In this scenario, we recently demonstrated that combustion-generated ultrafine particles (UFPs) induced COPD-derived peripheral blood mononuclear cells (PBMCs) to release IL-1-like cytokines, although in a non-canonical manner, via the involvement of caspase-4, rather than caspase-1 and -8 (De Falco et al., 2017a). Here, CASP4 is linked to chronic obstructive pulmonary disease.