Keratinocytes from patients with atopic dermatitis and psoriasis show a distinct chemokine production profile in response to T cell-derived cytokines

Background: Atopic dermatitis (AD) and psoriasis are genetically determined inflammatory skin disorders. Keratinocytes actively participate in cutaneo us inflammatory responses by elaborating various chemokines. Objective: We investigated the capacity of IL-4, IFN-gamma, and TNF-a to modulate the exp ression of CCL and CXCL chemokines in cultured keratinocytes from patients and healthy individuals, as well as chemokine expression in situ. Methods: Keratinocyte cultures were established from normal-looking skin of adult patients with AD or psoriasis vulgaris and from healthy subjects. Mo nocyte chemoattractant protein 1 (MCP-1)/CCL2, RANTES/CCL5, IL-8/CXCL8, and IFN-gamma -induced protein of 10 kd (IP-10)/CXCL10 production was evaluate d at the mRNA and protein levels by using RNase protection assay and ELISA, respectively. The expression of the same chemokines was studied in chronic Lesional skin by means of immunohistochemistry or in situ hybridization. Results: Only IL-8 mRNA was detected in unstimulated keratinocyte cultures. MCP-1 and IP-10 were potently induced by IFN-gamma, whereas IL-8 and RANTE S were preferentially upregulated by TNF-a and, to a lesser extent, by IFN- gamma. IL-4 weakly induced IP-10, RANTES, and IL-8 but not MCP-I. Keratinoc ytes of patients with AD invariably responded with significantly earlier an d higher RANTES expression. By contrast, keratinocytes of patients with pso riasis displayed much higher Levels of both constitutive and induced IL-8 a nd a stronger induction of MCP-1 and IP-10. RANTES and MCP-I mRNA(+) kerati nocytes were detected in the basal layer of lesions of patients with AD and psoriasis. IP-10 and IL-8 were consistently upregulated in the epidermis o f patients with psoriasis but not in lesions of patients with AD. Conclusions: Keratinocytes of patients with AD and psoriasis show an intrin sically abnormal and different chemokine production profile and may thus fa vor the recruitment of distinct leukocyte subsets into the skin.