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

Langfristentwicklungen in der Kinder- und Jugendrheumatologie

Im Gebiet der Kinderrheumatologie gab es in den letzten Jahrzehnten immense Fortschritte, die sowohl die Diagnostik, als auch die Therapie nachhaltig verbessert haben. Obwohl erst seit 2003 in Deutschland offiziell als Zusatzbezeichnung anerkannt, stehen heutzutage über 200 Kinder- und Jugendrheumatologen (d. h. 1,4 Kinderrheumatologen pro 100 000 Kinder) für die Erkennung und Behandlung von rheumatischen Erkrankungen bei Kindern und Jugendlichen bundesweit zur Verfügung. Neue Erkenntnisse in der Pathogenese rheumatischer Erkrankungen und die sich stetig weiterentwickelnde genetische Diagnostik haben das rheumatische Krankheitsspektrum und die Behandlungsmöglichkeiten dramatisch erweitert Internationale Forschungsnetzwerke und eine spezielle Gesetzgebung für die Entwicklung von pädiatrischen Medikamenten führten zur Zulassung von zahlreichen neuen Rheumamedikamenten, deren Sicherheit im klinischen Alltag seit der Jahrtausendwende systematisch in Deutschland untersucht wird. Maßnahmen zur Sicherung der Versorgungsqualität wurden implementiert, Standardinstrumente zur Bewertung der Krankheitsaktivität und Krankheitslast aus Patientensicht eingeführt sowie Initiativen zur Verbesserung der Versorgung Betroffener (z. B. die ProKind-Initiative) auf den Weg gebracht. Diese Veränderungen haben die Prognose und Lebensperspektive rheumakranker Kinder und Jugendlicher verbessert, wenngleich noch weiterer Optimierungsbedarf besteht.

[Polyarticular juvenile idiopathic arthritis and rheumatoid arthritis : Common features and differences]

The spectrum of polyarthritic diseases in childhood as well as in adulthood is wide. In the differential diagnostics different age-related diseases must be taken into consideration. Although, a clear similarity is obvious in all age groups for the classical diseases of polyarticular juvenile idiopathic arthritis and rheumatoid arthritis with respect to the pathogenesis, clinical manifestation and treatment options, this review points to specific differences. The prognosis of polyarthritis in children mainly depends on the joint manifestation, whereas extra-articular comorbidities play a predominant role in the older adult population.

The Etiology of Juvenile Idiopathic Arthritis

Over the years, the commonly used term to describe juvenile idiopathic arthritis (JIA) has changed. By definition, JIA includes all types of arthritis with no apparent cause, lasting more than 6 weeks, in patients aged less than 16 years at onset. JIA pathogenesis is still poorly understood: the interaction between environmental factors and multiple genes has been proposed as the most relevant working mechanism to the development of JIA. The concept that various microbes that colonize or infect not only the mucosal surfaces, like the oral cavity, but also the airways and gut might trigger autoimmune processes, resulting in chronic arthritides, and JIA was first drafted at the outset of last century. JIA development might be initiated and sustained by the exposure to environmental factors, including infectious agents which affect people at a young age, depending on the underlying genetic predisposition to synovial inflammation. Many data from patients with JIA suggest a scenario in which different external antigens incite multiple antigen-specific pathways, cytotoxic T cell responses, activation of classical complement cascade, and production of proinflammatory cytokines. In this review, emphasis is paid not only to the potential role of parvovirus B19 and Epstein-Barr virus in primis but also to the general involvement of different bacteria as Salmonella spp., Shigella spp., Campylobacter spp., Mycoplasma pneumoniae, Chlamydophila pneumoniae, Bartonella henselae, and Streptococcus pyogenes for the development of immune-mediated arthritides during childhood. No unequivocal evidence favoring or refuting these associations has been clearly proved, and today, the strict definition of JIA etiology remains unknown. The infection can represent a random event in a susceptible individual, or it can be a necessary factor in JIA development, always in combination with a peculiar genetic background. Further studies are needed in order to address the unsolved questions concerning this issue.

HLA-DR typing in polyarticular juvenile idiopathic arthritis: a study from a tertiary care hospital in northern India

INTRODUCTION

Many studies of human leukocyte antigen (HLA) association with juvenile idiopathic arthritis (JIA) have reported conflicting results, which were probably related to ethnic differences. Moreover, in India, studies on HLA-DR typing on JIA, particularly polyarticular JIA, is lacking.

OBJECTIVE

The aim of our study was to reveal the frequency of HLA DR types in a cohort of polyarticular JIA in northern India.

METHODS

Fifty-two polyarticular JIA patients were included as per the recent International League of Associations for Rheumatology classification, 2001. HLA-DR typing was performed in 21 patients (18 rheumatoid factor [RF]+ and three RF-) by a DNA-based polymerase chain reaction method for the determination of HLA alleles using sequence specific primers (SSP). The results were compared with that of 23 healthy controls of the same age and sex.

RESULTS

HLA-DR4 was present in five cases (23%) in the diseased group while only in one case (4.3%) in the control group with a relative risk of 5.47, but when compared with only RF+ polyarticular JIA, HLA-DR4 was found to be significantly high (27.7% vs. 4.43%; P < 0.05) with a relative risk of 6.3. Further, DR4, DR1, DR2, DR9, DR10 were also non-significantly high in these patients with relative risk of 3.2 for DR9 and 1.8 for DR10. In contrast, HLA-DR6 was seen only in 5.5% of polyarticular JIA cases, whereas it was present in 39% of controls (P < 0.05), a showing negative association.

CONCLUSION

HLA-DR4 codes for susceptibility to RF+ polyarticular JIA with a six-fold risk, whereas HLA-DR6 offers protection.

Do infections trigger juvenile idiopathic arthritis?

Juvenile idiopathic arthritis (JIA) is a disease that was prominent with increased inflammation response in immune system, appeared mostly with peripheral arthritis and endogenous and exogenous antigens play a role in the pathogenesis of disease. Two major reasons were thinking to be considerably important. First of them is immunological predisposition and the second one is environmental factors. Infections are considered to be the most important between environmental factors but also stress and trauma are also important in the etiology of the disease. However, the relation between JIA and infections is not clearly defined but the relation between adult chronic arthritis and infections was well-defined. A total of 70 patients, 26 with primer JIA, 20 with recurrent JIA, 24 healthy control were included in this study. Mycoplasma pneumoniae, Chlamydophila pneumoniae and C. Jejuni were detected in 4, 1 and 1 of 10 (38.46%) patients with primer JIA, respectively. Salmonella enteritidis, EBV, M. pneumoniae, C. jejuni and Borrelia burgdorferi were detected in 1, 2, 2, 2, and 1 of the 8(40%) patients with recurrent JIA, respectively. S. enteritidis were isolated in feces culture and also identified by agglutination method. Infection was detected in total 18 (39.13%) of patient groups. C. pneumoniae and C. jejuni were detected in 1 and 1 of 2(8.33) healthy control groups, respectively. Throat culture positivity was not detected in any of the patient and healthy control groups. In conclusion, etiopathogenesis of JIA is not clearly understood and suggested that various factors can trigger the disease and it is the most common rheumatoid disease of childhood. However, there are some studies focusing especially on one infectious agent but this is the first study including such a big range of infectious agents in the literature for the microorganisms that can be suggested to have a role in the etiopathogenesis of JIA. We have a conclusion in the light of our results and suggest that some microorganisms can trigger and increase the intensity of clinical situation according to the case. When we evaluate the primer and recurrent JIA groups; M. pneumoniae and C. jejuni come forward and seen common in JIA cases. We also suggest that the pre-diagnosis of microorganisms, which can play a role as primarily or by intervening in the etiopathogenesis of JIA and adding specific antimicrobial therapy to the standard JIA therapy, it is possible to perform new, extended, especially molecular based serial case studies.

A comprehensive review of the genetics of juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic arthropathy of childhood which is believed to be influenced by both genetic and environmental factors. The progress in identifying genes underlying JIA susceptibility using candidate gene association studies has been slow. Several associations between JIA and variants in the genes encoding the human leukocyte antigens (HLA) have been confirmed and replicated in independent cohorts. However it is clear that genetic variants outside the HLA also influence susceptibility to JIA. While a large number of non-HLA candidate genes have been tested for associations, only a handful of reported associations such as PTPN22 have been validated. In this review we discuss the principles behind genetic studies of complex traits like JIA, and comprehensively catalogue non-HLA candidate-gene association studies performed in JIA to date and review several validated associations. Most candidate gene studies are underpowered and do not detect associations, and those that do are often not replicated. We also discuss the principles behind genome-wide association studies and discuss possible implications for identifying genes underlying JIA. Finally we discuss several genetic variants underlying multiple clinically distinct autoimmune phenotypes.

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.

NFkappaB and its inhibitor IkappaB in relation to type 2 diabetes and its microvascular and atherosclerotic complications

Nuclear factor kappa B (NFkappaB) is an important transcription factor that together with its inhibitor (IkappaB) participates in the activation of genes involved in immune responses. We examined the CA repeat polymorphism of the NFKB1 gene (encoding for NFkappaB) and A/G point variation in the 3'UTR region of the nuclear factor kappa B inhibitor alpha (NFKBIA) gene (encoding for IkappaB) in Czech and German patients with type 2 diabetes. The sample consisted of 211 patients, both with and without kidney complications, and 159 controls. Additionally, 152 patients with systemic lupus erythematosus (SLE) were genotyped for NFKBIA polymorphism. We observed a significant increase in the homozygous AA genotype of the NFKBIA gene when compared with the control group (the highest value was in diabetics without diabetic nephropathy [p(c)* = 0.0015, odds ratio = 3.59]). No differences were seen between the SLE and control groups. With regard to the polymorphism of the NFKB1 gene, we did not observe any significant differences between the groups. Since the AA genotype of the NFKBIA gene presents a risk for type 2 diabetes development but not for diabetic nephropathy alone, we believe that the NFkappaB gene polymorphism can influence the pathogenesis of diabetes mellitus and affect its complications. Negative findings relative to other inflammatory autoimmune diseases, such as SLE, suggest a specific relationship between NFkappaB and type 2 diabetes mellitus.

HLA-DRB1 alleles and HLA-DRB1 shared epitopes are markers for juvenile rheumatoid arthritis subgroups in Colombian mestizos

We studied the association of human leukocyte antigen (HLA)-DRB1 and HLA-DQB1 alleles and HLA haplotypes with juvenile rheumatoid arthritis (JRA) in 65 patients and 65 controls from Colombia. The JRA subsets were distinguished on the basis of criteria established by the American College of Rheumatology. Two alleles were associated with protection, HLA-DRB1*1501 (p = 0.002) and HLA-DRB1*1402 (p = 0.01). HLA-DRB1*1602 (p = 0.0000002) was associated with susceptibility for systemic JRA and HLA-DRB1*1104 (p = 0.0002) for pauciarticular JRA. Amino acid sequences at residues 70-74 of DRB1 chain shared by HLA-DRB1 alleles (shared epitomes) were also informative. The polyarticular JRA subset revealed association with (70)QRRAA(74), which includes HLA-DRB1*04, 01, and (70)DRRAA(74), which includes DRB1*1601, 1602, 1101, and 1104. Two new findings of interest were the association of the haplotypes DRB1*1104, DQB1*0301(p = 0.0002) with pauciarticular JRA and DRB1*1602, DQB1*0301 (p = 0.0000002) association with systemic JRA. The DRB1 alleles of these two haplotypes share the epitope (70)DRRAA(74)and were associated with both the pauciarticular and the systemic subset of JRA. Our results suggest that studies of disease susceptibility in populations of admixed genetic background should take into account the contribution of different ethnic groups or nationalities in the recruitment of controls and patients studied in order to rule out genetic stratification.

Analysis of MHC region genetics in Finnish patients with juvenile idiopathic arthritis: evidence for different locus-specific effects in polyarticular vs pauciarticular subsets and a shared DRB1 epitope

This study used Finnish juvenile idiopathic arthritis (JIA) probands with pauciarticular and rheumatoid factor (RF) negative polyarticular subtypes of JIA to further define the genetic susceptibility to JIA. We examined 16 markers spanning an 18 cM region of chromosome 6 encompassing the MHC and surrounding genomic region in a set of 235 Finnish JIA nuclear families and 639 Finnish control individuals. Analysis by case/control association and transmission disequilibrium test (TDT) methods each demonstrated strong evidence for a susceptibility locus near the D6S2447 microsatellite (P<10(-6) for both methods) that is flanked by DQB1 and DRB1. Analysis of the DRB1 locus suggested that DRB1*0801 and DRB1*1101 rather than DQA1 or other HLA alleles may be responsible for conferring susceptibility to disease. These findings are consistent with the most compelling results of previous reports on HLA associations and suggest a JIA DRB1 shared epitope encompassing critical amino-acid residues in the third hypervariable region of this molecule. Most importantly, in pauciarticular patients, the strong association does not extend to proximal markers as it does in polyarticular patients (P<0.00001). Analysis strongly suggests that the difference is because of additional JIA susceptibility loci within the MHC being present in polyarticular RF negative patients.

A gene in the telomeric HLA complex distinct from HLA-A is involved in predisposition to juvenile idiopathic arthritis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is associated with particular alleles at 3 different HLA loci: HLA-A, HLA-DR/DQ, and HLA-DP. These associations are independent of each other (i.e., they cannot be explained by the known linkage disequilibrium between alleles at these loci). The purpose of this study was to look for additional JIA susceptibility genes in the HLA complex.

METHODS

One hundred two Norwegian JIA patients and 270 healthy individuals, all carrying the DQ4;DR8 haplotype, were investigated by scanning approximately 10 megabases of DNA covering the HLA complex with microsatellite polymorphisms. An expectation-maximization algorithm was used to estimate haplotype frequencies, and the distribution of microsatellite alleles on the high-risk DQ4;DR8 haplotype was compared between patients and controls, to exclude effects secondary to linkage disequilibrium with these susceptibility genes.

RESULTS

Allele 5 at the microsatellite locus D6S265 (D6S265* 5), 100 kb centromeric of HLA-A, showed a strong positive association with the disease (odds ratio 4.7, corrected P < 10(-6)). Haplotype analysis demonstrated that the D6S265*5 association was not caused by linkage disequilibrium to the gene encoding HLA-A*02, which has previously been reported to be associated with JIA. Instead, our data suggested that a gene in linkage disequilibrium with D6S265*5, but distinct from HLA-A*02, is involved in the predisposition to JIA.

CONCLUSION

We found that D6S265*5 could be a marker for an additional susceptibility gene in JIA which is distinct from A*02, adding to the risk conferred by DQ4;DR8.

Age-specific effects of juvenile rheumatoid arthritis-associated HLA alleles

OBJECTIVE

To define the onset and duration of effect of the HLA alleles that are associated with disease susceptibility and protection in juvenile rheumatoid arthritis (JRA) and 2 of its subtypes.

METHODS

We typed 680 patients with JRA and 254 ethnically matched unrelated controls for HLA class I and II genes. The frequency of each allele was calculated for each of the age-at-onset, onset type, and sex categories and plotted against the allele frequency in the control population. Survival analysis (with onset of disease as the terminating event) was used to calculate the age by which 50% (St0.5) and 80% (St0.2) of the children with particular alleles and combinations of alleles develop disease. This allele-specific survival analysis also allowed for the comparison of the overall survival functions for the various JRA subtype and sex categories.

RESULTS

Certain alleles are strongly associated with early susceptibility to pauciarticular JRA, including HLA-A2, DR8, DR5, and DPB1*0201. Fifty percent of the children carrying at least 1 of these alleles had disease onset prior to their third birthday. Among children who carried HLA-A2 and any 2 HLA-DR alleles (DR3, DR5, DR6, or DR8), the median age at the onset of pauciarticular disease was 2.7 years. Combinations of A2 and DPB1*0201 and one DR allele narrowed the window further to a median age at onset of 2.4 years. B27 and DR4 were associated with protection early in life but with increased risk later in childhood, with St0.5 values of 7.3 and 6.6 years, respectively, for pauciarticular JRA and St0.5 values of 10.2 and 10.7 years, respectively, for polyarticular JRA. Sex strongly influenced the age at which many of the alleles have their effect.

CONCLUSION

These data define at what age and for how long various HLA alleles influence susceptibility and protection (window-of-effect) in patients with JRA. In addition, these data establish more clearly the boundaries of ages-at-onset for 2 of the subtypes of the disease.

Nationwide collaborative study of HLA class II associations with distinct types of juvenile chronic arthritis (JCA) in Greece

The aim of this study was to investigate the association of different groups and subgroups of juvenile chronic arthritis (JCA) with HLA class II (DR, DP, DQ) alleles and/or haplotypes. Groups and subgroups were mainly distinguished on the basis of the type of onset, the course and complications of the disease, and some predefined disease markers according to the criteria proposed by the ILAR Standing Committee (Chile, 1994). On the basis of these criteria the following five JCA groups and their subgroups were included in the study: (1) define systemic onset (n = 25) and systemic progressing to persistent arthritis (n = 14); (2) JCA of oligoarthritis onset (O-JCA, n = 124) and of oligoarthritis onset and course (n = 98), O-JCA of early (< 6 years) or late (> 6 years) onset (EOO-JCA n = 71 and LOO-JCA n = 44), O-JCA with ANA positive (n = 69) or negative (n = 55) and O-JCA progressing to extended arthritis (n = 22); (3) JCA of polyarthritis onset (P-JCA) with rheumatic factor (RF) negative (n = 29), and P-JCA RF negative with antinuclear antibodies (ANA) positive (n = 13) or negative (n = 16); (4) JCA complicated with chronic anterior uveitis (CAU, n = 32); (5) juvenile psoriatic arthritis (n = 20). To assess the HLA allele frequencies in the above 223 Greek children with JCA, these frequencies were compared to those of 98 age-matched and 250 adult controls. The main findings were the following. A common HLA-DRB1* allele was not involved in the JCA groups and subgroups studied; on the other hand, the DQA1*0501 allele was found to be associated with different JCA groups/subgroups (O-JCA, P-JCA RF-negative ANA-positive, JCA with CAU), probably suggesting a closer relationship of this locus with the immunogenetic background of JCA. The DPB1*0201 allele was associated with the development of either EOO-JCA or CAU. Susceptibility to CAU was stronger when the DPB1*0201 was combined with the presence of DRB1*13. Another allele, DQB1*0301, was also associated with O-JCA and CAU. Finally, no specific HLA class II allele was found to be related to the presence of ANA or psoriatic lesions or to the severity of the arthritis. Our findings suggest that the wide clinical and laboratory spectrum of JCA is associated with an immunogenetic background that is linked with HLA alleles of more than one locus. Some of them, such as the DPB1*0201 allele, confer susceptibility to certain clinical onsets and courses or complications of the disease. The rapidly advancing techniques of typing of DNA profiles may lead to more definite conclusions.

HLA region microsatellite polymorphisms in juvenile arthritis

A number of microsatellite polymorphisms located in the MHC region of the human chromosome 6 have been analysed in a large group of patients with juvenile arthritis (JA) (n = 177) and in 157 controls. There have been no significant associations for the alleles of the microsatellite polymorphisms D6S-105, D6S-510, TNFA, TNFC, TNFD, TNFE, HSP. Allele frequencies and HLA associations were listed for the non-associated microsatellite loci. The microsatellite locus DQ CAR, which is localized between DQA1 and DQB1, shows a significant positive association with JA for the allele DQ CAR 121 and a negative association for the allele DQ CAR 111. The allele DQ CAR 121 is strongly associated with DQA1*0501 and with DQB1*0301 both in the normal controls and in the patient population. This pair of DQA/DQB alleles corresponds to the DQ molecule DQ7 on the cell surface, which has been described to be strongly associated with JA. Investigations of the two and three-point haplotypes of DQ CAR with alleles of its neighboring loci have shown that the association with DQ CAR 121 is secondary to the association with DQ7 previously observed. Thus, using eight HLA linked microsatellite polymorphisms in the region from HLA-A to HLA-DQ, we have not found any evidence for further loci which might be involved in the coding for susceptibility for JA.

HLA B27: a prognostic factor in juvenile chronic arthritis

This study was performed to assess the frequency of HLA B27 in patients with juvenile chronic arthritis (JCA) of varying severity and outcome by studying three patient categories: those in whom cytostatic treatment with azathioprine had been started, those with secondary amyloidosis, and those with arthroplasty of the knee or hip joints. In the first category the frequency of the HLA B27 allele was compared between those who had attained remission and those who had not. In the second and third categories the rate at which amyloidosis developed and the timing for the need of arthroplasty, were compared for HLA B27-positive and -negative patients. A control group consisted of 37 patients with uncomplicated seronegative polyarthritis. Ten of the 37 patients in the control group (27%) were HLA B27 positive as opposed to 84 out of 190 (44%) in the three study groups. Of the 101 patients treated with azathioprine, two out of 15 in remission were HLA B27 positive, whereas as many as 41 out of 86 with still active disease were HLA B27 positive (p = 0.013). Of the secondary amyloidosis patients, 29 out of 51 carried HLA B27. The HLA B27-positive patients contracted amyloidosis on average 5.9 (median 6.7) years earlier than the HLA B27-negative patients (p = 0.038). Of the arthroplasty patients, 39 out of 91 carried HLA B27. The HLA B27-positive patients underwent arthroplasty on average 2.9 (median 3.5) years earlier than the HLA B27-negative patients (p = 0.050). We conclude that HLA B27-positive cases are accumulated among the most severe cases of JCA.

Juvenile arthritis: genetic update

Juvenile arthritis (JA) is a term that covers a number of different disease entities, of which only three present with significant Human Leukocyte Antigen (HLA) associations. (1) Pauciarticular JA with late onset and a strong male proponderance is associated with HLA-B27 and represents the group of juvenile spondyloarthropathies related to adult ankylosing spondylitis. (2) Early onset pauciarticular JA with a preponderance of females and a frequent occurance of chronic iridocyclitis and the frequent presence of anti-nuclear antibodies is associated with alleles from three different regions of the HLA system: HLA-A2, which shows a very strong correlation with early age of onset; DR8, DR11 and DR12 as well as DQA1*0401, *0501, *0601 and finally DPB1*0201. These alleles show no linkage disequilibrium in the control population. (3) Rheumatoid factor positive polyarticular JA is associated, as is adult rheumatoid arthritis, with DR4. Concerning the possible mechanisms of the immunopathogenesis, it is speculated that the normal function of HLA molecules, namely the presentation of antigenic peptides, plays a major role. Data collected on HLA associations in early onset pauciarticular JA have been interpreted as indicating that alleles of the DQA1 locus (*0401, *0501, *0601) are probably responsible for presenting the hypothetical arthritogenic peptides. It is speculated that the pathogenic process includes the presentation of HLA-A2 or HLA-DPB1*0201 derived peptides presented by DQ molecules. It is clearly stated that typing for HLA alleles has very little or no importance for clinical diagnosis and prognosis.

Susceptible and protective major histocompatibility complex class II alleles in early-onset pauciarticular juvenile chronic arthritis

Oligonucleotide typing for alleles of the MHC loci DRB1, DQA1, and DQB1 was performed in 160 patients suffering from EOPA, JCA (or JRA = juvenile rheumatoid arthritis). Allele and haplotype frequencies of the patients were compared with the data of an unrelated healthy control group consisting of 200 individuals. Analysis of frequencies shows that HLA alleles are associated not only with susceptibility to EOPA-JCA but also with protection from the disease. The presence of protection connected with certain HLA alleles was assessed using a calculation which takes into account the condition that if one allele is increased, all other alleles of the same locus must be decreased in compensation. Protection can be assumed only in cases where a given allele has an observed frequency which is significantly beyond the expected compensatory decrease. Thus a hierarchy of associations was observed in EOPA-JCA patients. The alleles of the haplotypes DRB1*11 (12)-DQA1*0501-DQB1*0301 as well as DRB1*08-DQA1*0401-DQB1*0402 were found to be associated with susceptibility to disease, whereas the alleles DRB1*07 and DQA1*0201 converge with significant protection from the disease. Whereas the association with disease susceptibility seems to depend on a sequence motif encoded in certain DQA1 alleles, protection is associated either with alleles of DRB1 or DQA1.