IgG subclass serum levels in juvenile chronic arthritis

Gm phenotype linkage to subsets of juvenile chronic arthritis (JCA) with influence on IgG subclass response

The serum hyper IgG of 76 JCA patients of different clinical subsets, 8 systemic, 37 polyarticular and 31 oligoarticular, were investigated by IgG subclass quantitation and Gm allotype determination. The well known increased serum IgG in JCA was confirmed as increased IgG1, IgG2 and IgG3 in the whole group. Investigating the clinical subsets IgG1 was significantly increased in all subsets while IgG2 and IgG3 increased only in the polyarticular form. In search of a genetic linkage for the clinical JCA subsets and the different IgG subclass patterns found, the alternative Gm allotypes G1m(a), G1m(f) for IgG1, G2m(n), G2m(") for IgG2 and G3m(g) , G3m(b) for IgG3 gene loci were investigated. The Gm (a,",g) haplotype was significantly increased in the whole JCA group and in the polyarticular subset. In the systemic subset the Gm (a,",g/a",g) phenotype was significantly increased, but the Gm (a,'h,g/f,n,b) phenotype was increased in the oligoarticular subset. The number of JCA patients with G1m(f,f)-,G3m(b,b)-phenotypes were significantly decreased. In such phenotypes, remission was more common. The susceptibility of JCA, its different clinical subsets and outcome of the disease is determined by Gm allotypes, affecting characteristic IgG subclass patterns.

Variation of serum IgG subclass concentrations with disease activity in juvenile chronic arthritis

Nineteen patients with juvenile chronic arthritis were followed up and serum IgG subclass concentrations measured at different stages of disease activity. Patients were divided into three groups according to clinical activity of the disease: active disease, partial remission, and remission. The results were compared with normal values obtained in 448 healthy children aged 6 months to 18 years with a homogeneous distribution for each year of age. Serum IgG subclass concentrations of each child were first log transformed and then age corrected, taking the deviation of the log transformed value from that expected for a child of the same age. It was found that patients with partial remission had increased concentrations of IgG2 and decreased concentrations of IgG1 compared with patients with active disease. This suggests that the remission inducing process, at least in juvenile chronic arthritis, is accompanied by a switch of IgG subclass production.

Immunological abnormalities in juvenile chronic arthritis

The immunological alterations that have been reported in juvenile chronic arthritis are reviewed. Their role in patient management and classification as well as their possible etiopathogenetic relevance are discussed.