Emigration rate from cultured murine thymic lobes.

C57Bl/6 embryonic thymus lobes (from day 16 of gestation) were cultured at a medium-air interface by placing the lobe on a nylon mesh supported by a cylinder, adjusting the level of medium to the height of the mesh. Cells that emigrate from the thymus pass through the mesh and fall to the bottom of the tissue culture well. The day before harvest, the lobe and support apparatus were transferred to a new well. The following day, the lobe and cells that had emigrated from it over the preceding day were harvested and counted. In the experiment shown, 60 lobes were initially placed in culture, then, at each time point, 6 were removed to examine intrathymic cells, leaving at the last time point, 36 lobes. At each time point, emigrants were pooled from 60 lobes (beginning) to 36 lobes (end). Error bars (± SD) are shown for 3 experiments.