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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Which dietary change is most beneficial in reducing the risk of colorectal cancer?
- A. Increased fiber intake
- B. High-fat diet
- C. Reduced carbohydrate consumption
- D. Increased protein intake
Correct Answer: A
Rationale: Increased fiber intake promotes healthy digestion and reduces the risk of colorectal cancer.
A nurse attends a seminar on the immune system and learns about the different lymphocytes in the body. Where do the T lymphocytes originate from and where do they travel to?
- A. Bone marrow and the lymph nodes
- B. Bone marrow and plasma
- C. Bone marrow and spleen
- D. Bone marrow and thymus
Correct Answer: D
Rationale: T lymphocytes originate in the bone marrow and mature in the thymus where they become specialized for immune responses.
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.
The immunoglobulin class which is the least abundant in the normal adult is
- A. IgG
- B. IgA
- C. IgE
- D. IgD
Correct Answer: C
Rationale: The correct answer is C, IgE. IgE is the least abundant immunoglobulin in the normal adult because it is primarily involved in allergic responses and parasitic infections, leading to its lower baseline levels compared to other classes. IgG is the most abundant and provides long-term immunity. IgA is found in mucosal areas and secretions, crucial for local immunity. IgD functions primarily as a B cell receptor and its levels are relatively low in circulation. Therefore, IgE stands out as the least abundant in the normal adult due to its specialized role in immune responses.
Multi-photon microscopy has proved to be an invaluable tool for the evaluation of the dynamics of immune responses in vivo. The following is a list of observations derived from intra-vital microscopy. Identify the incorrect statement.
- A. T cells make stable and prolonged contacts with APC presenting the specific antigen in the paracortex
- B. In the absence of antigens B cells move at the same speed and randomly in follicles
- C. In the presence of infection specific B cells quickly direct themselves towards the source of antigen
- D. Dendritic cells move rapidly through the germinal centre during an immune response
Correct Answer: D
Rationale: The correct answer is D because dendritic cells do not typically move rapidly through the germinal center during an immune response. Dendritic cells usually interact with T cells in the paracortex to present antigens, and they are not known to migrate rapidly through the germinal center.
A: This statement is correct as T cells do make stable and prolonged contacts with APCs in the paracortex during immune responses.
B: This statement is incorrect as B cells do not move at the same speed and randomly in follicles in the absence of antigens. They respond to signals and cues in the microenvironment.
C: This statement is correct as specific B cells can quickly direct themselves towards the source of antigen during an infection.
In summary, choice D is incorrect because dendritic cells do not move rapidly through the germinal center during an immune response, while the other choices accurately describe behaviors of immune cells during immune responses.