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Cytokine-induced differentiation of cultured nonadherent macrophages
V Tsai1, G S Firestein, W Arend
1Division of Rheumatology, University of California, San Diego, La Jolla 92103-8417.
Abstract:
Monocytes were isolated from peripheral blood and cultured in vitro for more than 3 weeks in glass chamber slides. Phenotypically and ultrastructurally these nonadherent macrophages (NAM) appear similar to connective tissue resident macrophages. They constitutively secrete a high amount of IL-1ra and little or no IL-1 alpha or IL-1 beta. When exposed to GM-CSF, IL-2, or IFN-gamma for 24 hr, NAM become adherent and undergo dramatic morphological changes. Cytokines treatment primes NAM for increased LPS-mediated TNF production and these GM-CSF- and LPS-treated NAM are cytotoxic to WEHI 164, a TNF-sensitive target. Morphological changes and TNF production are both inhibited by antimetabolites and a variety of antineoplastic drugs. Although morphology inhibition is reversible under certain circumstances, inhibition of TNF synthesis is irreversible. These findings suggest that cytokines might play a role in differentiation and maturation of long-term cultured monocytes. Furthermore, the effects of antimetabolites and antineoplastic drugs on arresting the differentiation processes may significantly impair antitumor functions of macrophages.
Insights
Cytokines promote the differentiation of monocytes into macrophages, enhancing their tumor-fighting capabilities. However, antineoplastic drugs can irreversibly inhibit this crucial macrophage function.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Monocytes differentiate into macrophages, key immune cells involved in host defense.
- Long-term cultured monocytes (nonadherent macrophages, NAM) exhibit distinct characteristics, including high IL-1ra secretion.
- Understanding macrophage differentiation is crucial for developing effective immunotherapies.
Purpose of the Study:
- To investigate the role of cytokines in the differentiation and maturation of long-term cultured monocytes.
- To explore the impact of antimetabolites and antineoplastic drugs on macrophage differentiation and function.
- To assess the potential impairment of anti-tumor functions by these drugs.
Main Methods:
- Isolation and in vitro culture of human peripheral blood monocytes for over 3 weeks.
- Treatment of nonadherent macrophages (NAM) with cytokines (GM-CSF, IL-2, IFN-gamma).
- Assessment of morphological changes, IL-1ra, IL-1 alpha, IL-1 beta, and TNF production.
- Evaluation of the effects of antimetabolites and antineoplastic drugs on NAM differentiation and TNF production.
Main Results:
- Cultured NAM resemble resident macrophages, secreting high IL-1ra and low IL-1 alpha/beta.
- Cytokine treatment (GM-CSF, IL-2, IFN-gamma) induced NAM adherence, morphological changes, and primed them for increased LPS-mediated TNF production.
- GM-CSF and LPS-treated NAM demonstrated cytotoxicity against TNF-sensitive tumor cells (WEHI 164).
- Antimetabolites and antineoplastic drugs inhibited both morphological changes and TNF production, with TNF synthesis inhibition being irreversible.
Conclusions:
- Cytokines play a significant role in the differentiation and maturation of monocytes into functional macrophages.
- Antimetabolites and antineoplastic drugs can arrest macrophage differentiation, potentially impairing their anti-tumor activity.
- These findings highlight the delicate balance between therapeutic drug effects and essential immune functions.