IL9 and neoplasm: The seminal observation was reported by Purwar et al. (28), who incidentally found that B16F10 melanoma growth was inhibited in retinoid-related orphan receptor γ (ROR−/−γ)-deficient mice, which presented a greater number of infiltrating CD4+ and CD8+ T cells at tumor sites and secreted a high level of IL-9 compared with their Rorc+/+ch counterparts.