A Clq solid phase microenzymatic assay for the detection of soluble immune complexes

Area of Science:

• Immunology
• Biochemistry
• Clinical Chemistry

Background:

• Soluble immune complexes (SICs) are implicated in various autoimmune and infectious diseases.
• Accurate detection of SICs is crucial for diagnosis and monitoring disease progression.
• Existing methods for SIC detection can be time-consuming and less sensitive.

Purpose of the Study:

• To adapt a solid-phase Clq-binding assay into a rapid, sensitive enzymatic micromethod for SIC measurement.
• To validate the assay's performance using in vitro prepared immune complexes.
• To evaluate the prevalence of SICs in sera from patients with various clinical conditions.

Main Methods:

• Enzymatic micromethod utilizing alkaline phosphatase-labeled Staphylococcus aureus protein A.
• Assay performed in microtiter plates for high-throughput screening.
• Detection of soluble immune complexes prepared in vitro using bovine serum albumin and anti-BSA antibodies.

Main Results:

• The assay demonstrated high sensitivity (0.030 mg/ml of human heat-aggregated IgG detected) and reproducibility.
• All in vitro prepared soluble immune complexes across a range of antigen-to-antibody ratios were detected.
• SICs were frequently detected in systemic lupus erythematosus (52%) and chronic active hepatitis (57%).

Conclusions:

• The developed enzymatic micromethod is a rapid, sensitive, and reproducible tool for measuring soluble immune complexes.
• The assay is effective for screening large numbers of patient samples.
• Elevated SIC levels are common in systemic lupus erythematosus and chronic active hepatitis, suggesting clinical utility.