Although the Th2 cells that are characterized by the synthesis of IL-4, IL-5 and IL-13 are usually considered relevant for humoral immunity, protection from helminth infection and pathogenesis of the allergic inflammatory disease, the recent discovery of memory-type pathogenic Tpath2 cells by Nakayama et al. (2017) re-defined our understanding of IL-5 [34]. The gene discussed is IL5; the disease is helminthiasis.