Explain (A) why only memory B cells, and not naive B cells, participate in secondary immune responses to particular pathogens, and (B) why this is advantageous to the host

Question

What will be an ideal response?

Answer 1

A. Naive B cells carry the inhibitory Fc receptor FcγRIIB1. Complexes composed of antigen and IgG produced in the primary response, or by reactivated memory cells, cross-link FcγRIIB1 and the B-cell receptor, which suppresses naive B-cell activation. In contrast, memory B cells do not carry this receptor, and so are not inhibited in this way.
B. The suppression of naive B cells means that only reactivated memory B cells (which have already undergone isotype switching and somatic hypermutation) make antibodies. Thus all the antibodies made are of high affinity and are primarily of the IgG, IgA, or IgE isotype. Suppression of naive B cells eliminates repetition of the events that took place in the primary immune response, which would, if not inhibited, lead to the production of low-affinity IgM antibodies rather than high-affinity, isotype-switched antibodies that are more effective at removing the pathogen.