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Specific interferon genes are expressed in individual cells in the peritoneum and bone marrow of normal mice
E Proietti1, C Vanden Broecke, P Di Marzio
1Laboratory of Viral Oncology (UPR CNRS 274), Institut de, Recherches Scientifiques sur le Cancer, Villejuif, France.
Abstract:
The use of a highly sensitive method of in situ hybridization capable of detecting one copy of IFN mRNA per cell showed that from 20-50% of the cells from the peritoneum and bone marrow of both normal pathogen-free and axenic mice exhibited grain counts significantly greater than background levels following hybridization with riboprobes specific for the mouse interferon-alpha (IFN-alpha), IFN-beta, or IFN-gamma genes. Labeling was shown to be specific, as the labeled probe was displaced by a 200-fold excess of the specific unlabeled probe but not by a 200-fold excess of an unrelated probe. Grain counts were reduced to background levels when cells were pretreated with ribonuclease prior to in situ hybridization. The extent of labeling with either IFN-alpha or IFN-beta-specific probes increased following i.v. inoculation of mice with the IFN-inducer Newcastle disease virus (NDV) whereas the degree of labeling observed with a probe specific for beta-actin remained unchanged. No significant differences were observed in the number of bone marrow or peritoneal cells that expressed IFN-alpha or IFN-beta mRNA from either high (C57B1/6) or low (BALB/c) IFN-producing strains of mice. The majority of IFN-alpha and IFN-beta-containing cells from both the bone marrow and peritoneum of normal pathogen-free and axenic mice resembled monocytes morphologically, whereas the majority of IFN-gamma mRNA-containing cells resembled small lymphocytes. In addition, in the bone marrow a number of large cells which resembled megacaryocytes were found to express high levels of IFN-alpha mRNA. Nuclear run-on assays showed that IFN-alpha and IFN-beta genes were actively transcribed in both bone marrow and peritoneal cells from normal and axenic mice. Low levels of de novo IFN-gamma RNA synthesis were detected in the nuclei of peritoneal cells only. The expression of IFN genes in individual cells in the tissues of normal animals may constitute a basis for the regulation of both homeostasis and host defense against virus infection and neoplastic cells.
Insights
Normal mice possess interferon (IFN) mRNA in bone marrow and peritoneal cells, crucial for immune defense. This study identifies specific cell types expressing different types of IFN, revealing their role in homeostasis and antiviral responses.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Interferons (IFNs) are critical cytokines involved in immune responses.
- Understanding IFN gene expression in different cell types is essential for elucidating immune regulation.
Purpose of the Study:
- To investigate the presence and cellular localization of interferon-alpha (IFN-alpha), IFN-beta, and IFN-gamma mRNA in mouse bone marrow and peritoneal cells.
- To assess the regulation of IFN gene expression following viral induction and in different mouse strains.
- To determine the transcriptional activity of IFN genes in these cells.
Main Methods:
- Highly sensitive in situ hybridization using specific riboprobes for IFN-alpha, IFN-beta, and IFN-gamma mRNA.
- Specificity controls included probe displacement assays and RNase treatment.
- Newcastle disease virus (NDV) inoculation to induce IFN production.
- Nuclear run-on assays to assess gene transcription.
Main Results:
- 20-50% of bone marrow and peritoneal cells from normal mice expressed IFN-alpha, IFN-beta, or IFN-gamma mRNA.
- IFN-alpha and IFN-beta mRNA expression increased after NDV inoculation.
- IFN-alpha/beta expressing cells were predominantly monocytes, while IFN-gamma expressing cells were small lymphocytes. Megakaryocytes also showed high IFN-alpha mRNA levels.
- IFN-alpha and IFN-beta genes were actively transcribed in both normal and axenic mice; IFN-gamma transcription was detected in peritoneal cells only.
Conclusions:
- Constitutive expression of IFN genes in bone marrow and peritoneal cells suggests a role in maintaining tissue homeostasis.
- IFN-producing cells in these tissues contribute to innate immunity against viral infections and neoplastic cells.
- Cell-specific expression patterns of different IFN types highlight distinct regulatory mechanisms and functions.