Final answer:
The primary immune response is characterized by the delay before pathogen-specific antibodies are produced, while the secondary immune response is rapid due to the presence of memory cells, resulting in quick isotype switching and high-affinity antibodies production.
Step-by-step explanation:
The correct statement regarding the primary immune response is c. Delay before pathogen-specific antibodies are produced.
In the primary immune response, the adaptive immune system first encounters a pathogen and takes time to respond. Initially, there are no pathogen-specific cells available to immediately combat the pathogen. Memory B cells and T cells are not yet developed, so the body has to activate naïve B and T cells, which then differentiate into effector cells capable of fighting the infection. During this process, B cells take several days to proliferate and differentiate into plasma cells that can produce the necessary antibodies to fight the infection.
The primary immune response is characterized by a delay in the development of antibodies because it involves clonal expansion and differentiation of B cells, which needs time. Furthermore, the antibodies produced in the primary response are not isotype switched or highly affine until the immune system has had the chance to optimize them through processes that occur during and after the primary response. In contrast, a secondary immune response, which happens upon re-exposure to the same pathogen, is rapid because of the presence of memory cells created during the primary response, resulting in quick isotype switching and the production of high-affinity antibodies.