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Characterization of murine peritoneal macrophage receptors for fibrin(ogen) degradation products
Abstract:
The binding of human fibrinogen degradation fragments D1, E, X, and Y, as well as fibrin fragment D1 dimer, to mouse peritoneal macrophages was examined. A Scatchard plot of fragment D1 binding was biphasic, suggesting two classes of receptors. Fragments D1, D1 dimer, X, and Y in low concentrations bound to macrophages with high affinity (Kd = 23 to 73 X 10(-11) mol/L). Fragment E bound specifically but at a much lower level than the other fragments. Fragment D1 was able to compete for the binding of radiolabeled fragments X and Y but not radiolabeled fragment E. These studies indicate that fragments D and E are recognized by separate receptor systems but that all of the fibrinogen degradation products that contain the D domain are recognized by the same receptor system.
Insights
Mouse macrophages bind fibrinogen degradation fragments via distinct receptor systems. Fragments containing the D domain share a common receptor, while fragment E binds separately.
Area of Science:
- Immunology
- Biochemistry
- Cell Biology
Background:
- Fibrinogen degradation products (FDPs) play roles in inflammation and wound healing.
- Macrophages are key immune cells involved in inflammatory processes.
- Understanding FDP-macrophage interactions is crucial for inflammatory disease research.
Purpose of the Study:
- To investigate the binding characteristics of specific human fibrinogen degradation fragments (D1, E, X, Y) and a fibrin fragment (D1 dimer) to mouse peritoneal macrophages.
- To determine the receptor systems involved in these interactions.
Main Methods:
- Radioligand binding assays were employed to study the interaction of FDPs with macrophages.
- Scatchard plot analysis was used to characterize the binding kinetics and receptor affinity.
- Competitive binding experiments were performed to assess receptor specificity.
Main Results:
- Macrophage binding of fragment D1 exhibited biphasic kinetics, indicating two receptor classes.
- Fragments D1, D1 dimer, X, and Y demonstrated high-affinity binding to macrophages at low concentrations.
- Fragment E showed specific binding but at significantly lower levels compared to D-domain-containing fragments.
- Fragment D1 competed for the binding of fragments X and Y, but not fragment E.
Conclusions:
- Fibrinogen degradation fragments containing the D domain are recognized by a common macrophage receptor system.
- Fragment E is recognized by a separate and distinct receptor system on macrophages.
- These findings elucidate specific molecular interactions between FDPs and macrophages, relevant to inflammatory responses.