Figure 2.

Helminth‐induced immune responses mediated by ILC2s. Helminth parasites trigger the secretion of alarmins by endothelial or epithelial cells (IL‐33, TSLP)27, 28, 29 or by tuft cells (IL‐25).32, 33, 34 Myeloid cells (dendritic cells (DC) or macrophages) can also release IL‐33 and thereby activate ILC2s.30, 31 ILC2 activation is maintained and multiplied by IL‐4 and IL‐9 (acting in an autocrine manner)36 and require IL‐2 and IL‐7 for homoeostasis and activation. ILC2s secrets type 2 cytokines upon activation. IL‐5 induces eosinophilia,139, 151 and IL‐4 triggers B cells and induces isotype switching to IgE. Furthermore, IL‐13 can activate mucus secretion by goblet cells,1, 16, 152 act on mast cells (potentially in conjunction with IL‐9152) and regulate DC migration.153 IL‐4 and IL‐13 can also induce alternative activated macrophages (AAM).154 ILC2s also secrete amphiregulin (Areg) important for tissue repair.9 Furthermore, ILC2s interact with T_H2 CD4+ T cells (T_H2), which induces T_H2 immune response43, 155 and IL‐2 secreted by T cells could further sustain ILC2 responses and further affect generation of T‐cell memory,156 which is altered in chronic helminth infections.84 Helminth can induce regulatory T cells (Treg), which potentially can dampen the development of full protective immune response118