What is the primary mechanism by which innate immunity differentiates between self and non-self?

Correct Answer: B

Rationale: The correct answer is B: Recognition of PAMPs via PRRs. Innate immunity distinguishes self from non-self by recognizing Pathogen-Associated Molecular Patterns (PAMPs) via Pattern Recognition Receptors (PRRs). This recognition triggers an immediate response to eliminate potential threats. Choices A, C, and D are incorrect because somatic recombination is a process in adaptive immunity, MHC molecules present antigens for recognition by T cells in adaptive immunity, and antibody production is part of adaptive immunity involving B cells.

Correct Answer: B

Rationale: The correct answer is B: Dendritic cells. Dendritic cells are antigen-presenting cells that bridge the innate and adaptive immune responses by capturing and presenting antigens to T cells, thus initiating the adaptive immune response. They are crucial for activating T cells and initiating specific immune responses. A: B cells are responsible for antibody production in the adaptive immune response, not for linking innate and adaptive immunity. C: Eosinophils are primarily involved in parasitic infections and allergic reactions, not in linking innate and adaptive immunity. D: NK cells are part of the innate immune system and are involved in detecting and killing infected cells, but they do not directly link innate and adaptive immunity.

Correct Answer: B

Rationale: The correct answer is B: IL-10. Regulatory T cells produce IL-10 to suppress immune responses by inhibiting the activation and function of other immune cells. IL-2 (A) is mainly produced by activated T cells to promote proliferation. IFN-gamma (C) is produced by T cells and NK cells to enhance immune response. TNF-alpha (D) is produced by macrophages and T cells to induce inflammation. IL-10 stands out as the suppressor cytokine in this context.

Correct Answer: B

Rationale: The correct answer is B because adaptive immunity involves memory, meaning the immune system can recognize and respond more effectively to specific antigens upon subsequent exposure. This high antigen specificity allows for tailored responses to different pathogens. In contrast, innate immunity lacks memory and specificity, providing only a rapid but non-specific response to a wide range of pathogens. Choices A, C, and D are incorrect because they do not adequately capture the key distinguishing features of adaptive immunity.

Correct Answer: A

Rationale: The correct answer is A: Two heavy chains and two light chains. Antibodies are composed of two identical heavy chains and two identical light chains. Heavy chains provide structural support and effector functions, while light chains contribute to antigen binding. Choice B is incorrect as antibodies do not have three heavy chains. Choice C is incorrect as antibodies do not have three light chains. Choice D is incorrect as antibodies do not have four heavy chains.