IL-17 and neutrophils: unexpected players in the type 2 immune response.

The study of immunity to helminth infection has been central to understanding the function of type 2 cytokines and their targets. Although type 2 cytokines are considered anti-inflammatory and promote tissue repair, they also contribute to allergy and fibrosis. Here, we utilise data from helminth infection models, to illustrate that IL-17 and neutrophils, typically associated with pro-inflammatory responses, are intimately linked with type 2 immunity. Neutrophils work with IL-4Rα-activated macrophages to control incoming larvae but this comes at a cost of enhanced tissue damage. Chitinase like proteins (CLPs) bridge these diverse outcomes, inducing both protective IL-17 and reparative Th2 responses. Dysregulation of CLPs, IL-17 and neutrophils likely contribute to disease severity and pathology associated with type 2 immunity.