(A) Number of G418R MK colonies after transduction of CD34⁺ cells with LNL6 or LNC(SCL). Cultures were established using 3,000 CD34⁺ cells in the presence of 1.5 mg/mL G418. Each data point represents an individual patient sample. Equivalent titers between LNL6 and LNC(SCL) (2% to 13% G418R GM-CFC) were confirmed within each experiment. (B) The number of cells per G418R MK clone after transduction of CD34⁺ cells with LNL6 (▨) or LNC(SCL) (▪). The total number of retrovirally transduced MK clones is shown. Clones from a total of 9 agar culture plates, representing 4 individual patient samples, are shown. Equivalent titers were observed for the LNL6 and LNC(SCL) retroviruses, as assessed by determining the percentage of G418R GM-CFC for each of the 4 patient samples. MK colonies contained 3 or more cells. The number of cells per MK clone was counted using an inverted microscope at ×100 magnification.