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Background: Sweet's syndrome (acute febrile neutrophilic dermatosis) is characterized by fever, polymorphonuclear leukocytosis of blood, painful plaques on the limbs, face and neck, and histologically a dense dermal infiltration with mature neutrophils. Sweet's syndrome is often a complication of hematologic malignant disease or drug-induced sensitivity reactions and has a significant susceptibility correlated with certain human leukocyte antigen (HLA). Methods: A 5-week-old Japanese girl with Sweet's syndrome confirmed by skin biopsy was successfully treated and HLA analysis was performed. Results: The patient was one of the youngest patients reported with Sweet's syndrome, suggesting the importance of the genetic background. Although the HLA types of the patient did not have B54, which was reported as a significant susceptibility correlation, structural analysis of the patient's HLAs suggested a similar possible motif for the bound peptides. Conclusion: Studies on the HLA bound peptides and HLA structural analysis for patients with Sweet's syndrome would be valuable for understanding the molecular mechanism of the pathogenesis. [ABSTRACT FROM AUTHOR]

Interleukin-18 (IL-18), a cytokine formerly known as interferon-?- (IFN-?-) inducing factor, has pleiotropic immunoregulatory functions, including augmentation of IFN-? production, Fas-mediated cytotoxicity and developmental regulation of T-lymphocyte helper type I. We determined the solution structure of IL-18 as a first step toward understanding its receptor activation mechanism. It folds into a ß-trefoil structure that resembles that of IL-1. Extensive mutagenesis revealed the presence of three sites that are important for receptor activation: two serve as binding sites for IL-18 receptor a (IL-18Ra), located at positions similar to those of IL-1 for IL-1 receptor type I (IL-1RI), whereas the third site may be involved in IL-18 receptor ß (IL-18Rß) binding. The structure and mutagenesis data provide a basis for understanding the IL-18-induced heterodimerization of receptor subunits, which is necessary for receptor activation. [ABSTRACT FROM AUTHOR]