Specific binding of soluble fibrin to macrophages

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Culture of Macrophage Colony-stimulating Factor Differentiated Human Monocyte-derived Macrophages
06:46

Culture of Macrophage Colony-stimulating Factor Differentiated Human Monocyte-derived Macrophages

Published on: June 30, 2016

L A Sherman, J Lee

    The Journal of Experimental Medicine
    |January 1, 1977
    PubMed

    Insights

    Guinea pig macrophages bind soluble fibrin, a process crucial for removing fibrin from the bloodstream. This binding mechanism may help prevent microthrombi formation.

    Area of Science:

    • Immunology
    • Hematology
    • Cell Biology

    Background:

    • Fibrin plays a critical role in hemostasis and thrombosis.
    • The interaction between immune cells and fibrin is not fully understood.
    • Mechanisms for clearing soluble fibrin from circulation are important for preventing pathological thrombus formation.

    Purpose of the Study:

    • To investigate the binding of soluble fibrin to guinea pig peritoneal macrophages.
    • To characterize the nature of the fibrin-macrophage interaction.
    • To explore the potential role of this interaction in host defense.

    Main Methods:

    • Macrophages were incubated with radiolabeled (125I) soluble fibrin.
    • Binding assays were performed under various conditions, including the presence of metabolic inhibitors, trypsin, plasmin, calcium, and competing ligands.
    • Scatchard analysis was used to quantify binding.
    • Fibrin binding was assessed in other cell types, including polymorphonuclear leukocytes, lymphocytes, and fibroblasts.

    Main Results:

    • Macrophages selectively bind soluble 125I-fibrin and fibrin/fibrinogen complexes, but not fibrinogen or its degradation products.
    • Binding is mediated by surface receptors, as evidenced by trypsin sensitivity and occurrence in the presence of metabolic inhibitors.
    • Fibrin binding is specific, blocked by nonradioactive fibrin but not by IgG or immune complexes.
    • Binding is calcium-dependent and unaffected by plasmin or trypsin pretreatment.
    • Approximately 6.92 x 10^6 fibrin molecules bind per macrophage at saturation.
    • Similar binding was observed in polymorphonuclear leukocytes but not in lymphocytes or fibroblasts.

    Conclusions:

    • Guinea pig macrophages possess specific receptors for soluble fibrin.
    • This binding is likely a receptor-mediated process, calcium-dependent, and specific for fibrin.
    • Soluble fibrin binding by macrophages and polymorphonuclear leukocytes may represent a host defense mechanism to clear fibrin from the blood, preventing microthrombi.
    • This interaction highlights a potential pathway for the reticuloendothelial system in managing fibrin clearance.

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