Transduction of human hematopoietic cell lines by SCF-eco retrovirus is c-kit dependent. (A) Staining of 4 cell lines—MO7e, TF-1 cells, LAMA-84, and U937 cells—for surface expression of c-kit. The open traces show the mouse IgG1 isotype control used for setting the fluorescence gate. (B) The 4 lines expressing different levels of c-kit were transduced (mean ± SEM) with ampho, eco, and SCF-eco retroviral supernatants as indicated. In each case, the data were obtained from 6 independent transductions and were corrected for the background level of fluorescence obtained with mock-transduced cells.