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Influence of intestinal microflora on murine bone marrow and spleen macrophage precursors
P Nicaise1, A Gleizes, C Sandre
1Département de Microbiologie et Immunologie, Unité Associée INRA Ecologie Microbienne du Tube Digestif et Santé, Faculté de Pharmacie, Université Paris XI, Châtenay-Malabry, France.
Abstract:
To investigate the adjuvant effect of intestinal flora on macrophage-colony-stimulating factor-responsive macrophage progenitors from spleen and bone marrow, we compared progenitor numbers and phenotypic characteristics of in vitro matured macrophages in germ-free and flora-associated mice (conventional, Escherichia coli-monoassociated and conventionalized mice). The data obtained show that the flora affected differentially bone marrow and spleen progenitors. It increased the numbers of progenitors in the spleen but not in the bone marrow. It did not modify the expression of F4/80, Mac-1 and major histocompatibility complex (MHC) class II on bone-marrow-derived macrophages (BMDM), while it clearly up-regulated MHC class II expression on spleen-derived macrophages (SDM). This effect was more pronounced in flora-associated ex germ-free mice than in conventional mice and it was greatly enhanced in the absence of M-CSF. In vitro stimulation by lipopolysaccharide had no effect on marker expression of BMDM, while it decreased F4/80 and enhanced MHC class II molecules on SDM from germ-free and flora-associated mice. However, the expression of MHC class II remained lower in germ-free mice. Enhancement of MHC class II molecule expression on SDM may contribute to the protective role of flora, because successful immune responses are dependent on the expression of these molecules.
Insights
The gut microbiome influences immune cells. Intestinal flora boosts spleen progenitor cells and enhances major histocompatibility complex (MHC) class II expression on spleen macrophages, crucial for immune responses.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Intestinal flora plays a role in immune system development.
- Macrophage progenitors are key components of the immune response.
- The influence of gut microbiota on specific immune cell populations requires further elucidation.
Purpose of the Study:
- To investigate the adjuvant effect of intestinal flora on macrophage progenitors.
- To compare progenitor numbers and macrophage characteristics in germ-free versus flora-associated mice.
Main Methods:
- Comparison of progenitor cells and in vitro matured macrophages from germ-free and flora-associated mice.
- Analysis of macrophage markers (F4/80, Mac-1, MHC class II) on bone marrow-derived macrophages (BMDM) and spleen-derived macrophages (SDM).
- In vitro stimulation with lipopolysaccharide (LPS) and macrophage-colony-stimulating factor (M-CSF).
Main Results:
- Intestinal flora increased spleen progenitor numbers but not bone marrow progenitors.
- MHC class II expression was upregulated on SDM, particularly in flora-associated ex-germ-free mice and in the absence of M-CSF.
- Lipopolysaccharide stimulation affected SDM marker expression (decreased F4/80, enhanced MHC class II) but not BMDM.
Conclusions:
- Gut microbiota differentially affects bone marrow and spleen macrophage progenitors.
- Enhanced MHC class II expression on spleen-derived macrophages by flora may contribute to host defense.
- Understanding these interactions is vital for immune response modulation.