Follicular dendritic cells (FDCs) form a reticular FDC network in the lymphoid follicle that is essential for the retention and presentation of native antigens in the form of antigen-antibody immune complexes (ICs) to B cells during secondary immune response. Although the presence of migrating precursors of FDCs has been hypothesized, their entity has not been elucidated. Here we report the identification of murine splenic CD19(-)CD11c(-)CD35(+)B220(+) cells as an inducer of FDC network formation. We demonstrated that CD19(-)-CD11c(-)CD35(+)B220(+) cells, together with stromal cells, had the remarkable ability to form lymphoid-follicle-like structures that contained B220(+)FDC-M1(+) reticular cells originally derived from CD19(-)-CD11c(-)CD35(+)B220(+) cells in the CD35(+) reticulum. Our results indicate that CD19(-)CD11c(-)CD35(+)B220(+) cells function as an inducer of FDC network formation and that the interaction between CD19(-)CD11c(-)CD35(+)B220(+) cells and stromal cells is required to initiate lymphoid follicle formation.