Q: A diagnostic test for a viral infection gives a positive result in 95 out of 100 infected patients and a negative result in 90 out of 100 uninfected patients. What are the sensitivity and specificity of this test?

$$\text{Sensitivity} = \frac{95}{100} \times 100\% = 95\%$$, $$\text{Specificity} = \frac{90}{100} \times 100\% = 90\%$$

Question 1

Which of the following best explains why attenuated virus vaccines generally provide lifelong immunity?

Accepted Answer

They contain weakened but live microorganisms that replicate in the host, stimulating a robust and long-lasting immune response.

Question 2

A new vaccine is developed by combining a bacterial polysaccharide antigen with a protein carrier to enhance immunogenicity in infants. What type of vaccine is this?

Accepted Answer

Conjugated vaccine

Question 3

A diagnostic test for a viral infection gives a positive result in 95 out of 100 infected patients and a negative result in 90 out of 100 uninfected patients. What are the sensitivity and specificity of this test?

Accepted Answer

$$	ext{Sensitivity} = \frac{95}{100} 	imes 100\% = 95\%$$, $$	ext{Specificity} = \frac{90}{100} 	imes 100\% = 90\%$$

Question 4

Which of the following best describes the principle behind the ELISA (Enzyme-Linked Immunosorbent Assay) technique?

Accepted Answer

Antigen–antibody reactions are detected by enzyme activity linked to the antibody, producing a color change.

Question 5

A patient’s serum is tested for antibodies against a virus using a virus neutralization test. Which result indicates the presence of antibodies?

Accepted Answer

The serum prevents cytopathic effects of the virus in cell culture.

Question 6

Which of the following statements about monoclonal antibodies is correct?

Accepted Answer

They are produced by a single hybridoma cell line and are specific for one epitope.

Question 7

A laboratory is developing a new vaccine that uses mRNA to instruct host cells to produce a viral protein. What is the main advantage of this type of vaccine?

Accepted Answer

It causes the recipient’s cells to make the antigenic protein, leading to both humoral and cellular immunity.

Question 8

Which of the following best explains why herd immunity is important in controlling infectious diseases?

Accepted Answer

It reduces the number of susceptible hosts, thereby limiting the spread of disease even to unvaccinated individuals.

Question 9

A patient is suspected of having a recent infection. Which serological finding would best support this diagnosis?

Accepted Answer

A rising titer or seroconversion from no antibodies to the presence of antibodies.

Question 10

Which of the following is a key difference between precipitation and agglutination reactions in immunology?

Accepted Answer

Precipitation involves the interaction of soluble antigens with antibodies, while agglutination involves particulate antigens (such as cells) with antibodies.

Question 11

A diagnostic laboratory uses immunoelectrophoresis to analyze a patient’s serum proteins. What two techniques are combined in this method?

Accepted Answer

Electrophoresis and immunodiffusion

Question 12

Which of the following best describes the function of an adjuvant in a vaccine?

Accepted Answer

It improves the effectiveness of some antigens by enhancing the immune response.

Question 13

A patient’s blood sample is mixed with latex beads coated with a specific antigen. Agglutination is observed. What does this indicate?

Accepted Answer

The patient’s serum contains antibodies specific to the antigen on the latex beads.

Question 14

Which of the following is a major advantage of dry skin patch vaccines over traditional injectable vaccines?

Accepted Answer

They do not require refrigeration, making them easier to distribute in remote areas.

Question 15

In a Western blot, what is the primary purpose of using an enzyme-linked antibody after protein separation?

Accepted Answer

To detect specific proteins by producing a visible signal where the antibody binds.

Question 16

A new diagnostic test uses a fluorescence flow cytometer to count cells labeled with fluorescent antibodies. What is the main advantage of this technique?

Accepted Answer

It can detect and count specific cell types rapidly and with high sensitivity.

Question 17

Which of the following best describes the complement-fixation reaction used in serological testing?

Accepted Answer

It is based on the depletion of a fixed amount of complement in the presence of an antigen–antibody reaction.

Question 18

Which of the following is a potential future application of genetically modified plants in immunology?

Accepted Answer

Producing edible vaccines that can be administered orally.

Question 19

A patient is given an antitoxin after exposure to a bacterial exotoxin. What is the mechanism of action of the antitoxin?

Accepted Answer

It is an antibody that neutralizes the exotoxin, preventing its harmful effects.

Question 20

Which of the following best explains why combining several vaccines into a single injection is beneficial?

Accepted Answer

It reduces the number of injections required, improving patient compliance and coverage.

Vaccines and Diagnostic Immunology: Principles, Types, and Applications

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