Patients with granulomatosis with polyangiitis (i.e., Wegener's granulomatosis) and those with systemic lupus erythematosus showed elevated serum levels of IL-18 as well as IL-18BP, but the levels of IL-18BP were not sufficient to neutralize IL-18, and the levels of free IL-18 were higher than those of healthy subjects (42, 48). This evidence concerns the gene IL18 and granulomatosis with polyangiitis.