Fig. (1) Developing B cells in the bone marrow (BM) rearrange their H and L chain V domains before leaving the BM as naïve IgM/IgD expressing B cells which travel in the blood to secondary lymphoid tissues. After encountering antigen some B cells can enter the germinal center where antigen-specific memory B cells and plasma cells are generated. Plasma cells travel through the blood to the BM where they compete with developing B cells for long term survival. Circulating memory B cells can be antigen-selected again and form second generation memory B cells and plasma cells. Developing B cell,○, Naïve B cell, , Memory B cells, , Somatically mutated B cell, , Plasmablast, , and Plasma cell,●.