HLA antigens in juvenile arthritis. Pauciarticular and polyarticular juvenile arthritis are immunogenetically distinct

Using DNA techniques, we investigated the role of HLA-DR, DQ, and DP alleles in susceptibility to juvenile arthritis (JA). We studied 2 groups of patients with JA having a different disease prognosis and course. The pauciarticular form is usually benign, while the polyarticular disease frequently leads to joint destruction and disability. Persistent pauciarticular disease developed preferentially in patients having HLA-DRw13-Dw18 and DQw6-Dw18, but these antigens did not confer susceptibility in patients whose disease converted to the polyarticular form. HLA-DPw2.1 was an additional susceptibility factor for patients with JA of pauciarticular onset. In the polyarticular form of JA, HLA-DPw3 was the major factor for susceptibility, giving a relative risk of 10.3 (P less than 0.0001). In addition, we found that DRw8.1 and DQw4 were increased, and HLA-DR4 was markedly decreased, in patients with pauciarticular and polyarticular disease. These results indicate that in addition to some shared factors, distinct HLA class II alleles are important in pauciarticular or polyarticular JA. We conclude that typing with oligonucleotide probes may be useful in predicting the outcome in some children with arthritis.     

The immunogenetics of juvenile rheumatoid arthritis.

Recent major advances in understanding the genetic structure of the human leukocyte antigen (HLA) region and how HLA molecules contribute to immune responses have been paralleled by more precise identification of specific HLA genes conferring susceptibility to the various forms of juvenile rheumatoid arthritis (JRA). This article presents current models for HLA-associated autoimmune disease susceptibility and summarizes the HLA Class II alleles currently known to be associated with JRA: primarily DR8, DR5, DR6, and DPw2.1 in pauciarticular onset JRA; and DR4 in rheumatoid factor-positive polyarticular onset JRA. Rheumatoid factor-negative polyarticular onset JRA and systemic onset JRA are variously associated with several of these same genes. Gene interactions and the clinical utility of HLA typing in this disease are also discussed.     

DNA analysis of HLA-DR, DQ and DP genes in pauciarticular juvenile rheumatoid arthritis.

HLA-DR, DQ, and DP alleles were determined by restriction fragment length polymorphism (RFLP) and oligonucleotide hybridization analysis in 50 Caucasian children with pauciarticular juvenile rheumatoid arthritis (PaJRA) and 82 controls. There was an increased frequency of DR5, DRw8, and DQw4, as well as individual DQ alpha and beta chains, DQA*0401 and DQB1*0402, respectively, in this group of patients. There was an absolute association between DRw8, DQw4, DQA1*0401, and DQB1*0402 in the patient population. HLA-DPw2.1 was also increased in frequency. There was little evidence of linkage disequilibrium found between DPw2.1 and DR5, DRw8, or DQw4. These MHC Class II associations were more characteristic of those patients with young age of onset (less than 5 years), rather than those with onset greater than or equal to 5 years of age. Our data confirmed the previous associations of HLA-DR5, DRw8, and DPw2.1 with PaJRA and suggested a new association for DQ alpha and beta genes in the clinical expression of this disease.     

Immunogenetics of juvenile chronic arthritis in Israel

Typing for HLA-A,B,C and DR antigens was performed in 61 Israeli patients with juvenile chronic arthritis (JCA) and in 120 unrelated controls. No significant associations were apparent in the overall patient group. DR5 was significantly increased in the non-Ashkenazi patients with pauciarticular onset of disease. The only three DRw8 positive patients in the study had pauciarticular onset. DR5 and DRw8 were found in 9 of 10 patients with age of onset less than 3 years. Increased frequencies of Bw50 and Cw6 were observed in patients with systemic onset. Typing for properdin factor (Bf) and glyoxylase (GLO) was carried out in 45 and 50 of the patients, respectively. No associations with alleles of the complement Bf system or the HLA linked GLO system were evident. The confirmation in the ethnically distinct Israeli population of the previously described association of DR5 with pauciarticular JCA suggests that this gene may be closely related to the disease susceptibility gene.     

Juvenile rheumatoid arthritis, juvenile chronic arthritis, and juvenile spondyloarthropathies.

Immunogenetics are supporting the marked heterogeneity of chronic arthritis in children. Thus DRw13-DRw18 and DQw6-DQw18 were associated with persistent pauciarticular disease in children with an early onset of disease. Several studies have shown DPw2 as an additional susceptibility factor in this subgroup. Standardization of diagnostic criteria for juvenile onset spondyloarthropathy and psoriatic arthritis is necessary; various studies are in progress, and although HLA-B27 provides the common marker, this may only apply to a small group of juvenile psoriatics who have spondyloarthropathy. In the management of juvenile rheumatoid arthritis, methotrexate in moderate doses has been shown to be superior to lower doses of methotrexate and placebo in controlling polyarthritis. Methotrexate may be of particular value in treating the polyarthritis that follows a pauciarticular onset. The possible value of sulfasalazine in a B27 group with persistent polyarthritis has been suggested. Highlights of corticosteroid therapy were intra-articular injections, particularly in pauciarticular disease, the suggestion that deflazacort has a calcium sparing effect, and the possible role of intravenous methylprednisone in the management of severe disease.     

Rheumatoid arthritis in Israeli Jews: shared sequences in the third hypervariable region of DRB1 alleles are associated with susceptibility

Rheumatoid arthritis (RA) is known to be associated with class II HLA antigens in most populations, but recent studies in Israeli Jewish patients showed no significant differences in either DR4 or DR1 between patients and controls. In a previous DR4 subset study we found DR4-Dw15 to be associated with susceptibility (RR = 9.2) but this allele occurred in only 12% of the patients. We analyzed all DRB1 genes, using the polymerase chain reaction (PCR) and hybridization with allele specific oligonucleotides, in 49 Jewish patients with RA and 40 normal Jewish controls. Six DRB1 alleles that are similar to the prototype DR4-Dw4 (DRB1*0401) appeared to contribute to the risk for developing RA. In addition to DR4-Dw15 (DRB1*0405) 2 other alleles having substitutions in codons 71 only (DR1-Dw1/DRB1*0101, DR4-Dw14.2/DRB1*0408) or in codons 70 and 71 (DRw10/DRB1*1001) gave highly significant relative risks. Together, this group, with valine in position 85, and glycine in codon 86, gave a relative risk of 11.0 (p = 0.0002). Two other alleles with the same sequence in the third hypervariable region (amino acids 67-74) but with valine in codon 86 (DR4-Dw14.1/DRB1*0404) or alanine in 85 and valine in 86 (DR1-Dw20, DRB1*0102) gave a combined risk of 3.6 (p = 0.049). Altogether these 7 alleles with similar sequences in the third hypervariable region accounted for 55.6% of the patients, with an overall relative risk of 8.6 (p = 0.00002). Our results in this population indicate that shared epitopes in the third hypervariable region of DRB1 alleles also play a role in susceptibility to RA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Primarily chronic progressive and relapsing/remitting multiple sclerosis: two immunogenetically distinct disease entities

HLA class II gene polymorphism was investigated in 100 patients with clinically definite multiple sclerosis (MS) by restriction fragment length polymorphism analysis of Taq I-digested DNA using DRB, DQA, and DQB cDNA probes. Twenty-six patients had primarily chronic progressive MS and 74 had relapsing/remitting MS. The latter group included patients with a secondary progressive evolution of symptoms. Both clinical forms of MS were found to be associated with the DRw15,DQw6 haplotype. In addition, primarily chronic progressive MS was positively associated with the DQB1 restriction fragment pattern seen in DR4,DQw8, DR7,DQw9, and DRw8, DQw4 haplotypes, as well as negatively associated with the Taq I DQB1 allelic pattern corresponding to the serological specificity DQw7. Relapsing/remitting MS was positively associated with the DQB1 allelic pattern observed in the DRw17,DQw2 haplotype. These three DQB1 alleles are in strong negative linkage disequilibria with DRw15. The two susceptibility markers of each clinical form of MS act additively in determining the genetic susceptibility, as the relative risks for individuals carrying both markers roughly equal the sum of respective risks. Different alleles of the DQB1 locus defined by restriction fragment length polymorphisms contribute to susceptibility and resistance to primarily chronic progressive MS as well as to susceptibility to relapsing/remitting MS. The observed immunogenetic heterogeneity between the different clinical forms of MS favors the hypothesis that primarily chronic progressive MS and relapsing/remitting MS are two distinct disease entities.     

HLA antigens in juvenile arthritis

Serologic HLA typing was performed in 77 patients with juvenile arthritis (JA). The frequency of the DR4 antigen was significantly increased in the seropositive but decreased in the seronegative patients—53% and 17%, respectively (P < 0.025)—compared with 27% in healthy Norwegians. An increased frequency of the HLA-DR4 antigens was also found in polyarticular onset JA (50% compared with 27%, P < 0.05). The frequency of both the HLA-B27 (21%) and the DR5 antigen (21%) was increased in the whole patient group compared with controls (10% and 9%, respectively, P < 0.01). The DR5 antigen was also increased in the systemic onset patients (40%, P < 0.05). Both the DR5 and the DR8 antigens were increased in the pauciarticular onset group (P < 0.05 and P < 0.01, respectively). The results support the view that seropositive and seronegative JA are different disease entities and also that seropositive JA may be an early form of seropositive rheumatoid arthritis. The association between the DR4 antigen and IgM rheumatoid factor suggests that the HLA-DR4 gene or a closely linked gene may regulate autoimmune responses to self IgG.     

HLA–D region epitopes associated with juvenile arthritis. recognition by alloreactive t cell clones and alloantisera

The HLA–D region antigens DR5 (wll, w12), DRw6 (w13,w14), DRw8, DRw52, and DQw1 have previously been shown to be increased in frequency in subsets of patients with juvenile arthritis. Since the HLA–D region is complex (composed of at least 3 subregions encoding multiple molecules, each in turn presenting multiple alloantigenic epitopes), we sought to clarify whether one strongly associated factor might explain the previous findings. To search for the pertinent HLA–D region stimulatory epitopes, alloreactive T cells were primed against DR5 and DRw6 haplotypes and cloned by limiting dilution. Three T cell clones and 1 alloantiserum met the criteria for significant association with juvenile arthritis on patient testing, including DR5, DRw6, and DRw8 haplotypes. Monoclonal antibody blocking revealed that all 4 recognized epitopes on DR subregion products. For 2 of the clones, the relative risks for JA (10.5 and 9.4) were higher than the risks with any other previously described typing reagents.     

DNA restriction fragment length polymorphism of HLA-DR2 haplotypes in normal individuals and in patients with rheumatoid arthritis.

A strong association between HLA-DR4 and rheumatoid arthritis (RA) has been found in a number of populations. In contrast, the incidence of DR2 is decreased in patients with RA, suggesting that this specificity may confer some protection against the disease. A number of subtypes of DR2 have been defined by serology, by responses in mixed lymphocyte culture reaction, and, more recently, by restriction fragment length polymorphism. These subtypes of DR2 are in linkage disequilibrium with different subspecificities of DQw1. It is thus likely that the distribution of these subtypic DR,DQ haplotypes in DR2 positive patients with RA may be important in understanding the genetic basis of susceptibility/resistance to RA. In this paper a study of the subtypes of DR2,DQw1 haplotypes in 18 patients with RA, who required sodium aurothiomalate as a disease remitting drug, and unrelated healthy individuals is reported. Three subtypes of DR2 haplotypes, DRw15 (Dw2),DQw1.2(DQw6), DRw15(Dw12),DQw1.12(DQw6), and DRw16(Dw21),DQw1, AZH (DQw5), were analysed with a cDNA probe for the DQ beta gene. The data show that DR2 positive patients with RA carried either the DRw15(Dw2),DQw6 or DRw15(Dw12),DQw6 haplotype. No patient with RA was positive for the DRw16(Dw21),DQw5 subspecificity. In contrast, six of 29 (21%) normal healthy DR2,DQw1 positive individuals carried the DRw16(Dw21),DQw5 haplotype. These data together with earlier results on the distribution of the DR4,DQw7 haplotype in patients with RA support the hypothesis that DQB1 chain polymorphism may be important in determining susceptibility to severe RA.     

Structural analysis of the HLA-DR, -DQ, and -DP alleles on the celiac disease-associated HLA-DR3 (DRw17) haplotype

Celiac disease is strongly associated with the HLA class II D-region serologic markers DR3 (DRw17) and DQw2. Moreover, by restriction fragment length polymorphism analysis, greater than 90% of DR3 (DRw17), DQw2 celiac disease patients have a polymorphic 4.0-kilobase Rsa I DP B gene DNA fragment. The present study sought to determine if there is a unique HLA class II D-region A or B gene structural variant on the DR3 (DRw17) haplotype found in celiac disease. The polymorphic second exons of the coding DRB, DQA and DQB, and DPA and DPB genes in celiac disease patients with the DR3 (DRw17) haplotype were sequenced after amplification by the polymerase chain reaction. To define the DP B genes associated with celiac disease, the second exons of the coding DP B genes from 27 celiac disease patients were amplified similarly and probed by using a panel of sequence specific oligonucleotides. The HLA-DR, -DQ, and -DP A and B gene second exon sequences of celiac disease patients were noted to be identical to sequences that can be found also, although at a significantly lower frequency, in unaffected individuals. This is compatible with a disease model wherein the HLA class II genes on the DR3 (DRw17) haplotype are necessary, but not sufficient, for the phenotypic expression of celiac disease. Analysis of the DP B genes revealed a significant increase in the frequency of the alleles DPB1 and DPB3 in celiac disease. Furthermore, the increased frequency of the 4.0-kilobase Rsa I DP B gene restriction fragment length polymorphism in celiac disease can be accounted for by the overrepresentation in disease of the alleles DPB1 and DPB3. The HLA-associated susceptibility to celiac disease appears to be multigenic, with specific, but structurally normal, allelic variants in the DP and DQ/DR subregions contributing to disease susceptibility.     

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.     

HLA antigens in Italian type 1 diabetic patients: role of DR3/DR4 antigens and breast feeding in the onset of the disease

HLA-A, B, C, DR and DQ typing was performed in 381 Italian insulin-dependent diabetic patients and in 905 normal Italian subjects. The diabetic patients had significantly higher frequencies of HLA-Cw7, B8, B18, DR3, DR4, DQw2 and DQw3 and significantly lower frequencies of HLA-B17, Bw51, DR2, DR7 and DRw11. The frequency of heterozygosity for HLA-DR3/DR4 was significantly higher in patients who developed the disease in the first 2 years of life and DR3+/DR4-, DQw2 and DQw3 alleles were higher in those aged less than 14 years at onset. The HLA-DR4 allele was associated with onset of diabetes in autumn and HLA-B18 with onset in Autumn-winter. Diabetic children who were breast fed had a later onset of insulin-dependent diabetes mellitus than those who were bottle fed but these differences were independent of HLA typing (11.18±0.72 years vs 9.23±0.42 years; mean±SEM). We conclude that: (1) in general, HLA distribution in Italian insulin-dependent diabetic patients reflects previous data reported in other European and North American populations; (2) HLA-DR3 and DR4 are strongly associated with insulin-dependent diabetes in Italy as well, and these alleles seem to predispose to an earlier onset of the disease; and (3) breast feeding may delay the onset of the disease.     

Two Ro (SS-A) autoantibody responses in systemic lupus erythematosus. Correlation of HLA-DR/DQ specificities with quantitative expression of Ro (SS-A) autoantibody

Autoantibodies to Ro (SS-A), La (SS-B), and Sm/nuclear RNP were quantitated by enzyme-linked immunosorbent assay in 106 white patients with systemic lupus erythematosus. Two Ro autoantibody subgroups were identified that differed quantitatively, genetically, and clinically. The subgroup having anti-Ro only demonstrated significantly lower mean anti-Ro levels than did the subgroup with concomitant anti-La and showed a strong association with the linked HLA alleles DR2 and DQw1. The anti-Ro with anti-La subgroup was associated with the linked HLA alleles B8, DR3, DRw52, and DQw2 (DR3 was primary), and this subgroup consisted of patients with older ages at disease onset, sicca complex, and less renal involvement. Overall, the relative risk (RR) for having anti-Ro was highest in HLA-DR2/DR3 heterozygotes compared with non-DR2/DR3 heterozygotes (RR 15) and all other DR combinations (RR 7), suggesting a compound effect of 2 immune responses. Heterozygotes for HLA-DQw1/DQw2 demonstrated significantly higher mean levels of anti-Ro, which may be indicative of trans gene interaction at HLA-DQ. These data suggest the hypothesis that HLA genes exert their major effects on Ro/La autoantibody subsets of systemic lupus erythematosus.     

HLA antigens in juvenile arthritis. Genetic basis for the different subtypes

Serologic HLA typing was performed in 77 patients with juvenile arthritis (JA). The frequency of the DR4 antigen was significantly increased in the seropositive but decreased in the seronegative patients--53% and 17%, respectively (P less than 0.025)--compared with 27% in healthy Norwegians. An increased frequency of the HLA-DR4 antigens was also found in polyarticular onset JA (50% compared with 27%, P less than 0.05). The frequency of both the HLA-B27 (21%) and the DR5 antigen (21%) was increased in the whole patient group compared with controls (10% and 9%, respectively, P less than 0.01). The DR5 antigen was also increased in the systemic onset patients (40%, P less than 0.05). Both the DR5 and the DR8 antigens were increased in the pauciarticular onset group (P less than 0.05 and P less than 0.01, respectively). The results support the view that seropositive and seronegative JA are different disease entities and also that seropositive JA may be an early form of seropositive rheumatoid arthritis. The association between the DR4 antigen and IgM rheumatoid factor suggests that the HLA-DR4 gene or a closely linked gene may regulate autoimmune responses to self IgG.     

Two ro (ss-a) autoantibody responses in systemic lupus erythematosus

Autoantibodies to Ro (SS-A), La (SS-B), and Sm/nuclear RNP were quantitated by enzyme-linked immunosorbent assay in 106 white patients with systemic lupus erythematosus. Two Ro autoantibody subgroups were identified that differed quantitatively, genetically, and clinically. The subgroup having anti-Ro only demonstrated significantly lower mean anti-Ro levels than did the subgroup with concomitant anti-La and showed a strong association with the linked HLA alleles DR2 and DQw1. The anti-Ro with anti-La sub-group was associated with the linked HLA alleles B8, DR3, DRw52, and DQw2 (DR3 was primary), and this subgroup consisted of patients with older ages at disease onset, sicca complex, and less renal involvement. Overall, the relative risk (RR) for having anti-Ro was highest in HLA-DR2/DR3 heterozygotes compared with non-DR2/DR3 heterozygotes (RR 15) and all other DR combinations (RR 7), suggesting a compound effect of 2 immune responses. Heterozygotes for HLA-DQw1/DQw2 demonstrated significantly higher mean levels of anti-Ro, which may be indicative of trans gene interaction at HLA-DQ. These data suggest the hypothesis that HLA genes exert their major effects on Ro/La autoantibody subsets of systemic lupus erythematosus.     

Major histocompatibility complex haplotypes and class II genes in non-Jewish patients with pemphigus vulgaris.

Previous studies demonstrated that HLA-DR4 was markedly increased among Ashkenazi Jewish patients with pemphigus vulgaris (PV), almost entirely as the common Jewish extended haplotype [HLA-B38, SC21, DR4, DQw8] or as the haplotype HLA-B35, SC31, DR4, DQw8, and that HLA-DR4, DQw8 was distributed among patients in a manner consistent with dominant expression of a class II (D-region or D-region-linked) susceptibility gene. In the present study of major histocompatibility complex (MHC) haplotypes in 25 non-Jewish PV patients, DR4, DQw8 was found in 12 of the patients and DRw6, DQw5 was found in 15. Only 3 patients had neither. Only 1 of the DR4, DQw8 haplotypes was [HLA-B38, SC21, DR4, DQw8] and 2 were HLA-B35, SC31, DR4, DQw8; most were the presumed fragments (SC31, DR4, DQw8) or (SC21, DR4, DQw8) or DR4, DQw8 with some other complotype. Of the patients with DRw6, DQw5, all were DRw14, DQw5, and 6 had a rare Caucasian haplotype, HLA-Bw55, SB45, DRw14, DQw5. Four of 6 of these were found in patients of Italian extraction, as was the 1 normal example. The non-Jewish patients were of more Southern European extraction than our controls. This suggests that there are two major MHC susceptibility alleles in American patients with PV. The more ancient apparently arose on a haplotype in the Jews, HLA-B38(35), SC21(SC31), DR4, DQw8, and spread to other populations largely as D-region segments. The other arose in or near Italy on the haplotype HLA-Bw55, SB45, DRw14, DQw5 and has also partially fragmented so that many patients carry only DRw14, DQw5. The available data do not permit the specific localization of either the DR4, DQw8- or the DRw14, DQw5-linked susceptibility genes.     

Detection of disease-specific restriction fragment length polymorphisms in pemphigus vulgaris linked to the DQw1 and DQw3 alleles of the HLA-D region

Pemphigus vulgaris in Israeli Ashkenazi and non-Ashkenazi Jews and in Austrian non-Jewish patients is strongly associated with the DR4 and DRw6 alleles of the HLA-D region class II genes. Restriction fragment length polymorphism analysis was undertaken with DQ beta, DQ alpha, and DR beta cDNA probes. Hybridization with the DQ beta probe identifies Pvu II, BamHI, and EcoRV fragments that absolutely discriminate pemphigus vulgaris patients from healthy DR-, DQ-, and ethnic-matched controls. In contrast the DQ alpha and DR beta probes failed to identify disease-specific restriction fragment length polymorphism fragments. These studies indicate that DQw1 and DQw3 polymorphisms carried by pemphigus vulgaris patients may be directly involved in predisposition to the disease or may be tightly linked to the susceptibility gene itself. To our knowledge, this is the first example of an HLA restriction fragment length polymorphism that is highly associated with susceptibility to autoimmune disease.     

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

Summary 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 (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: linkage to HLA demonstrated by allele sharing in affected sibpairs

OBJECTIVE: To test for linkage between the HLA region and juvenile rheumatoid arthritis (JRA), with stratification by onset and course types, in a cohort of affected sibling pairs (ASPs). METHODS: Eighty pairs of siblings with JRA who were registered with the Research Registry for JRA ASPs (sponsored by the National Institute of Arthritis and Musculoskeletal and Skin Diseases) were typed for HLA-DR. The observed ratio of sharing of none, one, or both parental DR alleles was compared against the expected ratio of 1:2:1 by goodness-of-fit chi-square tests. A group of 265 unrelated control subjects served as a comparison population for HLA-DR allele frequencies among patients, by Fisher's exact test. RESULTS: Overall, there was excess sharing of 2 DR alleles among ASPs with JRA. The observed ratio of sharing 0, 1, or 2 DR alleles was 8:40:32, instead of the expected ratio of 20:40:20 (P < 0.001). When stratified by JRA onset type, excess allele sharing was demonstrated among ASPs who were concordant for onset type (P = 0.002). This was true for both pauciarticular and polyarticular onset. When stratified by disease course, excess allele sharing was also demonstrated among ASPs who were concordant for disease course (P < 0.001). This was true for both the pauciarticular and the polyarticular course. Among the 32 ASPs who shared two DR alleles, 5 pairs had both DR8 and DR11, which was significantly more frequent (P < 0.0001) than the incidence in the control group (n = 0). CONCLUSION: This study of an independent cohort of multiplex families confirms the previously reported linkage between pauciarticular JRA and the HLA-DR region that was identified using a different analytic method in a cohort of simplex families. Additionally, this study establishes evidence for linkage between polyarticular JRA and the HLA-DR region.