The humoral immunity process begins when a B cell binds to a free floating antigen in the lymph. B cells wait in the lymph node until antigen exposure.
The B cell presents the antigen to type II helper T cells, so that the helper T cells can stimulate the B cells into proliferation and antibody production.
Helper T cells express CD4 on the surface rather than CD8, which is expressed by killer T cells. The helper T cell binds to the presented antigen on the B cell receptor through the MHC-II complex. This causes cytokine release that stimulates the B cell to become active and produce antibodies specific to the presented antigen.
Plasma B cells are the active B cells that produce large amount of antibodies upon primary infection. They will eventually die, unlike memory cells which can last for the lifetime of an organism.
Memory B cells stay in the lymph nodes and wait to be re-exposed to the same antigen that previously infected the body. Upon exposure to that antigen, they proliferate rapidly and produce large amounts of antibodies for that antigen.
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