Interferon-beta specifically inhibits interferon-gamma-induced class II major histocompatibility complex gene transcription in a human astrocytoma cell line
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R M Ransohoff1, C Devajyothi, M L Estes
1Department of Molecular Biology, Cleveland Clinic Foundation, OH 44195.
Insights
Interferon-beta inhibits interferon-gamma’s induction of HLA-DR in astrocytes at the transcriptional level. This suppressive effect is gene-specific and tissue-specific, not affecting ICAM-1 or monocyte HLA-DR.
Area of Science:
- Neuroimmunology
- Molecular Biology
- Immunogenetics
Background:
- Class II Major Histocompatibility Complex (MHC) antigens are crucial for immune responses.
- Interferons (IFNs) modulate immune cell functions, including MHC expression.
- Previous studies indicated IFN-gamma induces and IFN-beta inhibits HLA-DR expression in astrocytes.
Purpose of the Study:
- To investigate the molecular mechanism of IFN-beta's inhibition on IFN-gamma-induced HLA-DR expression in human astrocytes.
- To determine the gene and tissue specificity of IFN-beta's suppressive effect.
Main Methods:
- Primary cultures of human astrocytes and astrocytoma cells.
- Nuclear run-on assays to assess transcriptional activity.
- Blot hybridization analysis for gene expression.
- Assessment of Intercellular Adhesion Molecule-1 (ICAM-1) expression.
- Comparison with human monocyte responses.
Main Results:
- IFN-beta's inhibition of IFN-gamma-induced HLA-DR alpha gene expression in astrocytes occurs at the transcriptional level.
- IFN-beta did not inhibit IFN-gamma-induced ICAM-1 expression in astrocytes, indicating gene-specific suppression.
- IFN-beta did not antagonize IFN-gamma-induced HLA-DR expression in human monocytes, suggesting tissue-specific inhibition.
Conclusions:
- IFN-beta exerts transcriptional repression on IFN-gamma-mediated HLA-DR induction in astrocytes.
- The inhibitory effect of IFN-beta is specific to certain genes like HLA-DR and tissues like astrocytes.
- These findings highlight the complex and context-dependent regulation of immune responses in the central nervous system.
Abstract:
We established cultures of human astrocytes and astrocytoma cells from surgical specimens, to study regulation of class II major histocompatibility (MHC) complex antigen expression by interferons. Using these cultures we previously showed that expression of the class II MHC determinant HLA-DR could be induced by interferon-gamma and this induction was inhibited by interferon-beta. In this report, we extend these observations by showing that the inhibitory effect of interferon-beta on interferon-gamma induction of the class II MHC gene HLA-DR alpha was exerted at the transcriptional level, as documented by nuclear run-on experiments and confirmed with blot hybridization analysis. Astrocyte expression of intercellular adhesion molecule-1 (ICAM-1) was induced efficiently by interferon-gamma, but not by interferon-beta, and induction of ICAM-1 expression by interferon-gamma could not be impaired by interferon-beta, suggesting that the suppressive effect on induction of HLA-DR was relatively gene-specific. Furthermore, interferon-beta did not antagonize interferon-gamma induction of HLA-DR expression in human monocytes, suggesting that the inhibition observed in astrocytes was relatively tissue-specific.