Which of the following statements is false about dendritic cells

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: 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.

Correct Answer: B

Rationale: The Black Death caused by Yersinia pestis is the correct answer because it led to immune adaptation in survivors. Yersinia pestis triggered the body to develop immunity. The Spanish flu pandemic, HIV/AIDS epidemic, and eradication of smallpox did not directly result in immune adaptation like the Black Death. The Spanish flu and HIV/AIDS were caused by viruses that did not lead to long-term immunity, and smallpox eradication was achieved through vaccinations, not natural immune adaptation.

Correct Answer: B

Rationale: Haematopoietic stem cells are responsible for producing immune cells. These stem cells differentiate into various types of blood cells, including white blood cells that play a crucial role in the immune system. They do not differentiate into lymph nodes (A), generate cytokines (C), or suppress pathogens directly (D). The correct answer (B) aligns with the primary function of haematopoietic stem cells in the production of immune cells.