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

HLA class II and autoimmunity: epitope selection vs differential expression

Autoimmune diseases like rheumatoid arthritis (RA), multiple sclerosis, psoriasis and insulin-dependent diabetes mellitus are subject to a complex pathogenesis controlled by multiple genes and numerous environmental factors. The strongest genetic association is with certain HLA class II haplotypes and we here summarize the evidence supporting differential expression as a mechanism supporting the autoimmune process.

Differential expression of HLA class II genes associated with disease susceptibility and progression in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA)-associated HLA class II genes are assumed to promote susceptibility to and/or progression of the disease. Among the various modes of action proposed so far is the effect of the differential expression of HLA class II genes in different types of antigen-presenting cells on the Th1/Th2 balance. The aim of this study was to investigate the differential expression of genes encoded within the RA-associated HLA-DR4 superhaplotype and within the neutral DR7 and DR9 superhaplotypes.

METHODS

The promoters encoded within these 3 haplotypes were first analyzed for sequence polymorphisms. To test for functional consequences, we assumed that the binding of nuclear factors to the promoter elements was correlated with the transcription activity, and we used surface plasmon resonance technology. To that end, oligonucleotides representing the polymorphic regulatory sequences and nuclear extracts from a monocyte cell line and a B cell line were used.

RESULTS

While the promoters of the highly polymorphic HLA-DRB1*04, *07, and *09 alleles showed comparable binding of nuclear factors, differential binding was observed for the 2 promoters that drive the relatively nonpolymorphic DRB4 alleles in linkage disequilibrium with DRB1. Interestingly, analysis of RA patients positive for DR4, DR7, and DR9 revealed the segregation of radiographic progression with the stronger of the 2 DRB4 promoters, independent of the DRB1 allele. Moreover, DRB1*04 alleles in RA patients showed a reduced association with the DRB4 splice variant, completely preventing DRB4 expression.

CONCLUSION

Our findings represent the first evidence of a correlation between the differential expression of HLA class II genes and both the susceptibility and the progression of RA.

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.

Tumor necrosis factor markers show sex-influenced association with rheumatoid arthritis

OBJECTIVE

The observation that not all shared-epitope genotypes confer the same risk suggests that a second HLA-region locus may confer risk. Tumor necrosis factor alpha (TNFgamma) is a possible candidate. We examined TNFalpha for sex influences on HLA-associated risk for rheumatoid arthritis (RA).

METHODS

DRB1 and TNF microsatellite typing of 297 Caucasian RA patients (132 men, 165 women) and 267 Caucasian controls was performed.

RESULTS

The TNFab microsatellite haplotype distribution differed among the male RA, female RA, and control groups (P < 0.01); the difference was largely an excess of TNFa2b1 haplotypes in the male RA group. However, this did not simply reflect an excess of shared-epitope haplotypes bearing TNFa2b1. In RA, not all shared-epitope-bearing haplotypes had the same TNFab. The *0401-bearing haplotypes commonly had TNFa6b5, TNFa2b1, TNFa10b4, and TNFa11b4, while the *0404-bearing haplotypes had TNFa11b4. In the female RA group, TNFa2b1 was most often on *0401-bearing haplotypes. In the male RA group, there was a surprise: TNFa2b1 was often on HLA haplotypes without shared-epitope DRB1 alleles. To estimate the relative strength of associated HLA markers, we performed logistic regression analyses stratified by sex and controlling for a potential confounder, age at disease onset. Among women, TNFa2b3 favored RA (odds ratio 1.932, P < 0.05) while TNFa6b5 was protective (odds ratio 0.522, P < 0.05). Among males, TNFa2b1 and TNFa11b4 conferred elevated odds ratios (2.58 and 1.681, respectively, P < 0.05). However, the odds ratios for TNFa2b1 in men and TNFa2b3 in women were generally well below those for RA-associated DRB1 markers (for example, DRB1*0401 3.553 in male RA patients and 6.991 in female RA patients).

CONCLUSION

Certain TNFab-bearing HLA haplotypes modify RA risk in a manner influenced by sex but independent of DRB1, particularly TNFa2b1 in men.

Complementation between HLA-DR4 (DRB1*0401) and specific H2-A molecule in transgenic mice leads to collagen-induced arthritis

We generated transgenic mice with DRB1*0401 gene with mutation in the beta2 domain (aa 110 and 139) for better interaction with mCD4. The DR4 transgene was introduced into H2-Aq (B10RQB3) and H2-Af (B10RFB3) to examine the role of DR4 in collagen arthritis. The HLA-DR molecules in these mice were found to be functional on the basis of their positive/negative selection of the Vbeta T cell repertoire. H2-Aq mice are resistant to porcine CII-induced arthritis. The RQB3/DR4 mice (H2Aq/DR4) developed severe collagen induced arthritis (CIA) when immunized with Porcine type II collagen while the negative littermates were resistant. RQB3.DR4 mice were also highly susceptible to CIA induced by Human CII while negative littermates got only mild disease. However, RFB3/DR4 mice (H2Af/ DR4) did not get CIA with any type II collagen. Therefore, the DR4 gene in the context of H2-Aq predisposes to severe arthritis but not in the context of H2-Af. Antibodies to renatured cyanogen bromide (CB) cleaved fragments of PII in RQB3/DR4 mice and negative littermates suggest that the presence of DR4 does not result in any differences in specificity of antibody response to CB fragments. These results indicate that a specific gene complementation occurring between DR4 and H2.Aq but not DR4 and H2Af promotes the induction of arthritis with PII and HII in these mice. A similar interaction may be involved between DR and DQ molecules in human RA.

Differential surface expression of HLA-DRB1 and HLA-DRB4 among peripheral blood cells of DR4 positive individuals

Increasing interest in the functional consequences of differential expression of MHC class II molecules prompted us to examine the surface expression of HLA class II molecules on fresh peripheral blood mononuclear cells. Differential regulation of DR4 and DRB4 was shown for peripheral blood monocytes. In addition, DR4 expression is upregulated on B cells of patients suffering from chronic inflammation and is reduced under prednisolone-treatment. The expression levels of total DR molecules on a given cell type are almost identical comparing different haplotypes among non-RA controls, suggesting that the alpha-chain determines the level of surface expression. The present findings fit the hypothesis that the differential expression of HLA class II molecules is involved in regulation of the immune response and may thus contribute to determining susceptibility to immunological diseases.

Functional significance of polymorphism among MHC class II gene promoters

The functional significance of polymorphism among MHC class II promoters in man and mouse is here reviewed, mainly in terms of the hypothesis of differential expression. The hypothesis proposes that differences between antigen-presenting cells in MHC class II expression exert a co-dominant effect on the Th1-Th2 cytokine balance, such that class II molecules of one type come to control to a greater extent the production of one group of cytokines, and those of another type the production of the alternative group. The survey deals with the influence of signal strength and antigen-presenting cell type on T-cell subset differentiation; functional differences between MHC class II molecules not obviously related to determinant selection; disease protection mediated by HLA alleles; mechanisms possibly responsible for allotypic and isotypic bias; overdominance (heterozygous advantage) in selection for expression of class II alleles; MHC class II promoter structure and function; inter-locus and inter-allele variability within human MHC class II gene upstream regulatory regions; a comparison of these polymorphisms in mouse and man; read-out of class II promoter function; and a comparison with expression of MHC class I. We conclude that the evidence that this variation is functionally active (i.e. controls expression) is increasing, but is not yet compelling. The crucial test still to come, we suggest, is whether or not the biological effects attributable to this polymorphism will line up with molecular studies on expression.

Altered Th1/Th2 balance associated with the immunosuppressive/protective effect of the H-2Ab allele on the response to allo-4-hydroxyphenylpyruvate dioxygenase

The H-2Ab allele exerts a dominant down-regulatory effect on the anti-allo-HPPD (4-hydroxyphenylpyruvate dioxygenase) antibody response, through a hitherto unknown mechanism. In the present study, the allo-variable peptide bound to responder H-2Ak molecules with higher affinity than to H-2Ab ones, arguing against the operation of an affinity hierarchy. Quantitative polymerase chain reaction revealed differences in cytokine mRNA expression between suppressed and high-responder mice. Lymph node cells of responder but not suppressed mice contained high levels of interleukin (IL)-4 mRNA as early as 11 h post-immunization and continued to do so for at least 8 days; this early burst was paralleled by a small burst in transforming growth factor (TGF)-beta mRNA level. Differences in IL-12 mRNA were not detected, although an early IL-12 effect could not be excluded. Interferon (IFN)-gamma appeared to contribute to the suppression at later time points. Early treatment of responder mice with anti-IL-4 monoclonal antibody (11B11) down-regulated the antibody response. The proliferative T cell response from hyperimmunized mice was reduced but still detectable in the presence of an H-2Ab allele. Thus, in the presence of this allele, the Th1 response is enhanced and that of Th2 cells suppressed, apparently as a result of the bias of H-2Ab-restricted T cells in favor of the Th1 subset.

Indirect gene diagnoses for complex (multifactorial) diseases--a review

The analysis of multifactorial diseases requires the efficient investigation of large numbers of (gene) loci and patient (family) samples. Since simple repetitive DNA markers are dispersed all over the chromosomes, molecular techniques employing these tools render most conventional screening procedures obsolete. Examples of tumors, autoimmune diseases and infections are presented to validate concepts of indirect gene diagnoses via simple, tandemly arranged, repetitive DNA sequences. The salient advantages of microsatellite technologies vs. those of multilocus DNA fingerprinting are weighed.

Association of H2Ab with resistance to collagen-induced arthritis in H2-recombinant mouse strains: an allele associated with reduction of several apparently unrelated responses

HLA class II alleles can protect against immunological diseases. Seeking an animal model for a naturally occurring protective allele, we screened a panel of H2-congenic and recombinant mouse strains for ability to protect against collagen-induced arthritis. The strains were crossed with the susceptible strain DBA/1, and the F1 hybrids immunized with cattle and chicken type II collagen. Hybrids having the H2Ab allele displayed a reduced incidence and duration of the disease. They also had a reduced level of pre-disease inflammation, but not of anti-collagen antibodies. The allele is already known to be associated with reduction of other apparently unrelated immune responses, suggesting that some form of functional differentiation may operate that is not exclusively related to epitope-binding. It is suggested that this may reflect allelic variation in the class II major histocompatibility complex promoter region.

Immunoprinting: various genes are associated with increased risk to develop rheumatoid arthritis in different groups of adult patients

To identify genes that contribute to the manifestation of rheumatoid arthritis we performed association studies via microsatellite analyses of immunorelevant loci (HLA-DRB, 5 T cell receptor loci, TNFa IL1, IL2, IL5R and CD40L). A total of 183 patients and 275 healthy controls were typed in terms of HLA and grouped according to the known predisposing HLA-DRB1 genes (DRB1*04; relative risk approx. 5; DRB1*01, relative risk approx. 2; a third group carried neither allele). Microsatellite polymorphisms characterizing the TCRBV6S3, CD3D, IL1A, IL2, and IL5R genes did not show significant associations with rheumatoid arthritis, whereas TCRBV6S1, TCRBV6S7, TNFa, and CD40L genes may influence relative protection or risk in certain groups of patients. Analysis of a microsatellite marker adjacent to the transcription element alpha (TEA) in the T cell receptor alpha delta complex indicates that in the cohort carrying neither the DRB1*04 nor the DRB1*01 allele the relative risk to acquire rheumatoid arthritis is increased (> 13) or decreased (< 0.07), depending on the inherited microsatellite allele adjacent to the TEA locus. Sequence analysis of the closely linked TEA region from patients and controls revealed a novel dimorphism. Only the newly identified TEA allele leads to binding of a nuclear protein that may be involved in the regulated expression of the TCRDA genes. Subsequent typing of rheumatoid arthritis patients and controls revealed, however, that the association of the microsatellite marker is largely independent of the TEA allele, confirming incomplete linkage in the 2 kb region of the TCRDA locus. These results are discussed in the context of hot spots of recombination in this genomic region and other linked candidate sequences that predispose to develop rheumatoid arthritis.

Anti-neutrophil cytoplasm antibodies (ANCA) in rheumatoid arthritis: relationship to HLA-DR phenotypes, rheumatoid factor, anti-nuclear antibodies and disease severity

To investigate a possible relationship between the presence of anti-neutrophil cytoplasm antibodies (ANCA), rheumatoid factors (RF), anti-nuclear antibodies (ANA), disease severity and HLA-DR phenotypes, 46 consecutive ANCA+ and 48 ANCA-, clinically well-documented RA patients were studied for RF, ANA and HLA-DR phenotypes. The 46 ANCA+ patients showed predominantly an atypical perinuclear staining pattern (89%). ANCA positivity was associated with higher RF titres (P < 0.005) and advanced functional Steinbrocker grades III/IV (P < 0.015). ANCA+ patients were also more often positive for ANA than ANCA- patients (P < 0.008). There was no correlation between ANCA positivity and certain HLA-DR phenotypes although the frequency of DR4+ (67% vs 52%) and, in particular, of DR4+ blanks (phenotypically homozygous) was increased in ANCA+ as compared to ANCA- patients (20% vs 8%). DR4-DR1-RA patients were twice as frequent in the ANCA- than in the ANCA+ group (22.9% vs 8.7%). Correspondingly, the DR4+DR1- phenotype was increased among ANCA+ RA patients. Regarding functional Steinbrocker grades, the DR4+ phenotypes were slightly but not significantly increased in grades III and IV whereas ANCA positivity was significantly associated with severe functional Steinbrocker grades III/IV (66% ANCA+ vs 39% ANCA-, P < 0.015). ANCA positivity identified a population of RA patients with a long-standing and severe clinical course of the disease. There was no correlation between ANCA positivity and certain HLA-DR phenotypes.

Susceptibility to relapsing polychondritis is associated with HLA-DR4

OBJECTIVE

To determine the frequency of HLA class II antigens in Caucasian central European patients with relapsing polychondritis (RP).

METHODS

HLA class I, DR, and DQ specificities were identified in 41 patients with RP, and the frequencies were compared with those in 204 healthy, unrelated control subjects. HLA typing was performed using the standard complement-dependent microcytotoxicity assay. HLA-DR genotyping of 12 DR4-positive RP patients and 57 controls was performed by allele-specific oligonucleotide probing after amplification of genomic DNA by polymerase chain reaction.

RESULTS

A significant increase in DR4 antigen frequency was found in the patients (56.1%) as compared with that in healthy controls (25.5%) (Pcorr < 0.001). Genotyping of DR4-positive patients and controls revealed no predominance of any DR4 subtype.

CONCLUSION

There are important clinical similarities and overlaps between RP and rheumatoid arthritis (RA). In RA, the association with DR4 has been well established. Our findings show that although there is a DR4 association with RP, the situation is sufficiently distinct from that of RA to imply considerable differences in pathogenesis of the two conditions.

HLA-DRB1 gene sequences in HLA-DR4 positive and negative patients with rheumatoid arthritis

The second exon of the DRB1 gene encoding for the first domain of the HLA-DR beta 1-chain was sequenced in 16 patients (10 DR4/DR1 positive, 6 DR4/DR1 negative) with seropositive rheumatoid arthritis (RA). We could confirm the strong association of susceptibility to RA with functionally equivalent conformations on otherwise distinct MHC molecules. At least one HLA-DR allele in all of the analysed DR4 or DR1 positive patients showed such an epitope with a minimal variability limited to residue 71. However, in HLA-DR4 and -DR1 negative patients such a similar epitope could not be detected.

Analysis of HLA DP, DQ, and DR alleles in adult Italian rheumatoid arthritis patients

We analyzed the distribution of DRB1, DQA1, DQB1, and DPB1 allelic variants in 48 rheumatoid arthritis (RA) patients, compared with 109 Italian random controls, using PCR amplification and hybridization with specific oligonucleotides. We confirm the previously reported increase of DR4 specificity, in comparison with healthy Italian individuals. In particular, we find a statistically significant positive association of DRB1*0401 and DRB1*0404 alleles with RA. However, when we compare the DR4+ groups, none of the DRB1*04 alleles is increased in the RA group. By sequence analysis, performed on 10 patients, we demonstrate that the DRB1*04 genes of RA show no difference from the DRB1*04 sequences previously published. From the molecular analysis of the other DRB1 polymorphic variants, we find a trend of positive association of DRB1*0101 in DR4-negative patients versus DR4-negative healthy controls and, in the group of DR4-negative and/or DR1-negative patients, a similar increase of DRB1*06. Also, we observe in RA patients a statistically significant increase of DQA1*0301 and DQB1*0302 accompanied by a significant decrease of DQA1*0201, DQA1*0501 and DQB1*0201. Finally, from the analysis of DPB1 gene, it can be assessed that the distribution of DPB1 alleles does not differ significantly between RA patients and healthy controls.