Oral use of interferon-alpha stimulates ISG-15 transcription and production by human buccal epithelial cells

ISG-15 is a 15-kDa protein encoded by an interferon (IFN)-stimulated gene ( ISG), which is transcriptionally regulated by IFN-alpha and IFN-beta. Consi dered as part of the cytokine network, ISG-15 has the potential to amplify the immunomodulatory effects of these IFNs by enhancing IFN-gamma productio n, natural killer cell proliferation, and lymphokine-activated killer cell cytotoxicity. To understand better the mechanism(s) of action of orally adm inistered IFN-alpha, we have studied the effect of IFN-alpha on ISG-15 gene expression by human buccal epithelial cells (BEC), For in vitro studies, I SG-15 mRNA and protein levels were measured in BEC incubated for 0.5, 2, an d 9 h with 100 or 1,000 IU/ml of human lymphoblastoid IFN-alpha. For in viv o studies, ISG-15 mRNA was measured in BEC samples collected at baseline, a nd 0.5, 2, and 9 h after 5-20 min of oral rinsing with 10 ml of IFN-alpha ( 1,000 IU/ml), ISG-15 mRNA was measured by reverse transcriptase polymerase chain reaction (RT-PCR), and ISG-15 protein production by Western Blot anal ysis, IFN-alpha augmented BEC ISG-15 gene expression in a concentration dep endent manner both in vivo and in vitro, We conclude that orally administer ed IFN-alpha exerts its immunomodulatory effects in humans in part by upreg ulating the production of ISG-15 by BEC, thereby enhancing the immune react ivity of mucose-associated lymphocytes.