Innate immunological function of TH2 cells in vivo

Type 2 helper T cells (T(H)2 cells) produce interleukin 13 (IL-13) when stimulated by papain or house dust mite extract (HDM) and induce eosinophilic inflammation. This innate response is dependent on IL-33 but not T cell antigen receptors (TCRs). While type 2 innate lymphoid cells (ILC2 cells) are the dominant innate producers of IL-13 in naive mice, we found here that helminth-infected mice had more T(H)2 cells compared to uninfected mice, and these cells became major mediators of innate type 2 responses. T(H)2 cells made important contributions to HDM-induced antigen-nonspecific eosinophilic inflammation and protected mice recovering from infection with Ascaris suum against subsequent infection with the phylogenetically distant nematode Nippostrongylus brasiliensis. Our findings reveal a previously unappreciated role for effector T(H)2 cells during TCR-independent innate-like immune responses.