Production of IL-18 (IFN-gamma-inducing factor) messenger RNA and functional protein by murine keratinocytes.
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.
Stoll
S
S
Department of Dermatology, University of Mainz, Germany.
Müller
G
G
Kurimoto
M
M
Saloga
J
J
Tanimoto
T
T
Yamauchi
H
H
Okamura
H
H
Knop
J
J
Enk
A H
AH
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis*; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D020382:Interleukin-18; D015603:Keratinocytes / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D012333:RNA, Messenger / Q000096:biosynthesis*
D016207:Cytokines; D020382:Interleukin-18; D012333:RNA, Messenger; D007371:Interferon-gamma