Separation and characterization of complement-fixing immune complexes in juvenile rheumatoid arthritis patients.

Immune complexes (IC) in sera from patients with juvenile rheumatoid arthritis (JRA) were isolated by the use of immunoabsorbent columns. Sera from 14 JRA patients (four seropositive for 19S IgM RF and 10 seronegative, but nine having hidden 19S IgM RF) were analyzed by the anti-human Clq (alpha HClq) and anti-human C3 (alpha HC3) columns. The columns were sequentially eluted with veronal buffer, 0.02 M EDTA, 0.5 M NaCl, and 1 M propionic acid. By the alpha HClq column, IgM RF were detected in at least one of the separated IC fractions of 13 of 14 patients and IgG RF in three patients. By the alpha HC3 column, only five patients demonstrated IgM RF and only one IgG RF in the eluted fractions. On sucrose density gradient analysis (SDGA), all IC were demonstrated in the peaks greater than or equal to 19S.19S IgM RF were demonstrated by ELISA in all 14 patients, but IgG RF in only three. These studies demonstrate that complement-fixing 19S IgM RF, IgG, and IgG RF containing IC can be detected in the serum of JRA patients.