Frequency histogram of LTC-IC densities (expressed as number per 10⁵ MNCs) in 53 BM samples measured by LDA using 2.5 × 10³, 5 × 10³, 10⁴, and 2 × 10⁴ MNCs per well. (A) BM MNC LTC-IC densities in the donor population were log-normally distributed. (B) The number of 2° CFCs generated per LTC-IC varied from donor-to-donor, with an apparent bimodal distribution.