Linear relationship between input cell concentration and number of output colonies from LTC of AML cells. PB cells from five patients with AML were plated at concentrations varying from 5 × 106 to 1 × 105 per mL on irradiated feeders in microtitre wells. Twenty-five to 30 duplicate long-term cultures were plated at each cell concentration. After 5 weeks in culture the total cell content of each culture was obtained and plated in methylcellulose assay as described in Materials and Methods. The log of the input cell number into the duplicate long-term cultures is plotted against the log of the mean number of colonies produced per duplicate long-term culture at that cell concentration. HMF were used for long-term cultures with each of the five patient samples, patient 3 (♦), patient 4 (▪), patient 7 (▴), patient 8 (•), and patient 9 (✶). In addition, mixed feeders producing human G-CSF, IL-3, and SF were used for duplicate cultures with cells from patients 7 (▵) and 8 (○). The mean (±SD) of these slope of the graphs generated is 0.85 ± 0.16.
