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Atopic dermatitis is caused by abnormal immunoglobulin-E–mediated Th2 immune responses in settings of barrier dysfunction. Colonization of lesional skin by Staphylococcus aureus is a hallmark of active disease. S. aureus species produce exotoxins that can act as super antigens in disease models, but the precise mechanism by which S. aureus aggravates atopic dermatitis has been unclear.
Nakamura et al. have now identified the major mechanism by which S. aureus engages allergic-type Th2 T-cell responses in skin. Given the established role of IgE-mediated mast cell activation in atopic dermatitis, the researchers hypothesized that S. aureus secretes a factor that causes mast cell degranulation. Painstakingly, they identified δ-toxin as the mast…