Growth of erythroid colonies in agar culture after transduction of human CD34⁺ cells with LNL6 or LNC(SCL). (A) through (D) show agar culture plates of LNL6-transduced (A and C) or LNC(SCL)-transduced (B and D) CD34⁺ cells stimulated for erythroid colonies in the presence (A and B) or absence (C and D) of G418. CD34⁺ cells were cultured at 1,000 cells/mL in the absence of G418 (C and D) and at 10⁴ cells/mL in the presence of G418 (A and B). Photographs were taken at day 13 of culture in agar. (E) and (F) show morphology of individual erythroid colonies (original magnification ×40) grown in the presence of G418 after transduction of CD34⁺ cells with LNL6 (E) or LNC(SCL) (F). The control erythroid colony shown in (E) was the largest colony in the culture, whereas that in (F) represents a typical erythroid colony. Colonies were photographed at day 13.