According to the initial ideas on iccosome formation, iccosomes formed by the process of transformation (maturation) of FDCs. As shown in the scanning electron micrographs in Figs. 1 through 3, the filliform dendrites of FDCs (1) begin to develope beads (2) and soon (within 72 hrs in vitro) dendrites become completely beaded. The beads are coated with a very thin layer of immune complexes (ICs). This immune complex layer, however, is much less than the layers found on fully developed iccosomes between days 1 and 3 in vivo. To develop the thick immune complex layer on the surface of each iccosomes, it is thought, based on transmission electron microscopic evidence, that two cells are involved in this process. One is a FDC, like the one shown in Fig. 3 and the other is a dendritic cell with dendrites and veils of many shapes. The flattened veil-like processes have thick accumulations of imune complexes on their surface in defined areas (large spots). Beaded dendrites of FDCs bind to these spots and the beads are "loaded" with a thick layer of immune complexes. For this proposed mechanism and illustrations click below.