IL-18 is produced by many cell types, such as Kupffer cells, keratinocytes, macrophages, dendritic cells, and activated T cells stimulated by LPS. It is an important regulator of both innate and acquired immune responses. IL-18 plays a central role in rheumatoid arthritis since the T cells and macrophages that invade the synovial. These finding support a role for IL-18 in inflammation, allergy and immune diseases.