試題詳解

18. Figure A shows antibodies bound to repetitive epitopes on the surface of a bacterial pathogen. Even though all of these epitopes are identical, not all of them have antibodies bound to them.

Which statement is CORRECT to explain why some of the antibodies fail to bind to every possible epitope on the surface of the pathogen?
(A) There is an insufficient amount of antibody to saturate all the epitopes.
(B) The pathogen has an immune evasion strategy to avoid antibody binding to all epitopes.
(C) Some of the epitopes cannot bind antibody due to steric hindrance.
(D) The antibodies are only able to bind when both antigen-binding sites are engaged on the pathogen surface.
(E) The epitopes on the pathogen are not all in the same conformation, so not all will bind the same antibody.