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Effect of human recombinant cytokines on the induction of macrophage procoagulant activity
1Institute of Veterinary Virology, University of Berne, Switzerland.
Abstract:
A panel of human recombinant cytokines was tested for induction of procoagulant activity (PCA) in human monocyte-derived macrophages. Nonadherent culture conditions were used, and PCA was determined with whole cells rather than cell lysates. It was assured by Limulus amebocyte lysate assay that tested cytokines displayed low levels of endotoxin activity within the range of biologic activity. Additional evidence to rule out an endotoxin effect was provided by heat-inactivation experiments. Interferon-gamma (IFN-gamma), interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) were strong macrophage PCA inducers. The low level of PCA induced by IL-2, granulocyte-macrophage colony-stimulating factor (GM-CSF), M-CSF, IL-4, IL-6, IL-10, and IFN-alpha could not be distinguished from that induced by traces of endotoxin contaminating the preparations. Transforming growth factor-beta decreased constitutively expressed PCA within 24 hours of exposure. PCA induced by IFN-gamma, IL-1 beta, and TNF-alpha depended largely on tissue factor expression, as evidenced by experiments with factor X-deficient plasma and antitissue factor antibodies. In macrophages subcultured in adherence, IL-1 beta was a strong PCA inducer, whereas IFN-gamma and TNF-alpha promoted little PCA increase. This observation and different kinetics of PCA induction suggested that mechanisms of PCA induction are distinct for the three cytokines. Thus, we showed that well-characterized cytokines critically involved in the promotion of cell-mediated antimicrobial defense/delayed-type hypersensitivity and considered for clinical application promote local fibrin deposition by a direct effect on macrophages.
Insights
Certain cytokines, including interferon-gamma (IFN-γ), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α), directly induce procoagulant activity in macrophages, promoting local fibrin deposition.
Area of Science:
- Immunology
- Hematology
- Cell Biology
Background:
- Cytokines are key mediators in immune responses, influencing various cellular functions.
- Procoagulant activity (PCA) in macrophages can contribute to local fibrin deposition.
- Understanding cytokine-induced PCA is crucial for evaluating their role in inflammation and clinical applications.
Purpose of the Study:
- To investigate the ability of various human recombinant cytokines to induce procoagulant activity (PCA) in human monocyte-derived macrophages.
- To differentiate direct cytokine effects from potential endotoxin contamination.
- To elucidate the mechanisms underlying cytokine-induced PCA, particularly the role of tissue factor.
Main Methods:
- Human monocyte-derived macrophages cultured under nonadherent conditions were exposed to a panel of recombinant cytokines.
- Procoagulant activity (PCA) was measured using whole cells, with endotoxin levels controlled and assessed via Limulus amebocyte lysate assay and heat inactivation.
- Tissue factor-dependent PCA was evaluated using factor X-deficient plasma and anti-tissue factor antibodies; adherence conditions were also tested.
Main Results:
- Interferon-gamma (IFN-γ), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) significantly induced PCA in macrophages.
- PCA induced by IFN-γ, IL-1β, and TNF-α was largely dependent on tissue factor expression.
- Transforming growth factor-beta (TGF-β) decreased constitutive PCA; IL-1β was a strong inducer in adherent macrophages, while IFN-γ and TNF-α showed weaker induction under these conditions.
Conclusions:
- Well-characterized cytokines, including IFN-γ, IL-1β, and TNF-α, directly induce procoagulant activity in macrophages.
- These cytokines, relevant to cell-mediated immunity and clinical applications, can promote local fibrin deposition.
- Distinct mechanisms underlie PCA induction by different cytokines, highlighting their specific roles in hemostasis and inflammation.