A novel assay for serum complement activity: C42 generation assay

Area of Science:

• Immunology
• Clinical Chemistry
• Complement System Analysis

Background:

• Current clinical laboratory tests for serum complement, such as C3, C4, and CH50, are often insufficient for analyzing low CH50 serum.
• Limitations exist in the diagnostic capacity of standard immunochemical and functional complement assays.

Purpose of the Study:

• To introduce and evaluate a novel C42 generation assay for assessing serum complement activity.
• To provide a more comprehensive analysis of serum complement function, particularly for cases with decreased CH50.

Main Methods:

• Development of a new assay based on the hemolysis of sensitized sheep erythrocytes (EA).
• The assay involves two stages: generation of C42 (classical pathway C3 convertase) and subsequent hemolysis by C3-C9.
• Utilizes two sera sequentially, with the second serum providing C3-C9 in the presence of EDTA.

Main Results:

• The C42 generation assay allows for the evaluation of two distinct serum complement activities: C1, C4, and C2 combined, and C3-C9 combined.
• Hemolysis levels directly correlate with the activity of these complement components.
• The assay proved helpful in analyzing clinical cases with decreased CH50 serum, with several examples presented.

Conclusions:

• The C42 generation assay is a valuable functional assay for serum complement.
• It provides additional information beyond the standard CH50 assay.
• The assay is rapid, economical, and does not require intermediate cells or isolated complement components, making it suitable for clinical settings.