To raise antibodies that interfere with the interaction of HIV with CD4+ T cells, vaccines should target which of the following HIV antigens

Correct Answer: C

Rationale: The correct answer is C: gp120. This is because gp120 is a key HIV antigen that plays a crucial role in binding to CD4 receptors on T cells, facilitating viral entry. By targeting gp120, vaccines can induce antibodies that block this interaction, preventing HIV from infecting CD4+ T cells. Conversely, choices A, B, and D (gp41, Reverse transcriptase, Matrix proteins) are not as effective targets for interfering with the CD4+ T cell interaction, as they do not directly impact the initial binding and entry process of HIV into the cells.

Correct Answer: C

Rationale: The correct answer is C because Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens, initiating the immune response. This recognition triggers the production of cytokines and chemokines, leading to inflammation and activation of immune cells. Choice A is incorrect because TLRs do not identify self-antigens but rather foreign antigens. Choice B is incorrect as TLRs do not directly mediate phagocytosis but rather initiate signaling pathways that lead to phagocytosis by immune cells. Choice D is incorrect because TLRs do not suppress cytokine secretion; rather, they stimulate cytokine production.

Correct Answer: B

Rationale: The primary function of lymph nodes is to filter lymph and facilitate immune responses. Lymph nodes contain immune cells that help recognize and fight off infections. They filter lymph by trapping and removing pathogens and foreign particles. This process helps in activating the immune response to protect the body. Choices A, C, and D are incorrect because lymph nodes do not produce red blood cells, synthesize antibodies, or generate cytokines. These functions are carried out by other organs and cells in the body.

Correct Answer: B

Rationale: The correct answer is B: Haematopoietic stem cells in the bone marrow. These cells are responsible for generating all immune cells, including lymphocytes, macrophages, and dendritic cells. They continuously replenish the immune system, allowing for proper immune function. Secondary lymphoid tissues (choice A) play a role in immune responses but are not the primary underpinning. Mucosal immune system activity (choice C) is important for defense at mucosal surfaces but is not the foundation of immune function. Rapid cytokine suppression (choice D) is a regulatory mechanism, not the fundamental basis of immune system functions.

Correct Answer: C

Rationale: The correct answer is C: C3. C3 is the central component of the complement system as it plays a crucial role in both the classical and alternative pathways by forming the C3 convertase enzyme. This enzyme initiates the cascade of reactions leading to opsonization, chemotaxis, and cell lysis. Choices A, B, and D are incorrect as C1 is the initiator of the classical pathway, C2 is involved in the formation of the C3 convertase, and C5 is necessary for the formation of the membrane attack complex.