What is the primary advantage of the memory function in adaptive immunity?

Correct Answer: A

Rationale: The correct answer is A because memory function in adaptive immunity allows for rapid and stronger responses to previously encountered antigens. This is achieved through the presence of memory cells, such as memory B and T cells, which can quickly recognize and respond to specific pathogens upon re-exposure. This leads to a faster and more efficient immune response, providing better protection against future infections. Choice B is incorrect because direct killing of pathogens without prior activation is a function of innate immunity, not adaptive immunity. Choice C is incorrect as enhanced cytokine secretion is not the primary advantage of memory function. Choice D is incorrect because while memory function provides protection against previously encountered antigens, it does not confer resistance to all infections without exposure.

Correct Answer: B

Rationale: The correct answer is B because adaptive immunity is characterized by antigen-specific responses and memory. This means that it can recognize and target specific antigens upon exposure and develop long-lasting immunological memory. Choice A is incorrect because physical barriers like skin are part of innate immunity, not adaptive immunity. Choice C is incorrect as adaptive immunity responds to specific antigens, not all antigens non-specifically. Choice D is incorrect because adaptive immunity typically takes longer to respond compared to innate immunity due to the need for activation and clonal expansion of specific immune cells.

Correct Answer: C

Rationale: The correct answer is C: Mucosal immunity. IgA plays a crucial role in protecting mucosal surfaces, such as the lining of the gut and respiratory tract, from pathogens. It helps prevent infections by neutralizing and blocking the entry of harmful substances. IgA is not involved in allergy mediation (choice A), placental transfer (choice B), or primary response (choice D), as those functions are typically associated with other types of antibodies. IgA's specificity for mucosal surfaces makes it uniquely suited for providing defense at these vulnerable sites.

Correct Answer: B

Rationale: The correct answer is B: Type I, II, III, and V. - Type I hypersensitivity involves IgE antibodies and immediate allergic reactions. - Type II hypersensitivity involves IgG and IgM antibodies attacking self-antigens on cells. - Type III hypersensitivity involves immune complex deposition. - Type V hypersensitivity involves autoantibodies stimulating receptors. Choices A, C, and D are incorrect because they do not include all types of hypersensitivity mediated by antibodies as specified in the question.

Correct Answer: B

Rationale: The correct answer is B because when immune complexes are not cleared in Type III hypersensitivity, they deposit in tissues, activating complement cascades and causing inflammation. This leads to tissue damage and the recruitment of inflammatory cells. A: Immune complexes do not directly activate T cells in Type III hypersensitivity. C: Phagocytosis of immune complexes can lead to cell activation and inflammation. D: Immune complexes do not suppress antibody production in Type III hypersensitivity.