Find the unmatched pair with respect to immune function:

Correct Answer: C

Rationale: The correct answer is C: Mast cells: acute phase response. Mast cells are actually involved in allergic responses, not the acute phase response of the immune system. The acute phase response is primarily mediated by cytokines and acute-phase proteins. Interferons protect against viral infections, ROS help kill pathogens inside cells, and selectins aid in leukocyte extravasation during inflammation.

Correct Answer: D

Rationale: Rationale: 1. A is correct as lymph is taken up from tissues by lymphatic capillaries. 2. B is correct as lymph carries antigens and mature dendritic cells to lymph nodes. 3. C is incorrect as lymph is not secreted by lymphocytes. 4. Therefore, D is correct as both A and B accurately describe the components and functions of lymph.

Correct Answer: D

Rationale: Dendritic cells play a crucial role in the immune system. Firstly, they provide costimulation to activate naïve T cells (A). Secondly, they process protein antigens into peptides for antigen presentation (B). Finally, dendritic cells present peptide-MHC complexes to T cell receptors for immune response activation (C). Therefore, the correct answer is D, as dendritic cells are involved in all these processes essential for initiating and regulating immune responses. Choices A, B, and C are incorrect as they are individual roles of dendritic cells and do not encompass the full range of functions that dendritic cells perform.

Correct Answer: B

Rationale: The correct answer is B: Opsonization. Both IgG and IgA antibodies can participate in opsonization, which involves tagging pathogens for destruction by phagocytes. IgG and IgA have specific receptors on phagocytes that recognize the tagged pathogens, enhancing their clearance. Neonatal immunity (choice A) is primarily mediated by IgG antibodies transferred from mother to fetus. Antibody-mediated degranulation of mast cells (choice C) is mainly associated with IgE antibodies in allergic reactions. Complement activation (choice D) mainly involves IgM and IgG antibodies, leading to a cascade of reactions for pathogen elimination.

Correct Answer: C

Rationale: The correct answer is C: Paneth cells. Paneth cells are specialized intestinal epithelial cells located in the small intestine that produce antimicrobial peptides to help defend against pathogens. They play a crucial role in maintaining gut homeostasis. Goblet cells (A) secrete mucus, enterocytes (B) absorb nutrients, and epithelial stem cells (D) are responsible for cell regeneration, but they do not produce antimicrobial peptides like Paneth cells do.