Final answer:
In a primary immune response, differentiated B cells called plasma cells are responsible for producing and secreting antibodies. Memory B cells are also formed but remain inactive until subsequent exposure to the same antigen, whereupon they facilitate a quicker and stronger response.
Step-by-step explanation:
In antibody-mediated immunity, during a primary immune response, antibodies are produced and secreted by differentiated B cells called plasma cells. After the helper T cell binds to the antigen-MHC class II complex, it releases cytokines which induce the B cell to proliferate into clonal cells. These cells differentiate into either plasma cells or memory B cells. While the memory B cells remain inactive at first, they are crucial for initiating a faster and stronger response upon a second exposure to the same antigen. It's the plasma cells, however, that are responsible for the production and secretion of large quantities of antibodies, which are essential for the body's defense against pathogens.
When encountering an antigen for the first time, there's a delay prior to antibody production, as it takes time for B cell clones to expand and differentiate into plasma cells. In contrast, during a secondary exposure, the memory B cells quickly differentiate into plasma cells and produce a higher quantity of antibodies with a faster response. This robust secondary response, facilitated by memory B cells, usually prevents symptoms by swiftly overwhelming the pathogens.