Nokea
After engagement of its pattern recognition receptors what happens to a dendritic cell to enable its role in naïve T cell activation?
- A. Expression of MHC class I molecules begins
- B. Increased uptake of antigens
- C. Expression of the B7 molecule
- D. PAMP-induced proliferation
Correct Answer: C
Rationale: After engagement of pattern recognition receptors, dendritic cells upregulate expression of the B7 molecule, which is essential for co-stimulation of naïve T cells. This step is crucial for activating T cells. MHC class I molecules present antigens to CD8+ T cells, not CD4+ T cells, so choice A is incorrect. Dendritic cells already have high antigen uptake ability, so choice B is not directly related to activation. PAMP-induced proliferation is not a typical response of dendritic cells after pattern recognition receptor engagement, making choice D incorrect.
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What happens when immune complexes are not cleared in Type III hypersensitivity?
- A. They activate T cells
- B. They deposit in tissues, causing inflammation
- C. They are phagocytosed by macrophages without effects
- D. They suppress antibody production
Correct Answer: B
Rationale: The correct answer is B because when immune complexes are not cleared in Type III hypersensitivity, they deposit in tissues, activating complement cascades and causing inflammation. This leads to tissue damage and the recruitment of inflammatory cells.
A: Immune complexes do not directly activate T cells in Type III hypersensitivity.
C: Phagocytosis of immune complexes can lead to cell activation and inflammation.
D: Immune complexes do not suppress antibody production in Type III hypersensitivity.
What are examples of type I or IgE-mediated hypersensitivity reactions (select all that apply)?
- A. Asthma
- B. Urticaria
- C. Angioedema
- D. Allergic rhinitis
Correct Answer: A
Rationale: Type I hypersensitivity reactions involve IgE-mediated responses, including asthma, urticaria, angioedema, and allergic rhinitis.
If the BCR of a developing cell has no binding affinity for self-antigens in the bone marrow the B cell will be:
- A. Clonally deleted
- B. Anergized
- C. A possible cause of autoimmunity in the periphery
- D. Allowed to mature and enter the periphery
Correct Answer: D
Rationale: The correct answer is D: Allowed to mature and enter the periphery. In this scenario, since the developing B cell has no binding affinity for self-antigens in the bone marrow, it will not undergo clonal deletion or anergy. Therefore, it will be allowed to mature and enter the periphery where it can encounter foreign antigens and participate in the immune response. Choices A and B are incorrect because clonal deletion and anergy are mechanisms used to eliminate or inactivate self-reactive B cells to prevent autoimmunity. Choice C is incorrect because a B cell without self-binding affinity is not a cause of autoimmunity in the periphery.
Thymocytes undergoing positive selection express:
- A. TCR
- B. CD4
- C. CD8
- D. All of the above
Correct Answer: D
Rationale: Thymocytes undergoing positive selection express both CD4 and CD8 co-receptors along with a functional T-cell receptor (TCR). CD4 and CD8 help in recognizing MHC molecules, while TCR is crucial for antigen recognition. Positive selection ensures that thymocytes with a functional TCR that can interact with self-MHC molecules survive. Therefore, the correct answer is D, as thymocytes undergoing positive selection express TCR, CD4, and CD8. Choice A, TCR alone, is incorrect as CD4 and CD8 are also expressed. Choices B and C are incorrect as positive selection involves the expression of both CD4 and CD8, not just one or the other.
Anemia
- A. cancer of white blood cells
- B. results in extra leukocytes that do not function properly
- C. is usually fatal unless treated
- D. Abnormally low amounts of hemoglobin or red blood cells
Correct Answer: D
Rationale: The correct answer is D because anemia is defined as having abnormally low amounts of hemoglobin or red blood cells, leading to reduced oxygen-carrying capacity. This results in symptoms such as fatigue and weakness. Choice A is incorrect because anemia is not related to cancer of white blood cells. Choice B is incorrect as anemia does not result in extra leukocytes; rather, it leads to a decrease in red blood cells. Choice C is incorrect as anemia is not usually fatal if treated promptly and effectively.