What determines a cell's response to a specific cytokine?

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: 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.

Correct Answer: C

Rationale: The correct answer is C: Recruitment and activation of immune cells. C5a is a potent chemoattractant that attracts immune cells to the site of infection or inflammation. It also activates these immune cells, leading to enhanced immune responses. Option A (Opsonization) and B (Cell lysis) are not the main functions of C5a. Option D (Inhibition of inflammation) is incorrect because C5a actually promotes inflammation by recruiting and activating immune cells.

Correct Answer: B

Rationale: The correct answer is B because cytokines act as signaling molecules to coordinate immune responses in innate immunity. They help regulate inflammation, activate immune cells, and promote clearance of pathogens. Option A is incorrect because cytokines do not directly kill pathogens. Option C is incorrect as cytokines play a crucial role in both innate and adaptive immunity. Option D is incorrect because cytokines do not inhibit phagocytosis; instead, they enhance this process to help eliminate pathogens.

Correct Answer: B

Rationale: The correct answer is B because Toll-like receptors (TLRs) recognize common molecular patterns shared by groups of microbes, allowing for rapid detection of a wide range of pathogens. This recognition triggers immune responses without the need for prior exposure to the specific pathogen. The other choices are incorrect because: A: TLRs are not highly specific to individual pathogens but rather recognize common patterns. C: TLRs do not directly activate B cell antibody production; they initiate immune responses by activating various immune cells. D: TLRs do not require antigen presentation to function; they directly recognize microbial patterns.