Type II innate lymphoid cells (ILC2) are a novel population of lineage-negative cells that produce high levels
of Th2 cytokines IL-5 and IL-13. ILC2 are found in human respiratory and gastrointestinal tissue as well as in skin.
Studies from mouse models of asthma and atopic dermatitis suggest a role for ILC2 in promoting allergic inflammation.
The epithelial cytokines IL-25, IL-33, and TSLP, as well as the lipid mediator leukotriene D4, have been shown to
potently activate ILC2 under specific conditions and supporting the notion that many separate pathways in allergic disease
may result in stimulation of ILC2. Ongoing investigations are required to better characterize the relative contribution of
ILC2 in allergic inflammation as well as mechanisms by which other cell types including conventional T cells regulate
ILC2 survival, proliferation, and cytokine production. Importantly, therapeutic strategies to target ILC2 may reduce
allergic inflammation in afflicted individuals. This review summarizes the development, surface marker profile, cytokine
production, and upstream regulation of ILC2, and focuses on the role of ILC2 in common allergic diseases.