The HLA-DQ7 and -DQ8 associations in DR4-positive rheumatoid arthritis patients. A combined analysis of data available in the literature

Differences in Expression of Human Leukocyte Antigen Class II Subtypes and T Cell Subsets in Behçet's Disease with Arthritis

It has been reported Human Leukocyte Antigen (HLA) gene polymorphism is a risk factor for the development of Behçet’s disease (BD). In this study, the association of HLA class II subtypes HLA-DP, DQ, DR, and T cell subsets in BD patients with arthritis was evaluated. Frequencies of HLA-DP, DQ, DR positive cells, and T cell subsets in peripheral blood leukocytes (PBL) were measured by flow cytometric analysis in BD, and compared to rheumatoid arthritis as disease controls and healthy controls. Frequencies of HLA-DQ were significantly decreased in whole PBL and granulocytes of BD active patients as compared to healthy controls. In monocytes populations, proportions of HLA-DR positive cells were significantly increased in BD active patients as compared to healthy controls. Proportions of CD4+CCR7+ and CD8+CCR7+ cells were significantly higher in BD active patients than in BD inactive in whole PBL. Frequencies of CD4+CD62L- and CD8+CD62L- cells in lymphocytes were significantly decreased in active BD than those in inactive BD. There were also correlations between disease activity markers and T cell subsets. Our results revealed HLA-DP, DQ, and DR expressing cell frequencies and several T cell subsets were significantly correlated with BD arthritis symptoms.

Shared epitope and radiologic progression are less prominent in elderly onset RA than young onset RA

The aim of this study was to determine the influence of HLA-DRB1 and HLA-DQB1 genes on the disease susceptibility and the disease severity in elderly onset rheumatoid arthritis (EORA) compared with young onset rheumatoid arthritis (YORA) in Korean patients. Genetic analysis of HLA-DRB1 and HLA-DQB1 alleles was performed in three groups. Group 1 included 63 patients who were diagnosed with (rheumatoid arthritis) RA after the age of 60 (EORA). Group 2 consisted of 109 patients who were diagnosed with RA before the age of 60 (YORA). Group 3 involved 133 normal controls. The shared-epitope-coding alleles included the members of the HLA-DRB1*04 allele group (*0401, *0404, *0405, *0408, *0410), HLA-DRB1*01 allele group (*0101,*0102), HLA-DRB1*1001, and HLA-DRB1*1402. The disease severity was assessed by the modified total sharp score (mTSS). The shared-epitope-coding alleles were more frequently observed in the RA patients than in the normal controls. The shared-epitope-coding alleles were less frequently found in EORA group than YORA group (31/63 (49.2%) in group 1, 72/109 (66.1%) in group 2, 45/133 (33.8%) group 3, p = 0.02). Although the mTSS of the group 1 was higher than group 2 at symptom onset, the overall mean mTSS of the group 1 was lower than that of group 2 (26.8 vs. 57.5, p < 0.05). HLA-DQ*04 showed the higher frequency in the patients group than in normal controls (p < 0.001). And HLA-DQ*04 was less commonly found in the patients with EORA than YORA (p < 0.05). The influence of shared epitope and HLA-DQ*04 alleles may be less significant on disease susceptibility in EORA. The presence of shared-epitope-coding alleles did not appear to influence on disease severity in EORA patients as well as in YORA patients. Radiologic deterioration in EORA group was less severe than in YORA group. The presence of shared epitope and radiologic progression are less prominent in EORA patients than YORA patients.

HLA-DR-DQ haplotypes and genotypes in Finnish patients with rheumatoid arthritis

OBJECTIVES

To elucidate the contribution of HLA-DR-DQ haplotypes and their genotypic combinations to susceptibility to rheumatoid arthritis, and to evaluate the various models for HLA associated risk for the disease in a series of Finnish patients.

METHODS

322 Finnish patients with rheumatoid arthritis were typed for common north European HLA-DR-DQ haplotypes and compared with a series of 1244 artificial family based control haplotypes.

RESULTS

The association of the so called shared epitope (SE) haplotypes (DRB1*0401, *0404, *0408, and *01) with rheumatoid arthritis was confirmed. The DRB1*0401 haplotypes carried a far stronger risk for the disease than the (DRB1*01/10)-(DQA1*01)-DQB1*0501 haplotypes. Seven protective HLA haplotypes--(DRB1*15)-(DQA1*01)-DQB1*0602; (DRB1*08)-(DQA1*04)-DQB1*04; (DRB1*11/12)-DQA1*05-DQB1*0301; (DRB1*1301)-(DQA1*01)-DQB1*0603; (DRB1*1302)-(DQA1*01)-DQB1*0604; (DRB1*07)-DQA1*0201-DQB1*0303; and (DRB1*16)- (DQA1*01)-DQB1*0502--were identified. In accordance with the reshaped shared epitope hypothesis, all the protective DRB1 alleles in these haplotypes share either isoleucine at position 67 or aspartic acid at position 70 in their third hypervariable region motif. However, differences in the disease risk of haplotypes carrying the same DR but different DQ alleles were also found: (DRB1*07)-DQA1*0201-DQB1*0303 was protective, while (DRB1*07)-DQA1*0201-DQB1*02 was neutral. The same haplotypes carried different risks for rheumatoid arthritis depending on their combination in genotypes.

CONCLUSIONS

When assessing the influence of HLA genes on the susceptibility to rheumatoid arthritis, not only should the HLA-DR or -DQ alleles or haplotypes be unravelled but also the genotype. The effect of HLA class II region genes is more complicated than any of the existing hypotheses can explain.

The role of HLA-DRB1*04 alleles and their association with HLA-DQB genes in genetic susceptibility to rheumatoid arthritis in Hungarian patients

We investigated the HLA-DRB, and DQB polymorphism and haplotypes in RA subjects of Hungarian origin by PCR typing using sequence-specific primers. Molecular subtyping of HLA-DRB1*04 alleles in RA patients showed strongest association with highest relative risk with DRB1*0404. A significantly decreased frequency of DRB1*0403 was observed in patients compared to controls. A significant number of patients carried DR4 haplotypes on DQB1*0302 (54%) relative to DQB1*0301 which was present on 36% of the haplotypes. When compared to controls, the frequency was higher in the latter allele only. Few unique DRB-DQB haplotypes were observed in Hungarian RA patients. In spite of the fact, that the Hungarian population has been isolated linguistically over centuries, a considerable racial admixture has occurred following immigration and invasions, thus the present study confirms in Hungarian patients with RA, previous findings for RA and HLA in European countries.

The autoimmune pathogenesis of rheumatoid arthritis: role of autoreactive T cells and new immunotherapies

OBJECTIVES

To review the role of T lymphocytes in the pathogenesis of rheumatoid arthritis (RA) and discuss the relevance of the components of the trimolecular complex (synovial T cells, autoantigens, and antigen presenting cells) in the pathogenic autoimmune response in RA.

METHODS

Currently available experimental data are combined into a hypothetical pathway that may explain some of the events in the RA process. The literature regarding the potential therapeutic strategies that interfere with specific components of the trimolecular complex and other mediators are discussed briefly.

RESULTS

T cells are activated in the peripheral blood, cross the endothelial cell wall, and migrate into the joints. Once in the synovial joints, T cells are reactivated by cross-reactive antigens and clonally expand. Clonally expanded T cells accumulate in the diseased joint and secrete proinflammatory cytokines that attract and activate other cells, such as monocytes and macrophages. Treatment with anti-CD4 monoclonal antibodies or anticytokine agents that prevents antigen presentation and/or T-cell activation were effective in RA. Other therapies, such as T-cell vaccination and T-cell receptor peptide vaccination targeting autoreactive T cells, showed clinical improvement, suggesting a pathogenic role of these lymphocytes in disease progression.

CONCLUSION

T cells appear to be actively involved in the pathogenesis of RA, but several parts of the pathway are hypothetical and further research is needed.

T-cell receptor repertoire in human germinal centres

A search for an antigen-driven expansion of T lymphocytes in the inflamed joints in rheumatoid arthritis (RA) patients have been going on for decades. We here analyzed the human germinal centre T-cell receptor (TCR) Vbeta gene usage with polymerase chain reaction (PCR) combined with sequence analysis, to address the question of clonality in tonsils and synovial tissue from RA patients. Our data show a large degree of TCR heterogeneity in both these histological structures. Furthermore, clonally related T cells were found within different closely located germinal centres indicating either an active T-cell migration between germinal centres (GC) or that a T-cell clone may seed more than one GC.

Protection against severe disease is conferred by DERAA-bearing HLA-DRB1 alleles among HLA-DQ3 and HLA-DQ5 positive rheumatoid arthritis patients

Experimental studies in transgenic mice have suggested that HLA-DQ predisposes to rheumatoid arthritis (RA), but could also modulate disease severity by presenting peptides derived from self-DR molecules. In particular, a short amino acid sequence, (70)DERAA(74), in the third hypervariable region of HLA-DRB1 confers protection for the disease, while particular HLA-DQ [DQB1*0501/DQA1*01 (DQ5) and DQB1*03/DQA1*03 (DQ3)] molecules predispose to the disease. We have therefore analyzed the allelic distribution of HLA-DRB1, DQA1, and DQB1 and the presence of rheumatoid factor and nodules among 199 German RA patients and 196 healthy controls. Our results show that HLA-DQB1*03/DQA1*03 (or DRB1*04) predisposes to RA more than HLA-DQB1*0501/DQA1*01 (i.e., DRB1*01 and DRB1*10). Homozygosity for DQ3 confers the strongest genetic risk for RA (OR = 19.79 compared to OR = 10.05 for two doses of shared epitope (SE) positive HLA-DRB1 alleles). Furthermore, patients carrying both predisposing DQ and (70)DERAA(74)-positive HLA-DRB1 alleles are more often rheumatoid factor (RF) negative than patients carrying predisposing DQ alleles alone. Only one out of 14 patients (7%) with a protective combination (DQ3/(70)DERAA(74) and DQ5/(70)DERAA(74)) had rheumatoid nodules compared to 67 out of 144 patients (46.5%) with predisposing DQ alleles alone (OR = 0.12, 95% CI: 0.02-0.72, p = 0.004). These results demonstrate a protective role of (70)DERAA(74)-positive DRB1 alleles against disease severity among RA patients.

HLA haplotype analysis in Finnish patients with rheumatoid arthritis

OBJECTIVE

To further characterize the HLA gene products that play an important role in the pathogenesis of rheumatoid arthritis (RA).

METHODS

One hundred thirty-four haplotypes from 67 Finnish RA patients and 77 control haplotypes were analyzed for HLA-DRB1 loci, associated alleles of the HLA-DQB1 locus, alleles of the type 2 transporter-associated antigen processing (TAP2) genes, and HLA-B27. In addition, a panel of microsatellite markers within the HLA class I and class III regions was studied.

RESULTS

The frequency of HLA-DRB1*04 in the haplotypes of RA patients was found to be 34% (45 of 134) compared with 14% (10 of 72) in control haplotypes (P = 0.004). The frequency of HLA-DRB1*13 was decreased in RA haplotypes (4%, or 5 of 134) in contrast to control haplotypes (24%, or 17 of 72) (P = 0.000031). The decrease in DRB1*13 was not secondary to the increase in DRB1*04, since it was also found among DRB1*04-negative haplotypes (P < 0.001). The DRB1*13-associated DQB1*0604 allele was similarly decreased in RA haplotypes (P = 0.025). The TAP2I allele of I/J dimorphism was increased in RA patients (85%, or 114 of 134) as compared with controls (69%, or 49 of 71) (P = 0.011). Of the tumor necrosis factor (TNF) microsatellite alleles, TNFa6 and TNFb5 were found to be increased in RA haplotypes (for a6 27% versus 5% in controls [P = 0.00043], and for b5 43% versus 26% in controls [P = 0.037]).

CONCLUSION

Both protection-associated and susceptibility-associated alleles can be found among HLA class II genes, and the results suggest that loci outside DR/DQ may contribute to the pathogenesis of RA.

Do the HLA-DQ and DP genes play a role in rheumatoid arthritis?

Whereas the DRB1 alleles have well-established associations with rheumatoid arthritis (RA), the DQ and DP alleles are of more controversial relevance to RA. Early studies of the DQB1 genes in RA determined the frequencies of the two DQB1*03 subtypes that are in linkage disequilibrium with DR4, DQB1*0301 (DQw7) and *0302 (DQw8). Their results are conflicting and difficult to interpret because molecular biology techniques for determining DR4 specificity polymorphism were not available at the time. None of the more recent studies found compelling evidence that the DQB1 alleles influenced the susceptibility to RA. A few studies suggest that the DQ alleles may influence the clinical or biological expression of the disease, perhaps through a complementary effect of the DRB1 and DQB1 alleles. DR-DQ complementarity has been demonstrated in the DQ8 transgenic mouse model, although this is not necessarily relevant to the human disease. The role of DPB1 remains hypothetical but may involve an influence of some alleles in relatively mild forms of RA. The DQB1 and DPB1 alleles are in strong linkage disequilibrium with the DRB1 alleles, making the elucidation of their independent effects a challenging task. Studies are needed to determine whether these linkage disequilibriums can influence the development of autoimmune diseases.

The genetics of rheumatoid arthritis and the need for animal models to find and understand the underlying genes

The causes of rheumatoid arthritis (RA) are largely unknown. However, RA is most probably a multifactorial disease with contributions from genetic and environmental factors. Searches for genes that influence RA have been conducted in both human and experimental model materials. Both types of study have confirmed the polygenic inheritance of the disease. It has become clear that the features of RA complicate the human genetic studies. Animal models are therefore valuable tools for identifying genes and determining their pathogenic role in the disease. This is probably the fastest route towards unravelling the pathogenesisis of RA and developing new therapies.

HLA class II association with rheumatoid arthritis: facts and interpretations

We have reviewed the literature on the association of HLA class II with rheumatoid arthritis (RA). Strong linkage disequilibrium among DQB1, DQA1 and DRB1 alleles makes it difficult to evaluate the individual contribution of each locus. Nonetheless, there is a strong case for the role of DQB1*03 and *04 combined with DQA1*03 in susceptibility to severe RA while DQB1*0501 combined with DQA1*0101 and *0104 weakly predisposes to a mild form of RA. However, it is also clear that DRB1*0401 has a particular role in predisposition to the most severe form of the disease while other DRB1 alleles might provide protection. We would like to propose that in RA, as in type I diabetes, both DQ and DR loci contribute to predisposition to the disease.

Human autoimmunity genes in mice

In the post-genomic era, the expression and investigation of human (auto)immunity genes seems more relevant than ever. The generation of humanized animal models of human diseases will be useful to study the interplay between genetic and non-genetic factors in disease development and may form a basis for the development of new drugs that act more specifically than the ones currently in use. Transgenic mice have been generated that express various human proteins--candidate autoantigens, disease-associated MHC class II molecules, TCRs and/or CD4--in order to study diseases such as rheumatoid arthritis, multiple sclerosis and diabetes.

Association of MHC and rheumatoid arthritis. HLA-DR4 and rheumatoid arthritis: studies in mice and men

Inherited susceptibility to rheumatoid arthritis (RA) is associated with the DRB1 genes encoding the human leukocyte antigen (HLA)-DR4 and HLA-DR1 molecules. Transgenic mice expressing these major histocompatibility complex (MHC) class II molecules have been developed to generate humanized models for RA. The relevance of these models for understanding RA will be discussed.

Rheumatoid arthritis and its animal models: the role of TNF-alpha and the possible absence of specific immune reactions

Rheumatoid arthritis is an organ-specific inflammatory disease of humans. Recent studies have focused on associations with non-MHC genes, new autoantigens and the role of innate immune responses. The success of anti-TNF-alpha in the majority (but, interestingly, not all) of patients has implications for disease mechanisms but the dangers of long-term therapy are becoming clearer. A number of new models of arthritis have been defined and emphasize the importance of the genetic make-up of the host. Attention has also focused on why the joint is a particularly vulnerable site for inflammatory responses.

DQCAR 113 and DQCAR 115 in combination with HLA-DRB1 alleles are significant markers of susceptibility to rheumatoid arthritis in the Korean population

We have investigated HLA region microsatellite polymorphisms in rheumatoid arthritis (RA) which are known to be associated with HLA class II alleles in the Korean population. Ninety patients with RA and 106 controls were employed for this study, in which TAP1CA, DQCAR, D6S273, HLA-DRB1, -DQA1 and -DQB1 allele typing were performed. DQCAR 113 (RR = 3.2, P<0.0002), DQCAR 115 (RR = 3.6, P<0.0001) and heterozygous DQCAR 113/115 (RR = 11.2, P<0.0001) frequencies were significantly increased in the RA group compared with the control group. The HLA-DRB1 genotypes of patients who had DQCAR 113/115 alleles were defined as DRB1*04 and/or DRB1*09. There was no significant difference between RA and controls in D6S273 and TAP1CA allele frequencies. We demonstrated that HLA-DRB1*0405 (RR = 6.6, P<10(-6)), DQA1*03 (RR = 5.2, P<10(-6)), DQB1*04 (RR = 3.5, P<0.002) alleles were useful markers of susceptibility to RA in Koreans. The frequency of HLA-DRB1*0405 was higher in DQCAR 113 allele-positive RA (68.1%) than in DQCAR 113 allele-negative (16.3%) and total RA (43.3%) groups, and the susceptibility risk of DQCAR 113 allele to RA was more increased in the DRB1*0405-positive group (RR = 5.5, P<0.04). On the other hand, DQCAR 115 allele was more significantly associated with susceptibility to RA in HLA-DRB1*0405-negative patients (RR = 5.1, P<0.0005), and the association between RA and HLA-DRB1*0405 was also significantly associated with DQCAR 115 allele-negative patients (RR = 13.2, P<0.00001) as compared with DQCAR 115 allele-negative control groups. HLA-DRB1*0405-DQA1*03-DQCAR113-DQB1*03 haplotype showed high relative risk value (RR= 17.7, P<0.0002). In conclusion, the DQCAR allele in combination with HLA class II, especially DR, is probably a useful risk marker for RA susceptibility in the Korean population.

Association of HLA alleles and clinical features in patients with synovitis of recent onset

OBJECTIVE

To determine how HLA alleles are associated with the clinical disease patterns of patients with synovitis of recent onset.

METHODS

The HLA alleles A, B, C, DRbeta1, and DQbeta1 were determined in a cohort of 211 patients (mean age 42 years, 64% female, 79% white) with recent-onset synovitis in 1 or more peripheral joints. At a mean disease duration of 33 weeks, 98 patients (46%) met the American College of Rheumatology (ACR) criteria for rheumatoid arthritis (RA), 38 (18%) met the European Spondylarthropathy Study Group criteria for spondylarthropathy (SpA), and 75 (36%) were classified as having undifferentiated arthropathy (UA). Controls were racially matched healthy individuals (n = 244).

RESULTS

Shared epitope (SE) alleles were significantly more common in rheumatoid factor-positive (RF+) patients fulfilling the ACR RA criteria than in other patients with early arthritis (65% versus 35%; P < 0.001). In addition, the RA patients had by far the highest frequency of radiographic erosions (52% and 39% in RF+ and RF- RA, respectively, versus 3% and 9% in SpA and UA patients, respectively; P < 0.0001). The presence of SE alleles was a particularly strong predictor of early erosions in the RF- RA patients (odds ratio [OR] 6.8, 95% confidence interval [95% CI] 1.2-45). The presence of 2 SE alleles or an associated DQbeta1*0301 (DQ7) or DQbeta1*0302 (DQ8) allele appeared to modestly increase the risk of early erosions, although these DQ alleles were in strong linkage disequilibrium with DRbeta1*0401, both in the patient and in the control populations. B27 was linked with the presence of SE alleles in the patients, including those patients fulfilling the RA criteria, but not in the controls (12% versus 3%; P < 0.001). Enthesitis was present in 23 (11%) of 211 patients, was highly associated with B27 (OR 4.2, 95% CI 1.5-11.5), and surprisingly, was not a feature specific only to the SpA group. The B8-DR3 haplotype was significantly increased in the patient subgroups compared with controls (17% versus 7%; P < 0.01), although the clinical significance of this association is unclear.

CONCLUSION

This study of HLA associations in a diverse cohort of early synovitis patients emphasizes the complex degree of genetic interaction between alleles at several major histocompatibility complex loci, which regulates clinical phenotypes. In particular, SE and B27, while predisposing patients to characteristic clinical syndromes, had an unexpected degree of association in this cohort, perhaps explaining the overlap in clinical features in many patients.

No support for HLA-DQ encoded susceptibility in rheumatoid arthritis

OBJECTIVE

To test predictions based on data from immunogenetic and peptide-binding studies of collagen-induced arthritis in mice, in which it has been suggested that susceptibility to rheumatoid arthritis (RA) might be determined by the interaction between susceptibility alleles at the HLA-DQ locus and protective alleles at the HLA-DRB1 locus (including susceptibility effects for HLA-DQ7 and DQ8).

METHODS

Predictions based on these models were tested in 166 healthy controls and 167 patients with RA, all of whom were typed for HLA-DRB1 and HLA-DQ alleles.

RESULTS

In this population, HLA-DQ7 did not encode an increased risk for RA. This lack of susceptibility effect of HLA-DQ7 could not be attributed to competing HLA-DQ susceptibility alleles, protective HLA-DRB1 alleles, or the absence of DQA1*0301.

CONCLUSION

These observations do not support the DR/DQ hypothesis in its present form.

Transgenic mouse models of rheumatoid arthritis

A combined analysis of data available in the literature has demonstrated that the strongest association in rheumatoid arthritis (RA) is with DR genes rather than DQ or DP genes. Functional and structural data of RA-associated DR molecules suggest that selective binding of peptides is the molecular basis for this association. The establishment of functional transgenic mice expressing RA-associated HLA class II molecules has proven to be useful in the delineation of the role of these molecules in immune responses possibly related to RA and in the development of humanized models for this disease. Such humanized mice develop arthritis upon immunization with type II collagen (CII), which shows similarities with RA. Interestingly, the immunodominant T-cell determinant in CII is derived from positions 261-273, which overlap with a previously identified CII T-cell epitope restricted by the mouse Aq molecule, which is associated with collagen-induced arthritis. Studies in collagen transgenic mice have shown that recognition of this peptide may lead either to T-cell tolerance or to an arthritogenic response. It is therefore proposed that the T-cell recognition of the CII peptide bound by DR molecules is one of the molecular interactions of critical importance in the development of RA and accordingly also an important target for prevention and treatment of this disease.

HLA-DR/DQ interaction in patients with erosive rheumatoid arthritis presenting articular and extraarticular disease manifestations

In the present study we have analysed the effect of HLA-DRB1 and -DQB1 alleles on disease progression and genetic predisposition among 201 RA patients. We clearly confirm the association of RA with HLA class II alleles sharing the (Q)R/KRAA amino acid (AA) cassette in the third hypervariable region (HVR3) of the DR beta-chain. The HVR3 (Q)R/KRAA motif was significantly overrepresented among RA patients (79% vs. 40%, P < 0.001), with one third of the patients homozygous (28% vs. 6.7%, P < 10(-9)) and the number of rheumatoid factor positive (RF+) patients was significantly increased among HVR3 (Q)R/KRAA homozygous in comparison to HVR3 (Q)R/KRAA negative individuals. Erosive disease defined by the Larsen Score and personal disability determined using the Health Assessment Questionnaire (HAQ) was significantly increased among patients positive for the HVR3 motif with the worst outcome among HVR3 (Q)R/KRAA homozygous patients. In contrast, there was no association of the shared HVR3 AA cassette and disease severity in the majority of patients presenting systemic (extraarticular) disease. Homozygosity for the shared HVR3 motif was only marginally increased among patients presenting 'severe' extraarticular disease in comparison to patients with articular disease (33% vs. 43%, P = ns). Similarly, patients with nodular disease were not more often homozygous for the HVR3 (Q)R/KRAA motif. Furthermore, we observed no HLA-DR independent association of DQB1 alleles among HVR3 (Q)R/KRAA positive patients and controls. Our analysis supports the predominant role of HLA-DR for genetic susceptibility to RA. In the clinical setting, however, HLA-DR typing may be limited to assess the individual risk of patients for disease progression.

Definition of MHC and T cell receptor contacts in the HLA-DR4restricted immunodominant epitope in type II collagen and characterization of collagen-induced arthritis in HLA-DR4 and human CD4 transgenic mice

Rheumatoid arthritis (RA) is an autoimmune disease associated with the HLA-DR4 and DR1 alleles. The target autoantigen(s) in RA is unknown, but type II collagen (CII) is a candidate, and the DR4- and DR1-restricted immunodominant T cell epitope in this protein corresponds to amino acids 261-273 (CII 261-273). We have defined MHC and T cell receptor contacts in CII 261-273 and provide strong evidence that this peptide corresponds to the peptide binding specificity previously found for RA-associated DR molecules. Moreover, we demonstrate that HLA-DR4 and human CD4 transgenic mice homozygous for the I-Abbeta0 mutation are highly susceptible to collagen-induced arthritis and describe the clinical course and histopathological changes in the affected joints.

DQCAR microsatellite polymorphism and susceptibility to rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease associated with HLA-DR genes that share a five amino acid sequence motif, QKRAA or QRRAA, from position 70 to 74 in the third hypervariable region of the DRbeta1 molecule. Since the associations between DRB1 genes and susceptibility to RA are incomplete, in this study we examined the CA repeat polymorphic marker DQCAR, located between DQA1 and DQB1 genes, alleles in 98 adult patients with seropositive RA and 100 normal healthy controls. The prevalence of the DQCAR 117 allele was significantly higher in RA patients as compared to normal controls. On the other hand, the frequency of DQCAR 99 was lower in patients than in normal subjects. Analysis of the data suggested that DRB1 genes sharing the QKRAA/QRRAA epitope have the primary association with disease susceptibility and DQCAR alleles do not provide an additional risk for the development of RA.

Relevant residues of DRbeta1 third hypervariable region contributing to the expression and to severity of rheumatoid arthritis (RA) in Mexicans

Rheumatoid arthritis (RA) is a chronic autoimmune disease leading to destruction of the joints. Residues at positions 67-74 of the DRB1 third hypervariable region are involved in susceptibility (S) and resistance (P) to RA. DNA from 83 patients and 175 controls, all of them Mexican Mestizos were oligotyped using PCR-SSOP and PCR-SSP. The (S) alleles are DRB*0404 (p = 0.000004), *0401 (p = 0.007) and *1001 (p = 0.008). Those associated with P are DRB1*0701 (p = 0.0001); *1101 (p = 0.01); *1503 (p = 0.02); *0801 (p = 0.04); *1401 (p = 0.04). Susceptibility/protection are recessive traits; SS genotypes are increased in the patients (p = 0.0003) while PP genotypes are decreased in them (p = 0.00004). The motif at 67-74 and the valine or glycine at position 86 are relevant in the development and severity of RA in Mexicans. The associations suggest that residues 67, 70, 71 are central for susceptibility. The P alleles have D-70 or carry V-86 in the absence of D-70. Thus, susceptibility/protection depends on the combination of basic residues at these positions and a non-polar aa at 86 contributes to resistance. Severity is also HLA influenced. DQA1*03011-DQB1*0302 are associated to severe lesions in the presence of any DR4 subtype. Analyzing different ethnic groups is essential to elucidate the etiopathogenesis of RA.