Genetic polymorphisms in PTPN22, PADI-4, and CTLA-4 and risk for rheumatoid arthritis in two longitudinal cohort studies: evidence of gene-environment interactions with heavy cigarette smoking

Introduction: PTPN22, PADI-4, and CTLA-4 have been associated with risk for rheumatoid arthritis (RA). We investigated whether polymorphisms in these genes were associated with RA in Caucasian women included in two large prospective cohorts, adjusting for confounding factors and testing for interactions with smoking. Methods: We studied RA risk associated with PTPN22 (rs2476601), PADI-4 (rs2240340), and CTLA-4 (rs3087243) in the Nurses' Health Study (NHS) and NHSII. Participants in NHS were aged 30 to 55 years at entry in 1976; those in NHSII were aged 25 to 42 years at entry in 1989. We confirmed incident RA cases through to 2002 in NHS and to 2003 in NHSII by questionnaire and medical record review. We excluded reports not confirmed as RA. In a nested case-control design involving participants for whom there were samples for genetic analyses (45% of NHS and 25% of NHSII), each incident RA case was matched to a participant without RA by year of birth, menopausal status, and postmenopausal hormone use. Genotyping was performed using Taqman single nucleotide polymorphism allelic discrimination on the ABI 7900 HT (Applied Biosystems, 850 Lincoln Centre Drive, Foster City, CA 94404 USA) with published primers. Human leukocyte antigen shared epitope (HLA-SE) genotyping was performed at high resolution. We employed conditional logistic regression analyses, adjusting for smoking and reproductive factors. We tested for additive and multiplicative interactions between each genotype and smoking. Results: A total of 437 incident RA cases were matched to healthy female control individuals. Mean (± standard deviation) age at RA diagnosis was 55 (± 10), 57% of RA cases were rheumatoid factor (RF) positive, and 31% had radiographic erosions at diagnosis. PTPN22 was associated with increased RA risk (pooled odds ratio in multivariable dominant model = 1.46, 95% confidence interval [CI] = 1.02 to 2.08). The risk was stronger for RF-positive than for RF-negative RA. A significant multiplicative interaction between PTPN22 and smoking for more than 10 pack-years was observed (P = 0.04). CTLA-4 and PADI-4 genotypes were not associated with RA risk in the pooled results (pooled odds ratios in multivariable dominant models: 1.27 [95% CI = 0.88 to 1.84] for CTLA-4 and 1.04 [95% CI = 0.77 to 1.40] for PADI-4). No gene-gene interaction was observed between PTPN22 and HLA-SE. Conclusion: After adjusting for smoking and reproductive factors, PTPN22 was associated with RA risk among Caucasian women in these cohorts. We found both additive and multiplicative interactions between PTPN22 and heavy cigarette smoking

The clinical and immunological significance of ectopic lymphoneogenesis in the rehumatoid synovial membrane

PhDDespite the development of new biomarkers predicting prognosis in rheumatoid arthritis (RA) remains challenging and targeting of powerful biologics difficult. The presence of ectopic germinal centres (GC) within synovium has long been recognised (ectopic lymphoneogenesis [ELN]) and data have suggested that they manufacture antibody (Ab). High affinity class switched Ab production occurs through class switch recombination (CSR) and somatic hypermutation (SHM) both critically dependent on activation induced cytidine deaminase (AID). However, whether ectopic GCs express AID has not been known. Nonetheless data associating ELN with disease severity suggest a role for ELN in RA pathogenesis and as a potential biomarker. A classification system for RA synovium, based on the concept of ELN has been proposed as: (i) aggregate, (ii) aggregate GC+ and, (iii) an unorganised infiltrate. However whether these distinct pathotypes and/or degree of aggregation equate to disease severity is unclear. Thus my first aim was to develop and validate a pathological scoring system for rheumatoid synovium capable of quantifying the degree of ELN. My second aim was to investigate whether the presence and/or degree of ELN within the synovial membrane correlated with both clinical phenotype and predicted erosive damage. I demonstrate that the aggregational score developed is highly reliable and that ELN within synovial tissue associates with a higher level of synovial inflammation but is not predictive of damage. My third aim was to investigate whether GCs within RA synovium were functional. I provide evidence of functionality by demonstrating that ectopic GCs invariably express AID, are surrounded by anti-CCP+ plasma cells, support ongoing CSR and the manufacture of anti-CCP Abs. My final aim was to characterise a cohort of synovial B cells consistently found surrounding ectopic GCs. I identify a novel B cell subset within RA synovium, interfollicular large B cells, (5)(5)(5) and demonstrate that interfollicular large B cells in lymph node express a somatically mutated IgH.Guys and St Thomas' Charity fellowship