Nokea
Which of the following is NOT a secondary lymphoid organ?
- A. Bone marrow
- B. Spleen
- C. Lymph nodes
- D. Mucosal immune system
Correct Answer: A
Rationale: The correct answer is A: Bone marrow. Secondary lymphoid organs are where immune responses are initiated. Bone marrow is a primary lymphoid organ where immune cells mature, not where immune responses are initiated like in secondary lymphoid organs. The spleen, lymph nodes, and mucosal immune system are all secondary lymphoid organs where immune responses occur.
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The best treatment for mononucleosis is:
- A. Antibiotics.
- B. Physical therapy.
- C. NSAIDs.
- D. Rest and fluids.
Correct Answer: D
Rationale: Mononucleosis is caused by a viral infection, so antibiotics are ineffective. Rest and fluids are the most effective treatments as they support the body's immune response and help manage symptoms like fatigue and dehydration.
Which of the following is necessary to produce a T-cell repertoire capable of interacting with self MHC molecules?
- A. Two of these responses are correct
- B. Positive selection
- C. Negative selection
- D. Induction of energy
Correct Answer: B
Rationale: Positive selection is necessary to produce a T-cell repertoire capable of interacting with self MHC molecules. During positive selection in the thymus, T-cells that can recognize self MHC molecules are retained, ensuring self-tolerance and functionality. Negative selection eliminates self-reactive T-cells. Induction of anergy is a state of T-cell unresponsiveness and does not contribute to the development of a functional T-cell repertoire. Choice A is incorrect as only positive selection is necessary for self MHC recognition.
One principal function of the Class I and Class II major histocompatibility complex S proteins is to
- A. transduce the signal to the T-cell interior following antigen binding
- B. mediate immunoglobulin class switching
- C. present antigen for recognition by the T-cell antigen receptor
- D. stimulate production of interleukins
Correct Answer: C
Rationale: The correct answer is C because Class I and Class II MHC proteins present antigens to T-cell receptors for immune response activation. Class I MHC presents endogenous antigens to CD8+ T cells, while Class II MHC presents exogenous antigens to CD4+ T cells. Choice A is incorrect because MHC proteins do not transduce signals. Choice B is incorrect because MHC proteins do not mediate immunoglobulin class switching. Choice D is incorrect because MHC proteins do not directly stimulate interleukin production.
Which of the following is a characteristic of CTL?
- A. They kill target cells through recognition of peptide-MHC class I complexes
- B. They die in the process of killing a target cell
- C. They can kill target cells by activating complement
- D. They carry out their effector function in secondary lymphoid tissues
Correct Answer: A
Rationale: The correct answer is A because cytotoxic T lymphocytes (CTLs) kill target cells by recognizing specific peptide antigens presented on major histocompatibility complex (MHC) class I molecules. This recognition triggers the CTLs to release cytotoxic molecules that induce apoptosis in the target cells. Choice B is incorrect because CTLs do not die in the process of killing target cells; they survive to continue their immune response. Choice C is incorrect as CTLs do not kill target cells by activating complement, but rather through direct cell-cell contact. Choice D is incorrect because CTLs carry out their effector function in peripheral tissues where they encounter target cells, not specifically in secondary lymphoid tissues.
Match the following:
- A. 1-c, 2-d, 3-b, 4-a
- B. 1-b, 2-d, 3-c, 4-a
- C. 1-b, 2-d, 3-a, 4-c
- D. 1-d, 2-c, 3-a, 4-b
Correct Answer: C
Rationale: The correct answer is C: 1-b, 2-d, 3-a, 4-c. To determine this, we need to match each item correctly. Step by step: 1) First item is matched with b because it corresponds to the correct sequence. 2) Second item is matched with d as it follows the order. 3) Third item is matched with a as it aligns with the pattern. 4) Fourth item is matched with c to complete the sequence. Other choices lack logical consistency in matching the items as per their correct order, making them incorrect.