Anti-IgG antibodies in juvenile rheumatoid arthritis.

Sixty-two patients, 48 children and 14 adults, with juvenile rheumatoid arthritis (JRA) and 62 age and sex matched controls were studied for anti-IgG antibodies of the classes IgG, IgM and IgA by an indirect immunofluorescence method. IgG anti-IgG occurred in 88% of 48 children less than or equal to 16 years and in 64% of 14 patients greater than 16 years with JRA against 2% of the controls. IgM anti-IgG occurred in 4% of the children, in 24% of the adults and in 2% of the controls. IgA anti-IgG occurred in 2% of the patients and in none of the controls. The prevalence of IgG anti-IgG was the same in pauciarticular, polyarticular and systemic cases, whereas the titres were higher in polyarticular than in pauciarticular cases, and higher in children with a disease duration of more than 5 years. Higher titres were related to higher ESR and lower hemoglobin values. The relationship of higher titres to clinically active disease was not statistically significant. No relationship was found to age, sex, age at onset, or to the duration of disease. The titres were not related to the concentrations of serum IgG or to the titres of antinuclear antibodies. IgG anti-IgG are common to all the clinical types of JRA, whereas antinuclear antibodies separate the systemic type from pauci- and polyarthritis. Their possible pathogenic significance must therefore be different.