Question 1

Which of the following best describes the mechanism underlying immediate (type I) hypersensitivity reactions?

Accepted Answer

Release of histamine and serotonin from mast cells coated with IgE upon allergen exposure

Question 2

A patient develops a severe allergic reaction within minutes of eating peanuts, including difficulty breathing and a sharp drop in blood pressure. Which treatment is most appropriate for this scenario?

Accepted Answer

Immediate injection of epinephrine to counteract smooth muscle contraction and increase blood pressure

Question 3

Which of the following statements about delayed-type (type IV) hypersensitivity is correct?

Accepted Answer

It is mediated by Th1 cells and typically peaks 24–48 hours after antigen exposure

Question 4

Which of the following best explains why infants are recommended to receive vaccinations even though they have maternal antibodies?

Accepted Answer

Vaccination induces the infant's own active immunity, which replaces temporary passive immunity from maternal antibodies

Question 5

Which of the following is a key advantage of mRNA vaccines over traditional attenuated vaccines?

Accepted Answer

mRNA vaccines allow for greater control of protein expression due to the short half-life of mRNA

Question 6

A laboratory strain of a virus is repeatedly cultured in vitro and loses its ability to cause disease in animals. What is the term for this process, and why does it occur?

Accepted Answer

Attenuation; nonvirulent mutants are selected in laboratory media where virulence is not advantageous

Question 7

Which of the following best describes the difference between active and passive adaptive immunity?

Accepted Answer

Active immunity involves the host's own immune response to an antigen, while passive immunity involves transfer of antibodies or immune cells from another individual

Question 8

A patient is diagnosed with systemic lupus erythematosus (SLE). Which of the following best characterizes the immunological basis of this disease?

Accepted Answer

It is a type III hypersensitivity involving autoantibodies against soluble self-antigens such as DNA

Question 9

Which of the following best explains why conjugate vaccines are more effective than polysaccharide-only vaccines for certain bacteria?

Accepted Answer

Conjugate vaccines couple poorly immunogenic polysaccharides to protein toxoids, inducing a stronger and longer-lasting immune response

Question 10

Which of the following is a function of Th1 cells in the immune response?

Accepted Answer

Production of cytokines that activate macrophages and promote T cell growth

Question 11

A person receives an injection of antiserum containing antibodies against rabies virus after being bitten by a potentially rabid animal. Which type of immunity is this an example of?

Accepted Answer

Artificial passive immunity

Question 12

Which of the following best describes the process of immune memory in adaptive immunity?

Accepted Answer

Memory cells are generated during the primary immune response and enable a faster, stronger response upon subsequent exposure to the same antigen

Question 13

Which of the following is a key feature of DNA vaccines?

Accepted Answer

They consist of bacterial plasmids encoding the antigen, which is then produced by host cells to elicit an immune response

Question 14

Which of the following is an example of natural passive immunity?

Accepted Answer

A child receives antibodies from breast milk

Question 15

Which of the following best explains why herd immunity can control the spread of infectious diseases even if not everyone is immunized?

Accepted Answer

A high proportion of immune individuals reduces the likelihood of transmission to susceptible individuals

Question 16

Which of the following is a characteristic of antibody-mediated (humoral) immunity?

Accepted Answer

It involves B cells producing antibodies that interact with extracellular antigens

Question 17

A patient develops a skin rash 36 hours after exposure to poison ivy. Which immune mechanism is most likely responsible for this reaction?

Accepted Answer

Type IV hypersensitivity mediated by Th1 cells

Question 18

Which of the following statements about autoimmunity is correct?

Accepted Answer

Autoimmunity results from immune reactions against self antigens due to failure of tolerance mechanisms

Question 19

Which of the following best describes the role of B cell receptors (BCRs) in the immune response?

Accepted Answer

BCRs are membrane-bound immunoglobulins that bind specific antigens, leading to B cell activation and antibody production

Question 20

A new vaccine is developed using a plant-based system where a pathogen gene is inserted into a plant using Agrobacterium tumefaciens. What is the main advantage of this approach?

Accepted Answer

It allows for rapid, large-scale production of recombinant antigens in plants for use as vaccines

Adaptive Immunity, Hypersensitivity, Autoimmunity, and Vaccination

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