Complement-mediated solubilization of immune complexes. Solubilization inhibition and complement factor levels in SLE...

Area of Science:

• Immunology
• Rheumatology
• Complement System Biology

Background:

• Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune complex deposition.
• The complement system plays a crucial role in clearing immune complexes.
• Dysfunction in complement-mediated solubilization of immune complexes (IC) may contribute to SLE pathogenesis.

Purpose of the Study:

• To investigate the complement-mediated solubilization capacity (CMSC) in SLE patients.
• To evaluate the presence and characteristics of CMSC inhibition in SLE sera.
• To correlate CMSC and its inhibition with clinical disease activity and complement component levels.

Main Methods:

• Serum samples from 19 SLE patients were analyzed for CMSC using a functional assay.
• A novel assay was developed to measure CMSC inhibition.
• Levels of complement components (C1q, C3, factor B, C3d, factor H) and circulating immune complexes were quantified.
• Correlation analyses were performed between CMSC, CMSC inhibition, and clinical parameters.

Main Results:

• Reduced CMSC was observed in 32 out of 36 SLE serum samples.
• CMSC was lowest in patients with nephritis and highest in those with inactive disease.
• CMSC inhibition was detected in 35 out of 36 samples, strongest in untreated new cases.
• Significant negative correlation between CMSC and CMSC inhibition (r = -0.67).
• Low CMSC correlated with low C1q, C3, factor B, or high C3d.
• Pronounced CMSC inhibition occurred with normal/high factor H and strongly positive circulating IC.

Conclusions:

• SLE sera exhibit impaired capacity to solubilize immune complexes, indicating complement system dysfunction.
• A novel assay revealed significant inhibition of CMSC in SLE, particularly in active disease.
• CMSC and its inhibition are linked to complement component levels and disease activity, suggesting a role in SLE pathogenesis.