IL1B and familial Mediterranean fever: At first sight, this may appear paradoxical because identification of FMF alleles by the ex vivo colchicine assay is based on the inability of high colchicine concentrations (in the range of 0.1–1 μM) to inhibit inflammasome activation by FMF-associated Pyrin mutants.24 However, plasma concentrations of colchicine that are therapeutically effective in patients with FMF (<4 ng/mL or <0.01 μM)51 fail to robustly inhibit TcdA-induced secretion of IL-1ß and IL-18 from TcdA-stimulated PBMCs of healthy donors (data not shown).