Influence of HLA–DR genes on the production of rheumatoid arthritis–specific autoantibodies to citrullinated fibrinogen

Objective

Antibodies directed against citrullinated fibrinogen are highly specific for rheumatoid arthritis (RA). This study was undertaken to test whether RA‐associated HLA–DR alleles are associated with anti–citrullinated fibrinogen in RA patient sera and whether replacement of arginyl by citrullyl residues on fibrinogen peptides modifies their binding to HLA–DR molecules and their recognition by T cells.

Methods

Antikeratin, antifilaggrin, and anti–citrullinated fibrinogen antibodies were assayed in RA patients who had undergone HLA–DR typing. Direct assays were performed to investigate binding of citrullinated or native fibrinogen peptides (encompassing the entire α‐ and β‐chains of fibrinogen) to purified HLA–DR molecules. T cell proliferative responses to citrullinated or native fibrinogen peptides were measured in RA patients and controls.

Results

HLA–DRB1*0404 was associated with anti–citrullinated fibrinogen in RA sera (P = 0.002). For the RA‐associated alleles HLA–DRB1*0401 and HLA–DR1, there was a nonsignificant trend toward association (P = 0.07). Multiple peptides from the α‐ and β‐chains of fibrinogen bound many HLA–DR alleles; DRB1*0404 was the best fibrinogen peptide binder. Citrullination did not influence fibrinogen peptide binding to HLA–DR or fibrinogen peptide recognition by T cells. Peripheral blood T cells that recognized native or citrullinated fibrinogen peptides were common in RA patients but not in healthy controls.

Conclusion

The RA‐associated HLA–DRB1*0404 allele is also associated with production of antibodies to citrullinated fibrinogen. DRB1*0401 and DRB1*01 tend to be associated with anti–citrullinated fibrinogen, but this is not statistically significant. Citrullination of fibrinogen peptide does not influence peptide–DR–T cell interaction. Finally, T cell proliferation in response to citrullinated or uncitrullinated fibrinogen peptides is frequent in RA patients and very infrequent in controls.

     

HLA-DRB1*0404 is strongly associated with high titers of anti-cyclic citrullinated peptide antibodies in rheumatoid arthritis

OBJECTIVE:To test whether the presence of RA associated HLA-DRB1*0101, HLA-DRB1*0401 and HLA-DRB1*0404 alleles individually influences anti-cyclic citrullinated peptide antibodies (anti-CCP) production. METHODS:The frequency of anti-CCP antibodies was calculated in the sera of 260 RA patients expressing either two (double dose genotypes SE+/SE+), one (single dose genotypes SE+/SE-) or no RA associated HLA-DR alleles (SE-/SE-). Anti-CCP antibodies titers were also determined.RESULTS:RA associated HLA-DR alleles are not mandatory for production of anti-CCP. We found that 68% of SE-/SE- patients were anti-CCP positive. There was no significant difference in anti-CCP between SE negative patient (SE-/SE-) and patients expressing at least one SE (SE+/SE+ and SE+/SE-) (p=0.140). We observed no statistical difference in anti-CCP between RA patients expressing one or two SE (82% vs. 77%, p=0.577). Among SE+/SE-patients, HLA-DRB1*0404 was associated with anti-CCP with a statistically significant difference compared with SE negative patients (90% anti-CCP positive, p=0.02). HLA-DRB1*0404 was also associated with high titers of anti CCP with a statistically significant difference compared with HLA-DRB1*0401 and HLA-DRB1*0101 patients (p=0.025).CONCLUSIONS:The RA-associated HLA-DRB1*0404 allele was the most strongly associated with the presence of anti-CCP in RA sera. Moreover, HLA-DRB1*0404 patients had higher titers of anti CCP than patients with other RA associated HLA-DR alleles.     

Dissection of class III major histocompatibility complex haplotypes associated with rheumatoid arthritis

OBJECTIVE: We have previously identified a single-nucleotide polymorphism (SNP) haplotype involving the lymphotoxin alpha (LTA) and tumor necrosis factor (TNF) loci (termed haplotype LTA-TNF2) on chromosome 6 that shows differential association with rheumatoid arthritis (RA) on HLA-DRB1*0404 and *0401 haplotypes, suggesting the presence of additional non-HLA-DRB1 RA susceptibility genes on these haplotypes. To refine this association, we performed a case-control association study using both SNPs and microsatellite markers in haplotypes matched either for HLA-DRB1*0404 or for HLA-DRB1*0401. METHODS: Fourteen SNPs lying between HLA-DRB1 and LTA were genotyped in 87 DRB1*04-positive families. High-density microsatellite typing was performed using 24 markers spanning 2,500 kb centered around the TNF gene in 305 DRB1*0401 or *0404 cases and 400 DRB1*0401 or *0404 controls. Single-marker, 2-marker, and 3-marker minihaplotypes were constructed and their frequencies compared between the DRB1*0401 and DRB1*0404 matched case and control haplotypes. RESULTS: Marked preservation of major histocompatibility complex haplotypes was seen, with chromosomes carrying LTA-TNF2 and either DRB1*0401 or DRB1*0404 both carrying an identical SNP haplotype across the 1-Mb region between TNF and HLA-DRB1. Using microsatellite markers, we observed two 3-marker minihaplotypes that were significantly overrepresented in the DRB1*0404 case haplotypes (P = 0.00024 and P = 0.00097). CONCLUSION: The presence of a single extended SNP haplotype between LTA-TNF2 and both DRB1*0401 and DRB1*0404 is evidence against this region harboring the genetic effects in linkage disequilibrium with LTA-TNF2. Two RA-associated haplotypes on the background of DRB1*0404 were identified in a 126-kb region surrounding and centromeric to the TNF locus.     

中国内地人群类风湿关节炎与HLA-DRB1共同表位基因关联性的Meta分析

目的探讨中国内地人群类风湿关节炎(RA)与人类白细胞抗原(HLA)-DRB1共同表位(SE)基因的关联情况。方法检索已发表的有关中国内地人群RA和HLA-DRB1的文献,进行汇总分析分析。结果14项研究共纳入1118例RA患者和1301名正常对照,中国内地人群RA的关联基因有HLA-DR4[比值比(OR)=4.05,P<0.0001)]、DRB1*0401(OR=2.66,P=0.004)、DRB1*0404(OR=2.10,P=0.02)、DRB1*0405(OR=3.98,P<0.0001)、DRB1*0410(OR=3.36,P=0.008)、SE(OR=2.75,P<0.00001)。其中DRB1*0405是主要基因亚型。结论汇总分析分析不仅证实了DRB1*0405与中国内地人群RA的关联,而且发现了相对少见基因亚型DRB1*0401、DRB1*0404、DRB1*0410与RA的关联,样本大小对基因关联分析的结论有重要影响。     

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.     

Noninherited maternal antigens do not increase the susceptibility for familial rheumatoid arthritis. European Consortium on Rheumatoid Arthritis Families (ECRAF)

OBJECTIVE: It has been proposed that noninherited maternal HLA-DR antigens (NIMA) might play a role in the susceptibility for rheumatoid arthritis (RA). This hypothesis has not been thoroughly tested in patients with familial RA, in whom genetic factors, either inherited or not, might have stronger influence than in patients with sporadic RA. We investigated the NIMA hypothesis in a large cohort of European patients with familial RA. METHODS: The distribution of NIMA, noninherited paternal antigens (NIPA), and inherited HLA-DR antigens was assessed in patients with familial RA from all family sets collected from 1996 onwards by the ECRAF. HLA-DRB1 oligotyping from patients and all available nonaffected siblings and parents was carried out. Familial RA was defined by the presence of at least 2 affected first-degree relatives in the same family. The frequencies of HLA-DR NIMA and NIPA were compared using odds ratios after stratification for HLA-DR*04, *0401, and/or *0404 and shared epitope (SE) status. NIMA/NIPA that coincided with inherited parental HLA-DR antigens were considered redundant and were excluded from analysis. RESULTS: NIMA and NIPA could be analyzed in 165 RA patients with familial RA and 84 nonaffected siblings. Patients were predominantly female, rheumatoid factor positive, and had erosive disease (81, 75, and 84%, respectively). Possession of HLA-DR*04 and *0401/*0404 alleles tended be more frequent in patients than in nonaffected siblings but this did not reach statistical significance. SE possession was similar in patients and healthy siblings, although the former had a double dose SE more often (37.6 vs 17.8%; p = 0.002). Transmission of SE encoding alleles from parents to offspring was skewed only in patients [OR (95% CI) 3.56 (2.55-4.95) vs 1.16 (0.75-1.79) in nonaffected siblings]. Using the NIPA as control, the frequencies of HLA-DRB1*04, *0401/*0404, and SE positive NIMA were not increased in patients lacking these susceptibility alleles. The frequencies of NIMA encoding susceptibility alleles in DR*04 and *0401/*0404 negative patients were lower than in nonaffected siblings. CONCLUSION: Our results corroborate the association between RA and inherited SE alleles and do not support a role for noninherited HLA-DR maternal antigens in the susceptibility for familial RA.     

HLA-DRB1 genes and disease severity in rheumatoid arthritis in Turkey

OBJECTIVE: Association with human leukocyte antigen (HLA)-DRB alleles, implicated in the aetiopathogenesis of rheumatoid arthritis (RA), is found to be different in various ethnic groups. This study aimed to investigate DRB1 alleles in RA patients in Turkey, and to examine the effect of these alleles on disease severity. METHODS: We performed PCR-based DRBI genotyping of 104 RA patients recruited from clinical settings and 110 healthy controls. HLA DRB1 alleles frequencies in RA patients and healthy controls were determined. Phenotype frequencies of patients and controls were compared. Disease severity was assessed by radiological erosion, presence of extra-articular involvement, and functional index. RESULTS: Significant differences were in the frequencies of DRB1*04 (46.2% versus 20.9%, p < 0.001), DRB1*0401 (10.6% versus 0%, p < 0.001), DRB1*0405 (8.7% versus 0%, p = 0.001), DRB1* 0404 (15.4% versus 3.6%, p < 0.01), DRB1*01 (21.2% versus 10.9%, p < 0.05) and DRB1*0101 (16.3% versus 5.5%, p = 0.01) between RA patients and controls. HLA-DRB1 alleles did not show any association with seropositivity, extra-articular involvement, radiological erosion, or functional index. CONCLUSION: Our results suggest that the HLA-DRB1 alleles, particularly HLA-DRB1*04 and subtypes, were associated with RA.     

BAT1 promoter polymorphism is associated with rheumatoid arthritis susceptibility

OBJECTIVE: To analyze whether the polymorphisms -22 (G/C) and -348 (C/T) of the BAT1 gene are associated with susceptibility to rheumatoid arthritis (RA). METHODS: One hundred fifty-six patients with RA and 154 controls were genotyped for HLA-DRB1 and the polymorphisms -22 and -348 of the BAT1 gene. RESULTS: HLA-DRB1*04 alleles were associated with RA susceptibility (33.9% vs 20.1%; pc = 0.04). Among these, HLA-DRB1*0401 (13.4% vs 5.1%; pc = 0.04) and HLA-DRB1*0404 (5.7% vs 1.2%; pc = 0.2) were increased in patients with RA. Additionally, carriage of BAT1 -348T polymorphism was strongly associated with RA (23.7% vs 12.1%; pc = 0.0002). Significantly, BAT1 -348T was in linkage disequilibrium with HLA-DRB1*0404 and HLA-DRB1*0405. However, BAT1 -348 T was associated independently with HLA-DRB1 shared-epitope alleles (42.6% vs 18.9%; p = 0.001). CONCLUSION: The BAT1 -348T polymorphism is associated with RA susceptibility independently of HLA-DRB1. The role of BAT1 in the regulation of tumor necrosis factor-a suggests that BAT1 may regulate the inflammatory response observed in patients with RA.     

Identification and functional characterization of T cells reactive to citrullinated vimentin in HLA–DRB1*0401–positive humanized mice and rheumatoid arthritis patients

Objective

Antibodies toward the citrullinated form of the synovial antigen vimentin are specific for rheumatoid arthritis (RA) and are associated with HLA–DRB1*0401. This suggests that T cells specific for peptides derived from citrullinated vimentin presented in the context of HLA–DRB1*0401 may contribute to the etiopathogenesis of RA. The aim of this study was to identify immunodominant epitopes from citrullinated vimentin presented by HLA–DRB1*0401 and to characterize the resulting T cell responses.

Methods

We first predicted an HLA‐binding T cell epitope from citrullinated vimentin based on the binding motif of HLA–DRB1*0401 and then confirmed its affinity. A class II major histocompatibility complex (MHC) tetramer loaded with the citrullinated form of vimentin aa 59–78 (cit‐vimentin aa 59–78) was constructed and used to screen for specific T cells in HLA–DRB1*0401–transgenic mice, patients with RA, and healthy control subjects. Additionally, the cytokine output following cit‐vimentin aa 59–78 challenge was analyzed in patients and healthy control subjects by multicolor flow cytometry and Luminex‐based analysis.

Results

The citrullinated form of vimentin aa 59–78 bound to HLA–DRB1*0401, but the native form could not. Subsequently, cit‐vimentin aa 59–78–specific T cells were detected in immunized mice and in the periphery of both HLA–DR*0401–positive healthy control subjects and HLA–DR*0401–positive patients with RA, using class II MHC tetramers, CD154 up‐regulation, and intracellular cytokine measurements. As demonstrated in cell culture supernatants, the production of cytokines (predominantly interferon‐γ) in response to cit‐vimentin aa 59–78 was significantly higher in patients compared with controls.

Conclusion

Here, we describe a posttranslational modification of an RA candidate autoantigen toward which HLA–DRB1*0401–restricted T cells can be detected in both patients with RA and healthy controls but for which a proinflammatory response is observed uniquely in patients with RA.

     

Association of tumor necrosis factor microsatellite polymorphisms with HLA-DRB1*04–bearing haplotypes in rheumatoid arthritis patients

Objective. To investigate 1) tumor necrosis factor (TNF) microsatellite allele frequencies in rheumatoid arthritis (RA), and 2) associations between TNF microsatellites and RA-associated HLA specificities in order to build up extended HLA haplotypes. Methods. Eighty-five caucasoid patients with RA and 109 healthy caucasoid controls were typed for TNF microsatellites a-d using fluorescent-labeled primers and semiautomated genotyping. A further 56 RA patients who were selected for having certain HLA-DRB1 types were also typed for these TNF microsatellites. Linkage disequilibria between TNF and HLA alleles were calculated, and extended haplotypes were established. Results. The TNFa6 allele frequency was significantly increased in the RA patients compared with the controls (P = 0.0019, odds ratio [OR] 2.5, 95% confidence interval [95% CI] 1.3–4.6), an increase that was further evident in patients who were HLA–DRB1*0401 homozygous (P =0.0003, OR 7.3, 95% CI 2.2–24.4). This increase was found to be due to association with HLA–DRB1*0401. No TNF microsatellite allele was found to be associated with HLA-DRB1*0404. Three HLA extended haplotypes were identified in the RA group: 1) HLA–DRB1*0401;TNFd4;TNFa6;TNFb5;HLA–B44;HLA–Cw5;HLA–A2, 2) HLA–DRB1*0301;TNFd2;TNFa2;TNFb3;HLA–B8;HLA–CW7;HLA–A1, and 3) TNFd5;TNFc2;TNFa2;TNFb1;HLA–B62;HLA–Cw3. Conclusion. TNF microsatellites found to be associated with RA do not appear to be independent of class II HLA associations.     

Association of DRB1 shared epitope genotypes with early mortality in rheumatoid arthritis: results of eighteen years of followup from the early rheumatoid arthritis study

OBJECTIVE: To determine whether the HLA-DRB1 shared epitope (SE) is associated with early mortality and specific causes of death in rheumatoid arthritis (RA). METHODS: HLA-DRB1 genotyping was carried out on blood samples from 767 patients recruited for the Early RA Study (ERAS), a multicenter, inception cohort study with followup over 18 years. Dates and causes of death (n = 186) were obtained from the Office of National Statistics. The association of HLA-DRB1 alleles with risk of mortality was assessed using Cox proportional hazards regression analyses. Multivariate stepwise models were used to assess the predictive value of HLA-DRB1 genotypes compared with other potential baseline risk factors. RESULTS: The SE was not significantly associated with overall mortality. However, the presence of 2 SE alleles was associated with risk of mortality from ischemic heart disease (hazard ratio [HR] 2.02 [95% confidence interval 1.04-3.94], P = 0.04), and malignancy (HR 2.18 [95% confidence interval 1.17-4.08], P = 0.01). Analysis of specific SE genotypes (corrected for age and sex) revealed that the HLA-DRB1*0101/*0401 and 0404/*0404 genotypes were the strongest predictors of mortality from ischemic heart disease (HR 5.11 and HR 7.55, respectively), and DRB1*0101/*0401 showed a possible interaction with smoking. Male sex, erythrocyte sedimentation rate, and Carstairs Deprivation Index were also predictive, but the Health Assessment Questionnaire score, rheumatoid factor, nodules, and swollen joint counts were not. Mortality due to malignancy was particularly associated with DRB1*0101 genotypes. CONCLUSION: The risk of mortality due to ischemic heart disease or cancer in RA is increased in patients carrying HLA-DRB1 genotypes with particular homozygous and compound heterozygous SE combinations.     

Weak CD4+?T-cell responses to citrullinated vimentin in rheumatoid arthritis patients carrying HLA-DR9 alleles

Citrullinated vimentin (cVIM) is one of the antigens specifically targeted by anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. The association between ACPA and certain HLA-DRB1 alleles, those coding for the shared epitope (SE), suggests that this response could be T-cell mediated. HLA-DR9 alleles, which do not code for the SE, have recently been associated with ACPA (+) RA. The objective of this work was to study CD4+?T cell responses to cVIM in RA patients and healthy controls carrying HLA-DR9 alleles. Fourteen RA patients and ten healthy controls previously genotyped for HLA-DRB1 were studied for the presence of serum anti-cVIM antibodies by Western blot and ELISA. Peripheral blood mononuclear cells were stimulated with native vimentin and cVIM, and CD4+?T cells proliferation was assessed by flow cytometry. Citrulline-specific CD4+?T cells proliferation was found not only in RA patients but also in healthy controls. Although most patients carrying HLA-DR9 alleles present anti-cVIM antibodies, HLA-DR9 alleles were associated with weaker cVIM-driven CD4+?T-cell responses among RA patients. These results suggest that HLA-DR9 alleles could exert a protective effect on the recognition of cVIM epitopes by CD4+?T cells. In this context, other citrullinated proteins may break T and B cell tolerance, with cVIM only acting as a cross-reactive target for ACPA.     

Antibodies to type II collagen and HLA disease susceptibility markers in rheumatoid arthritis

OBJECTIVE: To seek associations between antibodies to native and denatured type II collagen (NCII and DCII) and HLA in rheumatoid arthritis (RA). METHODS: One hundred fourteen patients with clinically well-defined RA were HLA-DR and DQ typed. Those who were DR4 positive were subtyped for DRB1*0401-*0408 alleles by polymerase chain reaction using allele-specific oligonucleotide probes. Antibodies to human NCII and DCII (heat-denatured) were measured by enzyme-linked immunosorbent assay. The frequency of HLA alleles was compared in patients grouped according to the presence and absence of antibodies to NCII and DCII. RESULTS: Twenty-seven patients (24%) were positive for antibodies to NCII. There was a significant increase in the frequency of HLA-DR7 in anti-NCII-positive patients compared with anti-NCII-negative patients (30% versus 9%; P = 0.019) and a significant decrease in HLA-DR3 (7% versus 28%; P = 0.044). Repeating the analyses after excluding the 16 patients who were DR7 positive revealed a significant increase in the frequency of HLA-DR1 in anti-NCII-positive patients compared with anti-NCII-negative patients (63% versus 27%; P = 0.045). Moreover, antibodies to NCII were associated with the third hypervariability region susceptibility sequence QRRAA that is present in DRB1*0101, *0404, *0405, and *0408 (84% versus 47%; P = 0.0085); 24 of 27 anti-NCII-positive patients were positive for either DR7, DR1, or DRB1*0404 or *0408. Thirty patients (26%) were positive for antibodies to DCII. There was a significant increase in the frequency of HLA-DR3 in anti-DCII-positive patients compared with anti-DCII-negative patients (40% versus 18%; P = 0.028). CONCLUSION: The genetic associations between HLA-DR alleles and antibodies to CII in RA patients is in keeping with the collagen-induced arthritis model and implicates autoimmunity to CII as a major component in the multifactorial pathogenesis of RA.     

MHC class I chain-related gene B (MICB) is associated with rheumatoid arthritis susceptibility

OBJECTIVES: Several recent studies have shown that the MHC class III region, located telomeric to HLA-DRB1, contains an additional genetic factor that predisposes to rheumatoid arthritis (RA). In this study, we investigate whether inhibitor of kappaB-like (IkappaBL), MICB or MICA located in the MHC class III region are the second susceptibility gene associated with RA. METHODS: A total of 154 healthy controls and 140 RA patients were genotyped for HLA-DRB1, MICA, MICB and the polymorphism -62 of the IkappaBL gene. RESULTS: A significant increase of HLA-DRB1 shared epitope (SE) alleles was detected in RA patients (61.4 vs 43.5%, P(c) = 0.01, OR = 2.1, 95% CI = 1.3-3.3). Among SE alleles, the HLA-DRB1*0401 (13.5 vs 5.1%, P(c) = 0.04, OR = 3.2, 95% CI = 1.3-8.1) and HLA-DRB1*0404 (6.4 vs 1.2%, P = 0.02, P(c) = NS) showed the most significantly association with RA. No increase of risk was associated with HLA-DRB1*01. Remarkably, the allele MICB*004 was also significantly associated with RA susceptibility (40.7 vs 23.3%, P(c) = 0.01, OR = 2.2, 95% CI = 1.3-3.7). MICB*004 was in linkage disequilibrium with HLA-DRB1*0404 (lambda(s) = 0.33) and HLA-DRB1*0405 (lambda(s) = 0.34). However, MICB*004 was also increased in HLA-DRB1 SE negative patients (37 vs 21.5%, P = 0.04). No significant association between IkappaBL and MICA with RA was found. CONCLUSIONS: MICB*004 allele was associated with RA susceptibility. This allele was in linkage disequilibrium with HLA-DRB1*0404 and DRB1*0405. The association of MICB with RA susceptibility and the functional role of MIC genes in the pathogenesis of RA converts MICB into a candidate to be an additional MHC gene associated with RA susceptibility.     

Genetic susceptibility and the link between cat exposure and rheumatoid arthritis

OBJECTIVES: Rheumatoid arthritis (RA) is a chronic inflammatory disease for which immunogenetic susceptibility factors have been defined. In a recent case control study, it was shown that a prior intimate relationship with pet cats or budgerigars confers risk for subsequent development of RA after a period of latency. Pets are a potential reservoir for putative microbial agents that could be a stimulus for chronic inflammation subject to the influence of immunogenetic factors. Therefore, a study was undertaken to determine whether the presence of HLA-DRB1 alleles bearing the RA susceptibility motif influenced risk for RA associated with prior exposure to pets. METHODS: Blood samples were obtained from available RA patients and their case controls who had participated in the prior epidemiologic study. DR and DQ genotypes were determined by sequence analysis of oligonucleotides amplified from the DRB1 and DQB1 genes by polymerase chain reactions (PCR). Subjects were segregated according to pet exposure (as determined previously) and genotype for statistical analyses. RESULTS: The odds ratio (OR) for prepubertal exposure to cats and RA in available subjects irrespective of DRB1 genotype was 4.2 (CI, 2.1 to 8.5; P<.00002). The OR between prior exposure to cats and RA in subjects with the RA susceptibility genotype DRB1 *0401 and *0404 was 5.8 (CI, 1.4 to 26; P<.02) and >24 (CI, 1.6 to 813; P<.01), respectively. In subjects with the genotype DRB1 *1501, the association between RA and prior cat exposure was OR 8.4 (CI, 1.7 to 45; P<.01). No significant association between RA and pet exposure was found in patients selected according to other genotypes. The association between RA and the recognized HLA-DR susceptibility motif was slightly stronger in subjects with a history of intimate cat exposure (OR 4.7 [CI, 1.5 to 14.8], P<.005) than subjects without prior intimate exposure (OR 3.3 [CI; 1.2 to 9.3], P<.02). In the small number of subjects who had reported an intimate association with pet birds, no influence of DR genotype on risk for RA was discerned. CONCLUSIONS: Risk for RA associated with prior intimate exposure to cats is concentrated in subjects with the RA-susceptibility conferring genotypes DRB1 *0401 and *0404. The findings suggest an interaction between an environmen-tal agent associated with pet cats and certain RA susceptibility-conferring DR genotypes. The risk for RA associated with intimate cat exposure also was significant in subjects with DRB1*1501, a genotype not otherwise associated with RA, but which shares with known RA susceptibility-bearing alleles the presence of an electropositive pocket (Pocket 4) in the DR peptide binding groove.     

Noninherited maternal antigens do not play a role in rheumatoid arthritis susceptibility in Europe. European Consortium on Rheumatoid Arthritis Families

OBJECTIVE: It has been proposed that noninherited maternal antigens (NIMA) (HLA-DR antigens) might play a role in susceptibility to rheumatoid arthritis (RA), especially in patients who are not genetically predisposed, such as those who are HLA-DR4 and/or shared epitope (SE) negative. The present study was undertaken to test the NIMA hypothesis in a large cohort of European RA patients assembled by the European Consortium on RA Families (ECRAF). METHODS: HLA-DRB1 oligotyping was performed in families of European RA patients for whom both parents were alive. These families were consecutively recruited by the ECRAF between 1996 and 1998, for association studies. The frequencies of HLA-DR NIMA were compared with those of the noninherited paternal antigens (NIPA) after stratification for HLA-DR*04, *0401 and/or *0404, and SE status. NIMA or NIPA that coincided with inherited HLA-DR antigens were considered redundant and excluded from analysis. Calculations concerning the whole group and restricted to patients lacking parental RA were performed. RESULTS: One hundred seventy families from France (n = 81), Belgium (n = 23), Spain (n = 24), Italy (n = 19), Portugal (n = 14), and The Netherlands (n = 9) were oligotyped. The group of probands was predominantly female (88%), positive for rheumatoid factor, DR*04, and SE (71%, 58%, and 75%, respectively), and had erosive disease (75%). Parental RA was reported in 21 families. Using the NIPA as control, the frequency of HLA-DRB1*04, *0401 and/or *0404-, or SE-positive NIMA was not found to be increased in patients lacking these susceptibility alleles. The same was true when the 21 probands with parental RA were excluded from analysis. In DRB1*04-positive patients, we found no evidence of a relevant effect of HLA-DR3 or DR6 in the NIMA. CONCLUSION: Our results do not support the notion that noninherited maternal antigens have a role in susceptibility to RA in the offspring.     

The impact of HLA-DRB1*0405 on disease severity in Korean patients with seropositive rheumatoid arthritis

Many reports have described HLA-DRB1 genes as having an influence on disease severity and susceptibility in rheumatoid arthritis (RA). Studies were undertaken to define the effect of RA-associated alleles on disease severity in Korean patients with seropositive RA. The results indicate that the most common RA susceptibility allele, HLA- DRB1*0405, is significantly associated with bony erosion, joint deformity and extra-articular manifestations. However, RA-associated alleles in Koreans have less effect on nodular disease than in Caucasians. This suggests that the presence of RA-associated alleles, especially HLA-DRB1*0405, seems to be a prognostic marker for severe erosive disease in Koreans.      

Identification of type II collagen peptide 261-273-specific T cell clones in a patient with relapsing polychondritis

OBJECTIVE: To characterize and clone T cells specific for type II collagen (CII) in a patient with relapsing polychondritis (RP) and to establish whether the immunodominant epitope of CII determined in HLA transgenic mice is used in the human autoimmune response to CII. METHODS: T cell responses to CII were examined in a patient with RP, who was heterozygous for the HLA-DR allele DRB1*0101/DRB1*0401. T cell clones were established from this patient and characterized for peptide specificity, class II restriction, cytokine production, and staining with HLA-DRB1*0401 class II tetramers. RESULTS: A response to CII and the peptide 255-273 was present in this patient. T cells specific for the CII epitope 261-273 were cloned. Evaluation of these clones demonstrated a response to CII 261-273 in the context of both DR alleles. HLA-DR4 CII tetramer did not demonstrate staining of either CII-specific DRB1*0401-restricted T cell clones or a polyclonal population of CII-reactive T cells from this individual. CONCLUSION: T cells directed against CII were present in this patient with RP. Also, T cell clones isolated from this individual were found to be specific for the CII peptide 261-273 and were restricted to either the DRB1*0101 or the DRB1*0401 allele. These findings establish that a T cell response directed against CII is present in this patient with RP and that the CII peptide 261-273 plays a role in the human immune response to CII.     

Identification of citrullinated vimentin peptides as T cell epitopes in HLA–DR4–positive patients with rheumatoid arthritis

Objective

Antibodies directed against citrullinated proteins (ACPAs) are highly specific for rheumatoid arthritis (RA). The production of ACPAs is most likely dependent on the presence of T cells, since ACPAs undergo isotype switching and are associated with the shared epitope (SE)–containing HLA–DRB1 alleles. Vimentin is a likely candidate protein for T cell recognition, since >90% of patients positive for ACPAs that are reactive with (peptides derived from) citrullinated vimentin carry SE‐containing HLA–DRB1 alleles. The aim of this study was to identify citrullinated vimentin peptides that are presented to HLA–DRB1*0401–restricted T cells.

Methods

HLA–DR4–transgenic mice were immunized with all possible citrulline‐containing peptides derived from vimentin, and T cell reactivity was analyzed. Peptides recognized in a citrulline‐specific manner by T cells were selected and analyzed for their ability to be processed from the entire vimentin protein. A first inventory of the selected epitopes recognized by T cells was performed using peripheral blood mononuclear cells (PBMCs) from ACPA+, HLA–DR4+ patients with RA.

Results

A citrulline‐specific response was observed for 2 of the peptides analyzed in DR4‐transgenic mice. These peptides were found to be naturally processed from the vimentin protein, since citrullinated vimentin was recognized by peptide‐specific T cells. T cell reactivity against these peptides was also observed in cultures of PBMCs from RA patients.

Conclusion

This study identifies, for the first time, 2 naturally processed peptides from vimentin that are recognized by HLA–DRB1*0401–restricted T cells in a citrulline‐specific manner. These peptides can be recognized by T cells in ACPA+, HLA–DR4+ patients with RA, as shown in a first inventory.

     

The HLA-DRB1 shared epitope alleles differ in the interaction with smoking and predisposition to antibodies to cyclic citrullinated peptide

OBJECTIVE: The HLA shared epitope (SE) alleles are primarily a risk factor for the presence of antibodies to cyclic citrullinated peptide (anti-CCP antibodies) rather than for the development of rheumatoid arthritis (RA). The SE alleles interact with the environmental risk factor tobacco exposure (TE) for predisposition to anti-CCP+ RA. The objectives of this study were to determine 1) whether different SE subtypes contribute differently to the presence of anti-CCP antibodies, 2) whether different SE subtypes all interact with TE for the development of anti-CCP antibodies, and 3) the effect of TE in relation to the SE alleles and anti-CCP antibodies on the risk of progression from undifferentiated arthritis (UA) to RA. METHODS: We assessed the effect of SE subtypes and TE on the presence and level of anti-CCP antibodies and on the risk of progression from UA to RA in 977 patients with early arthritis who were included in the Leiden Early Arthritis Clinic. RESULTS: The HLA-DRB1*0401, *0404, *0405, or *0408 SE alleles conferred the highest risk of developing anti-CCP antibodies (odds ratio [OR] 5.0, compared with an OR of 2.0 for the HLA-DRB1*0101 or *0102 SE alleles and an OR of 1.7 for the HLA-DRB1*1001 SE allele). Conversely, the TE-SE allele interaction was the strongest for the HLA-DRB1*0101 or *0102 SE alleles and the HLA-DRB1*1001 SE allele. TE in SE+, anti-CCP+ patients correlated with higher levels of anti-CCP antibodies and with progression from UA to RA. In logistic regression analysis, only the presence and level of anti-CCP antibodies were associated independently with RA development. CONCLUSION: The HLA-DRB1 SE subtypes differ in their interaction with smoking and in their predisposition to anti-CCP antibodies. TE contributes to the development of RA in SE+, anti-CCP+ patients, which is explained by its effect on the level of anti-CCP antibodies.