Follicular dendritic cells (FDCs) are specialized to display intact antigens for recognition by B cells. Here we show that inhibition of lymphotoxin α/β (LTα/β) leads to the disappearance of multiple markers on FDCs within one day, regardless of whether any immune reactions are taking place. Inhibition of the tumour necrosis factor (TNF) pathway was also effective, but only in the absence of a strong antigenic response. These treatments not only prevented trapping of newly formed immune complexes, but also eliminated previously trapped immune complexes on FDCs, rendering the FDC non-functional. Therefore lymphotoxin and/or TNF is required for the continual maintenance of FDC function.