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 a wide range of pathogens.

Question 2

Which structure acts as a physical barrier by forming tight junctions to prevent pathogen entry?

Accepted Answer

Tight junctions

Question 3

A patient with a genetic defect in the C3 protein would most likely have problems with which immune process?

Accepted Answer

Opsonization and efficient phagocytosis

Question 4

Which of the following is a chemical barrier that disrupts microbial membranes and recruits immune cells?

Accepted Answer

Antimicrobial peptides (AMPs)

Question 5

During a helminth (worm) infection, which innate immune cell is most critical for defense?

Accepted Answer

Eosinophils

Question 6

Which of the following best explains why opsonization is especially important for clearing encapsulated bacteria?

Accepted Answer

Capsules hide bacterial antigens, so complement proteins coat the capsule to allow immune recognition.

Question 7

Which of the following is NOT a function of the complement membrane attack complex (MAC)?

Accepted Answer

Producing antibodies against pathogens

Question 8

A virus-infected cell releases type I interferons (IFN-α, IFN-β). What is the primary effect on neighboring cells?

Accepted Answer

Induction of antiviral proteins that inhibit viral replication

Question 9

Which of the following best describes the role of pattern recognition receptors (PRRs) in innate immunity?

Accepted Answer

They detect conserved microbial structures (PAMPs) and trigger inflammation.

Question 10

Which PRR is most likely to recognize lipopolysaccharide (LPS) from Gram-negative bacteria?

Accepted Answer

Toll-like receptor 4 (TLR4)

Question 11

A patient with chronic inflammation is found to have excessive prostaglandin production. Which enzyme is most directly involved in prostaglandin synthesis from arachidonic acid?

Accepted Answer

Cyclooxygenase (COX)

Question 12

Which of the following is a correct statement about leukocytes and lymphocytes?

Accepted Answer

All lymphocytes are leukocytes, but not all leukocytes are lymphocytes.

Question 13

Which of the following is a function of dendritic cells in the immune system?

Accepted Answer

Presenting antigens to activate naïve T cells

Question 14

Which of the following best explains why PRRs recognize patterns shared by many microbes rather than specific species?

Accepted Answer

It allows rapid detection and broad early protection before the adaptive immune system is activated.

Question 15

Which of the following is a key difference between granulocytes and agranulocytes?

Accepted Answer

Granulocytes have visible cytoplasmic granules, while agranulocytes do not.

Question 16

A patient is unable to produce lysozyme in their tears and saliva. Which microbial structure would be most affected by this deficiency?

Accepted Answer

Peptidoglycan in bacterial cell walls

Question 17

Which of the following is a correct sequence of events in phagocytosis?

Accepted Answer

Chemotaxis → Adherence → Ingestion → Digestion → Exocytosis

Question 18

Which of the following is a function of C-reactive protein (CRP) during infection?

Accepted Answer

Acts as an opsonin and enhances complement activation

Question 19

Which of the following best describes the action of natural killer (NK) cells?

Accepted Answer

They kill virally infected and cancerous cells by detecting low MHC I expression.

Question 20

A patient with a bacterial skin infection is most likely to have an increased number of which innate immune cell at the infection site?

Accepted Answer

Neutrophils

The Innate Immune System: Structure, Function, and Cellular Components

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