Dynamic light scattering analysis of immune complexes in sera of rheumatoid arthritis patients

The size of circulating immune complexes (CICs) in rheumatoid arthritis (RA) could be an emerging criterion in disease diagnosis. This study analyzed size and electrokinetic potential of CICs from RA patients, healthy young adults, and RA patients age-matched controls aiming to establish their unique CIC features. Pooled CIC of 30 RA patients, 30 young adults, and 30 RA group's age-matched controls (middle-aged and older healthy adults), and in vitro IgG aggregates from pooled sera of 300 healthy volunteers were tested using dynamic light scattering (DLS). Size distribution of CIC in healthy young adults exhibited high polydispersity. RA CIC patients and their age-matched control showed distinctly narrower size distributions compared with young adults. In these groups, particles clustered around two well-defined peaks. Particles of peak 1 were 36.1 & PLUSMN; 6.8 nm in RA age-matched control, and 30.8 & PLUSMN; 4.2 nm in RA patients. Particles of peak 2 of the RA age-matched control's CIC was 251.7 & PLUSMN; 41.2 nm, while RA CIC contained larger particles (359.9 & PLUSMN; 50.5 nm). The lower zeta potential of RA CIC, compared to control, indicated a disease-related decrease in colloidal stability. DLS identified RA-specific, but also age-specific distribution of CIC size and opened possibility of becoming a method for CIC size analysis in ICmediated diseases.

Automated summary

This study analyzed the size and electrokinetic potential of circulating immune complexes (CICs) in rheumatoid arthritis (RA) patients, healthy young adults, and age-matched controls. The results showed that RA patients and their age-matched controls had narrower size distributions compared to young adults, and RA patients had larger particles compared to controls. The study suggests that CIC size analysis could be a potential method for diagnosing IC-mediated diseases.