What is Louis Pasteur's main contribution to immunology?

Correct Answer: C

Rationale: Louis Pasteur's main contribution to immunology is the germ theory of disease and vaccine development. Firstly, Pasteur's germ theory revolutionized our understanding of infectious diseases by demonstrating that microorganisms are the cause. Secondly, he developed the concept of vaccination by creating vaccines for diseases such as rabies and anthrax, laying the foundation for modern immunology. The other choices are incorrect because: A: Pasteur worked on the rabies vaccine, not the smallpox vaccine. B: Phagocytosis was discovered by Metchnikoff, not Pasteur. D: Pasteur did not propose the theory of innate immunity.

Correct Answer: B

Rationale: Neutrophils play a crucial role in the immune response by engulfing and destroying pathogens through a process called phagocytosis. This is essential for eliminating harmful invaders from the body. Neutrophils do not produce antibodies (choice A), activate lymphocytes (choice C), or synthesize cytokines (choice D), which are functions typically carried out by other immune cells like B cells and macrophages. Therefore, the correct answer is B as it directly aligns with the primary function of neutrophils in the immune response, which is to combat infections by destroying pathogens.

Correct Answer: C

Rationale: Pattern recognition in innate immunity, as proposed by Janeway, involves identifying common pathogen-associated molecular patterns (PAMPs). This is crucial for initiating the immune response against pathogens. PAMPs are specific molecular patterns found on pathogens but not on host cells. By recognizing these patterns, the innate immune system can quickly and effectively identify potential threats and trigger the appropriate immune response. Explanation of why other choices are incorrect: A: Specific recognition of antigens is a function of adaptive immunity, not innate immunity. B: Binding toxins to create immunity is not the primary role of pattern recognition in innate immunity. D: Suppressing lymphocyte activation is not the role of pattern recognition in innate immunity; rather, it is involved in activating immune responses against pathogens.

Correct Answer: C

Rationale: The main function of the Membrane Attack Complex (MAC) is to lyse pathogens by creating pores in their cell membranes. First, MAC assembles on the pathogen's surface. Then, it forms a pore, disrupting the pathogen's membrane integrity, leading to cell lysis. This mechanism is crucial for the immune system to effectively eliminate pathogens. Choice A (Recruitment of neutrophils) is incorrect because MAC is not involved in recruiting neutrophils. Neutrophil recruitment is typically mediated by other signaling molecules. Choice B (Phagocytosis activation) is incorrect as MAC does not directly activate phagocytosis. Phagocytosis is a separate process involving the engulfment of pathogens by immune cells. Choice D (Enhancing cytokine production) is incorrect because MAC does not directly enhance cytokine production. Cytokine production is mainly regulated by other immune cells and signaling pathways.

Correct Answer: C

Rationale: The correct answer is C: 10. Toll-like receptors (TLRs) are a family of proteins involved in the innate immune response. In humans, there are 10 known TLRs that recognize different pathogen-associated molecular patterns. Each TLR is specific to different types of pathogens, allowing for a diverse recognition and response system. Therefore, the correct answer is 10. Choices A, B, and D are incorrect because they do not match the known number of TLRs in humans, which is 10.