Immunogenetics of polymyalgia rheumatica

Human leucocyte antigens and Japanese patients with polymyalgia rheumatica: the protective effect of DRB1*09:01

OBJECTIVE

The hallmarks of the chronic inflammatory disease polymyalgia rheumatica (PMR) include pain, and morning stiffness in areas of the neck, shoulder and pelvic girdle. The human leucocyte antigen (HLA) gene was reported to be an important risk factor for PMR, but it has not been analysed precisely, especially in populations other than Europeans.

METHODS

Genotyping of DRB1 and DQB1 was performed in Japanese PMR patients (n=270) and controls (n=413). Associations between allele carrier and genotype frequencies were determined for PMR.

RESULTS

DRB1*04:05 was associated with a predisposition to PMR (p=0.0006, Pc=0.0193, OR 1.85, 95% CI 1.31 to 2.62). DRB1*09:01 was associated with protection against PMR (p=1.46×10-5, Pc=0.0004, OR 0.40, 95% CI 0.26 to 0.61). A shared epitope (SE) associated with PMR (p=3.07×10-6, OR 2.11, 95% CI 1.54 to 2.88). DQB1*03:03 (p=0.0010, Pc=0.0140, OR 0.52, 95% CI 0.35 to 0.77) was associated with protection against PMR and DQB1*04:01 (p=0.0009, Pc=0.0140, OR 1.82, 95% CI 1.28 to 2.58) was associated with predisposition to PMR. A gene dosage effect was observed for DRB1*09:01 and DQB1*03:03, but not for DRB1*04:05, SE or DQB1*04:01. Haplotype and logistic regression analyses suggested a protective effect for DRB1*09:01.

CONCLUSION

This study is the first to demonstrate predisposing associations of DRB1*04:05, SE, and DQB1*04:01, and protective associations of DRB1*09:01 and DQB1*03:03 with PMR in Japanese patients. Our data indicate HLA has predisposing and protective effects on the pathogenesis of PMR.

Association of HLA-DRB1 genotype with younger age onset and elder age onset rheumatoid arthritis in Japanese populations

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by joint destructions and human leukocyte antigen (HLA)-DRB1 is an important genetic risk factor for RA and influences the phenotype of RA. The clinical features of elder age onset RA (EORA) were known to be different from those of younger age onset RA (YORA). Previous studies reported the different association pattern of DRB1 alleles with YORA or EORA. The associations of DRB1 genotype with these RA subsets remained almost unknown. We investigated the genotype association of DRB1 with YORA or EORA in Japanese populations.HLA genotyping was performed in Japanese RA patients and the association of allele or genotype carrier frequencies were analyzed.The genotype frequency of DRB104:05/DRB104:06 (P = .0204, OR 7.69, 95%CI 1.39-42.72), DRB104:05/DRB112:01 (P = .0050, OR 5.53, 95%CI 1.71-17.88), and DRB104:05/DRB115:01 (P = .0124, OR 3.34, 95%CI 1.39-8.02) in YORA was higher than EORA. However, the frequencies of DRB101:01/DRB104:05 in YORA was tended to be lower than EORA (P = .0784, OR 0.14, 95%CI 0.01-2.42). The gene dosage effect of the shared epitope alleles was detected in EORA, but not in YORA. Trans-complementing DQ heterodimer molecules, formed by DQA1 and DQB1 of the haplotypes with and without shared epitope alleles, might explain the higher genotype frequencies of "shared epitope /not shared epitope". Linear regression analyses showed the primary role of DQB104:01 allele for the age at onset of RA.This is the first report for the associations of DRB1 genotype with YORA or EORA in the Japanese population and the differential distribution of the genotypes was noted between these RA subsets. The involvement of DQ molecules for the age at onset of RA was suggested.

HLA antigens in polymyalgia rheumatica in northern Sweden

The HLA-A, B and DR antigens were analyzed with serological methods in 75 patients with polymyalgia rheumatica (PMR). In PMR patients the frequency of the HLA-DR4 antigen was significantly higher (62.1%) compared to blood donors (40%), p < 0.05, but did not differ from patients with seropositive rheumatoid arthritis (RA) from the same area (63.1%). In contrast, the frequency of HLA-B27 in the PMR patients (9.3%) was significantly lower compared to RA (27.2%), p < 0.01, but did not differ from blood donors (16.9%). There was no association between DR4 and disease affliction or severity in PMR. The increased frequency of HLA-B27 in RA but not in PMR in the population of northern Sweden suggests an immunogenetic difference between these two HLA-DR4 associated diseases.

Aortic dissection in giant-cell arteritis

Twenty-three cases of aortic dissection in patients with giant-cell arteritis are reviewed and an additional case is reported. Forty-six percent presented catastrophically with aortic dissection and no prior history of giant cell arteritis. Eighty percent died within 2 weeks of the event; four patients had successful surgical grafts. There was diffuse involvement of the aorta with giant cells in 89%, but dissecting tears occurred primarily in the proximal aorta in 85% of cases. The majority of cases with a preceding history of giant cell arteritis were on low doses of steroid or on no treatment at the time of dissection, and the median erythrocyte sedimentation rate of these patients was 62 mm/h (range 21-98). Evidence of some form of hypertension, whether acute or chronic, mild or severe, was found in 77% of patients. Inadequate treatment of giant-cell arteritis and underlying hypertension (treated or untreated) are potential factors leading to aortic dissection in these patients.

[HLA DRB1 polymorphism in rhizomelic pseudo-polyarthritis and Horton disease]

Some studies have suggested that distribution of HLA DRB1 alleles in polymyalgia rheumatica (PMR) resembles that found in giant cell arteritis (GCA). However these data are controversial. OBJECTIVE--To evaluate in French native patients whether PMR immunogenetically resembles GCA in determining HLA DRB1 alleles. PATIENTS AND METHODS--Fourty-five patients were included in the study. Twenty-one patients with PMR alone (Bird's criteria) and 24 with GCA (ACR criteria). In 11 patients, GCA was associated with PMR. HLA DRB1 genotype was determined by PCR-RFLP analysis. Statistical analysis was performed by the chi 2 test and determination of the odds ratio (OR). Two hundred and thirty-three unselected normal healthy subjects served as controls. RESULTS--A significant increased prevalence of HLA DR1 was observed in patient with PMR alone and an absence of DR7 (0% vs 10.3%, p = 0.02, OR = 0.1). An increased incidence of DR4 and particularly *0401 allele was only found in patients with GCA (OR = 2.4). No patient with isolated PMR had DR7 genotype compared with 25% in GCA (p < 0.001, OR = 0.03). A comparative study between isolated PMR versus GCA showed a significant increased in DR1 and DR3 alleles in isolated PMR and a significant increased prevalence of DR4 and DRB1 *0701 allele in GCA. CONCLUSION--The present study emphasizes the absence of similarity in HLA DRB1 allele distribution between PMR and GCA. The association of DR7 in patient with GCA seems characteristic in French native patients.

Immunological studies in giant cell arteritis

The results of investigations on the humoral immunological mechanisms are conflicting in giant cell arteritis (GCA) and have not been able to explain the pathological findings in the inflamed arterial wall. Altogether, immunological studies suggest that a cell-mediated immune reaction, possibly against an autologous antigen, occurs locally in the arteritic lesions of GCA. The excellent effect of treatment with glucocorticosteroids on the inflammation in GCA can also be explained by this model. The glucocorticosteroids inhibit the synthesis of interleukin-1 (IL-1) by the macrophages and suppress the IL-2 production from the T cells (Palacios, 1982). The observed HLA-DR expression in the arterial wall can be accounted for by the sum of macrophages and activated T cells, the macrophages being the most probable antigen-presenting cells. The interdigitating reticulum cells observed in some of the GCA patients may also be involved in antigen presentation. What the antigen(s) may be is, however, still unknown, as are the factors initiating the inflammatory process. It has recently been possible to extract T lymphocytes from the inflamed tissue and to culture these cells in vitro. After culture, it is possible to study the gene for the T-cell receptor, and probably even the antigenic specificity of the T cells. I hope that this approach may lead to a better understanding of the pathogenic mechanisms in GCA.