CASP4 and idiopathic pulmonary fibrosis: Because caspase-8, besides caspase-1, are reported as understream NLRP3 activation, we can conclude that because NLRP3 is not involved in the release of IL-1α and IL-18 in PBMCs of IPF patients, it is likely that LPS triggers the intracellular caspase-4 (9, 21) that is released (although not in a statistically different manner) after LPS addition.