IL33 and chronic obstructive pulmonary disease: Regarding non-canonical inflammasome pathway, De Falco et al. demonstrated that IL-18 and IL-33 release from combustion-generated ultrafine particles (UFPs) treated PBMCs of unstable/exacerbated COPD patients correlated with caspase-4 release, and this effect was not observed in stable COPD-derived PBMCs.