Follicular Dendritic Cells (FDCs)

A Definition:  FDCs are located in lymphoid nodules (also called lymphoid follicles) of secondary lymphoid tissues and organs (e.g., in lymphoid nodules of mucosal lymphoid tissues -- solitary lymphoid nodules, Payer's patches, and tonsils and in organs such as lymph nodes and the spleen). FDCs are primarily found associated with the light region of germinal centers (GC) where their long convoluted dendritic processes interdigitate with dendrites of neighboring FDCs and form a three-dimensional "sponge-like" network (or reticulum). The spaces in the "sponge" are filled with lymphocytes. The FDCs forming this sponge-like microenvironment, trap and retain antigens on their dendrites in the form of antigen-antibody-complement complexes via Fc and CR2' (CD21) receptors. FDCs serve as an antigen repository, capable of long-term antigen retention and the antigenic stimulation of B lymphocytes. This antigenic stimulation, mainly during the secondary antibody response, leads to the formation of antibody producing plasma cells and memory B cells. FDCs appear to play a pivotal role in the long-term maintenance of humoral immunity.