Which of the following best describes the immune system's role in tissue regeneration?

Correct Answer: B

Rationale: The correct answer is B because the immune system plays a crucial role in promoting wound healing and eliminating cell debris. When tissue is damaged, the immune response helps remove dead cells and debris, initiates the healing process, and supports tissue regeneration. This involves the recruitment of immune cells to the site of injury, releasing growth factors to stimulate cell proliferation, and resolving inflammation. Choice A (Preventing pathogen invasion) is incorrect because while the immune system does play a role in preventing pathogen invasion, this is not directly related to tissue regeneration. Choice C (Increasing cytokine production) is incorrect because although cytokines are involved in the immune response and can influence tissue repair, simply increasing cytokine production does not fully describe the immune system's role in tissue regeneration. Choice D (Suppressing adaptive immunity) is incorrect because suppressing adaptive immunity would hinder rather than promote tissue regeneration, as adaptive immunity plays a role in immune memory and long-term protection against pathogens.

Correct Answer: B

Rationale: The correct answer is B: Lipopolysaccharide (LPS). TLR4 recognizes LPS, a component of the outer membrane of Gram-negative bacteria, triggering an immune response. This recognition is crucial in detecting bacterial infections. Peptidoglycan (A) is recognized by other TLRs, not TLR4. Double-stranded RNA (C) is recognized by TLR3, not TLR4. Mannose-binding lectin (D) is a pattern recognition receptor that binds to carbohydrate structures, not specifically recognized by TLR4.

Correct Answer: C

Rationale: Correct Answer: C Rationale: 1. Innate immunity is rapid: It provides immediate defense against pathogens. 2. Innate immunity is non-specific: It reacts in the same way to all pathogens. 3. Adaptive immunity, on the other hand, is slower and pathogen-specific. 4. Adaptive immunity develops memory to provide long-lasting protection. Summary: A: Innate immunity does not develop memory; adaptive immunity does. B: Adaptive immunity may not always be functional due to various factors. D: Adaptive immunity requires activation through exposure to specific antigens.

Correct Answer: B

Rationale: The correct answer is B: Granzyme. Granzyme is the molecule released by NK cells that induces apoptosis in target cells. It enters the target cell through perforin, which creates pores in the target cell membrane. Cytokines are signaling molecules released by various immune cells but do not directly induce apoptosis. Antibodies are produced by B cells and do not induce apoptosis. Perforin aids in the delivery of granzyme but is not responsible for inducing apoptosis itself. Therefore, Granzyme is the correct choice for inducing apoptosis by NK cells.

Correct Answer: B

Rationale: The correct answer is B: Alternative pathway. This pathway involves properdin, Factor B, and Factor D. Properdin stabilizes the C3 convertase complex formed by Factor B and Factor D, leading to the amplification of the complement cascade. The other choices are incorrect because: A: Classical pathway is initiated by antigen-antibody complexes binding to C1q. C: Lectin pathway is activated by lectins binding to carbohydrates on pathogen surfaces. D: Terminal pathway involves the formation of the membrane attack complex.