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Impaired chemotactic responsiveness of macrophages from gnotobiotic rats
Abstract:
Peptone-induced macrophages obtained from gnotobiotic (GB) rats responded poorly to chemotactic stimuli that have a powerful, attractive influence upon the cells of conventional donors. Monocyte recruitment from the circulation into peptone-induced exudates also was impaired in GB subjects. Although relatively more resident cells are present in exudates borne by GB donors, their number cannot in itself account for the sluggish response of peptone-induced cells from GB rats. Neutrophil accumulation in the inflamed peritoneal cavities and their responsiveness in vitro were similar in GB and conventional rats. The levels of serum-derived chemotactic factors were similar in such animals. Furthermore, germ-free rats exhibited no obvious defects in their capacity to generate lymphocyte-dependent monocyte chemotactic activity in situ upon specific stimulation with Listeria monocytogenes. It is suggested that the diminished chemotactic responsiveness of exudate macrophages is related in some way to the level of cell activation. This state of affairs might account for the impairment of delayed-type hypersensitivity in GB animals and their inability to resist intracellular bacterial infections.
Insights
Gnotobiotic rats exhibit impaired macrophage chemotaxis, impacting their immune response to bacterial infections. This suggests a link between cell activation levels and immune function in germ-free animals.
Area of Science:
- Immunology
- Microbiology
- Gnotobiology
Background:
- Macrophages are crucial immune cells involved in chemotaxis and host defense.
- Gnotobiotic (GB) animals lack a conventional microbiome, potentially affecting immune system development and function.
- Previous studies suggest microbiome influences immune cell behavior.
Purpose of the Study:
- To investigate the chemotactic responsiveness of macrophages in gnotobiotic rats.
- To compare immune cell recruitment and function between GB and conventional rats.
- To explore the implications of altered macrophage function in GB animals for host defense.
Main Methods:
- Induction of peritoneal exudates using peptone in GB and conventional rats.
- Assessment of macrophage and neutrophil chemotaxis in vitro and in vivo.
- Evaluation of monocyte recruitment into inflammatory sites.
- Stimulation of germ-free rats with Listeria monocytogenes to assess lymphocyte-dependent monocyte chemotaxis.
Main Results:
- Peptone-induced macrophages from GB rats showed significantly reduced chemotactic responsiveness compared to conventional rats.
- Monocyte recruitment into peptone-induced exudates was impaired in GB subjects.
- Neutrophil accumulation and responsiveness were comparable between GB and conventional rats.
- Germ-free rats demonstrated normal lymphocyte-dependent monocyte chemotactic activity in response to Listeria monocytogenes.
Conclusions:
- Diminished chemotactic responsiveness of exudate macrophages in GB rats is likely related to their level of cell activation.
- Impaired macrophage function in GB animals may contribute to their susceptibility to intracellular bacterial infections.
- The findings highlight the role of the microbiome in modulating macrophage function and overall immune competence.