Background-Eosinophils are likely key cells involved in the pathogenesis of asthma and allergic diseases; however, the mechanisms that regulate eosinophil dynamics and functions in mucosal tissues are incompletely understood. IL-33, which is produced by mucosal cells, is a new member of the IL-1 cytokine family. Mice injected with IL-33 display profound mucosal eosinophilia with associated pathologic changes. Although mast cells and Th2 cells express the IL-33 receptor, ST2, the roles of IL-33 and ST2 in eosinophil biology are unknown.

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Summary Scratching triggers skin flares in atopic dermatitis (AD). We demonstrate that scratching of human skin, and tape stripping of mouse skin, causes neutrophil influx. This influx in mice was largely dependent on the generation of leukotriene B4 (LTB4) by neutrophils and their expression of the LTB4 receptor BLT1. Allergic skin inflammation in response to epicutaneous (EC) application of ovalbumin to tape-stripped skin was severely impaired in Ltb4r1−/− mice, and required expression of BLT1 on both T cells and non-T cells. Co-transfer of WT neutrophils, but not neutrophils deficient in BLT1 or the LTB4 synthesizing enzyme LTA4H, restored the ability of WT CD4+ effector T cells to transfer allergic skin inflammation to Ltb4r1−/− recipients. Pharmacologic blockade of LTB4 synthesis inhibited allergic skin inflammation elicited by cutaneous antigen challenge in previously EC-sensitized mice. Our results demonstrate that a neutrophil-T cell axis reliant on LTB4-BLT1 interaction is required for allergic skin inflammation.