What term describes the secondary response to the same foreign antigen characterized by a rapid increase in antibody synthesis?

• A. Primary response
• B. Anamnestic response
• C. Clonal expansion
• D. Somatic hypermutation

Answer: (B)

The rapid antibody production upon re-exposure to the same antigen is called an anamnestic response. This secondary response is driven by memory B cells generated during the initial encounter. Because these memory cells persist, they respond quickly and differentiate into plasma cells, producing large amounts of antibody often with higher affinity and usually class-switched (such as IgG) compared with the first exposure. The lag time is short and the antibody titer rises rapidly to high levels.

In contrast, a primary response to the first encounter has a longer lag phase as naive B cells are activated, typically starting with IgM before class switching occurs. Clonal expansion simply refers to the proliferation of the antigen-specific B or T cells after activation, while somatic hypermutation is the process that increases antibody affinity in germinal centers during affinity maturation—important for quality of antibodies but not the description of the rapid secondary response.