Interleukin-18 in hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is characterized by dysregulated h yperactivation of macrophages and T helper 1 (Th1) cells accompanied by exc essive secretion of inflammatory cytokines. Although TNF-alpha and IFN-gamm a are known to be important factors for the development of the disease, the mechanism of their overproduction has not been clarified, yet. We measured serum IL-18 levels of patients with HLH to investigate the possible signif icance of IL-18 in its pathophysiology, especially in IFN-gamma production. IL-18 levels were significantly increased in all patients with HLH compare d with healthy controls. A significant correlation was observed between IL- 18 and IFN-gamma levels. In addition to IFN-gamma and soluble Fas ligand (s FasL), IL-18 levels significantly correlated with disease activity. IL-18 m ay play important roles in the pathogenesis of HLH, particularly through in duction of Th1 cells. In addition, IL-18 measurement may not only be useful for the diagnosis, but also for the evaluation of disease activity.