Which pathway in the complement system is activated by immune complexes containing IgG or IgM?

Correct Answer: B

Rationale: The correct answer is B: Classical pathway. This pathway is activated by immune complexes containing IgG or IgM. When these antibodies bind to antigens, they trigger the classical pathway by forming a complex that activates C1q, initiating a cascade of reactions leading to inflammation and opsonization. The alternative pathway (A) is activated by microbial surfaces, while the lectin pathway (C) is activated by mannose-binding lectin binding to carbohydrates on pathogens. The terminal pathway (D) involves the formation of the membrane attack complex.

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 because NK cells do not require prior antigen sensitization to recognize and attack infected cells. This distinguishes them from other lymphocytes, such as T and B cells, which are part of adaptive immunity and require prior exposure to specific antigens. NK cells are part of innate immunity and can directly recognize and kill infected or abnormal cells without prior activation. Choices A, C, and D are incorrect as NK cells are not part of adaptive immunity, do not directly produce antibodies, and do not phagocytose pathogens.

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.