This group of cells is found in the blood, spleen, intestines, liver, skin, fat-associated lymphoid clusters, and lymph nodes and is enriched in inflamed skin, nasal polyps, and lungs (data unpublished).1, 2, 4 Several previous studies have identified the innate epithelial cytokines IL-33, IL-25, and TSLP and the lipid mediator PGD2 as important stimulators for ILC2s.5, 7 Although cysLTs have been investigated in mice,8 in the current study we examined the previously unrecognized roles of cysLTs in human ILC2 activation. The gene discussed is TSLP; the disease is nasal cavity polyp.