A study conducted in Ireland also showed significant down regulation of IL-18 expression after response to the standard treatment for RA.22 This study also measured the serum levels of IL-18 by ELISA, which also showed marked reduction in serum levels of IL-18 in RA patients when given the standard methotrexate treatment for reducing the crippling and debilitating effect of inflammation. This evidence concerns the gene IL18 and rheumatoid arthritis.