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Interleukin‐4 and interferon‐γ interactions in the induction of intercellular adhesion molecule‐1 and major histocompatibility complex class II antigen expression of normal human keratinocytes

Abstract Interleukin‐4 (IL‐4) that may be produduced by T‐helper cells in atopic lesions has immunomodulatory activities on skin cells which are poorly known. Our study was aimed at determining whether the cytokine exerts some effects on keratinocyte activation and can either enhance or antagonize interferon‐γ (IFN‐γ)‐induced ICAM‐I or HLA‐DR antigen expression. Using normal keratinocytes cultured in defined medium and cytofluorography, we showed that treatments of the human cells with the cytokine IL‐4 alone had no effect on the induction of ICAM‐1 or HLA‐DR molecules. However, a transient, but significant enhanced expression of ICAM‐I was observed by the combination of IFN‐γ and IL‐4 after 24 h of stimulation, which was followed by a reduction at 48 and 72 h. Conversely, IL‐4, when added during the IFN‐γ activation stage, had no effect on MHC class II antigen expression of keratinocytes; however, the cytokine reduced the expression of these antigens when added 24 h before the stimulation by IFN‐γ. These results suggest that IFN‐γ and IL‐4 may interact to regulate ICAM‐1 and HLA‐DR expression on keratinocytes.