The fact that IL-13 deletion mirrored the effect of IL-4Rα deletion on AOM-induced ACF formation and that IL-13 deletion did not abrogate the effect of lack of IL-4Rα-mediated signalling in DKO mice implicates a tumour suppressor role for the type II IL-4R (of which IL-4 and IL-13 are both ligands), rather than a tumour suppressor role of the type I IL-4R, or pro-tumorigenic activity of the IL-13Rα2 receptor. This evidence concerns the gene IL13 and infectious otitis media.