Nokea
What distinguishes NK cells from other lymphocytes?
- A. They are part of adaptive immunity
- B. They do not require prior antigen sensitization
- C. They directly produce antibodies
- D. They phagocytose pathogens
Correct Answer: B
Rationale: The correct answer is B because NK cells do not require prior antigen sensitization to recognize and attack infected cells. This distinguishes them from other lymphocytes, such as T and B cells, which are part of adaptive immunity and require prior exposure to specific antigens. NK cells are part of innate immunity and can directly recognize and kill infected or abnormal cells without prior activation. Choices A, C, and D are incorrect as NK cells are not part of adaptive immunity, do not directly produce antibodies, and do not phagocytose pathogens.
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What is the primary cause of anaphylaxis?
- A. Immune complex deposition
- B. Systemic release of vasoactive mediators
- C. Localized mast cell degranulation
- D. T cell activation
Correct Answer: B
Rationale: The correct answer is B: Systemic release of vasoactive mediators. Anaphylaxis is a severe allergic reaction that is primarily caused by the systemic release of vasoactive mediators such as histamine, prostaglandins, and leukotrienes from mast cells and basophils. These mediators lead to widespread vasodilation, increased vascular permeability, bronchoconstriction, and systemic hypotension, resulting in the characteristic symptoms of anaphylaxis.
Choice A (Immune complex deposition) is incorrect because anaphylaxis is not caused by the deposition of immune complexes but rather by the immediate hypersensitivity reaction.
Choice C (Localized mast cell degranulation) is incorrect because anaphylaxis involves systemic mast cell degranulation leading to widespread effects throughout the body, not just localized reactions.
Choice D (T cell activation) is incorrect because anaphylaxis is primarily mediated by IgE antibodies and mast cells, not T cells.
Which of the following is not a function of the immune system?
- A. Protecting the body from foreign substances
- B. Producing hormones
- C. Repairing damaged tissues
- D. All of the above are functions of the immune system
Correct Answer: B
Rationale: The correct answer is B: Producing hormones. The immune system's main functions are to protect the body from foreign substances and repair damaged tissues. Producing hormones is not a direct function of the immune system. Hormone production is primarily regulated by the endocrine system, not the immune system. Therefore, option B is not a function of the immune system. Options A and C are incorrect as protecting the body from foreign substances and repairing damaged tissues are essential roles of the immune system. Option D is incorrect because not all functions listed are actually performed by the immune system.
Plaques are:
- A. clear areas in a lawn of cultured cells caused by virus infection.
- B. stained areas in a cell culture indicating cells infected by a virus.
- C. virus colonies on agar.
- D. bacterial colonies on agar.
Correct Answer: A
Rationale: Plaques are clear areas caused by virus infection in a lawn of cultured cells. This is because viruses infect cells, causing cell death and lysis, which results in clear areas. Choice B is incorrect because stained areas are not typically associated with plaques. Choices C and D are also incorrect as they refer to virus and bacterial colonies, respectively, not plaques.
Tolerogenic dendritic cells
- A. Induce T cell unresponsiveness
- B. Do not secrete IL-12
- C. Express high levels of co-stimulatory molecules
- D. Have recognized PAMPs
Correct Answer: E
Rationale: I apologize, but it seems like there was a mistake in the question. The correct answer is not provided as choice "E." Could you please provide the correct choices for the question so I can provide you with the detailed explanation you are looking for?
Which of the following are not examples of a terminal electron acceptor in anaerobic respiration?
- A. nitrate
- B. hydrogen sulfate
- C. iron hydroxide
- D. Hâ‚‚
Correct Answer: D
Rationale: The correct answer is D: H₂. In anaerobic respiration, H₂ can act as a terminal electron acceptor, so it is not an incorrect example. Nitrate, hydrogen sulfate, and iron hydroxide are all examples of terminal electron acceptors in anaerobic respiration. H₂ is commonly used in microbial processes as an electron donor, not as a terminal electron acceptor. This is because H₂ is typically oxidized to produce energy, rather than accepting electrons.