Comparison of some procedures detecting circulating immune complexes

Area of Science:

• Immunology
• Clinical Chemistry

Background:

• Circulating immune complexes (CICs) are implicated in various autoimmune and infectious diseases.
• Accurate detection of CICs is crucial for diagnosis and monitoring disease activity.

Purpose of the Study:

• To evaluate and compare the sensitivity and reliability of four distinct methods for detecting CICs.
• To assess the correlation between different CIC detection assays.

Main Methods:

• Four tests were employed: plain polyethylene glycol (PEG) precipitation (PEGprec), immunoelectrophoresis of PEG precipitates (IEpp), anti-antibody (AA) inhibition test with sera (AA-Is), and AA inhibition test with PEG precipitates (AA-Ipp).
• A total of 156 pathological sera (myasthenia gravis, syphilis, gastrointestinal adenocarcinomas, rheumatoid arthritis, systemic lupus erythematosus) and 51 normal sera were analyzed.
• Statistical analysis was performed to compare the results of the four tests.

Main Results:

• All four tests demonstrated a high degree of correlation (p < 0.005).
• PEGprec and IEpp showed higher sensitivity than AA-Is and AA-Ipp, attributed to their ability to detect both IgG and IgM complexes, while AA inhibition tests detect only IgG complexes.
• When rheumatoid arthritis and SLE sera were excluded, the four tests exhibited similar sensitivity. PEGprec identified two normal sera, while other tests were negative in normal controls.

Conclusions:

• The simultaneous application of PEGprec, IEpp, AA-Is, and AA-Ipp provides a sensitive and reliable procedure for detecting CICs.
• The study highlights the importance of considering immunoglobulin class specificity when interpreting CIC assay results.
• Combined use of these assays enhances diagnostic accuracy for immune complex-related conditions.