For the purposes of VCE, secondary lymphoid tissues are mainly associated with the lymph nodes, although they also encompass the spleen and tonsils. As for the process that occurs,
1) Antigen presenting cell digest pathogen and present antigen fragments on its MHC II molecules
2) T helper cell binds to this antigen-MHC II complex with a specific T cell receptor which activates the T helper cell
3) At the same time, the pathogen binds to a B cell receptor on a naive B cell (clonal selection) or the B cell can be presented with the antigen via an antigen presenting cell.
4) T helper cell activates this specific B cell by releasing cytokinesis
5) B cell undergoes clonal expansion and differentiates into B plasma cells and B memory cells
6) B plasma cells secrete specific antibodies into the blood to counter the pathogen
