Question 1

Which of the following best describes the primary function of the innate immune system?

Accepted Answer

It provides a rapid, nonspecific response to pathogens using barriers and internal defenses.

Question 2

A patient receives a cut on their skin, allowing bacteria to enter the tissue. Which sequence correctly describes the order of immune responses that occur?

Accepted Answer

Surface barriers → Internal defenses → Adaptive immune response

Question 3

Which of the following is NOT a function of complement proteins in the immune response?

Accepted Answer

Directly neutralizing viruses by binding to their surface proteins

Question 4

Which cell type is responsible for recognizing and killing virus-infected or cancerous cells by detecting a lack of MHC class I molecules?

Accepted Answer

Natural Killer (NK) cells

Question 5

A child is born with a genetic defect that prevents the production of both B and T cells. Which condition does this child most likely have?

Accepted Answer

Severe Combined Immunodeficiency (SCID)

Question 6

Which of the following best explains why organ transplants are often rejected by the recipient’s immune system?

Accepted Answer

Differences in MHC self-antigens between donor and recipient

Question 7

Which antibody class is most abundant in plasma and can cross the placenta to provide immunity to a fetus?

Accepted Answer

IgG

Question 8

A person is exposed to an allergen for the second time. Which immune mechanism is primarily responsible for the rapid allergic reaction?

Accepted Answer

Binding of the allergen to IgE antibodies on mast cells, causing histamine release

Question 9

Which process ensures that T cells do NOT react against self-antigens during their maturation in the thymus?

Accepted Answer

Negative selection

Question 10

Which of the following best describes the role of interferons in the immune response?

Accepted Answer

They alert neighboring cells to activate antiviral defenses and inhibit viral replication.

Question 11

Which of the following is a key difference between humoral and cell-mediated immunity?

Accepted Answer

Humoral immunity involves antibodies produced by B cells, while cell-mediated immunity involves direct killing by T cells.

Question 12

Which of the following best describes the process of opsonization?

Accepted Answer

Coating of pathogens by antibodies or complement proteins to enhance phagocytosis

Question 13

A dendritic cell engulfs a bacterium and presents its antigen on an MHC class II molecule. Which cell type will recognize this complex and become activated?

Accepted Answer

CD4 (Helper) T cell

Question 14

Which of the following is a correct statement about the secondary immune response?

Accepted Answer

It is faster and more robust due to the presence of memory B cells.

Question 15

Which of the following is a mechanism by which antibodies help eliminate pathogens?

Accepted Answer

Agglutination, where antibodies cross-link pathogens to form clumps for easier phagocytosis

Question 16

Which of the following best explains why a person with AIDS is more susceptible to infections?

Accepted Answer

Destruction of CD4 T helper cells impairs both humoral and cell-mediated immunity

Question 17

Which of the following is a real-life example of passive humoral immunity?

Accepted Answer

A newborn receiving antibodies from breast milk

Question 18

Which of the following is the correct equation for the rate of antibody production during the secondary immune response, assuming it is proportional to the number of memory B cells ($$N_{memory}) $$and the antigen concentration ($$[Ag]$$)?

Accepted Answer

$$Rate = k 	imes N_{memory} 	imes [Ag]$$

Question 19

Which of the following best describes the process of positive selection during T cell maturation?

Accepted Answer

T cells that recognize self-MHC proteins survive; those that do not undergo apoptosis.

Chapter 21: The Immune System – Innate and Adaptive Body Defenses

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