Evidence for a role of macrophage migration inhibitory factor in psoriaticskin disease

Macrophage migration inhibitory factor (MIF) was originally described as a T-cell-derived lymphokine with the potential to inhibit the random migratio n of macrophages. However, recent reports have shown a much broader tissue distribution, including the skin, Functionally, MIF appears to act as an an tagonist of anti-inflammatory glucocorticoid action. To elucidate the role of MIF in inflammatory skin diseases, we investigated the production and lo calization of this cytokine in human skin of patients with psoriasis by mea ns of reverse transcription-polymerase chain reaction, immunohistochemistry and Western blot analysis. In normal skin, our results showed a moderate b ut homogeneous MIF immunoreactivity in all epidermal layers, Endothelial ce lls and the outer root sheath of hair follicles were also positive for MIF. In lesional psoriatic human skin, a significant increase in MIF immunoreac tivity was visible in suprabasal keratinocytes, especially of the spinous l ayer. In addition, endothelial cells also showed increased immunolabelling for MIF in psoriatic lesions, indicating a cell-specific upregulation of th is mediator in untreated psoriasis, Western blot analysis also revealed a c lear increase in MIF in homogenates of lesional skin from psoriasis patient s. These results suggest a role for MIF in the inflammatory skin disease ps oriasis.