Fibronectin associated with Clq in a Clq isolation procedure

Area of Science:

• Immunology
• Biochemistry

Background:

• The complement system is crucial for innate immunity.
• Complement component Clq initiates the classical pathway of complement activation.
• Fibronectin (FN) is a multifunctional glycoprotein involved in various biological processes.

Purpose of the Study:

• To investigate the presence and interaction of fibronectin (FN) with complement component Clq.
• To elucidate the binding characteristics of FN and Clq to IgG and gelatin.

Main Methods:

• Preparation of Clq using euglobulin precipitation from serum.
• Detection of FN in Clq preparations via radioimmunoassay and immunodiffusion.
• Adsorption experiments using polymerized IgG and insolubilized gelatin as binding agents.
• Assessment of Clq and FN removal under various conditions (EDTA, high salt).

Main Results:

• Fibronectin (FN) was consistently detected in Clq preparations, ranging from 3-29% by weight.
• Adsorption with polymerized IgG removed both Clq and a significant portion of FN.
• Adsorption with insolubilized gelatin removed FN and also substantially reduced Clq levels.
• These binding interactions were not affected by high salt concentrations or EDTA, indicating stable associations.

Conclusions:

• Fibronectin (FN) is an intrinsic component of complement component Clq.
• Both FN and Clq appear to bind independently to IgG and gelatin.
• The results suggest a potential co-association between FN and Clq, influencing their binding to common adsorbents.