?

Anti-A, anti-B, anti-A,B, and anti-H antibodies. Signup and view all the answers

Weak B subgroups are typically recognized by which of the following criteria?

Variation in reaction strength with anti-B and anti-A,B. Signup and view all the answers

What is the primary consequence of not having an active FUT1 gene in individuals with Para-Bombay phenotypes?

Diminished ability to form any ABO antigen. Signup and view all the answers

Which factor primarily differentiates the A2 antigen formation from A1 antigen formation?

Inefficiency of H glycan modification. Signup and view all the answers

Study Notes

Introduction to ABO Blood Group System

ABO blood group system is crucial for blood transfusion and transplantation.
Unique feature: individuals have antibodies against absent RBC antigens without prior exposure, leading to immediate lysis of incompatible donor RBCs.
Incompatible transfusions can cause severe, potentially fatal transfusion reactions.

ABO Grouping Methods

Forward Grouping (Front Type): Utilizes known antisera (anti-A, anti-B) to identify antigens on RBCs.
Reverse Grouping (Back Type): Detects ABO antibodies in serum using known reagent RBCs (A1 and B cells).
There is a reciprocal relationship between forward and reverse typing, serving as validation for results.
Serum grouping is specific to the ABO blood group system.

Development of ABO Antibodies

At Birth: ABO antibody production begins but is undetectable until 3-6 months due to low titers.
Antibody levels peak between 5-10 years and decline in the elderly, possibly causing undetectable levels in reverse typing.
Predominantly IgM antibodies that activate complement, react at room temperature.
RBCs of newborns have 25-50% antigenic sites compared to adults, with full antigen expression by age 2-4.

Secretory Status

Soluble ABH antigens found in body secretions; 80% of random U.S population are "secretors."
Secretor status depends on inheritance of ABO genes and the secretor gene (Se or FUT2) on chromosome 19.
FUT2 gene modifies the precursor substance to express A and B substances in secretions like saliva.

Molecular Genetics of ABO

ABO gene located on chromosome 9 consists of 7 exons; exons 6 and 7 account for 77% of the gene.
Mutations lead to A, B, or O specificities due to changes in enzyme functionality.
A2 subgroup arises from specific mutations in the A2 gene affecting glycosyltransferase activity.

A Subgroups

Majority of group A individuals are A1 or A1B; 20% are A2 or A2B.
A2 has fewer antigen sites (240,000 to 290,000) resulting in less efficient conversion of H antigen to A antigen.

Characteristics of A2 Antigen

Four types of H antigens characterized as unbranched or branched chains.
A1 RBCs react with both anti-A and anti-A1, while A2 RBCs only react with anti-A and show more reactivity with anti-H lectin.
A2 group exhibits occasional formation of anti-A1 antibodies.

Weak A and Weak B Subgroups

Weak A subgroups are rare and identifiable through serological discrepancies.
Characteristics: fewer A antigen sites, varying agglutination with anti-A, and variability in H antigen detectability.
Weak B subgroups observed via reaction strength with anti-B and anti-A, B techniques.

Bombay Phenotype (Oh)

Caused by inheritance of hh genotype, resulting in absence of ABH antigens due to lack of H antigen.
Inherited as an autosomal recessive trait linked to mutations in FUT1 gene.
Bombay phenotype RBCs do not react with anti-A, anti-B, or anti-H antisera, mimicking O blood type.

Antibodies in Bombay Serum

Bombay serum contains anti-A, anti-B, anti-A,B, and anti-H antibodies capable of strong reactions at 37°C.
Only compatible blood for transfusion comes from other Bombay phenotype individuals.

Para-Bombay Phenotypes

Exhibit reduced or absent H antigens; genetic basis includes mutations in FUT1 and/or FUT2 genes.
Individuals show very low levels of A or B antigens, undetectable by routine methods but identifiable using adsorption and elution techniques.

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Description

This quiz explores the ABO blood group system, which is fundamental in the context of blood transfusions and organ transplantation. Understanding this system is crucial for medical professionals and students alike. Test your knowledge on the different blood types and their significance!