Complement-mediated solubilization in patients with systemic lupus erythematosus, nephritis or vasculitis

Area of Science:

• Immunology
• Clinical Chemistry

Background:

• Serum complement function is crucial for immune precipitate solubilization, involving both alternative and classical pathways.
• This process can be quantitatively assessed to evaluate complement system integrity.
• Immune complex diseases are often associated with impaired complement function and hypocomplementaemia.

Purpose of the Study:

• To develop and validate a simple quantitative assay for assessing complement function based on immune precipitate solubilization.
• To correlate this assay's performance with disease activity and circulating immune complexes (CIC) in patients with immune complex diseases.
• To evaluate the assay's potential as a diagnostic tool for immune complex-related conditions.

Main Methods:

• A preformed radiolabelled precipitate of Bovine Serum Albumin (BSA)-anti-BSA antibody was used.
• The solubilization capacity of serial sera from 75 patients with various immune complex diseases was investigated.
• Assay results were compared with clinical disease activity and measurements of CIC.

Main Results:

• Reduced solubilization (below 25% of normal range) was observed in a high proportion of patients with active Systemic Lupus Erythematosus (SLE), post-streptococcal glomerulonephritis, and other nephritis-related nephrotic syndromes.
• Solubilization capacity significantly correlated with disease activity in SLE, systemic vasculitis, and post-streptococcal glomerulonephritis.
• While CIC were more frequent, the solubilization assay identified patients with CIC more likely to have active disease.

Conclusions:

• The developed solubilization assay is a simple and effective method for assessing complement function in immune complex diseases.
• This assay provides valuable insights into immune complex disease activity and potential phlogistic effects, complementing standard CIC measurements.
• The assay shows promise as a tool for monitoring disease activity and guiding treatment in patients with immune complex-mediated conditions.