CD34⁺ cells and CD34⁻ cells were separated by using MACS from cord blood-derived cells cultured in the presence of SF + IL-6 for 3 weeks and were further cultured in the presence or absence of IL-4 for 3 more weeks. Each value represents a mean ± SEM of four experiments.

One thousand cells obtained from the MACS-separated CD34⁺fraction (4.5% tryptase-positive cells) at 3 weeks in culture were inoculated in 0.2 mL medium (total cells harvested at 3 more weeks) or 1 mL methylcellulose (total colonies formed at 3 more weeks) (see Materials and Methods). They were further cultured for 3 more weeks in the presence of SF + IL-6 without IL-4.

One thousand cells from the CD34⁺ fraction (4.5% tryptase-positive cells) were further cultured for 3 more weeks in the presence of SF + IL-6 with IL-4 at 10 ng/mL.

One thousand cells from the CD34⁻ fraction (67.5% tryptase-positive cells) were further cultured for 3 more weeks in the presence of SF + IL-6 without IL-4.

One thousand cells from the CD34⁻ fraction (67.5% tryptase-positive cells) were further cultured for 3 more weeks in the presence of SF + IL-6 with IL-4 at 10 ng/mL.

IL-4 reduced the number of the cells at 31%, although it was not significant (P = .19).

IL-4 slightly enhanced the SF/IL-6–dependent increase in the number of the cells, although it was not significant (P = .22).

#IL-4 significantly inhibited the colony formation (P = .011).

Numerous small cell clusters consisting of less than 10 cells were found.