Isolation and characterization of intermediate complexes and other components with common antigenic determinants

Area of Science:

• Immunology
• Biochemistry

Background:

• Intermediate complexes (IC) and rapidly sedimenting complexes (RC) are found in human sera.
• Heat-denatured human IgG (HDG) can form complexes with serum components.

Purpose of the Study:

• To isolate and characterize fractions with affinity for HDG from human sera containing IC.
• To investigate the composition and antigenic properties of these HDG-binding fractions.

Main Methods:

• Isolation of IC fractions from human sera.
• Characterization of IC and RC components (IgG subclasses, light chains).
• Affinity chromatography using specific antisera against IC fractions.

Main Results:

• Fractions with HDG affinity contained 7S IgG, IC (IgG1/IgG3), and RC (IgG/IgM).
• IgG in IC fractions showed elevated neuraminic acid levels, but no correlation with complex formation was found.
• Common antigenic determinants were identified in 7S, IC, and RC components, but only a minor part of HDG-binding fractions contained them.

Conclusions:

• IC formation may involve more than IgG self-association.
• Common antigenic determinants exist in various serum components, including those binding HDG.
• Rheumatoid factor (RF) activity is present in both determinant-containing and determinant-lacking HDG-binding components.