Immunochemical characterization of human plasma fibronectin

Area of Science:

• Biochemistry
• Immunology
• Cell Biology

Background:

• Human plasma fibronectin (Fn) is a crucial extracellular matrix protein.
• Understanding Fn's structure is key to its function.
• Previous purification methods existed, but antibody characterization was needed.

Purpose of the Study:

• To characterize antibodies raised against native human plasma fibronectin.
• To investigate the conformational dependence of fibronectin's antigenic determinants.
• To explore the utility of anti-fibronectin antibodies as conformational probes.

Main Methods:

• Purification of human plasma fibronectin using non-denaturing affinity chromatography.
• Immunization of rabbits with native fibronectin to generate antisera.
• Testing antisera reactivity against native, denatured, and fragmented fibronectin using various assays.

Main Results:

• Antisera reacted strongly with native fibronectin but weakly with denatured or reduced/alkylated forms.
• Denaturation affected fibronectin's haemagglutinating and gelatin-binding activities.
• Large fibronectin fragments retained high antigenicity, while smaller peptides showed reduced reactivity.
• Antigenic determinants were largely conformation-dependent, with few in the interchain disulfide bridge region.

Conclusions:

• Native fibronectin possesses an ordered conformation sensitive to denaturation.
• The majority of fibronectin's antigenic determinants are conformation-dependent.
• The interchain disulfide bridge region contributes minimally to antigenicity.
• Anti-fibronectin antibodies can serve as valuable tools for studying fibronectin conformation and structural integrity.