Bill first had the influenza vaccine in October. He experienced a headache, achiness, fatigue, and a fever. When he came into contact with the influenza virus a few months later, he hardly had any symptoms at all. Explain these two different immune

Question

responses seen with each exposure to the virus.

What will be an ideal response?

Answer 1

The primary immune response began with Bill's first exposure to the influenza virus. His B cells were activated and proliferated into plasma cells, which secreted antibodies, and memory B cells. This initial lag phase is slow as B cells proliferate over 4-5 days, with antibody production peaking 7-14 days after the first encounter with the antigen. The next time Bill was exposed to the same antigen, the response was much different since the memory B cells formed during the primary immune response are long-lived. When these memory B cells encounter the antigen for which they are specific, the secondary immune response began. The secondary immune response has a shorter lag phase (about 1-3 days), and its antibody levels peak more rapidly (3-5 days) and reach a peak 100-1000 times larger. For this reason, he had mild symptoms when exposed to the same antigen for the second time.