In healthy humans, IL-18BP is present in the serum at a 20-fold molar excess compared with IL-18 [114], suggesting IL-18BP provides a threshold at which IL-18 does not mediate its effects until the concentration of IL-18 reaches a point where it does not induce systemic excessive Th1-type immune responses against general infection with low pathogenicity. This evidence concerns the gene IL18 and infection.