HLA-DR antigens in rheumatoid arthritis

Gold salts, D-penicillamine and allopurinol

Gold salts have been used in the treatment of patients with rheumatoid arthritis since 1927 [1]. After a controlled study, the Empire Rheumatism Council [2], confirmed the effectiveness of gold salts for the treatment of rheumatoid arthritis. Even today, chrysotherapy has remained one of the major therapeutic modalities in the second line treatment of progressive rheumatoid arthritis. Gold salts are also used in the treatment of pemphigus vulgaris [3] and bronchial asthma [4]. Before the introduction of an orally administered gold compound, auranofin (triethylphosphine gold tetra-acetyl glycopyranoside), to clinical use [5-7], parenterally administered gold salts, such as sodium aurothiomalate and gold thioglucose comprised chrysotherapy. The frequency and severity of the side effects for patients treated with parenteral gold versus those given oral gold preparations are significantly different [8-10]. With introduction of newer parental DMARDs, toxicity has been reduced using combination therapy [10a, 10b].

HLA-DRB1 in eight Finnish monozygotic twin pairs concordant for rheumatoid arthritis

This study presents the results of HLA-DRB1 typing of the eight monozygotic twin pairs with both members affected by rheumatoid arthritis (RA), sampled in the nationwide Finnish twin cohort. The shared epitope, associated with RA in case-control studies, was present in all eight twin pairs, being significantly more frequent than among RA patients in a recent Dutch case-control study. Furthermore, 4 out of 8 twin pairs were homozygous for the shared epitope, while in 73 Dutch healthy controls encoding the shared epitope only 13 (18%) were homozygous: this suggests a gene dose effect in RA susceptibility. Combining these results with data from other sources may help to clarify the contribution of HLA alleles in the genetic predisposition to RA.

Only weak association between disease severity and HLA-DRB 1 genes in a Swiss population of rheumatoid arthritis patients

This study analyses the prognostic value of HLA-DRB 1 genes for Swiss patients with rheumatoid arthritis (RA). HLA-DRB 1 genotyping was performed in 83 patients using the polymerase chain reaction and subsequent oligonucleotide hybridisation. They were categorised according to the presence of one or two putatively relevant genes (DRB 1*01 and/or DRB 1*04) and retrospectively evaluated for sex, age at disease onset, seropositivity, erosive disease and extraarticular manifestations. Sixty-one patients (73%) had disease-associated alleles. Twenty-four patients showed HLA-DRB 1*04 variants on both alleles or combined an HLA-DRB 1*04 variant with HLA-DRB 1*01, while 37 patients expressed only one relevant allele. Interestingly, 22 patients did not express any relevant allele. Some 52% of patients had nodular disease, 88% were seropositive. 96% had joint erosions and 11% expressed vasculitis and/or rheumatoid organ disease. A significant difference was observed only for the number of seropositive individuals, which was slightly higher in the group of patients expressing a double dose of disease-associated alleles than in patients who had no relevant alleles. Moreover, patients expressing homozygous DRB 1 alleles had a significantly earlier onset of disease than those who were heterozygous. We conclude from these findings that HLA-DRB 1 genotyping in a Swiss population of RA patients only weakly identifies clinical subsets with distinct profiles of disease manifestations and is not of strong prognostic value to determine disease severity in individual patients.

Sjogren's syndrome in Israel: primary versus secondary disease

Sixty Israeli patients, 30 with primary Sjögren's syndrome (SS) and 30 with rheumatoid arthritis (RA) and secondary SS, were evaluated. The Schirmer-1 test and a positive labial salivary gland biopsy were found to be the most helpful tools in assessing the diagnosis of SS. Extraglandular features such as Raynaud's phenomenon, lymphadenopathy and CNS involvement as well as parotid gland enlargement (p < 0.05) were more common in primary SS. Antinuclear antibodies, especially anti-Ro (SSA) and anti-La (SSB) were also more common in primary SS (p < 0.05). Our results are in accord with those of many European centers, despite the different genetic background.

Dw14(DRB1*0404) is a Dw4-dependent risk factor for rheumatoid arthritis. Rethinking the "shared epitope" hypothesis

HLA-DR4 has been shown to be associated with risk for developing rheumatoid arthritis (RA) in multiple populations and racial groups. The allelic variants of DR4 share the DR4 serologic specificity but differ by 1 to 3 amino acids in the third hypervariable region (positions 67 to 74) and at positions 57 and 86 of the DR beta 1 chain. We have examined DR4 variants in 61 DR4+ RA cases and 55 DR4+ healthy controls. Dw14 was not associated with RA risk in DR4 heterozygous (DR4,X) cases. Only 15% of DR4,X cases had the Dw14 allele compared with 28% of DR4,X controls. In homozygous (DR4,4) individuals who also expressed Dw4, however, Dw14 was associated with increased RA risk. Moreover, the relative risk for Dw4,Dw14 (16.1, p = 0.001) actually exceeded that of Dw4,Dw4 (2.2, p = ns). Thus Dw14 is not an independent risk factor for RA but is a synergistic risk factor for individuals who also have the Dw4 allele.

HLA typing in families with multiple cases of rheumatoid arthritis

Thirty one white patients from 14 families with multiple cases of rheumatoid arthritis (RA) and 42 of their healthy relatives were completely HLA typed. In contrast with class I antigens, the class II antigens DR1 and DR4 were significantly more common in the patients than in a group of 200 healthy local white controls (DR1: 32% v 12%; DR4: 48% v 28%, in patients and controls respectively). Owing to the small number of cases the data from this study were combined with those of published reports. Examination of patients for DR1 and DR4 homozygosity and DR1/4 heterozygosity showed an increase of DR1 homozygous patients, which was not statistically significant. There was no striking deviation from random expectation in haplotype sharing of affected sib pairs. These results are compatible with a dominant influence of DR1 and DR4 in the mode of inheritance. The nearly random haplotype sharing and the molecular relation between DR1 and DR4 support the hypothesis of a direct influence of these antigens in the pathogenesis of RA. Only 68% of the patients in this study possessed either DR1 or DR4, possibly indicating a subtype of RA which is independent of HLA. Clinical and serological variables were measured and indicated no significant difference between DR1 (or DR4) positive and DR1 (or DR4) negative disease. In this small group of patients the clinical course of RA seemed to be determined mainly by other genetic or environmental factors.

HLA-DR1 and DRw6 association in DR4-negative rheumatoid arthritis patients

This study of 110 seropositive rheumatoid arthritis (RA) patients confirms the significant association of susceptibility to RA with HLA-DR4 specificity (P less than 0.001). The DR1 frequency is elevated in the entire seropositive patient group, reaching marginal significance (P less than 0.025). The DR4-negative patients, however, have a much higher prevalence of DR1 (P less than 0.001). Surprisingly, the DRw6 specificity is significantly increased in the remaining DR4- and DR1-negative patients (P less than 0.01). These results demonstrate that RA is not associated with a single HLA-specificity, but to various degrees with DR4, DR1, and DRw6. These findings, and particularly the newly recognized association with DRw6, support the hypothesis that functionally equivalent shared epitopes or conformations on otherwise distinct MHC molecules may confer risk for developing RA.

Destructive arthritis, rheumatoid factor, and HLA-DR4. Susceptibility versus severity, a case-control study

In response to the continuing debate as to whether seronegative rheumatoid arthritis (RA) and seropositive RA are part of the same disease spectrum or are distinct disorders, we evaluated 720 patients with definite and classic RA, of whom 53 subjects had definite persistently seronegative destructive disease. For all but 1 seronegative RA patient, a seropositive RA case control was identified and matched for age, disease duration, degree of destruction on hand radiographs, and disease-modifying drug therapy. DR typing was undertaken on these 105 patients, together with scoring of hand radiographs. The frequency of DR4 was 69% in seropositive RA patients and 60% in seronegative RA patients (P = 0.22), versus 36% in 318 healthy controls (P = 0.008 and P = 0.007 versus seropositive and seronegative RA, respectively). Patients were matched and rematched with different controls in a series of subanalyses in order to make comparisons of hand radiograph scores. We found that HLA-DR4 was associated with destructive RA in both seropositive and seronegative RA patients. In general, DR4+ patients had more severe disease by radiologic criteria than did DR4- patients. Thus, HLA-DR4 may be an additive factor to the serologic status and may be more closely related to disease severity than to disease susceptibility.

Haplotypes bearing HLA-A, -B, and -DR: Bf and C4 genes in rheumatoid arthritis families

We have compared haplotypes bearing HLA-A, -B, -DR; Bf and C4 genes in 54 rheumatoid arthritis (RA) and 24 control families. There was no statistically significant differences in C4A or C4B gene frequencies between RA and control groups, although there were trends for C4B*Q0 to be reduced and C4B2 to be increased in DR4 positive RA compared with DR4 positive controls. The lack of any strong association between C4 variants and RA overall makes it unlikely that the association between RA and genes within the MHS represents a direct effect of variants within the C4A or C4B loci themselves. On comparison of DR4-bearing haplotypes, the haplotype B15-BfS-DR4 was increased fourfold and the B44-Bfs-DR4 haplotype was less frequent in the RA group. When C4 variants were also considered, the haplotype B44-C4B*Q0-C4A3-BfS-DR4 was nine times less frequent in RA patients than in controls. The observation that different DR4 bearing haplotypes may confer either increased or decreased susceptibility to RA suggests either that it is unlikely that DR4 itself is involved in the disease process or that specific haplotypic combinations are important. Thirty-two RA patients were HLA-DR4 negative. No single DR4 negative haplotype was found to confer significantly increased susceptibility to RA.

Rheumatoid arthritis

The results of family and twin studies suggest that RA may result from an interaction between an oligogenic susceptibility and unknown environmental factors. Part of this genetic predisposition is accounted for by genes within the MHC where there is a well-documented association with HLA-DR4. Studies of DR and other MHC variants have shown different associations with particular subgroups. One subgroup is Felty's syndrome where there is a strong association with DR4, as well as associations with DQ-beta and C4B null variants when DR4-matched Felty's and RA subjects are analysed. These DQ-beta and C4B null variants may characterize a single haplotype which is associated with extra-articular disease. A further rheumatoid subgroup characterized by circulating antibodies to native type II collagen, shows an association with HLA-DR3 and 7. Genes on chromosome 14 may also influence susceptibility to RA, probably by interaction with MHC genes and there are different Gm associations for DR4-positive and collagen-antibody-positive rheumatoid subgroups. HLA and Gm markers so far identified only account for a small part of the total genetic predisposition to RA and a third or further loci may also be involved. Possible candidates include T-cell alpha- and beta-chain genes and immunoglobulin light chain genes. One present concept of the genetic predisposition to RA is of several independent immunogenetic pathways each including interactions at two or more loci.

Associations of HLA-DR4 with rheumatoid factor and radiographic severity in rheumatoid arthritis

Possible associations between HLA-DR4 and laboratory, radiographic, joint count, functional, and demographic measures of clinical status were analyzed in 154 white patients with rheumatoid arthritis. Overall, 65 percent of the patients were HLA-DR4 positive, similar to other series. HLA-DR4 was associated significantly with the presence of rheumatoid factor and more severe radiographic changes. HLA-DR4 was not associated with significant differences in demographic, joint count, or functional measures of clinical status. HLA-DR1 was not associated significantly with differences in the presence of rheumatoid factor, radiographic changes, or other measures of clinical status. Selective associations of HLA-DR4 with rheumatoid factor and radiographic scores were more marked in men than in women. Patients who were putatively homozygous for HLA-DR4 were all seropositive and had more severe radiographic changes than patients who were heterozygous for HLA-DR4.