Fig. 8. Model explaining the effect of Stat6/IL-4/IL-13 deficiency on mammary gland development. (A) Th2 cytokine production is orchestrated by Stat6-mediated Gata3 gene transcription. Gata3 induces a chromatin conformational change at the IL-4/IL-13/IL-5 locus, facilitating the binding of Stat6, Stat5 and c-Maf, which produces cytokines that trigger the differentiation process in undifferentiated cells. Gata3 is also activated by other pathways, such as Notch. (B) In the absence of Stat6, IL-4/IL-13/IL-5 production is reduced even in the presence of Gata3. We propose that this affects paracrine signalling between neighbouring cells and thus delays development.