Follicular dendritic cells (FDCs) are specialized immune cells found primarily in the germinal centers of lymph nodes, spleen, and other secondary lymphoid tissues. Unlike dendritic cells that present antigens to T cells, FDCs have a unique role in B cell activation and antibody production.
FDCs are characterized by their ability to trap and display immune complexes—antibodies bound to antigens—on their surface for extended periods. This allows them to present antigen-antibody complexes to B cells, which recognize them through their B cell receptors. This interaction is crucial for selecting B cells that produce high-affinity antibodies during the germinal center reaction, a process called affinity maturation.
These cells extend long, branching processes that form a network within germinal centers, creating an environment where B cells compete for access to trapped antigens. B cells with receptors that bind the displayed antigens more strongly receive survival signals and are selected to proliferate and differentiate into plasma cells (antibody factories) or memory B cells. Those with weaker binding are eliminated, resulting in an antibody response optimized for the specific pathogen.
FDCs also produce cytokines and chemokines that regulate immune cell traffic and survival within germinal centers. They are essential for generating protective, long-lasting antibody responses and are particularly important in vaccine responses and natural immunity to infections. Their dysfunction has been implicated in various immune disorders, and certain viruses like HIV and prion diseases can affect FDC function, potentially compromising immune responses.