Question 1

A patient presents with recurrent infections, low levels of immunoglobulins, and a history of thymic aplasia. Which type of immunodeficiency is most likely present, and what is a common cause?

Accepted Answer

Primary immunodeficiency; genetic defect in immune cell development

Question 2

Which of the following best describes a Type I hypersensitivity reaction, and what is a classic example?

Accepted Answer

Immediate, IgE-mediated; allergic rhinitis

Question 3

A patient with systemic lupus erythematosus (SLE) produces autoantibodies against which of the following targets?

Accepted Answer

Nuclear antigens (e.g., double-stranded DNA)

Question 4

Desensitization therapy for allergies works by which of the following mechanisms?

Accepted Answer

Gradually increasing exposure to allergen to shift immune response from IgE to IgG production

Question 5

Which antibody is primarily responsible for mucosal immunity and is found in secretions such as saliva and tears?

Accepted Answer

IgA

Question 6

Which of the following statements about the history of smallpox is correct?

Accepted Answer

Smallpox was eradicated worldwide through a global vaccination campaign using a live attenuated vaccine.

Question 7

Which type of vaccine contains a killed version of the pathogen and is safe for immunocompromised individuals?

Accepted Answer

Inactivated (killed) vaccine

Question 8

In a sandwich ELISA, which of the following sequences correctly describes the steps involved?

Accepted Answer

Capture antibody coating, sample antigen addition, detection antibody addition, substrate addition

Question 9

Alexander Fleming discovered penicillin after observing which phenomenon?

Accepted Answer

A mold inhibited bacterial growth on a petri dish

Question 10

Which of the following best describes the difference between bacteriostatic and bactericidal drugs?

Accepted Answer

Bacteriostatic drugs inhibit bacterial growth, while bactericidal drugs kill bacteria

Question 11

A patient is prescribed an aminoglycoside antibiotic. Which bacterial target is most likely affected?

Accepted Answer

30S ribosomal subunit

Question 12

A broth dilution test is performed to determine the minimum inhibitory concentration (MIC) of an antibiotic. If bacterial growth is observed in tubes with concentrations of 0.5 and 1.0 $$\mug/mL$$, but not in tubes with 2.0 $$\mug/mL $$and higher, what is the MIC?

Accepted Answer

$$2.0\ \mu\mathrm{g}/\mathrm{mL}$$

Question 13

Which of the following best describes intrinsic antibiotic resistance?

Accepted Answer

A natural property of a bacterial species due to its inherent structure or physiology

Question 14

Where in the respiratory tract is the normal microbiota most abundant?

Accepted Answer

Nasal cavity and oropharynx

Question 15

Which of the following is a key difference between Influenza A and Influenza B viruses?

Accepted Answer

Influenza A infects multiple species and causes pandemics, while Influenza B primarily infects humans and causes seasonal epidemics

Question 16

A patient presents with a rapidly spreading, red, swollen area on the skin, high fever, and low blood pressure. Blood cultures reveal Streptococcus pyogenes. Which syndrome is most likely?

Accepted Answer

Streptococcal toxic shock syndrome

Question 17

Which of the following best explains how the skin acts as a barrier to infection?

Accepted Answer

It provides a physical barrier, secretes antimicrobial peptides, and maintains an acidic pH

Question 18

Which of the following is a common causative agent of neonatal meningitis?

Accepted Answer

Group B Streptococcus (Streptococcus agalactiae)

Question 19

African sleeping sickness is characterized by which of the following features?

Accepted Answer

Cyclic fevers, neurological symptoms, and transmission by tsetse flies

Question 20

Which of the following best describes the gut-brain axis?

Accepted Answer

Bidirectional communication between the gastrointestinal tract and the central nervous system

MCB 2010 Exam 3 Study Guide – Step-by-Step Guidance

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