IL33 and chronic obstructive pulmonary disease: However, recent evidence suggests that IL-33 is secreted via endosomes by epithelial cells in chronic obstructive pulmonary disease (31), via Toll-like receptors by vascular endothelial cells (32) and via perforin 2 by dendritic cells (33), suggesting that IL-33 can be produced by cells not undergoing necrosis.