Differences in Primary and Secondary

Primary and secondary responses both have a latent period even though secondary response latent period is shorter due to already formed plasma cells producing antibodies. Both responses then have an increase in antibody titer, with the exception that secondary response increases faster in ab titer because they already have plasma cells producing more abs. Also in secondary response, the antibody persists longer because it has higher affinity due to class switch. Secondary response is predominantly IgG even though there are IgM being produced. Also in secondary response, there are memory cells which remember the antigen and activates more B cells faster leading to faster immune response.

Handout 16, Figure 1

During a primary immune response, mostly IgM class antibodies are produced during the early stage. This happens because there are a low amount of B cells and T cells due to the present of a non-replicating protein antigen being introduced for the very first time into the body. After about 5-7 days, maturation time for cells, antibody to the antigen will peak and then decline. During this decline stage, class switch of IgM to IgG may occur. The amount of IgG present depends mainly on the type and amount of antigen being inoculated.