Nokea
What role do Toll-like receptors (TLRs) play in the immune response?
- A. They identify self-antigens
- B. They mediate phagocytosis directly
- C. They recognize pathogen-associated molecular patterns
- D. They suppress cytokine secretion
Correct Answer: C
Rationale: The correct answer is C because Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens, initiating the immune response. This recognition triggers the production of cytokines and chemokines, leading to inflammation and activation of immune cells. Choice A is incorrect because TLRs do not identify self-antigens but rather foreign antigens. Choice B is incorrect as TLRs do not directly mediate phagocytosis but rather initiate signaling pathways that lead to phagocytosis by immune cells. Choice D is incorrect because TLRs do not suppress cytokine secretion; rather, they stimulate cytokine production.
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A patient’s breast tumor originates from embryonal ectoderm. It has moderate dysplasia and moderately differentiated cells. It is a small tumor with minimal lymph node involvement and no metastases. What is the best description of this tumor?
- A. Sarcoma,grade II,T3 N4 M0
- B. Leukemia,grade I,T1 N2 M1
- C. Carcinoma,grade II,T1 N1 M0
- D. Lymphoma,grade III,T1 N0 M
Correct Answer: C
Rationale: This tumor is classified as a carcinoma, grade II, with a small size, limited lymph node involvement, and no metastases.
Which of the following statements is most correct?
- A. MHC class I proteins typically bind to peptides from proteins taken up from outside the cell, and present these to CD8+ Tc cells
- B. MHC class I proteins typically bind to peptides from proteins made inside the cell, and present these to CD8+ Tc cells
- C. MHC class I proteins typically bind to peptides from proteins made inside the cell, and present these to CD4+ Th cells
- D. MHC class I proteins typically bind to peptides from proteins taken up from outside the cell, and present these to CD4+ Th cells
Correct Answer: B
Rationale: The correct answer is B. MHC class I proteins bind to peptides from proteins made inside the cell and present them to CD8+ Tc cells. This statement is correct because MHC class I proteins are responsible for presenting endogenous peptides, derived from proteins synthesized within the cell, to CD8+ Tc cells for immune surveillance and response.
Explanation for why other choices are incorrect:
- A is incorrect because MHC class I proteins present endogenous peptides, not peptides from proteins taken up from outside the cell.
- C is incorrect because MHC class I proteins present antigens to CD8+ Tc cells, not CD4+ Th cells.
- D is incorrect because MHC class I proteins present peptides to CD8+ Tc cells, not CD4+ Th cells.
Avian Influenza has not so far caused a human pandemic because
- A. Avian flu causes only mild infection in humans compared to birds
- B. Avian flu recognizes a variant of sialic acid found only on avian cells
- C. Avian flu recognizes a variant of sialic acid only found deep in the lung tissue of humans, not in the upper airways
- D. H5N1 is included in the composition of the annual trivalent inactivated vaccine
Correct Answer: C
Rationale: The correct answer is C because avian flu recognizing a variant of sialic acid only found deep in the lung tissue of humans, not in the upper airways explains why it has not caused a human pandemic. This specificity limits human-to-human transmission as the virus cannot efficiently attach in the upper airways where respiratory droplets are expelled. Choices A and B are incorrect because avian flu can cause severe infections in humans and recognizes a variant of sialic acid found in both birds and humans, not just avian cells. Choice D is incorrect as the presence of H5N1 in the annual trivalent vaccine does not prevent human pandemic potential.
What disease is associated with autoantibodies binding to type IV collagen?
- A. Sarcoidosis
- B. Goodpasture's syndrome
- C. Systemic lupus erythematosus (SLE)
- D. Rheumatoid arthritis
Correct Answer: B
Rationale: The correct answer is B: Goodpasture's syndrome. This disease is specifically associated with autoantibodies targeting type IV collagen in the basement membranes of the kidneys and lungs, leading to glomerulonephritis and pulmonary hemorrhage. Sarcoidosis (A) involves non-caseating granulomas, not collagen autoantibodies. Systemic lupus erythematosus (SLE) (C) is associated with various autoantibodies but not specifically targeting type IV collagen. Rheumatoid arthritis (D) is characterized by autoantibodies against citrullinated peptides and synovial tissue, not type IV collagen.
An HIV-positive patient who has been started on antiretroviral therapy (ART) is seen in the clinic for follow-up. Which test will be most helpful in determining the response to therapy?
- A. Lymphocyte count
- B. ELISA testing
- C. Western blot analysis
- D. Viral load testing
Correct Answer: D
Rationale: Viral load testing measures the amount of HIV RNA in the blood and is the most direct way to assess the effectiveness of antiretroviral therapy. A decrease in viral load indicates that the therapy is working. The other tests provide useful information but are not as directly related to the effectiveness of ART.