ILC2s in infectious diseases and organ-specific fibrosis.

Type 2 immune responses evolved to provide host protection against parasitic infections and to support the repair of infection-induced tissue injury. However, persistent chronic organ damage can result in dysregulated production of critical type 2 cytokines supporting tissue remodeling and fibrosis development. Recently, group 2 innate lymphoid cells (ILC2s) were newly described as central innate mediators of type 2 responses. In particular, by secretion of the cytokines IL-5, IL-9, and IL-13 and the growth factor amphiregulin in response to the release of tissue-derived alarmins, ILC2s have been shown to substantially contribute to both the dismissal of metazoan parasites and the repair of infection-dependent or sterile tissue damage. Conversely, cytokine production by ILC2s emerged as a driving force for tissue remodeling and excessive fibrosis in several organ systems including the lung, liver, and skin. In this review, we discuss how ILC2s are specifically implicated in the body's immune response to different pathogenic infections and how dysregulated ILC2s may promote organ-specific fibrosis.