HLA-DR Synthesis Induction and Expression in HLA-DR-Negative Carcinoma Cell Lines of Diverse Origins by Interferon-γ but not by Interferon-β<xref ref-type="fn" rid="FN2">2</xref>

Abstract

De novo synthesis of major histocompatibility complex (MHC) class II antigens was induced by affinity-purified preparations of interferon (IFN)-gamma, but not by IFN-beta (as judged by the criteria of cell surface expression and protein synthesis) in human osteogenic sarcoma, colorectal carcinoma, and melanoma cell lines that were not constitutive producers of these antigens. The synthesis of heavy-chain and light-chain (beta 2-microglobulin) components of MHC class I antigens was enhanced by both IFN-gamma and IFN-beta; IFN-gamma showed the greater activity. IFN-gamma and IFN-beta also enhanced the expression of class I antigens on the plasma membrane in a dose-dependent manner; IFN-gamma was again the more active agent. Only IFN-gamma induced the membrane appearance of class II antigens in cell lines that appeared negative for HLA-DR expression by all criteria. However, in SW480 cells, which spontaneously express low levels of HLA-DR, IFN-gamma and IFN-beta both enhanced the expression of class II antigens. These results suggest that IFN of both types amplify the products of actively transcribed genes, but that type II IFN is unique in its capacity to induce HLA-DR expression in nonconstitutive cell lines. Kinetic studies showed that enhancement of class I membrane expression preceded the induction of class II expression and peaked earlier. The specificity of these responses was underlined by the inability of either IFN to enhance the synthesis or expression of the tumor-associated membrane glycoprotein gp22. The data indicate that tumor cell lines of diverse tissue origin that do not synthesize or express class II antigens by the criteria of immunoprecipitation or monoclonal antibody binding can be induced to do so by IFN-gamma and may therefore be subject to therapeutic and immunoregulatory modulation.