Which vitamin is essential in treating osteoporosis?

Correct Answer: B

Rationale: The correct answer is B: Vitamin D. Vitamin D is essential in treating osteoporosis because it helps the body absorb calcium, a crucial mineral for bone health. Without sufficient Vitamin D, the body cannot effectively utilize calcium, leading to weakened bones. Vitamin A (Choice A) is not directly linked to osteoporosis treatment. Vitamin B12 (Choice C) is important for red blood cell production but not specifically for osteoporosis. Vitamin C (Choice D) aids in collagen formation but does not play a primary role in treating osteoporosis.

Correct Answer: B

Rationale: The correct answer is B because dendritic cells are not only found in lymph nodes but also in tissues. These cells are antigen-presenting cells that capture and present antigens to T cells. A, C, and D are true statements about dendritic cells: A) They are found in tissues, C) They express high levels of MHC molecules for antigen presentation, and D) They are best at activating naive T cells due to their ability to prime adaptive immune responses.

Correct Answer: C

Rationale: The correct answer is C because memory T cells have a lower threshold of activation than naïve T cells. This is because memory T cells have already been primed by previous exposure to antigens, making them more responsive upon re-exposure. This heightened sensitivity allows memory T cells to mount a faster and stronger immune response upon encountering the same antigen again. Choice A is incorrect because memory T cells primarily reside in peripheral tissues and not in secondary lymphoid tissues. Choice B is incorrect because memory T cells have encountered antigens before. Choice D is incorrect because memory T cells exist in a lower frequency compared to naïve T cells due to clonal expansion during the primary immune response.

Correct Answer: B

Rationale: The correct answer is B. Individuals over 60 were not especially affected by the 2009 H1N1 pandemic. This is because older individuals had some level of immunity due to previous exposure to similar strains. The other choices are incorrect because: A: The 2009 H1N1 virus originated from a combination of 2 different strains, not 4. C: WHO declared a level 6 pandemic phase in June 2009. D: The 2009 H1N1 virus was considered less virulent compared to other strains.

Correct Answer: D

Rationale: The correct answer is D: Activation of TLRs. The earliest event in an inflammatory response is the activation of Toll-like receptors (TLRs) by recognizing pathogen-associated molecular patterns (PAMPs). This triggers a signaling cascade leading to the release of pro-inflammatory cytokines and chemokines, which then recruit neutrophils to the site of infection. Activation of adaptive immunity (choice C) occurs later in the immune response, as it involves the activation of T and B cells. While chemokines (choice A) are involved in recruiting immune cells, their release is a consequence of TLR activation. Neutrophils (choice B) are recruited after the release of chemokines.