IL33 and idiopathic pulmonary fibrosis: To assess whether IL-33 secreted either from fibroblasts themselves or from other cell types within the lung could mediate pro-fibrotic effects on fibroblasts, we stimulated non-IPF and IPF HLFs with exogenous IL-33 and found no evidence of increased expression of pro-inflammatory or pro-fibrotic genes suggesting that this cytokine does not promote fibrogenesis.