Further researches tried to explain the cause behind the impaired body response. Impaired functions of the immune cells and the massive amounts of catabolic cytokines such as IL-1, IL-6, Il-17, TNF- α and prostaglan¬din E2 (PGE2) are usually released during the active periods of the disease. On the other hand, matrix-metalloproteinases are destructive enzymes that released in an uncontrollable manner. Host modulators were suggested to control the released of the destructive agents.