Question 1

A patient develops a sudden, severe allergic reaction after being stung by a bee. Which immunoglobulin is primarily responsible for this response, and what is the mechanism of action?

Accepted Answer

IgE; binds to mast cells causing release of histamine and other mediators

Question 2

A hospital patient develops a urinary tract infection with E. coli after catheterization. This infection is best classified as which of the following?

Accepted Answer

A healthcare-associated infection (HAI)

Question 3

Which of the following best explains why Streptococcus pneumoniae is more virulent when it possesses a capsule?

Accepted Answer

The capsule prevents phagocytosis by host immune cells

Question 4

A laboratory is testing a new strain of bacteria for its ability to cause disease. They determine the minimum number of bacteria required to infect 50% of a test population. What is this value called?

Accepted Answer

ID_{50}

Question 5

A patient with tuberculosis is found to have Mycobacterium tuberculosis living inside their macrophages. Which cell wall component allows this bacterium to survive within phagocytes?

Accepted Answer

Mycolic acid

Question 6

Which of the following is a key difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are proteins secreted by living bacteria, while endotoxins are lipopolysaccharides released from dead Gram-negative bacteria.

Question 7

A child receives the MMR vaccine and later develops a strong, rapid antibody response upon exposure to measles. Which type of immunity and which immunoglobulin class are primarily responsible for this secondary response?

Accepted Answer

Artificial active immunity; IgG

Question 8

A patient with a history of multiple blood transfusions develops hemolytic anemia due to antibodies attacking transfused red blood cells. Which type of hypersensitivity reaction is this, and which immunoglobulins are involved?

Accepted Answer

Type II; IgG and IgM

Question 9

Which of the following best describes the process of opsonization?

Accepted Answer

Antibodies coat microbes, enhancing phagocytosis by immune cells

Question 10

A patient with DiGeorge syndrome is most likely to experience recurrent infections with which types of pathogens, and why?

Accepted Answer

Fungi, protozoa, and viruses, due to T cell deficiency

Question 11

A researcher is studying the complement system. Which of the following is the correct sequence of events leading to cell lysis?

Accepted Answer

Initiation $$\rightarrow$$ amplification $$\rightarrow$$ polymerization $$\rightarrow$$ Membrane Attack Complex (MAC) formation $$\rightarrow$$ cell lysis

Question 12

A patient is exposed to Salmonella via contaminated food. Which portal of entry and mode of transmission does this represent?

Accepted Answer

Gastrointestinal tract; vehicle (foodborne)

Question 13

Which of the following best explains why fever can be beneficial during infection?

Accepted Answer

Fever inhibits multiplication of temperature-sensitive microbes and enhances phagocytosis

Question 14

A patient with HIV is found to have a severely reduced number of CD4+ T cells. Which aspect of the immune response is most directly impaired?

Accepted Answer

Activation of cytotoxic T cells and B cells

Question 15

A laboratory uses PCR to detect the presence of a specific bacterial pathogen in a patient's sample. What is the main advantage of PCR in this context?

Accepted Answer

It amplifies DNA, allowing detection of very small amounts of pathogen

Question 16

A patient with rheumatoid arthritis produces antibodies against their own IgG molecules. Which type(s) of hypersensitivity are involved in this disease?

Accepted Answer

Type II, III, and IV

Question 17

A newborn receives IgG antibodies from its mother through the placenta. Which type of immunity is this, and does it provide immune memory?

Accepted Answer

Natural passive immunity; no, does not provide memory

Question 18

A patient is diagnosed with contact dermatitis after exposure to poison ivy. Which immune cells mediate this response, and what is the time course?

Accepted Answer

T cells; delayed (24–48 hours)

Question 19

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

Accepted Answer

They enhance the immune response to the vaccine antigen

Question 20

A patient is exposed to influenza virus and develops symptoms after a few days. Which stage of disease is characterized by the most severe signs and symptoms and the highest number of pathogens?

Accepted Answer

Period of illness

BIO 150 – Exam 3: Principles of Disease, Immunity, and Immune Disorders

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