Production of IL-18 (IFN-gamma-inducing factor) messenger RNA and functional protein by murine keratinocytes

• Published in: The Journal of immunology (1950) Vol. 159; no. 1; pp. 298 - 302
• Main Authors: Stoll, S, Muller, G, Kurimoto, M, Saloga, J, Tanimoto, T, Yamauchi, H, Okamura, H, Knop, J, Enk, AH
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.07.1997
• Subjects: Animals; Cells, Cultured; Cytokines - biosynthesis; Interferon-gamma - immunology; Interferon-gamma - metabolism; Interleukin-18; Keratinocytes - immunology; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; RNA, Messenger - biosynthesis
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.159.1.298

Recently, the novel cytokine IL-18 (IFN-gamma-inducing factor) has been described as a growth and differentiation factor for Th1 cells. Epidermal keratinocytes (KC) are known to direct T cell education by production of cytokines. Therefore, expression of IL-18 was sought in KC. Epidermal RNA was analyzed following stimulation with contact sensitizers or controls for IL-18 mRNA expression by semiquantitative reverse transcription-PCR. Constitutive expression of IL-18 mRNA was low in untreated epidermal cells (EC), but early up-regulation of IL-18 mRNA signals was detected following application of a contact allergen in vivo. The peak strength of IL-18 signals was observed within 4 to 6 h following stimulation with an allergen. Application of an irritant (benzalconiumchloride) or solvents did not result in increased signal strength. To determine the cellular origin of IL-18 mRNA in EC, depletion experiments were performed. IL-18 signals were not affected by depletion with anti-CD3 (T cells) or anti-MHC class II mAb-coupled beads identifying KC as a major source of IL-18. These results were confirmed by analysis of mRNA derived from the KC cell line PAM 212. Strong IL-18 signals could be detected by reverse transcription-PCR. To delineate whether IL-18 protein was produced by EC/KC, a sandwich ELISA was used to assay for IL-18 production. Supernatants from allergen-stimulated EC and KC showed production of IL-18 protein. To confirm that IL-18 protein was functional, EC or KC supernatants were tested for their ability to induce IFN-gamma production. Significant amounts of IFN-gamma were detected in supernatants of allergen-treated cells. In aggregate, our data indicate that murine KC are a source of both IL-18 mRNA and functional protein.