IL18 and rheumatoid arthritis: Elevated levels of IL-18 were found in situ of the lesion or in the peripheral circulatory system, including the synovial fluid of patients with RA [6], the skin of patients with PsO [7], the intestinal samples of patients with IBD [8], the serum and glomeruli of patients with SLE [9], and the serum of patients with AS [10].