Comparison of effects of RAs with those of IL-4, IL-6, or IL-4+IL-6 on mast cell growth supported by SCF.

The 1 × 10⁴ 10-week cultured mast cells were incubated in wells containing 100 ng/mL of SCF, ATRA or 9-cisRA at 10⁻⁷ mol/L, 20 ng/mL of IL-4, or 50 ng/mL of IL-6, alone or in combination. After 2 weeks, the viable cells were enumerated. Results shown are the mean ± SD of 3 experiments. Significantly different from ATRA (*P < .002, **P < .0001) and from 9-cis RA (^#P < .001,^##P < .0001).