Immunological memory and the germinal centre reaction
The immune system requires the cognate interactions of T cells, B cells, and antigen presenting cells to respond to invading antigens/pathogens. The peripheral organs where the immune response occurs are organized into microanatomic compartments that are composed of T cell zones and B cell follicles. B cell responses to thymus dependent (TD) antigens begin in the T cell zones of secondary lymphoid tissues where T and B cells initiate antigen and costimulus dependent proliferation. These initial cognate interactions are essential for humoral immunity, but alone result in only transient, low affinity antibody responses. It is a subsequent set of cellular encounters, collectively known as the germinal centre (GC) reaction, that drives affinity maturation and memory.