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

We have examined the influence of human recombinant interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma) 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-beta. IFN-gamma increased class II expression in a dose-dependent fashion. We demonstrate that IFN-beta is either antagonistic or synergistic with IFN-gamma 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-gamma alone. Pretreatment with IFN-beta for 72 h, followed by both interferons yielded a 90% reduction. In contrast, lower concentrations (10 IU/ml) of both interferons were synergistic.