Interferon-γ promotes exaggerated cytokine production in keratinocytes cultured from patients with atopic dermatitis

Recent studies suggest that skin keratinocytes from patients with atopic dermatitis (AD) and nonatopic subjects differ in their intrinsic ability to respond to proinflammatory stimuli. In this study keratinocyte cultures established from the normal-looking skin of six adult patients with AD and six healthy, nonatopic control subjects were compared in their response to interferon-gamma, a potent proinflammatory lymphokine whose expression is increased in chronic AD lesions. Basal expression of IFN-gamma receptor as well as IFN-gamma-induced membrane expression of HLA-DR and intercellular adhesion molecule (ICAM)-1 were evaluated by flow cytometry. Keratinocyte release of IL-1 alpha, IL-1 receptor antagonist (IL-1ra), granulocyte-macrophage colony stimulating factor (GM-CSF), and tumor necrosis factor (TNF)-alpha were measured by ELISA on culture supernatants after treatment with IFN-gamma or medium alone. Expression of membrane IFN-gamma receptor was similar in keratinocytes cultured from nonatopic subjects and subjects with AD. IFN-gamma (10 to 500 U/ml) induced comparable levels of membrane HLA-DR and ICAM-1 in both groups of keratinocytes. In contrast, spontaneous release of IL-1 alpha, IL-1ra, GM-CSF, and TNF-alpha were measured by ELISA on culture supernatants after treatment with IFN-gamma or medium alone. Expression of membrane IFN-gamma receptor was similar in keratinocytes cultured from nonatopic subjects and subjects with AD. IFN-gamma (10 to 500 U/ml) induced comparable levels of membrane HLA-DR and ICAM-1 in both groups of keratinocytes. In contrast, spontaneous release of IL-1 alpha, IL-1ra, GM-CSF, and TNF-alpha was increased in the supernatants of unstimulated keratinocytes from control subjects, with IL-1ra and GM-CSF reaching statistically significant difference. Moreover, IFN-gamma-induced release of all the cytokines tested was much higher for keratinocytes from patients with AD, but the IL-1ra/IL-1 alpha ratio for the two groups of keratinocytes was not substantially different, either basally or after IFN-gamma stimulation. The results indicate that keratinocytes from patients with AD are hyperresponsive to IFN-gamma in terms of cytokine release.