The critical role of IL-13 and related Th2 cytokines in allergic sensitization and its clinical manifestations is emphasized in a recent study documenting that a subset of IL-13-producing T follicular helper (Tfh) cells, termed Tfh13, is critically required for the expression of high-affinity specific IgE and the subsequent development of severe anaphylaxis [146]. The gene discussed is IL13; the disease is hypersensitivity reaction disease.