Chicken interferon-mediated induction of major histocompatibility complex Class II antigens on peripheral blood monocytes

Conditioned medium containing immune interferon (IFN) activity was prepared by stimulating spleen lymphocytes obtained from inbred SC chickens with 10 μg concanavalin A (Con A) for 48 h. Pretreatment of spleen cells with monoclonal antibody against CD4, but not CD8, abrogated IFN production suggesting that CD4+ lymphocytes are responsible for immune IFN production. Immune IFN was purified 25-fold from Con A conditioned medium using controlled-pore glass column chromatography resulting in an increase in specific antiviral activity from 7 to 3290 units mg −1. Partially purified immune IFN retained antiviral and macrophage-activating factor (MAF)-like activities. Normal peripheral blood macrophages, when cultured in the presence of partially purified immune IFN, showed a dose-dependent increase in cell surface major histocompatibility complex Class II antigen expression by flow cytometry. Northern blot analysis of mRNA obtained from IFN-treated macrophages showed a concomitant increase in Class II gene expression. This effect was more obvious in cells induced for 48 h than in those induced for 24 h. These results strongly suggest the existence of an avian homologue of the MAF-like activity.