CD8+ T cells

Correct Answer: E

Rationale: In the context of the Adaptive Immune System Quizlet focusing on CD8+ T cells, the correct answer is E, as it is missing. The correct options should be: A) Have cytotoxic function B) Recognize antigen in the context of MHC I molecules C) Can kill virus-infected cells D) Can kill tumor cells The correct answer is A, B, C, and D. CD8+ T cells, also known as cytotoxic T cells, are a crucial component of the adaptive immune system. They possess cytotoxic functions, which allow them to recognize antigens presented by MHC I molecules on infected or abnormal cells, such as virus-infected cells or tumor cells, and subsequently induce cell death. Therefore, all the provided options are correct in describing the functions and capabilities of CD8+ T cells. Educationally, understanding the role of CD8+ T cells in immunity is essential for comprehending how the immune system responds to infections and malignancies. Recognizing the specificity of these cells in targeting abnormal cells while sparing healthy ones underscores the precision and effectiveness of the adaptive immune response. By grasping the functions of CD8+ T cells, learners can appreciate the intricacies of immune surveillance and the body's defense mechanisms against various threats.

Correct Answer: D

Rationale: Step 1: Viral antigenic shift involves major changes in the surface proteins of the virus, particularly the hemagglutinin (HA) protein. Step 2: These changes result in the emergence of new variants that are not recognized by preexisting antibodies. Step 3: This process is distinct from antigenic drift, which involves minor changes due to random mutations. Step 4: Choice D correctly states that viral antigenic shift refers to the appearance of new HA variants not recognized by preexisting antibodies. Summary: Choice A is incorrect because viral antigenic shift is not caused by multiple random mutations. Choice B is incorrect as antigenic shift involves major changes, not a single mutation. Choice C is incorrect as it affects surface proteins like HA, not just internal proteins.

Correct Answer: A

Rationale: Defensins are cationic antimicrobial peptides that play a crucial role in the innate immune system by disrupting the microbial cell membrane. This property allows them to kill a wide range of pathogens. Option A is correct because it accurately describes the primary function of defensins. Option B, opsonins, are proteins that enhance phagocytosis but are not specific to defensins. Option C, DAMPs, are damage-associated molecular patterns released by damaged cells and are not related to defensins. Option D, fatty acids, are not directly related to the antimicrobial properties of defensins.

Correct Answer: B

Rationale: The correct answer is B: Membrane-disrupting peptides. Defensins are antimicrobial peptides that disrupt bacterial cell membranes. This disrupts the integrity of the bacterial cell, leading to cell lysis and death. Choice A is incorrect because mast cells release histamines, not defensins. Choice C is incorrect as acute phase proteins are involved in the immune response to inflammation. Choice D is incorrect as opsonins are molecules that enhance phagocytosis of pathogens by immune cells.

Correct Answer: C

Rationale: The correct answer is C because avian flu recognizing a variant of sialic acid only found deep in the lung tissue of humans, not in the upper airways explains why it has not caused a human pandemic. This specificity limits human-to-human transmission as the virus cannot efficiently attach in the upper airways where respiratory droplets are expelled. Choices A and B are incorrect because avian flu can cause severe infections in humans and recognizes a variant of sialic acid found in both birds and humans, not just avian cells. Choice D is incorrect as the presence of H5N1 in the annual trivalent vaccine does not prevent human pandemic potential.