Relative to the primary immunological response, secondary and later booster responses to a given hapten-protein complex can be associated with which one of the following?

With repeated immunization, higher titers of all antibodies are observed, and, as priming is repeated, the immune response recruits B cells of progressively greater affinity. The affinity of antibody for a hapten-protein complex rises, cross-reactivity also rises, and the response becomes wider in specificity. As the number of antigenic sites detected per reacting particle increases, the avidity increases. In addition to shifts in the class of immunoglobulin synthesized in response to an antigen (IgM to IgG), shifts also may occur in the idiotype of antibody.