Species specificity of a novel factor which augments the expression of MHC class I antigens on tumor cell lines

Abstract

A novel factor which augments the expression of major histocompatibility complex I (MHC augmenting factor or MHC-AF) antigens on tumor cell lines, has been isolated from the culture supernatants of human peripheral blood mononuclear cells activated by concanavalin-A. A mouse equivalent of this factor has also been isolated from the culture supernatants of mouse spleen cells activated by mitogens or in a mixed lymphocyte reaction. Mouse MHC-AF enhances the expression of class I MHC antigens on murine tumor cell lines (EL-4 and BW5147) but not on human tumor cell lines (K562 and HR-7). Human MHC-AF on the other hand enhances the MHC I expression on both human as well as murine cell lines. Interferon γ (IFN-γ), a cytokine also known to enhance the expression of MHC I antigens, acts in a highly species specific manner with mouse IFN-γ augmenting the MHC I on murine tumor cell lines and human IFN-γ augmenting the MHC I on human tumor cell lines only. These results indicate important differences in the cross species biological activities of MHC-AF and IFN-γ, and provide additional evidence for MHC-AF being distinct from IFN-γ.