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Ontogeny of macrophage function to release superoxide anion in conventional and germfree mice
Abstract:
To determine whether the presence of bacterial flora contributes to the ontogenic development of macrophage function, the ability of macrophages to release superoxide anion (O2-) in response to stimulation with phorbol myristate acetate was compared in conventional and germfree mice of various ages after birth. One-week-old conventional mice showed a very low level of O2- release by their macrophages, and gradual increases were observed in 2-, 3-, and 4-week-old mice in an age-dependent manner. Macrophages from germfree mice always showed a significantly lower level of O2- release compared with conventional mice of the same age; however, age-dependent functional development was seen also in the germfree group. The poor level of O2- release by macrophages from adult germfree mice could be restored to more than the level by conventional mice when the mice were conventionalized for 3 weeks. These results suggested that the ontogenic development of macrophage function is not controlled by the presence of bacterial flora but that the full-scale expression of function at each age is under the influence of microflora.
Insights
Bacterial flora does not control macrophage development, but influences their function. Germfree mice showed age-dependent macrophage development, which improved with microbial exposure.
Area of Science:
- Immunology
- Microbiology
- Developmental Biology
Background:
- Macrophage function is crucial for immune responses.
- The role of microbial colonization in immune system development is not fully understood.
Purpose of the Study:
- To investigate the influence of bacterial flora on the ontogenic development of macrophage function.
- To compare superoxide anion release in macrophages from conventional and germfree mice.
Main Methods:
- Comparison of superoxide anion (O2-) release from macrophages stimulated with phorbol myristate acetate.
- Assessment in conventional and germfree mice of various ages.
- Evaluation after microbial colonization (conventionalization) in germfree mice.
Main Results:
- Macrophages from young conventional mice exhibited low O2- release, increasing with age.
- Germfree mice showed lower O2- release than conventional mice, but still exhibited age-dependent development.
- Conventionalization of adult germfree mice restored and enhanced macrophage O2- release.
Conclusions:
- Macrophage functional development is intrinsic and not solely dependent on bacterial flora.
- Microbial presence significantly influences the full expression of macrophage function at different life stages.
- Early-life microbial exposure is critical for optimal immune cell maturation and responsiveness.