Which of the following best describes the relationship between innate and adaptive immunity?

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.

Correct Answer: C

Rationale: The correct answer is C: IgM. During the primary immune response, IgM is the first antibody produced by the immune system in response to an antigen. IgM is efficient in agglutination and complement fixation, aiding in the elimination of pathogens. IgG is more prominent in the secondary immune response. IgA is mainly found in mucosal areas. IgE is associated with allergic reactions and parasitic infections, not the primary immune response. So, IgM dominates the primary immune response by being the initial antibody produced to combat antigens.

Correct Answer: B

Rationale: The correct answer is B: Major Histocompatibility Complex (MHC). MHC molecules present antigens to T cells for immune response activation. They bind to antigenic peptides and present them on the cell surface for recognition by T cells. This is crucial for the immune system to distinguish between self and non-self antigens. Antibodies (A) are produced by B cells and do not directly present antigens to T cells. Complement protein C3 (C) is involved in the complement system for immune defense, not antigen presentation. Cytokines (D) are signaling molecules that regulate immune responses but do not directly present antigens to T cells.

Correct Answer: C

Rationale: The correct answer is C: Neutralization, opsonization, and complement activation. Antibodies play a crucial role in adaptive immunity by neutralizing pathogens, facilitating their destruction through opsonization, and activating the complement system for pathogen elimination. This is achieved through binding to antigens on pathogens, marking them for destruction by phagocytes, and triggering the complement cascade. Options A, B, and D are incorrect because antibodies do not directly present antigens, perform phagocytosis, or kill infected cells.

Correct Answer: B

Rationale: The correct answer is B: Immediate phase and late phase. In Type I hypersensitivity, the immediate phase occurs rapidly after exposure to an allergen, leading to the release of mediators like histamine. The late phase occurs several hours later, involving sustained inflammatory response. A: Early phase and latent phase - Incorrect because the terms do not accurately describe the phases of Type I hypersensitivity. C: Acute phase and chronic phase - Incorrect because Type I hypersensitivity does not typically progress to a chronic phase. D: Primary phase and secondary phase - Incorrect as these terms are not commonly used to describe the phases of Type I hypersensitivity.