LEGEND This color enhanced TEM shows the development of ATCs after passing through the floor of the subcapsular sinus. A non- colorized version of this EM was published in the original paper on antigen transport (for reference click the REF button). The process (P1) of the cell labeled ATC is still being drawn through the pore of the SS floor. This processes extends to the cell body which possess an irregularly cleaved nucleus. The cell body also developed several additional processes which interdigitate with similar cell processes of the deeper lying FDCs. Judging from the lack of complicated convolutions, some of these cell processes may be more veil like then dendritic. These are antigen retaining cell processes as can be seen from the associated black immune complex deposits. Deeper in the cortex the processes of FDCs show a more dendritic pattern as suggested by the more convoluted appearance of the processes and immune complex deposits. The multi-cleaved nucleus is typical of early ATCs. It is believed that these lobes will completely separate giving rise to distinct nuclei without conventional karyokinezis. With maturation this would help form more FDCs. In support of this idea, it perhaps should be noted that FDCs could not be shown to replicate with conventional tritiated-Thdn labeling.