Which statement best describes how antibodies contribute to opsonization?

Which statement best describes how antibodies contribute to opsonization?

• A. They neutralize toxins directly.
• B. They mark pathogens for phagocytosis.
• C. They lyse cells by perforin.
• D. They activate T cells through direct contact.

Answer: (B)

Antibodies contribute to opsonization by tagging pathogens for phagocytosis. When an antibody binds a pathogen with its Fab region, its Fc region becomes available to bind Fc receptors on phagocytes like macrophages and neutrophils. This interaction signals the phagocyte to engulf and digest the coated microbe more efficiently, increasing the chances of clearance. Antibodies can also recruit the complement system, leading to deposition of opsonins such as C3b that further promote phagocytosis. Other options describe mechanisms like neutralizing toxins directly, cytotoxic cell–mediated lysis, or T cell activation, which are different immune strategies and do not capture the tagging and enhanced ingestion central to opsonization.

Antibodies contribute to opsonization by tagging pathogens for phagocytosis. When an antibody binds a pathogen with its Fab region, its Fc region becomes available to bind Fc receptors on phagocytes like macrophages and neutrophils. This interaction signals the phagocyte to engulf and digest the coated microbe more efficiently, increasing the chances of clearance. Antibodies can also recruit the complement system, leading to deposition of opsonins such as C3b that further promote phagocytosis. Other options describe mechanisms like neutralizing toxins directly, cytotoxic cell–mediated lysis, or T cell activation, which are different immune strategies and do not capture the tagging and enhanced ingestion central to opsonization.