Induction of interferon gamma in human gingival fibroblasts challenged with phytohaemagglutinin

Interferon gamma (IFN-gamma) is a potential immunoregulatory cytokine, which is secreted mainly by cells of immune origin. In this study, we examined the capacity of human gingival fibroblasts as non-professional immune cells to express IFN-gamma messenger RNA (mRNA) and to produce the protein. Cultures of fibroblast cells were established from gingival biopsies from three children. The expression of mRNA for IFN-gamma was studied by in situ hybridization, and the level of IFN-gamma was determined by cell-released capturing ELISA. Treatment of the cells with phytohaemagglutinin (PHA) (2.5, 5.0, and 10 microg/ml) increased the number of IFN-gamma mRNA expressing cells and the protein production at 1, 6, and 24 h. Non-stimulated cells did not reveal measurable levels of IFN-gamma mRNA or the protein. The inflammatory cytokines interleukin 1beta (IL-1beta) (100 microg/ml) and tumour necrosis factor alpha (TNFalpha) (10 ng/ml) did not affect IFN-gamma mRNA expression or protein production. Treatment of the cells with 1 microM phorbol 12-myristate-13-acetate (PMA) stimulated IFN-gamma mRNA expression but had no effect on IFN-gamma protein production. We conclude that human gingival fibroblasts not only transcribe IFN-gamma mRNA but also produce the IFN-gamma protein in response to PHA. The finding that human gingival fibroblasts, produce the cytokine IFN-gamma, further support the concept that these cells take an active part in the modulation of the inflammatory and immune response in the periodontal tissue.