Reducing sample complexity of polyclonal human autoantibodies by chromatofocusing.

Area of Science:

• Biochemistry
• Immunology
• Protein Chemistry

Background:

• Polyclonal human immunoglobulins (IgGs) are complex mixtures with subtle variations.
• Analyzing individual IgGs within these mixtures is challenging due to their similar molecular weights.
• Existing methods may not adequately reduce the complexity of polyclonal IgG preparations for detailed analysis.

Purpose of the Study:

• To evaluate chromatofocusing as a method for separating polyclonal antigen-specific human IgGs.
• To reduce the complexity of IgG mixtures for subsequent analytical steps.
• To confirm the preservation of IgG antigen-binding activity after separation.

Main Methods:

• Antigen-specific IgGs were isolated from plasmapheresis material using affinity and size exclusion chromatography.
• Chromatofocusing was employed to separate IgGs based on their distinct isoelectric points.
• Two-dimensional gel electrophoresis (2-DE) was used to assess the reduction in protein heterogeneity.

Main Results:

• Chromatofocusing significantly decreased the diversity of IgG light and heavy chains compared to the starting material.
• Analysis via 2-DE indicated a less complex protein profile in the chromatofocusing eluate.
• Despite separation, the isolated IgGs retained their native conformation and antigen-binding capacity.

Conclusions:

• Chromatofocusing is a viable and reproducible first step for simplifying complex polyclonal IgG mixtures.
• This technique facilitates the analysis of individual or small groups of similar proteins.
• The method preserves the functional integrity of separated immunoglobulins.