The earliest event of an inflammatory response is

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: 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.

Correct Answer: B

Rationale: Rationale: C1q is a component of the classical complement pathway, crucial for immune complex clearance. Its deficiency is associated with SLE due to impaired immune complex removal, leading to autoantibody deposition and inflammation. Cancer, HIV/AIDS, and COPD are not directly linked to C1q deficiency.