Juvenile chronic arthritis--clinical sub-groups with particular relationship to adult patterns of disease

Class I associations and frequencies of class II HLA-DRB alleles by RFLP analysis in children with rheumatoid-factor-negative juvenile chronic arthritis

A total of 94 patients with juvenile chronic arthritis (JCA) was tested for HLA class I by serology and for class II by RFLP typing. Early onset JCA (EOPA) is associated with HLA-A2, DR5 and DR8 in both males and females. The combination (joint occurrence) of these JCA associated alleles (A2, DR5, DR8) is frequently seen in patients with chronic iridocyclitis. Late onset pauciarticular disease has an increased frequency of HLA-B27, especially in males. Our data confirm that polyarticular JCA with early childhood onset (< or = 4 years) is associated with DR5 and DR8 and has a different immunogenetic background from polyarticular JCA with later childhood (> 4 years) onset (associated with DR4).

Juvenile rheumatoid arthritis patients manifest immune reactivity to the mycobacterial 65-kDa heat shock protein, to its 180-188 peptide, and to a partially homologous peptide of the proteoglycan link protein

Immune reactivity to the 65-kDa mycobacterial heat shock protein (hsp65) has been associated with arthritis in rats and humans. In this report we evaluated patients with juvenile rheumatoid arthritis for such immunity. A high proportion of affected children showed both antibody and T lymphocyte responses to hsp65 and to two related peptides: the nonapeptide 180-188 sequence of hsp65 and a partially homologous peptide of the cartilage proteoglycan link protein. The titer of circulating antibodies was generally higher in patients with clinically active disease. In contrast to the juvenile rheumatoid arthritis patients, patients with adult rheumatoid arthritis tended to have lower responses of their peripheral blood T lymphocytes to the whole hsp65 molecule. Moreover, the adult rheumatoid arthritis patients did not respond to the peptides. Thus, there appear to be immunological differences between juvenile and adult forms of rheumatoid arthritis related to hsp65 reactivity.

Population genetics and molecular biology of the childhood chronic arthropathies

Recent immunogenetic studies of JRA patients have both helped to clarify subdivision into distinctive subtypes and identified those subtypes which may be related to adult rheumatic disease. Despite the variability of HLA associations from different geographic sources, a consensus appears to be emerging as to the most important associations. In addition to the HLA-DR locus, distinct associations with the HLA-DP and HLA-DQ loci have been described. Family studies have suggested an increased risk with certain haplotypes, particularly in the EOPA JRA population. Although inheritance patterns remain to be defined, recent studies with monoclonal antibodies, alloreactive T cell clones, and DNA have identified the existence of specific epitopes encoded by a variety of Ia molecules which may be more directly related to disease susceptibility. The concept of an epitope dose effect is put forward to account for the variable HLA association with disease, particularly with regard to EOPA JRA. Further developments in the definition of micropolymorphisms of Ia molecules at the genomic level as well as the possible involvement of other genetic loci, in particular T cell receptor variable gene products, should help clarify our understanding of the role of genetic factors in the aetiology of JRA. The studies of the last two decades indicate that inferences made by Carter (1969) on the 'polygenic, weakly penetrant genetic effect' in autoimmune disease are indeed applicable to JRA.

Autoantibody profile in juvenile chronic arthritis

Patients with juvenile chronic arthritis (JCA) may be subdivided into a minority, who carry IgM rheumatoid factor and have erosive polyarthritis resembling adult rheumatoid arthritis, and the majority (90%), who are seronegative by conventional means. Between 30 and 60% of patients with JCA have positive antinuclear antibodies (ANAs) according to the choice of substrate for indirect immunofluorescence. The importance of ANAs is the frequent development of associated asymptomatic chronic iridocyclitis, which may impair vision causing worse handicap than the arthritis, which remains predominantly pauciarticular in two thirds of these young children. ANA positive patients rarely possess antibodies to deoxyribonucleic acid (DNA) or extractable nuclear antigens (ENA), and current studies suggest that several different nuclear antigens, including histones, may be involved.