Which of the following statement is incorrect

Correct Answer: B

Rationale: The correct answer is B because migrating dendritic cells do not enter the draining lymph node (LN) via high endothelial venules (HEV); instead, they enter through afferent lymphatic vessels. HEVs are specialized post-capillary venules in LN where lymphocytes enter from the bloodstream. Dendritic cells, carrying antigens from tissues, travel via afferent lymphatic vessels to reach the LN where they present antigens to lymphocytes. Option A is correct as antigens in tissues reach LN via afferent lymphatic vessels. Option C is correct as infection-induced signals can increase blood flow to LN, facilitating lymphocyte migration. Option D is incorrect because the thoracic duct returns lymph back to the bloodstream, not specifically lymphocytes.

Correct Answer: D

Rationale: Protease inhibitors interfere with the final step in HIV replication, which is the cleavage of the polyprotein into individual functional proteins. Inhibiting protease prevents the formation of mature infectious viral particles. This step occurs after reverse transcription of viral RNA into DNA, making choice D the correct answer. Choices A, B, and C are incorrect because protease inhibitors do not affect the release of new viral particles, processing of gp160, or the proviral stage of HIV replication.

Correct Answer: B

Rationale: The correct answer is B: To orchestrate and drive immune responses. Cytokines are signaling molecules that coordinate various aspects of the immune response, such as inflammation, cell proliferation, and differentiation. They regulate communication between immune cells to mount an effective defense against pathogens. A: To act as a physical barrier to pathogens - Incorrect. Physical barriers include skin and mucous membranes, not cytokines. C: To destroy red blood cells - Incorrect. Cytokines are not involved in destroying red blood cells. D: To generate antibodies - Incorrect. While cytokines can influence antibody production, their primary role is not in generating antibodies.

Correct Answer: C

Rationale: The correct answer is C: Rapid pathogen reproduction and mutations drive the emergence of immuno-resistant pathogen strains. This is because the high rate of reproduction allows for more opportunities for mutations to occur, some of which may confer resistance to the host's immune system or medical interventions. Slow mutation rates in pathogens (B) would not lead to the rapid emergence of resistant strains. Host immune system failure (A) occurs after the pathogen has already developed resistance. The absence of host immune adaptation (D) does not directly drive the emergence of resistant strains as it is the rapid reproduction and mutations of pathogens that play a crucial role.

Correct Answer: A

Rationale: The correct answer is A: Bone marrow. Secondary lymphoid organs are where immune responses are initiated. Bone marrow is a primary lymphoid organ where immune cells mature, not where immune responses are initiated like in secondary lymphoid organs. The spleen, lymph nodes, and mucosal immune system are all secondary lymphoid organs where immune responses occur.