HLA-DRB1*04 subtypes are associated with increased inflammatory activity in early rheumatoid arthritis

Interleukin-34-regulated T-cell responses in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a multifaceted etiology, which primarily affects and results in the deterioration of the synovium of patients. While the exact etiology of RA is still largely unknown, there is growing interest in the cytokine interleukin-34 (IL-34) as a driver or modulator of RA pathogenesis on the grounds that IL-34 is drastically increased in the serum and synovium of RA patients. Several studies have so far revealed the relationship between IL-34 levels and RA disease progression. Nevertheless, the significance and role of IL-34 in RA have remained ambiguous, as illustrated by two most recent studies, which reported contrasting effects of genetic IL-34 deletion in RA. Of note, IL-34 is a macrophage growth factor and is increasingly perceived as a master regulator of T-cell responses in RA via macrophage-dependent as well as T cell-intrinsic mechanisms. In this regard, several studies have demonstrated that IL-34 potentiates helper T-cell (Th) responses in RA, whereas studies also suggested that IL-34 alleviates synovial inflammation, potentially by inducing regulatory T-cells (Treg). Herein, we provide an overview of the current understanding of IL-34 involvement in RA and outline IL-34-mediated mechanisms in regulating T-cell responses in RA.

Human leukocyte antigen-G polymorphism influences the age of onset and autoantibody status in rheumatoid arthritis

The study was conducted to investigate the frequency of three gene polymorphisms in the 3'-untranslated region (3'-UTR) of human leucocyte antigen-G (HLA-G) gene in south Indian patients with rheumatoid arthritis (RA) and analyze their influence on disease susceptibility, phenotype and treatment response. HLA-G 14 bp insertion (Ins)/deletion (del) (rs66554220), HLA-G +3142G>C (rs1063320) and +3187A>G (rs9380142) polymorphism was analyzed in 221 RA patients and 200 healthy controls. Frequency of HLA-G genotypes or alleles did not differ between patients and controls. Analysis based on rheumatoid factor (RF) status revealed that the frequency of allele 'A' (rs9380142) was significantly higher in RF-positive than in RF-negative patients [84% vs 74%, Yates-corrected P value (Pc) = 0.04, odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.0-3.2]. A similar difference was maintained in RF-positive female patients than their RF-negative counterparts (83% vs 71%, Pc = 0.02, OR = 1.9, 95% CI = 1.0 to 3.4) and between RF-positive and RF-negative young onset RA (YORA) patients (84% vs 73%, Pc = 0.03, OR = 1.9, 95% CI = 1.0-3.2), suggesting that rs9380142 polymorphism influenced RF status. The 14 bp Ins allele of rs66554220 was significantly more prevalent in RF-positive YORA than in RF-positive late onset RA (LORA) patients (51% vs 25%, P = 0.03, OR = 3.1, 95% CI = 1.1-9.8). Frequency of the four major haplotypes [InsGA (48%), DelGA (22%), DelCG (18%), DelCA (9.7%)] observed did not differ between cases and controls. HLA-G does not appear to be a risk factor for development of RA in south Indian Tamils but may act as a genetic modifier of clinical phenotype in terms of autoantibody production, gender preference and age at disease onset.

Gene expression profiles of systemic lupus erythematosus and rheumatoid arthritis

Gene expression profiling using microarray technology is being employed to define specific molecular mediators and pathways involved in immunobiology, to understand the intricate interplay of genes participating in the pathogenesis, and to develop biomarkers of disease activity in both systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). This review summarizes the latest information on the pathogenesis of SLE and RA and describes the utilization of microarray technology in these systemic autoimmune diseases.

Association of rheumatoid arthritis with HLA-DR1 and HLA-DR4 in Hungary

Susceptibility to and outcome for rheumatoid arthritis (RA) have been associated with particular HLA-DR alleles, but these alleles vary among ethnic groups and geographic areas. The frequency of HLA-DR1 (HLA-DRB1*0101, DRB1*0102) and HLA-DR4 (DRB1*0401, DRB1*0404) alleles is elevated among Caucasian patients with RA. We studied a northeastern Hungarian population of RA patients to determine the frequency of HLA-DR1 and HLA-DR4 phenotypes in this population and to compare it with healthy control subjects, as well as to investigate whether the presence of these alleles could be a marker for RA. We performed HLA-DRB1 genotyping (DRB1*01-DRB1*16) in 83 RA patients and 55 healthy controls using polymerase chain reaction with sequence-specific primers (PCR-SSP). In the case of HLA-DR1- or HLA-DR4-positive patients, the DR1 and DR4 subtypes were also determined. The frequency of HLA-DR4 alleles was significantly higher in RA patients than in controls (31.3 vs. 10.9%; P <.05). HLA-DR1, in particular, tended to be more frequent in patients than in controls (32.5 vs. 18.1%). Among the HLA-DR4 subtypes, DRB1*0401 and DRB1*0404 were the most common alleles found in both groups. However, no significant differences were seen in the frequency of HLA-DRB1*0401 and HLA-DRB1*0404 between RA patients and controls. In contrast, HLA-DRB1*0405 and HLA-DRB1*0408 were significantly more common in RA patients than in control subjects. Among HLA-DR1 subtypes, the DRB1*0101 allele was most commonly detected, but HLA-DRB1*0101 as well as DRB1*0102 and DRB1*0105 were similarly frequent in RA patients and controls. HLA-DR12 was more common among controls than in RA patients (18.1 vs. 0%; P <.05). Our results generally agree with the findings in other Caucasian populations. Nonetheless, we found differences in the frequency of HLA-DR1 and HLA-DR4 subtypes among Hungarian patients compared with reports from other geographic regions (e.g., Finland and Asia). Our data suggest that in northeastern Hungary, HLA-DR4 as well as its subtypes DRB1*0405 and DRB1*0408 may be involved in susceptibility to RA, but HLA-DR1 may not. In addition, the presence of HLA-DR12, at least in Hungary, may protect from this disease.

HLA-DRB1 genotype associations in 793 white patients from a rheumatoid arthritis inception cohort: frequency, severity, and treatment bias

OBJECTIVE

The HLA-DRB1 "shared epitope" (SE) genotypes are associated with rheumatoid arthritis (RA), but it remains controversial whether the association is with incidence, severity, or both, whether there are associations in seronegative patients, and whether different DRB1 alleles that contain the SE have similar effects on RA susceptibility and/or severity. The present study was undertaken to study these issues in a large cohort of patients with RA.

METHODS

White patients with RA of <6 months' duration (n = 793) were enrolled in an inception cohort. HLA-DRB1 typing was performed, and patients were categorized into 21 DRB1 genotype groups. The disability index of the Health Assessment Questionnaire was the primary outcome measure.

RESULTS

DRB1 associations in seronegative RA patients closely resembled those in controls. Of seropositive patients, 21% had 2 copies of the epitope, 52% had 1 copy, and 27% had none. However, not all genotypes with 1 copy were associated with increased susceptibility; for example, frequencies of DRB1*0404/X and *01/X did not differ from those in controls. Absolute differences between seropositive RA patients and controls were greatest for DRB1*0401 homozygosity (3.8% versus 0.8%, respectively) and *0401/0404 heterozygosity (4.7% versus 1.0%). DRB1*0404 was increased in frequency in seropositive RA but, unlike *0401, an increased frequency was seen only with 2 epitope copies. The relatively rare DRB1*10 had an unexpected association with seropositive RA, being present in 1.7% of seropositive RA patients and 0.7% of controls, and also showed a trend toward association with greater disease severity. The presence of 2 epitope copies was associated with increased frequency of seropositivity and younger age at disease onset, not with disease severity. Treatment indication bias was substantial and may have accounted for some of these effects. HLA-DRB1*0401/0404 was found much more frequently in men and in patients with a lower age at disease onset, and there was a trend toward a higher frequency of *0404/0401 in women.

CONCLUSION

This large inception cohort study confirms previously identified major associations and provides additional insights. Only one dominant association was found: *0401, which differs from other SE alleles in a single Lys-for-Arg substitution. The association of the rare DRB1*10 allele has not previously been postulated. Sex associations were confirmed. Associations with seronegative RA were not seen. Not all genotypes containing an SE copy showed increased susceptibility to RA. The association of SE genotypes found in this study related to disease susceptibility rather than severity.

Reshaping the shared epitope hypothesis: HLA-associated risk for rheumatoid arthritis is encoded by amino acid substitutions at positions 67-74 of the HLA-DRB1 molecule

OBJECTIVE

To further analyze the association of HLA-DRB1 alleles with disease susceptibility in recent-onset rheumatoid arthritis (RA).

METHODS

One hundred sixty-seven Caucasian RA patients and 166 healthy controls were typed for HLA-DRB1.

RESULTS

The association of susceptibility to RA with the group of alleles encoding the shared epitope susceptibility sequences (SESSs) was confirmed in recent-onset RA. Among non-SESS alleles, DRB1*07, *1201, *1301, and *1501 showed significant protective effects. Even after correction for the influence of SESS alleles, significant independent protective effects of DRB1 alleles were observed. Protective alleles shared a third hypervariable region motif. Independent homozygosity effects were observed both for susceptibility and for protective alleles.

CONCLUSION

Nonsusceptibility alleles differ significantly with regard to RA risk. Protective alleles show clear homology at positions 67-74, often encoding isoleucine at position 67 or aspartic acid at position 70. Susceptibility and protective alleles both show homozygosity effects. Based on these results and on data reported in the literature, in order to incorporate the finding of differential risks among nonsusceptibility alleles, we propose to reshape the shared epitope hypothesis as follows: HLA-associated risk for RA is encoded by amino acid substitutions at positions 67-74 of the HLA-DRB1 molecule.

Genetic studies, clinical heterogeneity, and disease outcome studies in rheumatoid arthritis

HLA haplotypes influence various clinical RA features considered to reflect severity in case-control and cohort studies. Of particular note is the fact that HLA generally influences the development of erosive and sometimes seropositive and nodular disease; in prospective studies, it noticeably affects joint surgical intervention. These are valuable clues indicating that HLA influences RA severity and chronicity. Nevertheless, HLA influences are generally weak enough so as to require large study subject numbers for detection. As a result, HLA genotyping has restricted usefulness for prediction of clinical severity in individual patients.

Prognostic use of human leukocyte antigen genotyping for rheumatoid arthritis susceptibility, disease course, and clinical stratification

HLA markers of the class II region are important for determination of the predisposition to RA, clinical manifestations, and rate of progression of joint destruction in this autoimmune disease. Furthermore, evidence emerges indicating that HLA markers also have an impact on treatment outcome in RA. Currently, several immunopathogenetic models of HLA-dependent influences in RA are under debate. These models insufficiently explain the graded influence of HLA-DR and HLA-DQ on manifestation and joint destruction, however. Currently, there is not enough evidence to unequivocally identify a primary susceptibility locus or to pinpoint the HLA-dependent mechanism in RA. Overall, the influence of HLA class II markers on disease susceptibility is rather restricted, and, in turn, their utility in establishing the diagnosis of RA is of limited use. Although relative risks are higher for the association of particular genotypes with extra-articular forms of RA, HLA genotyping may not contribute to prognostication in individual patients but may aid in disease stratification. In contrast, HLA genotyping in early RA, particularly when combined with the determination of RFs and determination of the presence of bony erosions, is of value to identify patients at risk for poor outcome. In turn, these patients may benefit from early aggressive therapy, and HLA genotyping should be useful to aid in risk stratification in patients and thus helpful for the choice of treatment. Lastly, disease and risk stratification based on HLA markers along with the elucidation of HLA-dependent mechanisms may facilitate the development of specific immunotherapy modalities.

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.

Crucial role of donor-derived stromal cells in successful treatment for intractable autoimmune diseases in mrl/lpr mice by bmt via portal vein

We have recently established a new bone marrow transplantation (BMT) method for the treatment of intractable autoimmune diseases in MRL/lpr mice; the method consists of fractionated irradiation (5.5 Gy x 2), followed by BMT of whole bone marrow cells (BMCs) from allogeneic C57BL/6 mice via the portal vein (abbreviated as 5.5 Gy x 2 + PV). In the present study, we investigate the mechanisms underlying the early engraftment of donor-derived cells in MRL/lpr mice by this method. In the mice treated with this method, the number of donor-derived cells possessing the mature lineage (Lin) markers rapidly increased in the BM, spleen, and liver; almost 100% were donor-derived cells by 14 days after the treatment. The number of donor-derived hemopoietic progenitor cells (defined as c-kit(+)/Lin(-) cells) increased in the BMCs, hepatic mononuclear cells, and especially spleen cells by 14 days after the treatment. Simultaneously, hemopoietic foci adjoining donor-derived stromal cells were observed in the liver when injected via the PV, but not via the peripheral vein (i.v.). When adherent cell-depleted BMCs were injected via the PV, recipients showed a marked reduction in the survival rate. However, when mice were transplanted with adherent cell-depleted BMCs with cultured stromal cells, all the recipients survived. These findings suggest that not only donor hematopoietic stem cells (HSCs) but also donor stromal cells administered via the PV were trapped in the liver, resulting in the early engraftment of donor HSCs in cooperation with donor-derived stromal cells. This new strategy to facilitate the early recovery of hemopoiesis would therefore be of great advantage in human application.

Association of MHC and rheumatoid arthritis. HLA polymorphisms in phenotypic variants of rheumatoid arthritis

Genes in the human leukocyte antigen (HLA) region remain the most powerful disease risk genes in rheumatoid arthritis (RA). Several allelic variants of HLA-DRB1 genes have been associated with RA, supporting a role for T-cell receptor-HLA-antigen interactions in the pathologic process. Disease-associated HLA-DRB1 alleles are similar but not identical and certain allelic variants are preferentially enriched in patient populations with defined clinical characteristics. Also, a gene dosing effect of HLA-DRB1 alleles has been suggested by the accumulation of patients with two RA-associated alleles, especially in patient subsets with a severe disease course. Therefore, polymorphisms in HLA genes are being explored as tools to dissect the clinical heterogeneity of the rheumatoid syndrome. Besides HLA polymorphisms, other risk genes will be helpful in defining genotypic profiles correlating with disease phenotypes. One such phenotype is the type of synovial lesion generated by the patient. HLA genes in conjunction with other genetic determinants may predispose patients to a certain pathway of synovial inflammation. Also, patients may or may not develop extraarticular manifestations, which are critical in determining morbidity and mortality. HLA genes, complemented by other RA risk genes, are likely involved in shaping the T-cell repertoire, including the emergence of an unusual T-cell population characterized by the potential of vascular injury, such as seen in extraarticular RA.

The influence of HLA-DRB1 alleles and rheumatoid factor on disease outcome in an inception cohort of patients with early inflammatory arthritis

OBJECTIVE

There are conflicting data concerning the role of HLA-DRB1 alleles in disease outcome in early rheumatoid arthritis. The exact role of these alleles in short-term outcome is determined in this large, prospective, population-based study.

METHODS

We recruited 532 patients with inflammatory polyarthritis from the Norfolk Arthritis Register and typed their sera for HLA-DRB1 alleles using polymerase chain reaction-based methods. Disease outcome was assessed at 2 years in terms of persistent joint inflammation, functional disability, and radiologic erosions. Results are expressed as risk ratios (RR) with 95% confidence intervals (95% CI).

RESULTS

There was no influence of HLA-DRB1 alleles, in any combination, on the likelihood of disease persistence, and only a modest effect on functional disability (Health Assessment Questionnaire score > or = 1). The most obvious effect was on the development of erosions (RR 1.9, 95% CI 1.4-2.6 for those who carried at least 1 DRB1 shared epitope [SE] allele), with slightly greater effects for those who were homozygous for SE-bearing alleles (RR 2.5, 95% CI 1.8-3.6). This effect of HLA-DRB1 was restricted to patients whose sera were negative for rheumatoid factor. Among patients with erosions, HLA-DRB1 had no influence on the severity of radiologic damage (defined as the number of eroded joints, or total Larsen score).

CONCLUSION

These data do not support routine HLA-DRB1 screening of patients with early arthritis to identify those at risk for subsequent severe 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.

An endogenous retroviral long terminal repeat at the HLA-DQB1 gene locus confers susceptibility to rheumatoid arthritis

Human endogenous retrovirus (HERV) long terminal repeat (LTR) elements contain regulatory sequences that can influence the expression of adjacent cellular genes, which may contribute to breakdowns of the immune function leading to autoimmune disease. Rheumatoid arthritis (RA) is associated with particular HLA-DR/DQ haplotypes that modulate the pathogenesis of this autoimmune disease. We have therefore studied a solitary LTR element (DQ-LTR3) of the HERV-K family at the HLA-DQB1 locus for a possible disease association among 228 RA patients and 311 unrelated blood donors. The DQ-LTR3 was significantly more frequent among patients (76% vs 33%, OR = 5.07,p < 0.0001), with the majority of patients being heterozygous for the DQ-LTR3 (61% vs 22%, p < 0.0001). HLA-DRB1*04 positive patients did still differ for the presence of the DQ-LTR3 (88% vs 70%, OR = 3.03, p < 0.001), with an increase of both DQ-LTR3 homozygous and heterozygous patients, when compared to DRB1*04 positive controls (p = 0.0015). HLA-DR/DQ genotype analysis among HLA-DRB1*04 positive individuals revealed significantly more DQ-LTR3 homozygotes among HLA-DRB1*04-DQBI*03 homozygous patients (72% vs 27%, P = 0.015), and the number of DQ-LTR3 homozygous (23% vs 19%) and heterozygous (66% vs 53%) individuals was also increased among HLA-DRB1*04 heterozygous patients (p = 0.034). The presence of the DQ-LTR3 element increased both the relative risk and the positive predictive value for either DRB1*04-DQB1*03 positive/negative individuals when compared to the presence of HLA-DRB1*04-DQB1*03 alone. In conclusion, these data suggest that this DQ-LTR3 enhances susceptibility to RA.