In opsonization with IgG, why would it be important that IgG react with the antigen BEFORE a phagocytic cell recognizes the antibody molecule?
A) If the IgG is bound to the phagocyte BEFORE opsonization, it would most likely be ingested by the phagocyte before it could bind to a pathogen (it would be "naked," so to speak).
B) Binding of IgG by phagocytes would block the antigen binding sites on the IgG molecules, preventing them from binding to the microbes.
C) Binding of IgG by phagocytes changes their conformation-and by changing their protein conformation, their antigen binding sites are changed and they can no longer recognize their specific antigenic epitopes.
D) Binding of antibody by phagocytes results in immediate release of protein-destroying enzymes to the outside of the cell. Since antibodies are proteins, they would be destroyed by these enzymes (and would then be unable to bind to their specific antigenic epitopes).

Question

In opsonization with IgG, why would it be important that IgG react with the antigen BEFORE a phagocytic cell recognizes the antibody molecule?
A) If the IgG is bound to the phagocyte BEFORE opsonization, it would most likely be ingested by the phagocyte before it could bind to a pathogen (it would be "naked," so to speak).
B) Binding of IgG by phagocytes would block the antigen binding sites on the IgG molecules, preventing them from binding to the microbes.
C) Binding of IgG by phagocytes changes their conformation-and by changing their protein conformation, their antigen binding sites are changed and they can no longer recognize their specific antigenic epitopes.
D) Binding of antibody by phagocytes results in immediate release of protein-destroying enzymes to the outside of the cell. Since antibodies are proteins, they would be destroyed by these enzymes (and would then be unable to bind to their specific antigenic epitopes).

Quizplus · Accepted Answer

If the IgG is already bound to the phagocytic cell, it will not be able to bind to the pathogen and carry out opsonization.

Answer: B 
 Antibody binding to phagocytes can block the antigen binding sites on the antibody molecules, preventing them from binding to the microbes.

Answer: C 
 This statement is not accurate. Binding of IgG by phagocytes should not change their conformation and should not affect their ability to recognize their specific antigenic epitopes.

Answer: D 
 This statement is not accurate. Binding of antibodies by phagocytes does not result in the immediate release of protein-destroying enzymes to the outside of the cell.

In Opsonization with IgG, Why Would It Be Important That