Interferon-α and Interferon-β Induce Ia Expression in Limited Protein Synthesis Condition

Abstract

We investigated the regulatory effect of interferons (IFNs) on macrophage (mϕ) Ia antigen expression. Unlike type II IFN (IFN-γ), type I IFNs (IFN-α and IFN-β) were incapable of inducing the accumulation of Ia mRNA. However, when cultured with type I IFN plus cycloheximide (CHX), Mϕ accumulated significant amounts of Ia-specific mRNA, which was translated into Ia molecules expressed on the cell surface after the removal of CHX. Significant enhancement of Ia mRNA accumulation and the Ia expression were observed also in Mϕ stimulated with IFN-γ plus CHX. Type I IFNs suppressed IFN-γ-dependent Ia expression through the inhibition of Ia mRNA accumulation, but such suppression was not directed to the post-transcriptional step in Mϕ that had accumulated Ia mRNA in response to stimulation by type I or type II IFN plus CHX. These results seem to indicate that type I IFNs can induce Ia mRNA accumulation but that they also induce some inhibitory protein, the synthesis of which precedes it and is dominant, so that the Ia expression is masked.