Question 1

Which of the following best describes the principle of herd immunity?

Accepted Answer

Immunity in most of the population prevents outbreaks by reducing the number of susceptible individuals.

Question 2

Which type of vaccine is most likely to confer lifelong immunity and why?

Accepted Answer

Attenuated vaccines, because the weakened pathogen replicates in the body, stimulating both humoral and cellular immunity.

Question 3

A child under 2 years old receives a vaccine containing a polysaccharide antigen conjugated to a protein. Why is this conjugation necessary?

Accepted Answer

Children under 2 do not respond well to T-independent antigens like polysaccharides, so conjugation to a protein makes the vaccine immunogenic.

Question 4

Which of the following best explains why mRNA vaccines do not require the use of animal hosts for production?

Accepted Answer

mRNA vaccines are synthesized in vitro and packaged in lipid nanoparticles, eliminating the need for pathogen growth in animals.

Question 5

A patient receives a rapid antigen test for SARS-CoV-2. What is the principle behind this test?

Accepted Answer

Antigens in the sample bind to labeled antibodies on a paper strip, forming a colored line if present.

Question 6

Which of the following statements about monoclonal antibodies (Mabs) is correct?

Accepted Answer

They are produced by hybridomas, which are fusions of myeloma cells and antibody-producing B cells.

Question 7

In a precipitation reaction, why does a visible precipitate only form in the zone of equivalence?

Accepted Answer

The optimal ratio of antigen to antibody allows for large, interlocking antigen-antibody complexes to form.

Question 8

A laboratory uses a direct agglutination test to determine the titer of antibodies in a patient's serum. What does a rise in titer indicate?

Accepted Answer

A greater immunity to the disease or recent exposure to the antigen.

Question 9

Which of the following best describes the function of adjuvants in vaccines?

Accepted Answer

They enhance the innate immune response, improving vaccine effectiveness.

Question 10

A patient’s serum is tested using an indirect fluorescent-antibody (FA) test. What is being detected in this assay?

Accepted Answer

The presence of a specific antibody in the patient’s serum.

Question 11

Which of the following is a key advantage of recombinant vector vaccines?

Accepted Answer

They use avirulent viruses or bacteria to deliver DNA coding for antigens, reducing the risk of disease.

Question 12

Why are oral vaccines particularly effective against pathogens that enter through the gastrointestinal tract?

Accepted Answer

They stimulate mucosal immunity at the site of pathogen entry.

Question 13

Which of the following best explains why the oral polio vaccine is not recommended for immunocompromised patients?

Accepted Answer

There is a risk that the attenuated virus could revert to a virulent form.

Question 14

A Western blot is used to confirm the presence of HIV proteins in a patient sample. What is the principle behind this technique?

Accepted Answer

Proteins are separated by electrophoresis, transferred to a membrane, and detected with enzyme-linked antibodies.

Question 15

Which of the following is a reason why some vaccine-preventable diseases persist in certain regions?

Accepted Answer

Lower rates of vaccination due to poverty and lack of health infrastructure.

Question 16

In an ELISA test, what is the main difference between a direct and an indirect assay?

Accepted Answer

Direct ELISA detects antigens, while indirect ELISA detects antibodies.

Question 17

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

Accepted Answer

The patient’s serum prevents cytopathic effects in cell cultures.

Question 18

Which of the following best describes the use of the fluorescence-activated cell sorter (FACS) in immunology?

Accepted Answer

It separates cells based on fluorescence and size, allowing enumeration of specific cell types such as CD4+ T cells.

Question 19

Which of the following is a characteristic of subunit vaccines?

Accepted Answer

They use only antigenic fragments of a pathogen to stimulate an immune response.

Practical Applications of Immunology: Vaccines and Diagnostic Immunology

Study Guide - Practice Questions