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Alteration of macrophage differentiation into accessory and effector cells from exposure to dimethylnitrosamine (DMN)
Abstract:
DMN exposure modulates cellular immunity through alterations in the maturation and hematopoiesis of macrophages. DMN-exposed bone marrow stem cells gave rise to increased colony-forming unit-macrophage (CFU-M) colonies while the resulting colonies produced fewer cells/colony. Bone marrow-derived macrophages phenotypically had decreased cells expressing Ia antigens or cells in the S-phase following DMN treatment. Concanavalin A-elicited peritoneal exudate cells from DMN-treated animals demonstrated an increase in the percentage of macrophages and in the number of immature, bi-nucleated cells obtained as well as a concomitant increase in the percentage of Ia antigen-expressing cells. Concanavalin A-elicited peritoneal exudate cells from DMN-exposed animals also had an increased secreted interleukin-1 activity following lipopolysaccharide stimulation without any alteration in the expression of membrane-bound interleukin-1. Thioglycolate-elicited peritoneal exudate cells from DMN-exposed animals demonstrated no changes in cellularity and only showed increases in the percentage of bi-nucleated cells. There were no alterations in the capacity of T cells obtained from DMN-treated animals to respond to either soluble (keyhole limpet hemocyanin) or allo-antigens; nor were there alterations in the capacity of these T cells to either produce or respond to interleukin-2. These findings suggest that the observed DMN-induced modulation(s) in cell-mediated immunity results from changes in macrophage hematopoiesis due to alterations in: the production of regulatory factors controlling their production and/or differentiation or their ability to respond to these factors.
Insights
Dimethylnitrosamine (DMN) exposure alters macrophage development and function, impacting cellular immunity. These changes in macrophage hematopoiesis affect immune responses without altering T-cell activity.
Area of Science:
- Immunology
- Hematopoiesis
- Cellular Biology
Background:
- Dimethylnitrosamine (DMN) is a chemical agent known to affect various biological systems.
- Cellular immunity relies heavily on the proper function and maturation of immune cells, particularly macrophages.
- Understanding how environmental factors like DMN exposure influence immune cell development is crucial for assessing health risks.
Purpose of the Study:
- To investigate the effects of DMN exposure on macrophage maturation and hematopoiesis.
- To determine how DMN-induced alterations in macrophages impact overall cellular immunity.
- To examine the specific changes in macrophage populations and their functional capacities following DMN treatment.
Main Methods:
- Assessing colony-forming unit-macrophage (CFU-M) from bone marrow stem cells after DMN exposure.
- Analyzing phenotypic changes in bone marrow-derived macrophages (e.g., Ia antigen expression, S-phase).
- Evaluating peritoneal exudate cells (macrophages) for maturation markers, interleukin-1 activity, and cellularity after DMN exposure.
- Testing T-cell responses to antigens and interleukin-2 in DMN-treated animals.
Main Results:
- DMN exposure increased CFU-M colonies but reduced cells per colony, indicating altered macrophage production.
- Bone marrow-derived macrophages showed decreased Ia antigen expression and S-phase activity post-DMN.
- Peritoneal macrophages from DMN-treated animals exhibited increased immature, bi-nucleated cells and enhanced secreted IL-1 activity.
- T-cell responses to soluble antigens, allo-antigens, and IL-2 remained unaffected by DMN treatment.
Conclusions:
- DMN exposure significantly modulates macrophage hematopoiesis and maturation.
- These macrophage alterations are the primary drivers of DMN-induced changes in cell-mediated immunity.
- The observed effects are likely due to altered production or response to regulatory factors controlling macrophage development.