Final answer:
The second immune response is mediated by memory B cells. These cells provide a robust and swift response upon subsequent exposure to a previously encountered pathogen.
Step-by-step explanation:
The second immune response is mediated by c. Memory B cells. These cells are crucial for the body's ability to 'remember' a pathogen once an individual has been exposed to it. The first time the body encounters a pathogen, naïve B cells are stimulated to differentiate into plasma cells, which produce antibodies to combat the pathogen. Some of these B cells also become memory cells. During subsequent exposures to the same pathogen, these memory B cells can quickly differentiate into plasma cells to produce a stronger and faster response, ensuring a more efficient immune reaction compared to the first exposure.
Naïve B cells, when first encountering an antigen, do not mediate the second immune response but are instead responsible for the initial immune response. Plasma cells derive from activated B cells and are responsible for producing antibodies during the first immune response. Upon reexposure to a pathogen, memory B cells can quickly differentiate into plasma cells and proliferate, which leads to the enhanced secondary immune response.