The nature of the events that precipitate autoimmune diseases varies. Interleukin-1 and tumor necrosis factor do not precipitate autoimmune diseases but rather act as effector molecules. They induce eicosanoid and nitric oxide synthesis, stimulate collagenases and collagen synthesis, and trigger the genes for other cytokines, namely interleukin-2, interleukin-6 and interleukin-8. The ability to block interleukin-1 with the receptor antagonist, and tumor necrosis factor with soluble receptors, has given investigators specific tools to test the role of these two cytokines in the pathological processes of autoimmune disease.