Juvenile idiopathic arthritis and HLA class I and class II interactions and age-at-onset effects

Abstract

Objective: The aim of this study was to quantitate risk and to examine heterogeneity for HLA at high resolution in patients with the most common subtypes of juvenile idiopathic arthritis (JIA), IgM rheumatoid factor-negative polyarticular JIA and oligoarticular JIA. Use of 4-digit comprehensive HLA typing enabled great precision, and a large cohort allowed for consideration of both age at disease onset and disease subtype.

Methods: Polymerase chain reaction-based high-resolution HLA typing for class I and class II loci was accomplished for 820 patients with JIA and 273 control subjects. Specific HLA epitopes, potential interactions of alleles at specific loci and between loci (accounting for linkage disequilibrium and haplotypic associations), and an assessment of the current International League of Associations for Rheumatology classification criteria were considered.

Results: An HLA-DRB1/DQB1 effect was shown to be exclusively attributable to DRB1 and was similar between patients with oligoarticular JIA and a younger subgroup of patients with polyarticular JIA. Furthermore, patients with polyarticular JIA showed age-specific related effects, with disease susceptibility in the group older than age 6 years limited to an effect of the HLA-DRB1*08 haplotype, which is markedly different from the additional susceptibility haplotypes, HLA-DRB1*1103/1104, found in the group with oligoarticular JIA and the group of younger patients with polyarticular JIA. Also in contrast to findings for oligoarticular JIA, patients with polyarticular arthritis had no evidence of an HLA class I effect. Markers associated with a reduced risk of disease included DRB1*1501, DRB1*0401, and DRB1*0701. DRB1*1501 was shown to reduce risk across the whole cohort, whereas DRB1*0401 and DRB1*0701 were protective for selected JIA subtypes. Surprisingly, the disease predisposition mediated by DPB1*0201 in individuals without any disease-predisposing DRB1 alleles was great enough to overcome even the very strong protective effect observed for DRB1*1501.

Conclusion: Inherited HLA factors in JIA show similarities overall as well as differences between JIA subtypes.

Figure 1

Principal component analysis for HLA class I and II loci showing clustering of important subsets of the patient population. The first two coordinates are shown, comprising 56% and 17% respectively of the total variation observed. Key: oligoextended = oligoarticular extended disease; oligopersistent = oligoarticular persistent disease; poly = IgM RF negative polyarticular disease; <6 = age of onset prior to six years of age; >6 = age of onset after to six years of age; F = female patients; M = male patients.

Figure 2

Survival curves for age of onset effects for HLA class II alleles associated with JIA. A. An earlier age of onset in polyarticular disease is mediated by DRB1*0801 and *1103/4. B-C. An earlier age of onset in oligoarticular disease (B), including both persistent and extended as well as polyarticular disease (C) is mediated by DPB1*0201 in the absence of the predisposing alleles DRB1*0801 and *1103/4. D. Later age of onset in oligoarticular disease (persistent and extended) mediated by DRB1*0701