Direct Antiglobulin Test (DAT)

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What is the purpose of the Direct Antiglobulin Test (DAT)?

To confirm the absence of antibodies in the bloodstream
To demonstrate circulating antibodies in the serum
To examine the repulsion forces between red blood cells
To identify antibodies attached to red blood cells in vivo (correct)

What does a positive Direct Antiglobulin Test (DAT) indicate?

Antibody sensitization of red cells in vivo (correct)
Insufficient antibodies on red cell surface
Presence of circulating antibodies in serum
Absence of globulin or complement molecules on red cells

In the Direct Antiglobulin Test, what is the function of Coomb's serum?

Detecting repulsion forces between red blood cells
Inducing agglutination of sensitized red cells (correct)
Washing the red cells with saline
Demonstrating antibodies in the serum

What is the main difference between Direct Antiglobulin Test (DAT) and Indirect Coomb's Test?

DAT identifies antibodies attached to red cells in vivo, but Indirect Coomb's Test shows circulating antibodies. (A) Signup and view all the answers

What does a negative Direct Antiglobulin Test (DAT) imply?

Lack of antibodies in the patient's serum (A) Signup and view all the answers

Why is it necessary to centrifuge the red cell suspension in the Direct Antiglobulin Test?

To separate agglutinated cells from non-agglutinated ones (B) Signup and view all the answers

What is the purpose of using a known antiserum in a test?

To detect the corresponding antigen (D) Signup and view all the answers

Why should the sensitized red cells be checked against known, sensitized cells?

To assess the validity of the Coombs Test (A) Signup and view all the answers

What should be done to prepare check cells for the Coombs Test?

Mix 1 ml serum from a D-positive patient with washed O negative cells (B) Signup and view all the answers

What is a potential source of error that could lead to a false negative result in the Coombs Test?

Inadequate washing of red cells (A) Signup and view all the answers

What would be a consequence of using plasma instead of serum in the Coombs Test?

False positive results (B) Signup and view all the answers

How does under-centrifugation affect the Coombs Test results?

Causes false negative results (A) Signup and view all the answers

What is the main reason why some IgG antibodies fail to agglutinate red blood cells?

The negative charge on the red blood cell surface. (A) Signup and view all the answers

How do the FAB portions of AHG molecules cause agglutination of sensitized red blood cells?

By reacting with the FC portions of adjacent IGG molecules. (D) Signup and view all the answers

Why are Coomb's serum antibodies necessary for the Direct Antiglobulin Test?

To prepare antibodies against IGG and complement. (D) Signup and view all the answers

What is the primary purpose of using AHG serum in testing for immune hemolytic reactions?

To overcome the forces causing red blood cells to repel one another. (B) Signup and view all the answers

In a Coomb's test, what is sensitized by attaching to red cell membranes?

Antibodies (A) Signup and view all the answers

What prevents small antibody molecules like IgG from producing agglutination directly?

Negative charge on red blood cell surfaces. (A) Signup and view all the answers

Which of the following statements is true about the formation of ABO antigens?

The formation of ABO antigens involves the addition of specific sugar residues to precursor oligosaccharide chains on glycoproteins and glycolipids. (B) Signup and view all the answers

According to Landsteiner's laws, which of the following statements is correct?

Anti-A antibodies are naturally present in individuals with blood group B, and anti-B antibodies are naturally present in individuals with blood group A. (A) Signup and view all the answers

Which of the following genes is associated with the formation of the A antigen?

The $ABO$ gene, encoding the $\alpha(1,3)$-N-acetylgalactosaminyltransferase enzyme. (C) Signup and view all the answers

Which of the following statements accurately describes the ABO antigens?

ABO antigens are glycoproteins and glycolipids that are present on the surface of red blood cells and other cells. (C) Signup and view all the answers

Which of the following statements accurately describes the precursor oligosaccharide chains involved in the formation of ABO antigens?

The precursor oligosaccharide chains are composed of a sequence of specific sugar residues that serve as a starting point for the addition of further sugar residues. (B) Signup and view all the answers

According to Landsteiner's laws, which of the following statements is correct regarding the inheritance of ABO blood groups?

The ABO blood group is determined by a single gene with multiple alleles. (D) Signup and view all the answers

What is the role of the H gene in the formation of ABO antigens?

The H gene encodes for a precursor substance that is modified to form the A and B antigens. (B) Signup and view all the answers

According to Landsteiner's laws, which of the following statements is true?

Individuals with the A phenotype can produce anti-B antibodies, and individuals with the B phenotype can produce anti-A antibodies. (D) Signup and view all the answers

What is the genetic basis for the Bombay phenotype?

The presence of a recessive allele that prevents the formation of the H antigen precursor. (D) Signup and view all the answers

What is the role of the A and B genes in the formation of ABO antigens?

The A and B genes encode for enzymes that modify the H antigen precursor to form the respective A and B antigens. (D) Signup and view all the answers

What is the significance of the precursor oligosaccharide chains in the formation of ABO antigens?

The precursor oligosaccharide chains are intermediates that are further modified to form the A and B antigens. (B) Signup and view all the answers

According to Landsteiner's laws, which of the following statements is false?

Individuals with the AB phenotype cannot produce anti-A or anti-B antibodies. (B) Signup and view all the answers

What is the key difference between Type 1 and Type 2 precursor oligosaccharide chains?

Type 1 chains have a beta-1,3 linkage, while Type 2 chains have a beta-1,4 linkage (A) Signup and view all the answers

According to Landsteiner's Laws, which of the following statements is true?

Individuals with blood group O have both anti-A and anti-B antibodies in their serum (D) Signup and view all the answers

Which of the following statements correctly describes the formation of the H antigen?

The H antigen is formed by the action of the a-2-L-fucosyltransferase enzyme on the precursor substance (C) Signup and view all the answers

Which of the following genes is responsible for the formation of the A antigen?

A gene (C) Signup and view all the answers

What is the order of the amount of h-antigen present on red blood cells, from highest to lowest?

o > a2 > b > a2b > a1 > a1b (C) Signup and view all the answers

Which of the following statements correctly describes the formation of the AB antigen?

The AB antigen is formed by the action of the a-3-D-galactosyltransferase enzyme on the precursor substance, followed by the action of the a-3-N-acetylgalactosaminyl transferase enzyme (B) Signup and view all the answers

Which of the following statements is true regarding the ABO antibodies?

Anti-A and anti-B antibodies are predominantly IgM, but anti-AB antibodies are predominantly IgG and can cross the placenta (C) Signup and view all the answers

Which gene is responsible for the absence of ABO antigens on red blood cells, resulting in the O blood group?

O gene (B) Signup and view all the answers