PTGDR2 and pulmonary fibrosis: Additionally, specific overexpression of CHI3L1 in the ILC2 population using the IL-7Rcre driver, which was associated with increased fibroproliferation, indicates that ILC2-mediated, CRTH2-dependent mechanisms might contribute to optimal CHI3L1-induced fibroproliferative repair in HPS-associated pulmonary fibrosis.