First, urushiol, which is found within poison ivy and historically considered to be a hapten, was shown to directly induce CD1a-dependent T-cell responses.10,119 Using a hCD1a-Tg mouse model, Kim et al. discovered that skin inflammation was driven by urushiol-specific CD1a-dependent CD4+ T cells with secretion of IL-17 and IL-22.10 This characteristic type 17 cell signature corresponded to the cytokine changes observed in humans with poison ivy dermatitis. Here, CD1A is linked to dermatitis.