Which scientist is credited with introducing the germ theory of disease?

Correct Answer: A

Rationale: Louis Pasteur is credited with introducing the germ theory of disease. He conducted experiments that demonstrated the role of microorganisms in causing infections. He also developed pasteurization to kill harmful bacteria in food and beverages. Edward Jenner is known for developing the smallpox vaccine, not the germ theory. Elie Metchnikoff studied the immune system and phagocytosis. Paul Ehrlich is known for his work on chemotherapy and the concept of the "magic bullet," targeting specific pathogens.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: The primary trigger for NK cell activation is the lack of normal self-surface structures. NK cells are part of the innate immune system and recognize cells with altered or missing self-antigens. This triggers their activation to eliminate these abnormal cells. Presence of PAMPs (A) activates other immune cells like macrophages. High levels of complement proteins (C) activate the complement cascade but do not directly trigger NK cell activation. Antigen presentation by dendritic cells (D) activates adaptive immune responses through T cells, not NK cells. Therefore, the correct answer is B as it directly relates to NK cell function.

Correct Answer: C

Rationale: The correct answer is C: C5b. The Membrane Attack Complex (MAC) is formed by a sequence of complement proteins, with C5b playing a crucial role as the initiator. After C5b binds to the target cell membrane, it triggers the assembly of C6, C7, C8, and multiple C9 molecules to form the MAC pore. C1 (A) is the initiator of the classical pathway, not a component of the MAC. C3 (B) is involved in the formation of the C3 convertase and opsonization but is not the main component of the MAC. C4b (D) is part of the classical pathway and is involved in the formation of the C3 convertase, not the MAC.

Correct Answer: C

Rationale: The correct answer is C because innate immunity plays a crucial role in initiating and influencing adaptive immunity. Innate immunity activates and stimulates adaptive immune responses by recognizing pathogens and initiating the adaptive immune system to produce specific responses. This relationship is essential for the body's overall immune defense. Choice A is incorrect because innate immunity does not suppress adaptive immunity; instead, they work together synergistically. Choice B is incorrect because adaptive immunity does not enhance innate immune functions, but rather complements them. Choice D is incorrect because innate and adaptive immunity are interconnected and work together to provide comprehensive immune protection.