Question 1

Which of the following best describes the principle behind the ELISA assay?

Accepted Answer

It depends on specific antigen-antibody binding, with detection via an enzyme-linked colorimetric reaction.

Question 2

A patient’s serum is tested for anti-HIV antibodies using a Western blot. Which step ensures that only antibodies specific to HIV proteins are detected?

Accepted Answer

Separation of proteins by size using SDS-PAGE before antibody probing.

Question 3

Which of the following statements about the ABO blood group system is CORRECT?

Accepted Answer

Type O individuals have neither A nor B antigens but have anti-A and anti-B antibodies.

Question 4

In a hemagglutination test, what does the clumping of red blood cells indicate?

Accepted Answer

The presence of antibodies that bind to antigens on the red blood cells.

Question 5

Which diagnostic test would be most appropriate for quantifying the amount of IgM in a patient’s serum?

Accepted Answer

Nephelometry

Question 6

A laboratory is using an indirect ELISA to detect antibodies against a viral antigen. Which of the following best describes the detection step?

Accepted Answer

A substrate is added that reacts with an enzyme linked to a secondary antibody, producing a color change.

Question 7

Which of the following is a key advantage of ELISA over radioimmunoassay (RIA)?

Accepted Answer

ELISA does not require radioactive materials, making it safer and more practical.

Question 8

A scientist wants to separate and analyze different cell populations based on the presence of a specific surface marker. Which technique should they use?

Accepted Answer

Flow cytometry (FACS)

Question 9

Which of the following best explains why type O blood is considered a universal donor?

Accepted Answer

Type O blood lacks A and B antigens, so recipient antibodies do not react with donor red blood cells.

Question 10

A newborn develops hemolytic disease due to Rh incompatibility. Which treatment can prevent this condition in future pregnancies?

Accepted Answer

Administering anti-Rh antibodies (Rho-Gam) to the mother after delivery.

Question 11

Which of the following is TRUE regarding confocal microscopy?

Accepted Answer

It uses lasers to scan layers of a cell and can assemble 2D or 3D images.

Question 12

In the complement fixation test, what does the absence of hemolysis indicate?

Accepted Answer

The patient’s serum contains antibodies specific to the test antigen.

Question 13

Which of the following best describes the function of antibodies in an affinity column?

Accepted Answer

They specifically bind and retain target proteins or tags, allowing purification from a mixture.

Question 14

A patient’s serum is serially diluted and tested for antibody reactivity. The highest dilution that still gives a positive result is called:

Accepted Answer

The titer

Question 15

Which of the following is a distinguishing feature of the sandwich ELISA compared to the indirect ELISA?

Accepted Answer

It uses a capture antibody to immobilize the antigen before detection.

Question 16

Which of the following best explains why pre-existing antibodies against ABO antigens are common in humans?

Accepted Answer

They are made against bacterial and food antigens that cross-react with A and B antigens.

Question 17

Which of the following is a real-world application of flow cytometry (FACS)?

Accepted Answer

Separating CD4+ T cells from a mixed population for HIV research.

Question 18

Which of the following statements about immunofluorescence is CORRECT?

Accepted Answer

It uses fluorescent dye-labeled antibodies to detect antigens or antibodies under UV light.

Question 19

A colorimetric reaction in ELISA is catalyzed by horseradish peroxidase (HRP). Which substrate is commonly used, and what is the result?

Accepted Answer

TMB (tetramethylbenzidine); a yellow color forms upon reaction.

Question 20

Which of the following best describes the genetic basis of the ABO blood group system?

Accepted Answer

The A and B alleles are co-dominant, and the O allele is recessive.

Lab Techniques for Immune

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