Which class of biological molecules can be bound by an immunoglobulin?

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Immunoglobulins are antibodies produced by the immune system to recognize and bind to foreign molecules called antigens. These antigens can be proteins (choice A), carbohydrates (choice B), or lipids (choice C). Therefore, immunoglobulins can bind to all classes of biological molecules. Choices A, B, and C are incorrect as they each represent individual classes of molecules that can be targeted by immunoglobulins, but the correct answer encompasses all of them.

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.

Correct Answer: A

Rationale: The correct answer is A: IgG: Opsonization. IgG antibodies are known for their role in opsonization, where they tag pathogens for phagocytosis by immune cells. This process enhances the removal of pathogens. IgA is mainly involved in mucosal immunity and not complement activation, making choice B incorrect. IgE is associated with allergic reactions and not antibody-dependent cell-mediated cytotoxicity as stated in choice C. IgM is the first antibody produced in response to an infection and plays a role in neonatal immunity, making choice D incorrect.