Correlation analysis of gene transfer efficiency to CRU and LTC-IC (A) and to CRU and CFU-GM (B). Results shown include data from protocols in which either FCS (solid symbols) or BIT-containing (open symbols) viral supernatants were used. The average number of colonies counted to calculate the efficiency of gene transfer to CFU-GM ranged from 77 to 404 (mean = 154) and from 41 to 350 (mean = 123) in the presence and absence of G418, respectively. For assessment of LTC-IC, the numbers of colonies counted ranged from 12 to 115 (mean = 57) and from 1 to 85 (mean = 20) in the presence and absence of G418, respectively.