Adaptive Immune System Quizlet

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Which of the following represents the correct sequence of host immune defenses as encountered by a pathogen?

  • A. Innate responses; physical barriers; adaptive responses
  • B. Physical barriers; innate responses; adaptive responses
  • C. Adaptive responses; physical barriers; innate responses
  • D. Physical barriers; adaptive responses; innate responses
Correct Answer: B

Rationale: The correct sequence is B: Physical barriers; innate responses; adaptive responses. Physical barriers like skin and mucous membranes are the first line of defense, followed by innate responses (e.g., inflammation, phagocytosis) that provide immediate, non-specific protection. Adaptive responses (e.g., antibody production, T cell activation) are the final defense mechanism, specifically targeting the pathogen. Choices A, C, and D are incorrect because they do not follow the correct chronological order of how host immune defenses are encountered by a pathogen. Option A and D have the innate and adaptive responses in the wrong order, while option C places adaptive responses before physical barriers, which is not accurate in terms of the sequence of host immune defenses.

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Which T cell type helps activate B cells?

  • A. Cytotoxic T cells
  • B. Helper T cells
  • C. Regulatory T cells
  • D. Memory T cells
Correct Answer: B

Rationale: The correct answer is B: Helper T cells. Helper T cells play a crucial role in activating B cells by releasing cytokines that stimulate B cell proliferation and differentiation into plasma cells, which produce antibodies. Cytotoxic T cells (A) are involved in directly killing infected cells. Regulatory T cells (C) suppress immune responses. Memory T cells (D) are responsible for maintaining immunological memory for future responses. Thus, Helper T cells are the key cell type that helps activate B cells.

The hypervariable regions

  • A. Are also called Complementary Determining Regions
  • B. Are localized in the constant region of an antibody molecule
  • C. Are not found in the secreted form of antibodies
  • D. Are found only in heavy chains
Correct Answer: A

Rationale: Step 1: Hypervariable regions are responsible for antigen binding specificity.
Step 2: Complementary Determining Regions (CDRs) are the specific locations within the hypervariable regions.
Step 3: As CDRs are part of the hypervariable regions, choice A is correct.
Summary: Choices B, C, and D are incorrect because hypervariable regions are not in the constant region, are present in secreted antibodies, and are found in both heavy and light chains.

An HIV-positive patient who has been started on antiretroviral therapy (ART) is seen in the clinic for follow-up. Which test will be most helpful in determining the response to therapy?

  • A. Lymphocyte count
  • B. ELISA testing
  • C. Western blot analysis
  • D. Viral load testing
Correct Answer: D

Rationale: Viral load testing measures the amount of HIV RNA in the blood and is the most direct way to assess the effectiveness of antiretroviral therapy. A decrease in viral load indicates that the therapy is working. The other tests provide useful information but are not as directly related to the effectiveness of ART.

A monoclonal antibody called '3F8' was developed to treat neuroblastoma and was subsequently improved by:

  • A. Making it more specific for neuroblastoma antigens
  • B. Engineering a form that has human rather than mouse variable region protein sequences
  • C. Engineering a form that has human rather than mouse constant region protein sequences
  • D. Two of these responses are correct
Correct Answer: D

Rationale: The correct answer is D. By engineering a form of the antibody with human variable region protein sequences (choice B), it reduces the risk of immune response in patients. Similarly, by engineering a form with human constant region protein sequences (choice C), it further reduces immunogenicity. Therefore, both B and C contribute to making the antibody more suitable for human use, enhancing its efficacy and safety in treating neuroblastoma. Choices A and D are incorrect as they do not address the crucial aspect of reducing immunogenicity through humanization of the antibody.

Which of the following is not a systemic cytokine?

  • A. TNF
  • B. IL-1
  • C. IL-6
  • D. IL-8
Correct Answer: D

Rationale: The correct answer is D: IL-8. IL-8 is not a systemic cytokine because it mainly acts locally at the site of inflammation to recruit neutrophils. Systemic cytokines like TNF, IL-1, and IL-6 have widespread effects throughout the body, influencing various immune responses and inflammatory processes. IL-8's localized action distinguishes it from systemic cytokines, making it the correct choice. TNF, IL-1, and IL-6 are all systemic cytokines that play key roles in regulating the immune response and inflammation at a systemic level, unlike IL-8.

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