Successive stages in the isolation of DCs from C57BL/6 mouse spleen (Ly5.2) were sampled and assayed for the ability to produce CD8α⁺ DCs in the spleens of nonirradiated recipient Ly5.1 mice 3.5 days after intravenous transfer. Immediate CD8α⁺ DC precursor activity is expressed on a specific activity basis (Ly5.2⁺CD8α⁺CD11c⁺ DCs per recipient spleen per 10⁶ cells transferred) or on a total activity per original donor spleen basis (calculated as Ly5.2⁺CD8α⁺CD11c⁺ DCs per recipient spleen per cell transferred multiplied by the total cells obtained in each fraction from 1 donor spleen). On average, 5% of the original viable nucleated spleen cells were found in the light-density fraction and 2% were found in the DC-enriched fraction. Autofluorescent cells constituted on average 10% of the DC-enriched fraction. Results are the means from 4 experiments, with the error bars indicating ranges