IL-4 expression by neutrophils in psoriasis lesional skin upon high-dose UVB exposure

BACKGROUND: Upon a single high dose of UVB irradiation of psoriatic lesional skin, IFN-gamma expression is decreased, whereas IL-4 expression is enhanced. A similar type 1 to type 2 shift was found in dermal T cells derived from irradiated lesional skin as compared to unexposed lesional psoriatic skin. We have found recently that the IL-4 protein detected in situ upon UVB exposure of normal skin was not associated with T cells but with infiltrating neutrophils. OBJECTIVE: To determine which cell types express IL-4 in psoriatic skin after UVB irradiation. METHODS: Skin biopsies were obtained from healthy controls and psoriasis patients before and after local UVB exposure. Double immunohistochemical stainings were performed to determine the identity of IL-4-expressing cells. RESULTS: In the irradiated skin of both healthy controls and patients, IL-4-positive cells coexpressed elastase and CD15, but not CD3. CONCLUSION: IL-4-expressing cells found in psoriatic skin after a single high-dose UVB exposure appeared to be neutrophils.