Q: Which of the following equations correctly represents the formation of the membrane attack complex (MAC) in the complement system?

$$C5b + C6 + C7 + C8 + C9 \rightarrow \text{MAC formation}$$

Question 1

Which of the following best describes the role of Toll-like receptors (TLRs) in innate immunity?

Accepted Answer

TLRs recognize pathogen-associated molecular patterns (PAMPs) and induce cytokine production to regulate immune responses.

Question 2

A patient with a genetic defect that prevents the production of lysozyme would be most susceptible to which of the following?

Accepted Answer

Increased risk of bacterial infections due to reduced ability to break down peptidoglycan in bacterial cell walls.

Question 3

Which of the following is NOT a physical factor involved in the first line of defense against pathogens?

Accepted Answer

Lysozyme in saliva

Question 4

A newborn is delivered via cesarean section and is not breastfed. Compared to a vaginally delivered, breastfed infant, this newborn is more likely to have which of the following?

Accepted Answer

Reduced microbial antagonism, increasing susceptibility to opportunistic pathogens.

Question 5

During the process of phagocytosis, which step immediately follows chemotaxis?

Accepted Answer

Adherence

Question 6

A bacterial pathogen produces a capsule that prevents complement activation. Which complement-mediated effect is most directly inhibited by this capsule?

Accepted Answer

Opsonization

Question 7

Which of the following equations correctly represents the formation of the membrane attack complex (MAC) in the complement system?

Accepted Answer

$$C5b + C6 + C7 + C8 + C9 ightarrow 	ext{MAC formation}$$

Question 8

A patient develops a fever after a bacterial infection. Which of the following best explains the physiological mechanism leading to the increased body temperature?

Accepted Answer

The hypothalamus releases prostaglandins in response to interleukin-1 (IL-1) from phagocytes, resetting the body's temperature set point.

Question 9

Which of the following is a function of gamma interferon ($$\gamma-$$IFN) in innate immunity?

Accepted Answer

Stimulates neutrophils and macrophages to phagocytize bacteria.

Question 10

A laboratory test shows a patient has a low percentage of neutrophils in their white blood cell count. Which of the following would most likely be impaired in this patient?

Accepted Answer

Phagocytosis of bacteria during the early stages of infection.

Question 11

Which of the following best describes the role of transferrins in innate immunity?

Accepted Answer

Transferrins bind serum iron, limiting its availability to bacteria and inhibiting their growth.

Question 12

Which of the following is a chemical factor that contributes to the first line of defense?

Accepted Answer

Low pH of gastric juice

Question 13

A patient with a deficiency in C3 protein would have impaired function in which of the following processes?

Accepted Answer

Opsonization, inflammation, and cytolysis

Question 14

Which of the following best explains why normal microbiota are considered part of innate immunity?

Accepted Answer

They compete with pathogens for nutrients and space, reducing pathogen colonization.

Question 15

A patient is exposed to a bacterial endotoxin. Which of the following is the correct sequence of events leading to fever?

Accepted Answer

Endotoxin stimulates phagocytes to release IL-1 $$\rightarrow$$ Hypothalamus releases prostaglandins $$\rightarrow$$ Body temperature set point increases

Question 16

Which of the following is a correct description of the alternative pathway of complement activation?

Accepted Answer

It is activated by proteins C3, B, D, P, and a pathogen, independent of antibodies.

Question 17

Which of the following is a plausible consequence if a bacterium produces an enzyme that digests C5a?

Accepted Answer

Reduced recruitment of phagocytes to the site of infection.

Question 18

Which of the following best describes the process of opsonization?

Accepted Answer

Coating of a pathogen with molecules such as C3b to enhance phagocytosis.

Question 19

A patient with a burn injury loses a large portion of their epidermis. Which of the following best explains why this patient is at increased risk for infection?

Accepted Answer

Loss of the physical barrier provided by tightly packed keratinized cells allows easier entry of pathogens.

Question 20

Which of the following is a correct sequence of events in the inflammatory response?

Accepted Answer

Tissue damage $$\rightarrow$$ Vasodilation $$\rightarrow$$ Phagocyte migration $$\rightarrow$$ Tissue repair

Innate Immunity: Nonspecific Defenses of the Host

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