IL-9-deficient mice establish fundamental roles for IL-9 in pulmonary mastocytosis and goblet cell hyperplasia but not T cell development

Interleukin-9 is a cytokine produced by Th2 cells and is a candidate gene f or asthma and atopy. We have generated IL-9-deficient mice to delineate the specific roles of IL-9 in Th2 responses. Using a pulmonary granuloma model , we have demonstrated a distinct requirement for IL-9 in the rapid and rob ust generation of pulmonary goblet cell hyperplasia and mastocytosis in res ponse to lung challenge. In contrast, eosinophilia and granuloma formation were not affected. IL-9 was not required for T cell development or differen tiation, the generation of naive or antigen-driven antibody responses, or t he expulsion of the intestinal parasitic nematode Nippostrongylus brasilien sis. Thus, deletion of IL-9 manifests as a highly defined phenotype in Th2 responses modulating mucus production and mast cell proliferation.