Down-regulation of interferon-γ-induced class II expression on human glioma cells by recombinant interferon-β: effects of dosage treatment schedule

We have examined the influence of human recombinant interferon-β (IFN-β) and interferon-γ (IFN-γ) on class II antigen expression on cultured glioblastoma multiforme cells by flow cytometry. Class II molecules were not constitutively expressed on these cells, nor induced by IFN-β. IFN-γ increased class II expression in a dose-dependent fashion. We demonstrate that IFN-β is either antagonistic or synergistic with IFN-γ in class II induction depending upon dose and schedule of administration. Both interferons at 100 IU/ml reduce class II expression by 18%, compared to IFN-γ alone. Pretreatment with IFN-β for 72 h, followed by both interferons yielded a 90% reduction. In contrast, lower concentrations (10 IU/ml) of both interferons were synergistic.