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 allotye determination. The well kn own increased serum IgG in JCA was confirmed as increased IgG1, IgG2 a nd IgG3 in the whole group. Investigating the clinical subsets IgG1 wa s significantly increased in all subsets while IgG2 and IgG3 increased only in the polyarticular form. In search of a genetic linkage for th e clinical JCA subsets and the different IgG subclass patterns found, the alternative Gm allotypes G1 m(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 gr oup and in the polyarticular subset. In the systemic subset the Gm (a, '',g/a,'',g) phenotype was significantly increased, but the Gm (a,'',g /f,n,b) phenotype was increased in the oligoarticular subset. The numb er of JCA patients with G1 m(ff)-,G3m(b,b)-phenotypes were significant ly decreased. In such phenotypes, remission was more common. The susce ptibility of JCA, its different clinical subsets and outcome of the di sease is determined by Gm allotypes. affecting characteristic IgG subc lass patterns.