When an antigen is presented to a B cell, the B cell takes up the antigen and chemically modifies it in the form of an antibody, prior to rapid cellular division of the specific B cell.

A large pool of B cells exist, all of which have the same base structure of an antibody on its surface, which are rapidly modified to upon exposure to an antigen

A large pool of B cells exist, all with a different antigen recognition site. Rapid division of a particular B cell is activated once an antigen binds to a specific antibody on a B cell

When an antigen binds to a generic antibody, the structure of the antibody rapidly changes to ensure a good fit, which is followed by rapid cellular division of the specific B cell