IL-4 regulation of RANK mRNA expression. BMMs were isolated from wild-type and STAT6^-/- mice. These cells were cultured with rmM-CSF (20 ng/mL) and RANKL (150 ng/mL) in the presence (▴) or absence (•) of rmIL-4 (10 ng/mL) for up to 72 hours, as indicated, and cDNA was generated from total RNA. Using Light-cycler PCR, we measured the expression of RANK and β-actin in the samples and calculated the ratio RANK versus actin values in arbitrary fluorescent units for each sample. (A) Expression of RANK in 1 representative experiment. (B) Levels of RANK normalized to that of β-actin (^*) mRNA were expressed as a percentage of the control (no IL-4). Average value from 3 independent experiments is shown.