Nokea
A patient with acquired immunodeficiency syndrome (AIDS) has a negative tuberculosis (TB) skin test. Which nursing action is indicated next?
- A. Obtain a chest x-ray and sputum smear.
- B. No further action is needed after the negative skin test.
- C. Teach about the anti-tuberculosis drug isoniazid (INH).
- D. Schedule TB testing again in 6 months.
Correct Answer: A
Rationale: A negative TB skin test in an immunocompromised patient such as one with AIDS does not rule out TB infection. Further diagnostic testing such as a chest x-ray and sputum smear is necessary to confirm the absence of TB. Teaching about INH or scheduling another test is premature without further diagnostic confirmation.
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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.
A critical role of secondary lymphoid tissues is to:
- A. Provide a place for B and T lymphocytes to mature and begin expression of antigen receptors
- B. Allow co-localization of the components required to activate naïve lymphocytes
- C. Minimize contact of naïve lymphocytes with self antigens
- D. All of the above
Correct Answer: B
Rationale: Step 1: Secondary lymphoid tissues bring together antigen-presenting cells and lymphocytes, facilitating the activation of naïve lymphocytes.
Step 2: Co-localization of these components is essential for efficient immune response initiation.
Step 3: Maturation and expression of antigen receptors primarily occur in primary lymphoid tissues, not secondary.
Summary:
A: Incorrect. Maturation of lymphocytes occurs mainly in primary lymphoid tissues.
C: Incorrect. Contact with self-antigens is necessary for self-tolerance and occurs in primary lymphoid tissues.
D: Incorrect. Only choice B accurately describes the critical role of secondary lymphoid tissues.
Dendritic cells migrating from tissues enter the lymph nodes through
- A. Thoracic duct
- B. HEV
- C. Afferent lymphatics
- D. Efferent lymphatics
Correct Answer: C
Rationale: The correct answer is C: Afferent lymphatics. Dendritic cells migrate from tissues to lymph nodes through afferent lymphatics, which are small vessels that carry lymph into the lymph nodes. Once inside the lymph nodes, dendritic cells interact with T cells to initiate immune responses. The thoracic duct (A) drains lymph from the entire body into the bloodstream, not directly into lymph nodes. High endothelial venules (HEV) (B) are specialized blood vessels in lymph nodes where lymphocytes enter from the bloodstream, not dendritic cells. Efferent lymphatics (D) carry lymph out of the lymph nodes, not into them.
Select the wrong statement concerning TLR4
- A. TLR4 is expressed on dendritic cells and macrophages
- B. It represents an example of a phagocytic receptor
- C. It is expressed on the membrane in complex with a protein called MD2
- D. Mice resistant to endotoxic shock harbor a mutation of TLR4
Correct Answer: B
Rationale: The correct answer is B because TLR4 is not a phagocytic receptor, but rather a pattern recognition receptor involved in recognizing pathogen-associated molecular patterns (PAMPs).
A: Correct, TLR4 is expressed on dendritic cells and macrophages.
C: Correct, TLR4 is expressed on the membrane in complex with MD2.
D: Correct, mice resistant to endotoxic shock have a mutation in TLR4, indicating its role in the immune response to endotoxins.
What is the function of IgA?
- A. Allergy mediation
- B. Placental transfer
- C. Mucosal immunity
- D. Primary response
Correct Answer: C
Rationale: The correct answer is C: Mucosal immunity. IgA plays a crucial role in protecting mucosal surfaces, such as the lining of the gut and respiratory tract, from pathogens. It helps prevent infections by neutralizing and blocking the entry of harmful substances. IgA is not involved in allergy mediation (choice A), placental transfer (choice B), or primary response (choice D), as those functions are typically associated with other types of antibodies. IgA's specificity for mucosal surfaces makes it uniquely suited for providing defense at these vulnerable sites.