Nokea
The mucociliary escalator protects
- A. The gut
- B. The skin
- C. The respiratory tract
- D. All of the above sites
Correct Answer: C
Rationale: The mucociliary escalator is a defense mechanism in the respiratory tract that traps and removes inhaled particles and pathogens by using cilia to move mucus out of the lungs. This helps to prevent infections and maintain lung health. Choices A and B are incorrect because the mucociliary escalator specifically functions in the respiratory tract, not the gut or skin. Choice D is incorrect because the mucociliary escalator does not protect all of the mentioned sites, only the respiratory tract.
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What are the important functions of cell-mediated immunity (select all that apply)?
- A. Fungal infections
- B. Transfusion reactions
- C. Rejection of transplanted tissues
- D. Immunity against pathogens that survive outside cells
Correct Answer: A
Rationale: Cell-mediated immunity targets intracellular pathogens, such as viruses and fungi, and is critical in transplant rejection and certain hypersensitivity reactions.
What underpins most functions of the immune system?
- A. Secondary lymphoid tissues
- B. Haematopoietic stem cells in the bone marrow
- C. Mucosal immune system activity
- D. Rapid cytokine suppression
Correct Answer: B
Rationale: The correct answer is B: Haematopoietic stem cells in the bone marrow. These cells are responsible for generating all immune cells, including lymphocytes, macrophages, and dendritic cells. They continuously replenish the immune system, allowing for proper immune function. Secondary lymphoid tissues (choice A) play a role in immune responses but are not the primary underpinning. Mucosal immune system activity (choice C) is important for defense at mucosal surfaces but is not the foundation of immune function. Rapid cytokine suppression (choice D) is a regulatory mechanism, not the fundamental basis of immune system functions.
What role do Toll-like receptors (TLRs) play in the immune response?
- A. They identify self-antigens
- B. They mediate phagocytosis directly
- C. They recognize pathogen-associated molecular patterns
- D. They suppress cytokine secretion
Correct Answer: C
Rationale: The correct answer is C because Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens, initiating the immune response. This recognition triggers the production of cytokines and chemokines, leading to inflammation and activation of immune cells. Choice A is incorrect because TLRs do not identify self-antigens but rather foreign antigens. Choice B is incorrect as TLRs do not directly mediate phagocytosis but rather initiate signaling pathways that lead to phagocytosis by immune cells. Choice D is incorrect because TLRs do not suppress cytokine secretion; rather, they stimulate cytokine production.
When comparing the types of viruses that infect bacteria, plants, and vertebrate animals, what trends appear from bacterial to vertebrate viral groups?
- A. Less complex-type forms
- B. more enveloped forms
- C. fewer enveloped forms
- D. same number of DNA-containing forms
Correct Answer: B
Rationale: The correct answer is B: more enveloped forms. This trend can be explained by the complexity of host organisms. Bacteria have simple cell structures, making enveloped viruses less common. As we move from bacteria to plants and vertebrate animals, the complexity of host cells increases, leading to a higher prevalence of enveloped viruses. This trend is due to the need for enveloped viruses to evade the host's immune system and facilitate entry into host cells. Choices A, C, and D are incorrect because they do not consider the relationship between virus structure and host complexity.
Which of the following processes does not require the involvement of an antigen-specific T helper cell?
- A. Somatic hypermutation
- B. VDJ gene rearrangement
- C. Immunoglobulin class switching
- D. Memory cell differentiation
Correct Answer: B
Rationale: Correct Answer: B (VDJ gene rearrangement)
Rationale:
1. VDJ gene rearrangement occurs during B cell development in the bone marrow, independent of T helper cells.
2. Somatic hypermutation and immunoglobulin class switching require T helper cell interactions.
3. Memory cell differentiation also involves T helper cells for activation and differentiation.
4. Therefore, VDJ gene rearrangement is the only process not directly dependent on antigen-specific T helper cells.