Nokea
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.
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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.
The clonal selection theory explains:
- A. That one given lymphocyte expresses multiple antigen receptors with different specificity
- B. That antigens influence the generation of antigen receptors during lymphocyte development
- C. How the immune response to an antigen increases the number of lymphocytes specific for that antigen
- D. The increase in blood neutrophils observed during bacterial infections
Correct Answer: C
Rationale: Rationale:
1. Clonal selection theory states that specific lymphocytes are activated by antigens.
2. Upon activation, these lymphocytes proliferate to form a clone of cells specific to the antigen.
3. This increases the number of lymphocytes specific for the antigen.
4. Choice C correctly aligns with the essence of clonal selection theory.
Summary:
A: Incorrect - Clonal selection theory does not involve a single lymphocyte expressing multiple antigen receptors.
B: Incorrect - Antigens do not influence the generation of antigen receptors, but rather activate specific lymphocytes.
D: Incorrect - Clonal selection theory focuses on lymphocyte response to antigens, not neutrophil increase during infections.
During an adaptive immune response to a pathogen an important outcome of the clonal selection process is:
- A. An increase in the number of lymphocytes specific for the pathogen that activated the response
- B. Elimination of lymphocytes that are not specific for the pathogen that activated the response
- C. An increase in the number of antigen receptor specificities expressed by each lymphocyte
- D. All of the above
Correct Answer: A
Rationale: The correct answer is A because during clonal selection, lymphocytes specific to the pathogen are activated, leading to their proliferation and differentiation into effector cells. This results in an increase in the number of lymphocytes specific for the pathogen, enhancing the immune response.
Choice B is incorrect because clonal selection does not involve the elimination of non-specific lymphocytes but rather the expansion of specific lymphocytes.
Choice C is also incorrect because clonal selection does not change the antigen receptor specificities expressed by lymphocytes but instead focuses on expanding the population of lymphocytes with receptors specific to the pathogen.
Therefore, the correct outcome of clonal selection is the increase in the number of lymphocytes specific for the pathogen that activated the response, making choice A the most accurate option.
Why must clients,who will undergo diagnostic skin tests,avoid taking antihistamine or cold preparations for at least 48 to 72 hours before testing?
- A. Antihistamines may increase the potential for excessive bleeding.
- B. Antihistamines may aggravate the allergic reaction.
- C. Antihistamines may increase the potential for false-negative test results.
- D. Antihistamines may cause wheezing.
Correct Answer: C
Rationale: Antihistamines can suppress the allergic response,leading to false-negative results in skin tests.
Which organ is most commonly affected in sarcoidosis?
- A. Kidney
- B. Lungs
- C. Liver
- D. Thyroid
Correct Answer: B
Rationale: The correct answer is B: Lungs. Sarcoidosis is a systemic inflammatory disease that primarily affects the lungs in about 90% of cases. This is due to the formation of granulomas, inflammatory nodules, in the lung tissue. Kidney (A), Liver (C), and Thyroid (D) are less commonly affected organs in sarcoidosis. Kidney involvement occurs in about 20-30% of cases, liver involvement in about 10-30% of cases, and thyroid involvement is relatively rare. Therefore, based on the prevalence of organ involvement in sarcoidosis, the lungs are the most commonly affected organ.