In mammals, B lymphocytes produce antibodies to foreign antigens, such as virus, bacteria and fungus. When the body is exposed to such antigens, B cells respond by becoming activated to high-rate antibody secreting plasma cells. The immune reactions take place in the secondary lymphoid organs, for example lymph nodes and spleen. In these organs, B cells get signals by antigen, T cells and dendritic cells. Activated B cells form so-called germinal centres, consisting of rapidly proliferating cells.
