Follicular dendritic cells (FDCs) maintain pools of native antigen within germinal centers so B cells can repeatedly sample intact antigen during affinity maturation. This retention is central to durable, high-affinity antibody responses after infection or vaccination and influences outcomes in autoimmunity and chronic infection.
Molecular mechanisms of antigen capture and display
FDCs bind antigen as antigen–antibody or complement–antigen complexes through surface complement receptors and Fc receptors. Complement tagging of antigens with fragments such as C3d markedly increases attachment via complement receptor 2 CD21, while Fc gamma receptors capture immune complexes coated with antibody. Research by Miroslav Heesters and Michael C. Carroll at Harvard Medical School describes how immune complexes on FDCs are maintained in non-degradative compartments and can be recycled to the cell surface, keeping antigen in a native, multivalent form accessible to B cell receptors. Ian C. M. MacLennan at University of Birmingham has detailed how this physical persistence within the germinal center light zone promotes repeated B cell interrogation and selection.Relevance, causes, and consequences
Retention arises from the interplay of complement activation, antibody production, and specialized FDC biology: complement opsonization facilitates capture, early antibody formation generates immune complexes, and FDC membrane trafficking prevents destruction of antigen. The consequence is prolonged antigen availability that drives somatic hypermutation and clonal selection, improving antibody affinity and breadth. When complement components or FDC networks are impaired, as described in clinical and experimental immunology literature, vaccine efficacy and long-term humoral immunity decline. Shiv Pillai at Massachusetts General Hospital emphasizes the translational importance for human vaccination strategies and for understanding antibody-mediated autoimmune pathology when self-antigens are similarly displayed.Human, cultural, and environmental nuances shape these processes. Aging and malnutrition correlate with disrupted germinal center architecture and weaker FDC function, reducing vaccine responsiveness in older or resource-limited populations. In regions endemic for certain chronic pathogens, persistent antigen and altered complement activity can skew germinal center dynamics and influence disease progression. Understanding how FDCs retain antigen therefore has direct implications for vaccine design, autoimmune disease management, and public health strategies across different populations. Maintaining intact, accessible antigen on FDCs is a linchpin of adaptive humoral immunity and a critical target for clinical intervention.