Figure 4
Interleukin (IL)-4 drives mast cell activation, growth, and survival largely via STAT6 (signal transducer and activator of transcription factor 6). (a) immunoglobulin E (IgE) receptor (FcɛRIα) upregulation by IL-4 in mast cells is STAT6-dependent. Wild-type and STAT6−/− bone marrow–derived mast cells (BMMC) were fluorescently tagged and co-cultured in the presence of increasing amounts of IL-4. After 24 h, cells were stained for FcɛRIα and analyzed by flow cytometry. (b) IL-4 enhances mast cell growth in combination with IL-3 and stem cell factor (SCF) only when STAT6 is expressed. BMMC were co-cultured as in a for 5 days. (c) Mast cell death in the absence of IL-3 and SCF is prevented by IL-4 via STAT6. Data for day 5 of culture are shown. IL-4 induces (d) Bcl-2 and (e) Bcl-XL expression in wild-type but not STAT6−/− BMMC. Statistical analysis by two-way analysis of variance (ANOVA).*P<0.05, and ***P<0.0001 by Bonferroni post-test where indicated. Data are representative of at least three experiments. MFI, mean fluorescent intensity.
