Final answer:
The germinal center is where B cells proliferate and differentiate into memory B cells and plasma cells during an immune response. The secondary response by memory B cells is faster and produces more effective antibodies. Plasma cells migrate back to the bone marrow and are dedicated to antibody secretion until they die.
Step-by-step explanation:
As the immune response proceeds, the germinal center of secondary lymphoid tissues like the palatine tonsil undergoes significant changes. During the primary immune response, B cells are activated through their interaction with an antigen and begin to proliferate rapidly in the germinal centers. Some of these B cells will differentiate into memory B cells, which are programmed to respond more efficiently to future exposures to the same antigen. The secondary immune response initiated by these memory B cells is significantly quicker and more robust than the primary response, featuring a shorter lag period, higher production of IgG antibodies, and the generation of more effective antibodies with higher affinity for the targeted epitopes. Moreover, plasma cells formed in the secondary response are more long-lived, outlasting those from the primary response, hence maintaining elevated levels of specific antibodies for an extended duration.
Additionally, after their activation, B cells may differentiate into plasma cells which then exit the secondary lymphoid organs and migrate back to the bone marrow. These plasma cells are termed 'terminally differentiated' because they are predominantly dedicated to the secretion of antibodies before they eventually perish. The outcome of a successful adaptive immune response, involving clonal expansion and the interplay of various immune cells, leads to the clearance of the pathogen, a process observed as seroconversion, where antibody levels inversely correlate with viral levels.