Measuring the 50% haemolytic complement (CH50) activity of serum

Area of Science:

• Immunology
• Biochemistry

Background:

• The complement system comprises proteins crucial for immune responses, including cell lysis and phagocytosis.
• Quantifying individual complement components doesn't reflect overall pathway activity.
• The CH50 assay assesses the functional integrity of the classical complement pathway.

Purpose of the Study:

• To detail the methodology for quantifying classical complement pathway activity using the CH50 assay.
• To illustrate the functional assessment of complement-mediated hemolysis.

Main Methods:

• The CH50 assay involves incubating serum dilutions with antibody-coated sheep red blood cells (SRBC).
• Complement-mediated lysis of SRBC releases hemoglobin, quantified spectrophotometrically.
• Assay sensitivity to complement component reduction, absence, or inactivity is highlighted.

Main Results:

• Decreased or absent complement components result in reduced or zero CH50 levels, respectively.
• The degree of hemolysis directly correlates with classical complement pathway activity.
• The assay quantifies functional complement activity through serial serum dilutions.

Conclusions:

• The CH50 assay provides a functional measure of the classical complement pathway.
• This assay is essential for evaluating complement system integrity and diagnosing deficiencies.
• Understanding CH50 assay methodology is key for accurate complement activity assessment.