Illustration showing the immune response to parasitic worms (helminths, green-black cylindrical tubes) that have damaged an area of the gut (centre). This damage activates a group of cytokines (signalling molecules) called alarmins. Alarmins are released by damaged, dead or dying cells. An example of an alarmin is interleukin-25 (centre, green fog), which induces another group of cells called innate lymphoid cells (ILC-2, blue spheres). ILC-2 cells also produce cytokines, including interleukin-13 (IL-13, purple fog), that initiate and amplify the type 2 immune response. The type 2 immune response responds to parasites, external toxins, venom and allergens in the body. IL-13 also modulates the secretion of mucus (far right, green) to repair the area damaged by helminths. Dendritic cells (yellow sphere, lower left) capture and display helminth antigens.