An additional susceptibility gene for juvenile idiopathic arthritis in the HLA class I region on several DR-DQ haplotypes

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

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.

Primary sclerosing cholangitis is associated with extended HLA-DR3 and HLA-DR6 haplotypes

Primary sclerosing cholangitis (PSC) is associated with the human leukocyte antigen (HLA)-DRB1*0301-DQA1*0501-DQB1*0201 (DR3) and HLA-DRB1*1301-DQA1*0103-DQB1*0603 (DR6) haplotypes. Recently, the extended HLA class I region has been found to harbour genes that modulate or confer susceptibility independently of the HLA class II genes in several immune-mediated diseases. The aim of the present study was to evaluate the influence of genes in the extended HLA class I region on susceptibility to PSC. Seven microsatellite markers (MIB, D6S265, D6S2222, D6S464, D6S2223, D6S2225 and D6S2239) were analysed together with HLA class II alleles in 219 Norwegian patients with PSC and 282 random controls. To control for associations because of linkage disequilibrium (LD), 142 HLA-DR3 homozygous and 187 DR6-positive controls were included. The unstratified analysis showed significant associations with the alleles MIB*349 [odds ratio (OR) = 3.0, corrected P value (P(c)) = 3 x 10(-12)], D6S265*122 (OR = 1.7, P(c)= 0.004), D6S464*209 (OR = 1.8, P(c)= 0.03) and D6S2225*147 (OR = 2.7, P(c)= 4 x 10(-6)), which were mainly secondary to the DR3 association. When stratifying for DR6, an association with the D6S265*122 allele was still observed (OR = 3.7, P(c)= 0.0004). In the presence of the D6S265*122 allele, the risk to develop PSC conferred by DR6 was increased four times compared with the risk conferred by DR6 alone. In addition, a novel negative association of PSC with DR11 was observed (OR = 0.21, P(c)= 2 x 10(-4)). In conclusion, our study shows that a gene in LD with D6S265 contributes to susceptibility to develop PSC in individuals carrying DR6. Moreover, we found that the PSC-associated DR3 haplotype extends more telomeric than that previously reported. We also report a possible protective effect of DR11 on development of PSC.

Microsatellite typing of the human leucocyte antigen region: analytical approach and contribution to rheumatoid arthritis immunogenetic studies

Within the major histocompatibility complex (MHC), the human leucocyte antigen (HLA)-DRB1 locus is clearly associated with rheumatoid arthritis (RA). Using a microsatellite (MSat) typing approach, we aimed to identify other loci associated with RA susceptibility and/or severity within the MHC. A panel of nine MSat HLA loci [D6S291, D6S2876 (G51152), D6S1666 (DQCAR II), D6S273, D6S2789 (TNFd), D6S2810 (MIB), D6S265, D6S2222, D6S2239], and HLA-A, -B and -DRB1 genes were typed in 170 RA cases and 282 controls. For susceptibility analysis, MSat and HLA allele distribution were compared between cases and controls, before and after stratification on HLA-DRB1*04. Haplotype frequencies were estimated using an expectation-maximization algorithm in a permutation test procedure. For severity analysis, we compared the distribution of structural damage score at onset and after 4 years of follow-up in RA cases carrying susceptibility alleles. Two MSat polymorphisms were positively associated with RA susceptibility: allele*136 of D6S265 [odds ratio, OR (confidence interval, CI) = 1.55 (1.11-2.17), P= 0.007], allele*116 of D6S2239 [OR = 1.34 (1-1.79), P= 0.03] and HLA-A2 [OR = 1.46 (1.08-1.98), P= 0.01]. Two MSat polymorphisms were negatively associated with RA susceptibility: allele*133 of D6S273 [OR = 0.3 (0.1-0.75), P= 0.005] and allele*177 of D6S291 [OR = 0.72 (0.53-0.96), P= 0.02]. The association between allele*136 of D6S265 and RA susceptibility remained unchanged after stratification on HLA-DRB1*04. The haplotypic analysis showed an overrepresentation of D6S265*136/HLA-A*02 haplotype, which suggests an effect independent of HLA-DRB1 locus in RA susceptibility. While HLA-A2 and HLA-DR4 were associated with RA severity, no MSat polymorphism was associated with structural damage score.

Genetics of juvenile idiopathic arthritis: an update

PURPOSE OF REVIEW

Juvenile idiopathic arthritis (JIA) refers to a collection of chronic arthritides in children, and the major subtypes of JIA are similar to the subtypes of juvenile rheumatoid arthritis (JRA). Several genetic variants influencing susceptibility to JIA have been identified, including genes encoding the HLA molecules, cytokines, and other modulators of immune responses. This review outlines the principles behind genetic studies and summarizes recent studies on the genetics of JIA.

RECENT FINDINGS

Recent studies confirm the association/linkage between JIA and the HLA region and provide evidence for additional loci involved in susceptibility to JIA. Several studies suggest that polymorphisms in other candidate genes also influence susceptibility to JIA. In addition, some genetic variants seem to influence the phenotype of JIA. A genome-wide scan for JRA in 121 affected sibling pair families confirms that gene(s) in the HLA region influence susceptibility to JRA and identifies other chromosomal regions that possibly influence susceptibility to JRA or subtypes of JRA. Functional studies suggest that biologic markers could be useful in defining the phenotype of individuals with JIA. Familial studies and gene expression profiling are useful tools in the dissection of the genetic basis of JIA.

SUMMARY

Although there are challenges to the identification of genetic factors underlying complex diseases such as JIA, considerable progress has been made in JIA genetics. Candidate gene studies remain important to identify genetic variants with small to moderate effects on the JIA phenotype.

The MICA-A4 triplet repeats polymorphism in the transmembrane region confers additional risk for development of psoriatic arthritis in the Croatian population

The aim of this study was to investigate possible differences in the frequencies of alleles at the HLA loci and at microsatellite loci within the HLA region among patients suffering from psoriatic arthritis (PsA) and healthy controls. Fifty-eight Croatian PsA patients (28 male and 30 female) and 157 healthy unrelated controls were typed for HLA alleles (A, B, Cw and DRB1) by the polymerase chain reaction-sequence-specific primers (PCR-SSP) method, while microsatellite alleles (D6S265, D6S273, MHC class I chain-related gene (MICA) and MIB) were analysed by electrophoresis in an ALFexpress sequencer (Pharmacia Biotech, Uppsala, Sweden). The findings from this study were: (1) the frequencies of B*39 and B*57 were significantly increased in PsA patients; (2) differences in the frequencies of B*13 and B*27 were not statistically significant after correction; (3) the B*0702, B*18, and B*38 alleles were decreased in patients only before correction; (4) none of the alleles at other HLA loci tested were associated with PsA in Croatia; (5) polymorphism at D6S265, D6S273, and MIB microsatellites in patients did not show any statistically significant differences when compared to controls; (6) the increase in the MICA-A4 allele frequency in PsA patients was independent of the B*39 and B*57 alleles.

Pemphigus vulgaris in Jewish patients is associated with HLA-A region genes: mapping by microsatellite markers

Pemphigus vulgaris (PV) is the most severe autoimmune blistering disorder of the skin that is mediated by circulating autoantibodies against desmoglein 3 (Dsg3). It has been reported that in Jews the associated haplotype in PV is human leukocyte antigen (HLA) B38, DRB1*0402, DQB1*0302. Significant associations with HLA were observed also in non-Jews. Dsg3-specific T-cell responses were detected in PV patients but also in healthy individuals who were either carriers of the PV-associated DRB1*0402 allele or alleles that share similar or identical peptide binding motifs to DRB1*0402. This suggests that genes other than the classical major histocompatibility complex (MHC) genes are associated with the development of the autoimmune response. We used 16 microsatellite probes that span the entire MHC region to screen DNA samples from 38 PV patients and 76 healthy controls. Results demonstrated that some markers were associated with class II region including a TAP associated marker. However, four probes, D6S265, C_527, D6S510, and MOGC, which are all mapped to the region of HLA-A, were highly associated with PV. These results suggest that a gene, or genes in the class I region are important in the initiation of the autoimmune cascade. Activation/suppression of these genes might act as the trigger mechanism that starts the autoimmune destructive process.