Which of the following statements about the 2009 H1N1 pandemic is NOT true

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: 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.

Correct Answer: C

Rationale: The correct answer is C because a cell's response to a specific cytokine is determined by the specific cytokine receptors expressed on the cell. Cytokine receptors are proteins on the cell surface that bind to specific cytokines, triggering intracellular signaling pathways that lead to various cellular responses. The amount of antigen present (A) is related to the initiation of the immune response but not the cell's response to cytokines. The type of pathogen encountered (B) may influence the overall immune response but not the specific response to cytokines. The tissue location of the immune cell (D) can affect the types of cytokines present in the microenvironment but does not directly determine the cell's response to a specific cytokine.

Correct Answer: B

Rationale: The correct answer is B because innate immunity instructs and activates adaptive immunity. Innate immunity serves as the first line of defense against pathogens, recognizing and initiating a response to pathogens. It then communicates with adaptive immunity, providing signals and antigens to activate and guide the adaptive immune response. This collaboration is crucial for the effective elimination of pathogens. Choices A, C, and D are incorrect because innate immunity does not suppress, replace, or function independently of adaptive immunity; rather, they work together in a coordinated manner to provide a comprehensive immune response.