Relationship between area-level socio-economic deprivation and autoantibody status in patients with rheumatoid arthritis: multicentre cross-sectional study.

OBJECTIVES: The aims of this study were to assess the association between area-level socio-economic deprivation and the phenotype of rheumatoid arthritis (RA), defined by rheumatoid factor (RF) and anticitrullinated peptide antibody (AC PA) status, and to determine whether any observed association can be explained by smoking. METHODS: The authors performed logistic regression analysis of 6298 patients with RA, defined by American College of Rheumatology classification criteria modified for genetic studies. Analysis was stratified by cohort/recruitment centre. Socio-economic deprivation was measured using the Townsend Index. RESULTS: Deprivation predicted RF but not ACPA positivity, independent of smoking. The ORs for trend across tertiles, adjusted for smoking, gender, period of birth and cohort/recruitment centre, were 1.14 (95% CI 1.01 to 1.29) for RF and 1.01 (95% CI 0.87 to 1.16) for ACPA. Even after adjusting for deprivation, smoking was strongly associated with ACPA positivity (OR 1.38, 95% CI 1.22 to 1.55). There was no evidence of any effect modification by the RA risk alleles (HLA-DRB1 shared epitope and PTPN22 rs2476601) that have previously been shown to modify the effect of smoking on ACPA and RF positivity. CONCLUSIONS: Among patients with RA, deprivation predicted RF positivity but not ACPA positivity. The effect of deprivation did not appear to be explained by smoking. Deprivation may be a marker for previously unrecognised, potentially modifiable environmental influences on the immunological phenotype of RA. Furthermore, given the known associations of RF positivity with prognosis and response to treatment in RA, these findings have potential implications for resource allocation and healthcare delivery.

Confirmation of association of FCGR3B but not FCGR3A copy number with susceptibility to autoantibody positive rheumatoid arthritis.

The FCGR locus encoding the low-affinity Fcγ receptors (FcγR) for immunoglobulin G has largely been missed by genome-wide association studies due to complications with structural variation and segmental duplication. Recently identified copy number variants (CNVs) affecting FCGR3A and FCGR3B have been linked to a number of autoimmune disorders. We have developed and validated a novel quantitative sequence variant assay in combination with an adapted paralogue ratio test to examine independent CNVs carrying FCGR3A and FCGR3B in rheumatoid arthritis (RA) compared with healthy volunteers (n = 1,115 and 654, respectively). Implementation of a robust statistical analysis framework (CNVtools) allowed for systematic batch effects and for the inherent uncertainty of copy number assignment, thus avoiding two major sources of false positive results. Evidence for association with neither duplications nor deletions of FCGR3A was found; however, in line with previous studies, there was evidence of overrepresentation of FCGR3B deletions in RA (odds ratio [OR] 1.50, P = 0.028), which was more apparent in rheumatoid factor positive disease (OR 1.61, P = 0.011). The level of FcγRIIIb, encoded by FCGR3B, expression on neutrophils was shown to correlate with gene copy number. Thus, our results may highlight an important role for neutrophils in the pathogenesis of RA, potentially through reduced FcγRIIIb-mediated immune complex clearance.

FcγRIIIa expression on monocytes in rheumatoid arthritis: role in immune-complex stimulated TNF production and non-response to methotrexate therapy.

OBJECTIVE: The expression of FcγRIIIa/CD16 may render monocytes targets for activation by IgG-containing immune complexes (IC). We investigated whether FcγRIIIa/CD16 was upregulated in rheumatoid arthritis (RA), associated with TNF production in response to IC-stimulation, and if this predicted response to methotrexate therapy. METHODS: FcγRIIIa/CD16 expression on CD14(low) and CD14++ monocytes was measured by flow cytometry in healthy controls and RA patients (early and long-standing disease). Intracellular TNF-staining was carried out after in vitro LPS or heat-aggregated immunoglobulin (HAG) activation. FcγRIIIa/CD16 expression pre- and post-steroid/methotrexate treatment was examined. RESULTS: Increased FcγRIIIa/CD16 expression on CD14++ monocytes in long-standing RA patients compared to controls was demonstrated (p = 0.002) with intermediate levels in early-RA patients. HAG-induced TNF-production in RA patients was correlated with the percentage of CD14++ monocytes expressing FcγRIIIa/CD16 (p<0.001). The percentage of CD14++ monocytes expressing FcγRIIIa/CD16 at baseline in early DMARD-naïve RA patients was negatively correlated with DAS28-ESR improvement 14-weeks post-methotrexate therapy (p = 0.003) and was significantly increased in EULAR non-responders compared to moderate (p = 0.01) or good responders (p = 0.003). FcγRIIIa/CD16 expression was not correlated with age, presence of systemic inflammation or autoantibody titers. CONCLUSION: Increased FcγRIIIa/CD16 expression on CD14++ monocytes in RA may result in a cell that has increased responsiveness to IC-stimulation. This monocyte subset may contribute to non-response to methotrexate therapy.

Evaluation of the rheumatoid arthritis susceptibility loci HLA-DRB1, PTPN22, OLIG3/TNFAIP3, STAT4 and TRAF1/C5 in an inception cohort.

INTRODUCTION: This study investigated five confirmed rheumatoid arthritis (RA) susceptibility genes/loci (HLA-DRB1, PTPN22, STAT4, OLIG3/TNFAIP3 and TRAF1/C5) for association with susceptibility and severity in an inception cohort. METHODS: The magnitude of association for each genotype was assessed in 1,046 RA subjects from the Yorkshire Early RA cohort and in 5,968 healthy UK controls. Additional exploratory subanalyses were undertaken in subgroups defined by autoantibody status (rheumatoid factor and anti-cyclic citrullinated peptide) or disease severity (baseline articular erosions, Health Assessment Questionnaire (HAQ) score and swollen joint count (SJC)). RESULTS: In the total RA inception cohort, the HLA-DRB1 shared epitope (per-allele odds ratio (OR) = 2.1, trend P < 0.0001), PTPN22 (per-allele OR = 1.5, trend P < 0.0001), OLIG3/TNFAIP3 locus (per-allele OR = 1.2, trend P = 0.009) and TRAF1/C5 locus (per-allele OR = 1.1, trend P = 0.04) were associated with RA. The magnitude of association for these loci was increased in those patients who were autoantibody-positive. PTPN22 was associated with autoantibody-negative RA (per-allele OR = 1.3, trend P = 0.04). There was no evidence of association between these five genetic loci and baseline erosions or SJC in the total RA cohort, after adjustment for symptom duration. TRAF1/C5 was significantly associated with baseline HAQ, however, following adjustment for symptom duration (P trend = 0.03). CONCLUSIONS: These findings support the mounting evidence that different genetic loci are associated with autoantibody-positive and autoantibody-negative RA, possibly suggesting that many of the genes identified to date are associated with autoantibody production. Additional studies with a specific focus on autoantibody-negative RA will be needed to identify the genes predisposing to this RA subgroup. The TRAF1/C5 locus in particular warrants further investigation in RA as a potential disease severity locus.

Reevaluation of the interaction between HLA-DRB1 shared epitope alleles, PTPN22, and smoking in determining susceptibility to autoantibody-positive and autoantibody-negative rheumatoid arthritis in a large UK Caucasian population.

OBJECTIVE: To define interactions between the HLA-DRB1 shared epitope (SE), PTPN22, and smoking in cyclic citrullinated peptide (CCP) antibody- and rheumatoid factor (RF)-positive and -negative rheumatoid arthritis (RA). METHODS: Data on approximately 5,000 RA patients and approximately 3,700 healthy controls recruited from 6 centers in the UK were analyzed; not all centers had both genotype data and smoking data available for study. The magnitude of association was assessed in autoantibody-positive and -negative subgroups. The effect of smoking on antibody status among cases was assessed following adjustment for year of birth and center, using Mantel-Haenszel analysis. Analyses of the combined effects of PTPN22, HLA-DRB1 SE, and smoking were performed using additive and multiplicative models of interaction within a logistic regression framework. RESULTS: The combined effects of PTPN22, HLA-DRB1 SE, and smoking were defined, with no evidence of departure from a multiplicative model. Within the case population, all 3 factors were independently associated with the generation of CCP antibodies (odds ratio [OR] 11.1, P < 0.0001), whereas only HLA-DRB1 SE and smoking were independently associated with RF production (OR 4.4, P < 0.0001). There was some evidence of increasing likelihood of antibody positivity with heavier smoking. Finally, we demonstrated that smoking was associated with the generation of both CCP and RF antibodies (OR 1.7, P = 0.0001). CONCLUSION: PTPN22 appears to be primarily associated with anticitrulline autoimmunity, whereas HLA-DRB1 SE is independently associated with RF. This study has confirmed associations of specific gene-environment combinations with a substantially increased risk of developing RA. Further work is needed to determine how these data can be used to inform clinical practice.

The shared epitope hypothesis in rheumatoid arthritis: evaluation of alternative classification criteria in a large UK Caucasian cohort.

OBJECTIVE: Many classification systems for the HLA-DRB1 allelic association with rheumatoid arthritis (RA) have been reported, but few have been validated in additional populations. We sought to evaluate 3 different DRB1 allele classification systems in a large cohort of Caucasian RA patients and control subjects in the UK. METHODS: HLA-DRB1 typing was undertaken in 1,325 Caucasian RA patients and 462 healthy Caucasian controls who were residents of the UK. Logistic regression analyses were performed to investigate the different classification systems. RESULTS: We confirmed the association between the susceptibility alleles S2 and S3P, as proposed by Tezenas du Montcel, and the presence of RA in UK Caucasians. A significant hierarchy of risk was observed within the S3P allele group. There was no evidence of a significant association between DRB1*1001 and RA. Our data did not support the hypothesis that an isoleucine at position 67 conferred protection against RA, other than in contrast to the susceptibility alleles. However, the presence of an aspartic acid at amino acid 70 did appear to confer some degree of protection. CONCLUSION: We were unable to fully substantiate any of the 3 recent revisions of the shared epitope hypothesis in this large cohort of Caucasian RA patients and control subjects in the UK. This reinforces the importance of evaluating disease susceptibility alleles in different Caucasian populations as well as in other ethnic groups. In particular, it will be important to clarify the precise DRB1 association in a given population before DRB1 genotyping is incorporated into clinical diagnostic or treatment algorithms.