Rheumatoid Epitope Research Articles

The Influence of MHC Class II Molecules Containing the Rheumatoid Arthritis Shared Epitope on the Immune Response to Aggrecan G1 and Its Peptides

Aggrecan has been implied as an autoantigen in rheumatoid arthritis (RA). Immunization with aggrecan induces arthritis in BALB/c (H-2(d)) mice but not in other strains of mice [e.g. C57BL/6 (H-2(b))]. In humans, the strongest genetic association with RA is to the shared epitope (SE), and aggrecan peptides are predicted to bind to the SE. Therefore, we hypothesized that C57BL/6 mice transgenic (tg) for the RA SE (DR4 tg mice) may be susceptible to aggrecan-induced arthritis. C57BL/6 and DR4 tg mice were immunized with a mixture of SE-binding aggrecan peptides and tested for immune responses to the corresponding peptides as well as aggrecan. Sustained T- and B-cell immune responses to aggrecan and several of its peptides were detected in DR4 tg mice. C57BL/6 mice showed only transient T-cell responses to different immunizing peptides and little B-cell response. Therefore, an immune response to peptides of aggrecan can be induced experimentally in DR4 tg mice as anticipated from the predicted and actual binding affinities of these peptides for the RA SE. Failure to induce arthritis in these DR4 tg mice may be due to a lack of appropriate non-MHC genes.

Screening for the RA‐associated shared epitope by flow cytometry: comparison of two methods with high resolution genotyping

AbstractObjective: To assess flow cytometry‐based detection of the shared rheumatoid epitope (SE) as a potential screening test for high resolution genotyping in patients with rheumatoid arthritis.Methods: Peripheral blood mononuclear cells or white blood cell preparations from 84 patients with RA (1987 ACR criteria) were stained with a monoclonal antibody to the SE and analyzed by flow cytometry. The need for additional staining of T‐cells was also assessed. Results with both approaches were compared to high resolution genotyping.Results: The test had a positive predictive value of 100%, however, the negative predictive value was 77% due to poor staining in HLA‐DRB1*0101 or *0102 and HLA‐DRB1*1001 positive samples. Although there were no false positive tests with the simplified staining method, the negative predictive value was 61% with poor staining in HLA‐DRB1*0101 and failure to detect 4/22 samples with the high risk allele HLA‐DRB1*0401.Conclusions: Without further modification, this approach cannot be recommended as a screening test for high resolution genotyping.

Is rheumatoid arthritis in African descendants from North and South America the same?

RHEUMATOID ARTHRITIS (RA) is known to occur worldwide but not with the same frequency or degree of severity among various population groups. These differences have been related to the uneven distribution of the rheumatoid epitope and the HLA-DR alleles carrying it, although other genes acting alone or in conjunction with the rheumatoid epitope (polymorphisms of tumor necrosis factor alpha, T-cell receptors, Fcgamma receptor IIIA, and interferon gamma, for example) as well as nongenetic factors may be important determinants of the predisposition to RA and to its severity (1-7). Some populations with a relatively low frequency of the rheumatoid epitope are known to have a relatively mild disease; such is the case for Caucasians from the Mediterranean basin and their descendants elsewhere in the world (8-15). In contrast, African descendants from North America, who also have a low frequency of the rheumatoid epitope, have a disease as severe as that of the Caucasians from the same geographic area (16,17). The study by Anaya et al in this issue of the journal (18) includes 2 Colombian subpopulations, one of African descendants from Quibdo and the other of Mestizos (an admixture of the original inhabitants of the region and Spanish conquistadors) from Medellin. The investigators studied with some detail the Quibdo patients, characterizing their clinical and immunogenetic features. The Medellin patients, attending a rheumatology clinic at a general hospital, served as a frame of reference to indicate that in fact patients with erosive RA are being seen in Colombia. There are 2 obvious angles to this report: the first is the comparison between the RA patients from the 2 Colombian ethnic groups and the second is the comparison between the Quibdo African descendants (“African Colombians”) and the African descendants from North America (“African Americans”). In both cases the report posits more questions than provides answers. Given the different methodologies used to study the 2 Colombian populations (case ascertainment and clinical and immunogenetic characterization), I have chosen to concentrate my comments on the 2 populations of African ancestry, the one from Quibdo reported in the Anaya article (18) and the one from the United States studied by McDaniel et al several years ago (16). The African Colombian patients had in general a relatively mild disease as evidenced by the paucity of erosions and low levels of IgM-rheumatoid factor (18). These findings are in clear contrast with the patients from the U.S. whose disease was as severe as that of Caucasians from the same geographic area (16). The African Colombian patients also carried the rheumatoid epitope sparingly (as did a small number of local controls); the investigators then concluded that the infrequency of the rheumatoid epitope was probably the reason for the mild disease observed in their Africandescendant patients, pointing out that this is probably not the sole explanation. I concur with their assessment, as the rheumatoid epitope also was found to be infrequent among the African Americans studied by McDaniel et al (16). If in fact African descendants in South America had a much milder disease than those in North America (granted, this is only 1 study in a relatively small community of African descendants in 1 South American country), were the phenotypic differences observed real or artifactual (since the methods used to study these 2 populations are different and thus not directly comparable)? (19).

The HLA-DRB1*0401 Allele and the Development of Methotrexate-Induced Accelerated Rheumatoid Nodulosis

The HLA-DRB1*0401 Allele and the Development of Methotrexate-Induced Accelerated Rheumatoid Nodulosis

Positivity of HLA-DRB1 rheumatoid epitope does not predict the course of juvenile idiopathic arthritis in Czech children

Positivity of HLA-DRB1 rheumatoid epitope does not predict the course of juvenile idiopathic arthritis in Czech children

Clinical utility of the flow cytometric technique for shared rheumatoid epitope.

The shared rheumatoid epitope (SRE) on the MHC class II antigen-presenting molecule constitutes a probable genetic risk factor for the occurrence of rheumatoid arthritis (RA) and may also determine disease severity. We have used a novel flow cytometric technique to determine the SRE in over 500 predominantly Caucasian patients attending a general rheumatology clinic. This technique has been validated against a polymerase chain reaction (PCR)/SSO molecular method. The SRE was observed in 90% of patients with Felty's syndrome (n = 10) and 75% of patients with RA (n = 178) as compared with 39% of patients with osteoarthritis or non-inflammatory rheumatic disorders (n = 73). Thus, the SRE determined by this method has a sensitivity for RA of 0.75, a specificity of 0.62 and an estimated positive predictive value of 0.02. In our RA cohort, there was no correlation between the functional outcome (health assessment questionnaire score) and SRE status. In conclusion, the determination of the SRE status by a flow cytometric method was found to have only modest sensitivity and specificity for RA; furthermore, the SRE did not correlate with functional outcomes. The clinical utility of the SRE assay is yet to be defined.

Shared rheumatoid epitope as a risk factor in determining outcome in rheumatoid arthritis.

A genetic component is thought to contribute to 30-40% of the expression of rheumatoid arthritis (RA) with the HLA-DR4, w4 (B1*0401), w14 (B1*0404) genes (and associated shared rheumatoid epitope) constituting a substantial portion of this risk. Our objective was to determine the presence of these risk factors in a group of patients with RA and to correlate presence with disease outcome. Forty-three RA patients who had been regularly assessed up to a ten year period since their initial entry into two gold treatment trials were studied. DR4, w4, w14 and shared rheumatoid epitope were determined on peripheral blood lymphocytes using flow cytometry and specific monoclonal antibodies. Disease outcome was measured by Health Assessment Questionnaire (HAQ) score and C-Reactive Protein (CRP) as a serological measure of joint inflammation. To confirm accuracy of the flow cytometric technique, DR typing and epitope status was compared with results obtained by genotyping in a subset of 14 patients. There was complete concordance between these two techniques for the rheumatoid epitope. However, concordance was not complete (both false positives and false negatives) for DR4, w4 and w14. Hence the presence of rheumatoid epitope was only evaluated further in the larger group. The presence of the shared rheumatoid epitope correlated positively with poorer outcome on serological assessment (p < 0.05). No significant correlation between HAQ score and rheumatoid epitope status was observed although a weak trend was noted. These studies suggest that determination of rheumatoid epitope status by flow cytometry may provide useful data concerning the long term outcome of patients with RA.

HLA-DRB1 alleles associated with rheumatoid arthritis in Northern Italy: correlation with disease severity.

The aim of the study was to evaluate the relationship between the presence of the 'rheumatoid epitope', defined by a sequence motif in the HLA-DRB1 alleles, rheumatoid factor and disease severity in Northern Italian patients with rheumatoid arthritis (RA). Twenty-nine DR4-positive and 57 DR4-negative RA patients were studied. Each DR4-positive patient was matched with two DR4-negative controls of similar disease duration and sex. HLA-DRB1 alleles were determined in the 86 patients and 351 controls from the same geographical area. The patients were retrospectively evaluated for extra-articular features (EAF) and radiographic damage. The rheumatoid epitope was expressed in 45% of patients. No significant differences in the presence of rheumatoid factor, EAF and articular damage were observed between patients with no, one or two doses of epitope. However, the patients encoding the epitope by an HLA-DR4 allele had a higher number of eroded joints and a higher Larsen score compared to those without the epitope. No differences were present between patients expressing HLA-DRB1*01 alleles and those lacking the rheumatoid epitope. Even in the absence of expression of the rheumatoid epitope, seropositive patients had more EAF and more erosive disease compared to those who were seronegative. Even if most Northern Italian RA patients do not express the rheumatoid epitope, the radiological severity of disease is associated with HLA-DRB1*04 alleles.

HLA-DRB1 genes and disease severity in rheumatoid arthritis. The MIRA Trial Group. Minocycline in Rheumatoid Arthritis.

To examine the effect of alleles encoding the "shared"/"rheumatoid" epitope on rheumatoid arthritis (RA) disease severity in patients who participated in the minocycline in RA (MIRA) trial. Of 205 patients with a week-48 visit, blood was available for typing of HLA-DRB1 and HLA-DQB1 in 174 (85%) and successfully completed in 169 (82%). Baseline erosions were used to assess disease severity and new erosions at the last visit served as a proxy for progression. At baseline, there was no association between the presence of erosive disease or rheumatoid factor status and the dose of rheumatoid epitope (homozygous, heterozygous, none) or the specific alleles identified. At the final visit, a gradient was observed for the 3 allelic subgroups (and their gene doses) in the occurrence of new erosions among the Caucasian placebo-treated, but not the minocycline-treated, patients. A treatment group/HLA-DR4 epitope interaction was demonstrated in multivariate analyses. Approximately two-thirds of African-American patients did not have the rheumatoid epitope. HLA-DRB1 oligotyping may be useful in predicting the progression of disease in some Caucasian patients. Our study corroborates the infrequency of the epitope among African-American patients with RA.

Most African-American patients with rheumatoid arthritis do not have the rheumatoid antigenic determinant (epitope)

To evaluate the relation between the presence of the "rheumatoid epitope," defined by a sequence motif in the HLA-DRB1 alleles, and disease severity in African-American patients with rheumatoid arthritis. Cross-sectional study. Rheumatology outpatient clinics at two university medical centers. 86 African-American patients with rheumatoid arthritis (66 seropositive and 20 seronegative for the rheumatoid factor) attending the clinics and 88 healthy African-American persons. HLA-DRB1 alleles were determined by restriction fragment length polymorphism and by allele-specific oligonucleotide typing of polymerase chain reaction-amplified HLA-DRB1 second exons. With the exception of an increased frequency of HLA-DRB1*04 alleles in seropositive patients with rheumatoid arthritis (27.3%) compared with controls (13.1%) (P = 0.02), the frequencies of HLA-DRB1 alleles were similar in patients and controls. Most seropositive (48 of 66) and seronegative (15 of 20) patients were HLA-DR4 negative, but some (7 of 48 seropositive patients and 3 of 15 seronegative persons) inherited the rheumatoid epitope on a non-DR4 allele. Disease features, including severity, were similar for patients without the epitope and for those with either a single or a double dose of an epitope-positive allele. Positivity for rheumatoid factor, but not for the rheumatoid epitope, was weakly associated with severity in these patients. Most African-American patients with rheumatoid arthritis did not express the rheumatoid epitope. The predisposition to and severity of rheumatoid arthritis in African-Americans appears to be independent of the presence and dose of the shared rheumatoid epitope.