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Published on: April 1, 2015
Evidence that fibronectin-immunoglobulin complexes occur normally in plasma
B A Bray1, M Osman, G M Turino
1Columbia University College of Physicians and Surgeons, New York, New York 10032.
Insights
Plasma fibronectin (PFn) forms complexes with immunoglobulins (Igs) in humans and dogs. These PFn-Ig complexes appear to be a normal component of circulating plasma, indicating a potential role in immune function.
Area of Science:
- Biochemistry
- Immunology
- Proteomics
Background:
- Plasma fibronectin (PFn) is a key protein involved in various physiological processes.
- The interaction between PFn and immunoglobulins (Igs) in plasma is not fully understood.
- Investigating PFn-Ig complexes is crucial for understanding plasma composition and immune responses.
Purpose of the Study:
- To determine if complexes of plasma fibronectin (PFn) and immunoglobulins (Igs) are normally present in plasma.
- To quantify the immunoglobulin content within PFn preparations.
- To provide evidence for circulating PFn-Ig complexes.
Main Methods:
- Competitive ELISA was used to analyze PFn preparations for IgG, IgM, and IgA.
- Sephacryl S-300 chromatography was employed to investigate circulating complexes.
- Crossed immunoelectrophoresis and SDS-PAGE were utilized to detect and characterize PFn-Ig complexes.
- Canine plasma was used as a model to study PFn-IgM complexes.
Main Results:
- PFn preparations contained significant levels of IgG, IgM, and IgA, varying by donor.
- Chromatography revealed distorted PFn peaks due to Ig presence, suggesting complex formation.
- Crossed immunoelectrophoresis confirmed the presence of PFn-Ig complexes in both human and canine plasma.
- Canine PFn analysis identified specific PFn-IgM complexes.
Conclusions:
- Complexes of immunoglobulins with plasma fibronectin are normally present in plasma.
- These findings suggest a potential physiological role for PFn-Ig complexes in the immune system.
- Further research is warranted to elucidate the functional significance of these complexes.
Abstract:
This study was done to ascertain whether complexes of plasma fibronectin (PFn) and immunoglobulins (Igs) are normally present in plasma. PFn preparations from plasmas of six random human donors were analyzed for IgG, IgM, and IgA by competitive ELISA procedures. To look for direct evidence of circulating complexes, two of the plasma samples were chromatographed on Sephacryl S-300. PFn prepared from a pool of three plasmas by cryoprecipitation was studied by crossed immunoelectrophoresis to detect PFn-Ig complexes. The Ig content of PFn ranged from 0.78% to 9.0% IgG; 0.25% to 4.9% IgM, and 0.15% to 0.71% IgA. The relative amounts were IgG > IgM > IgA in every sample, but the total Ig content of PFn varied with the plasma donor. The Sephacryl S-300 chromatogram of the plasma from which Ig-rich PFn was made showed distortion of the PFn peak by Ig peaks. PFn prepared by cryoprecipitation contained PFn-immunoglobulin complexes. Plasma from adult beagle dogs was used to prepare canine PFn. IgM was detected in canine PFn by SDS-Page and by double diffusion experiments against antiserum to canine IgM. By crossed immunoelectrophoresis, a PFn-IgM complex was detected in canine plasma. The cryoprecipitate recovered from a Sephacryl S-300 chromatogram of canine plasma contained equivalent amounts of IgM and PFn. These data suggest that complexes of Igs with PFn are normally present in plasma.
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