A new model for an etiology of rheumatoid arthritis: smoking may trigger HLA-DR (shared epitope)-restricted immune reactions to autoantigens modified by citrullination

Early rheumatoid arthritis: strategies for prevention and management

The treatment of rheumatoid arthritis (RA) has changed considerably in the past few years since new tools and new concepts have been developed and validated highlighting the need for guidelines focused on early RA. The treatment goal should now be to achieve clinical remission, in order to prevent structural damage and long-term disability. A very early use of effective disease-modifying anti-rheumatic drugs (DMARDs) is a key point in patients at risk of developing persistent and erosive arthritis. Intensive treatment such as combination DMARDs plus steroids or biological therapies can induce a high rate of remission, control of radiological progression and provide better outcome than DMARD monotherapy in early RA and should be considered in at risk patients. Regarding the risk:benefit ratio and the cost-effectiveness of these strategies, a reasonable course of action in early RA should be initial DMARD monotherapy such as methotrexate. However, a close monitoring of disease activity and radiographic progression is mandatory in order to change DMARD therapy and strategy if necessary. Systemic glucocorticoids are effective in the short-term relief of pain and swelling and should be considered, but mainly as a temporary therapy part of the DMARD strategy. Information and education for patients, as well as some non-pharmacological interventions, can be proposed as treatment adjuncts. Finally, the reduction or stopping of smoking, which could prevent the development and progression of early RA, is the only prevention tool currently available.

Public health perspective--how to improve the musculoskeletal health of the population

Musculoskeletal disorders are the most common cause of long-term sick leave in several western countries and individuals with chronic musculoskeletal pain score very low on health status measurements. Musculoskeletal health is multidimensional and is best understood from a biopsychosocial perspective. Body structure and function interacts with personal and environmental factors, affecting the ability to perform activities and participate in society. Interventions aimed at the whole population must attend to the underlying causes of musculoskeletal disorders and promote a healthy lifestyle. Safe environments and activities could reduce the risk of traumatic events and also make participation possible for those with a disability. Public beliefs about musculoskeletal symptoms and consequences need to be changed in order to minimise fear and avoidance, which, together with other psychosocial factors, could lead to chronicity. Public awareness and identification of those at risk for the development of musculoskeletal problems could lead to early and properly timed management.

Gene-gene and gene-environment interactions involving HLA-DRB1, PTPN22, and smoking in two subsets of rheumatoid arthritis

Gene-gene and gene-environment interactions are key features in the development of rheumatoid arthritis (RA) and other complex diseases. The aim of this study was to use and compare three different definitions of interaction between the two major genetic risk factors of RA--the HLA-DRB1 shared epitope (SE) alleles and the PTPN22 R620W allele--in three large case-control studies: the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study, the North American RA Consortium (NARAC) study, and the Dutch Leiden Early Arthritis Clinic study (in total, 1,977 cases and 2,405 controls). The EIRA study was also used to analyze interactions between smoking and the two genes. "Interaction" was defined either as a departure from additivity, as interaction in a multiplicative model, or in terms of linkage disequilibrium--for example, deviation from independence of penetrance of two unlinked loci. Consistent interaction, defined as departure from additivity, between HLA-DRB1 SE alleles and the A allele of PTPN22 R620W was seen in all three studies regarding anti-CCP-positive RA. Testing for multiplicative interactions demonstrated an interaction between the two genes only when the three studies were pooled. The linkage disequilibrium approach indicated a gene-gene interaction in EIRA and NARAC, as well as in the pooled analysis. No interaction was seen between smoking and PTPN22 R620W. A new pattern of interactions is described between the two major known genetic risk factors and the major environmental risk factor concerning the risk of developing anti-CCP-positive RA. The data extend the basis for a pathogenetic hypothesis for RA involving genetic and environmental factors. The study also raises and illustrates principal questions concerning ways to define interactions in complex diseases.

Palmoplantar pustulosis and gluten sensitivity: a study of serum antibodies against gliadin and tissue transglutaminase, the duodenal mucosa and effects of gluten-free diet

BACKGROUND

Palmoplantar pustulosis (PPP) is a chronic inflammatory disease affecting mainly smoking women. Some patients also have psoriasis. A subgroup of patients with psoriasis has been shown to have silent gluten sensitivity with relevance for their psoriasis. Nothing is known about gluten sensitivity in PPP.

OBJECTIVES

To find out whether any patients with PPP are gluten-sensitive and whether this might be relevant for the PPP activity.

PATIENTS AND METHODS

One hundred and twenty-three patients (113 women) with PPP participated. Screening for IgA antibodies against gliadin and tissue transglutaminase (tTG) was performed, the duodenal mucosa in patients with and without these antibodies was studied and the effect of a gluten-free diet (GFD) was followed up.

RESULTS

Twenty-two patients (18%) had IgA antibodies against gliadin and nine of 94 (10%) against tTG. Twelve patients with antibodies and 11 without underwent gastro-duodenoscopy. Four displayed villous atrophy, whereas all other specimens were judged as essentially normal at routine staining. However, with immunohistochemistry, the numbers of CD3+ and CD8+ lymphocytes in the epithelium were found to be increased in patients with any type of antibody, although they were most numerous in those with both types of antibodies. Seven of 123 patients (6%) had coeliac disease (three previously diagnosed). Patients with antibodies who adhered to the GFD displayed total or nearly total clearance of the skin lesions and normalization of the antibody levels.

CONCLUSIONS

Patients with PPP should be screened for antibodies against gliadin and tTG. Those with antibodies can be much improved on a GFD regardless of the degree of mucosal abnormalities.

B cells in rheumatoid arthritis

Though its etiology remains unknown thus far, the role that autoimmune processes play in rheumatoid arthritis (RA) pathogenesis has been widely proven. Given the easier accessibility of humoral components, the first feature of this contribution to be recognized has been the occurrence of the so-called rheumatoid factor in a large proportion of RA patients. This antibody recognizes the Fc portion of human IgG. By investigating RA pathologic processes and also through experimental models where immune complexes play a fundamental role, many other autoantibodies have then come to our knowledge to be associated with the disease. Their presence and persistence implies that clones of autoreactive B cells survive and proliferate in RA patients under a continuous stimulation. Whether this is a mechanism of disease initiation or just an epiphenomenon is still unclear but no doubt exists that autoantibodies represent a very useful tool in both diagnostic and prognostic terms. Being much more than simple autoantibody producers, B cells are able to secrete many important cytokines and to efficiently present antigens to T lymphocytes in the synovial environment. All of these functions are essential in the development of RA, and lately have claimed attention as B cell depletion has become a common and effective strategy of treatment in RA.

Epidemiology and health services: year in review

PURPOSE OF REVIEW

Epidemiology began as the study of the occurrence of disease in populations. Initial studies focused on the presence of diseases by person, place, and time to identify risk factors for disease. The field has grown to include many subfields recognizing the contributions of multiple factors to disease susceptibility.

RECENT FINDINGS

This review will focus on articles published October 2005-November 2006 relevant to genetic epidemiology, pharmacoepidemiology, and social determinants of health and health disparities.

SUMMARY

Genetic epidemiology is the study of genetic contributions to disease occurrence, and of population-based genetic risks for disease. Genetics influences not only susceptibility to disease, but also the phenotype and severity of disease. Pharmacoepidemiology examines the outcomes of medication use, including clinical benefits and adverse effects. Gene-environment interactions are also included in this area. Typical topics in pharmacoepidemiology include studies of medication use, risks, benefits and genetic factors influencing the metabolism of medications. Social epidemiology is the study of social determinants of health, including psychosocial behaviors, socioeconomic status, interactions of individuals, the collective health of the community in which a person lives, and the position of the individual within society. Social epidemiology is directly relevant to studies of socioeconomic and ethnic disparities.

Mechanisms of Disease: environmental factors in the pathogenesis of rheumatic disease

Most rheumatic diseases are complex disorders for which pathogenetic mechanisms are poorly understood. Nonetheless, increasing evidence suggests that many of these illnesses result from one or more specific environmental exposures in genetically susceptible individuals. Although much progress has been made over the past few decades in advancing our knowledge of the genetics of rheumatic diseases, few studies have assessed environmental features and understanding of which exposures are important in pathogenesis remains limited. In this article, we review the difficulties inherent in deciphering the interacting environmental and genetic risk factors for rheumatic diseases, the current state of knowledge of infectious and noninfectious risk factors, possible mechanisms by which environmental exposures might induce pathologic processes and future directions. The advances in technologies and statistical approaches, development of collaborating consortia and focused resources that have resulted in the explosion of genetic information must now be applied to environmental studies so we can eventually interrupt pathogenesis before the onset of disease and transform the practice of medicine from curative to pre-emptive paradigms.

Aspects of early arthritis. What determines the evolution of early undifferentiated arthritis and rheumatoid arthritis? An update from the Norfolk Arthritis Register

Over 3500 patients with recent onset inflammatory polyarthritis (IP) have been recruited by the Norfolk Arthritis Register (NOAR) since 1990. Longitudinal data from this cohort have been used to examine the prevalence and predictors of remission, functional disability, radiological outcome, cardiovascular mortality and co-morbidity and the development of non-Hodgkin's lymphoma. Rheumatoid factor titre, high baseline C-reactive protein and high baseline HAQ score are all predictors of a poor outcome. There is a strong association between possession of the shared epitope and the development of erosions. Patients who satisfy the American College of Rheumatology criteria for rheumatoid arthritis (RA) have a worse prognosis than those who do not. However, it appears that these patients are a poorly defined subset of all those with IP rather than having an entirely separate disease entity. New statistical techniques offer exciting possibilities for using longitudinal datasets such as NOAR to explore the long-term effects of treatment in IP and RA.

Environmental risk factors differ between rheumatoid arthritis with and without auto-antibodies against cyclic citrullinated peptides

The aim of this study was to evaluate new and previously hypothesised non-genetic risk factors for serologic subtypes of rheumatoid arthritis (RA) defined by the presence or absence of auto-antibodies to cyclic citrullinated peptides (CCP). In a national case-control study, we included 515 patients recently diagnosed with RA according to the American College of Rheumatology 1987 classification criteria and 769 gender- and age-matched population controls. Telephone interviews provided information about non-genetic exposures, and serum samples for patients were tested for anti-CCP-antibodies. Associations between exposure variables and risk of anti-CCP-positive and anti-CCP-negative RA were evaluated using logistic regression. A series of RA subtype-specific risk factors were identified. Tobacco smoking (odds ratio [OR] = 1.65; 95% confidence interval: 1.03–2.64, for >20 versus 0 pack-years) was selectively associated with risk of anti-CCP-positive RA, whereas alcohol consumption exhibited an inverse dose-response association with this RA subtype (OR = 1.98, 1.22–3.19, for 0 versus >0–5 drinks per week). Furthermore, coffee consumption (OR = 2.18; 1.07–4.42, for >10 versus 0 cups per day), ever use of oral contraceptives (OR = 1.65; 1.06–2.57) and having a first-degree relative with schizophrenia (OR = 4.18; 1.54–11.3) appeared more strongly associated with risk of anti-CCP-positive RA. Obesity was selectively associated with risk of anti-CCP-negative RA, with obese individuals being at more than 3-fold increased risk of this subtype compared with normal-weight individuals (OR = 3.45; 1.73–6.87). Age at menarche was the only examined factor that was significantly associated with both serologic subtypes of RA (p-trends = 0.01); women with menarche at age ≥ 15 years had about twice the risk of either RA subtype compared with women with menarche at age ≤ 12 years. Major differences in risk factor profiles suggest distinct etiologies for anti-CCP-positive and anti-CCP-negative RA.

CD56-expressing T cells that have features of senescence are expanded in rheumatoid arthritis

OBJECTIVE

T cells deficient in CD28 expression have been implicated in the pathogenesis of rheumatoid arthritis (RA). Given that CD28-null T cells are functionally heterogeneous, we undertook this study to screen for novel receptors on these cells.

METHODS

Seventy-two patients with RA (ages 35-84 years) and 53 healthy persons (32 young controls ages 19-34 years, 21 older controls ages 39-86 years) were recruited. Phenotypes and proliferative capacity of T cells from fresh leukocytes and of long-term cultures were monitored by flow cytometry. Lung biopsy specimens from patients with RA-associated interstitial pneumonitis (IP) were examined by immunohistochemistry. Receptor functionality was assessed by crosslinking bioassays.

RESULTS

Chronic stimulation of CD28(+) T cells in vitro yielded progenies that lacked CD28 but that gained CD56. Ex vivo analysis of leukocytes from patients with extraarticular RA showed a higher frequency of CD56(+),CD28-null T cells than in patients with disease confined to the joints or in healthy controls. CD56(+),CD28-null T cells had nil capacity for proliferation, consistent with cellular senescence. CD56(+) T cells had skewed T cell receptor (TCR) alpha/beta-chain usage and restricted TCR third complementarity-determining region spectra. Histologic studies showed that CD56(+) T cells were components of cellular infiltrates in RA-associated IP. CD56 crosslinking on T cells sufficiently induced cytokine production, although CD56/TCR coligation induced higher production levels.

CONCLUSION

Chronic activation of T cells induces counterregulation of CD28 and CD56 expression. The loss of CD28 is accompanied by the gain of CD56 that confers TCR-independent and TCR-dependent activation pathways. We propose that accumulation of CD56(+) T cells in RA contributes to maladaptive immune responses and that CD56(+) T cells are potential targets for therapy.

The cutaneous non-neuronal cholinergic system and smoking related dermatoses: studies of the psoriasis variant palmoplantar pustulosis

Palmoplantar pustulosis (PPP) is probably the inflammatory skin disease most strongly associated to smoking. The disease is common in middle-aged, smoking women, and is chronic, sometimes disabling and characterized by pustules, erythema and scaling on the soles and palms. It is often treatment-resistant. PPP patients have a co-morbidity with an increased risk of autoimmune thyroid disease, celiac disease/gluten intolerance, abnormal calcium homeostasis, diabetes type 2, and depression. The sweat gland apparatus is involved in the pathogenesis of PPP since a) the normal structure of the acrosyringium is abolished so the keratin pattern differs to that in normal palmar skin; b) granulocytes migrate outwards in the acrosyringium forming the pustule in the stratum corneum. Acetylcholine (ACh) is the main inducer of sweating. With immunohistochemistry the ACh synthesizing enzyme choline acetyltransferase (ChAT) and the ACh-degrading enzyme acetylcholinesterase (AChE) were found to be strongly expressed in the gland and duct as were the alpha-3 and alpha-7 nicotinic acetylcholine receptors (nAChRs). Smoking influenced the staining intensity of the enzymes and the alpha-3 nAChR in healthy subjects. In involved PPP skin there was a massive infiltration of granulocytes expressing ChAT and alpha-3 nAChR, and mast cells expressing AChE indicating a role for acetylcholine in inflammation. Cessation of smoking resulted in fewer pustules, and less scaling and erythema. The mechanisms for the effect of nicotine/smoking in PPP are still unknown but nicotine may lead to enhanced inflammation in consideration of the properties of the sweat duct and/or nicotine might facilitate autoimmune reactions.

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.

Perinatal and early childhood risk factors associated with rheumatoid factor positivity in a healthy paediatric population

OBJECTIVE

To examine perinatal and childhood risk factors for the presence of rheumatoid factor in healthy children.

METHODS

The Diabetes Autoimmunity Study in the Young (DAISY) is a longitudinal study of children at increased risk of type 1 diabetes, based on possession of human leucocyte antigen (HLA)-DR4 and DR3 alleles or a family history of diabetes. 651 children who participated in DAISY, with an average age of 6.4 (range 1-15) years, were tested for the presence of rheumatoid factor in their most recent serum sample. 23 children were positive for rheumatoid factor. Exposure data were collected prospectively by interview. HLA-DR4 alleles were identified using polymerase chain reaction-based Class II genotyping.

RESULTS

While exploring risk factors for rheumatoid factor positivity in a multivariate model, several important interaction terms involving HLA-DR4 status suggested the need to evaluate risk factors in HLA-DR4-positive and HLA-DR4-negative children separately. In HLA-DR4-negative children, rheumatoid factor-positive infants were less likely to have been breast fed for >3 months (odds ratio (OR) 0.18; 95% confidence interval (CI) 0.04 to 0.99), more likely to have been exposed to non-parental tobacco smoke (OR 5.38; 95% CI 0.93 to 31.27) and more likely to be a race/ethnicity other than non-Hispanic white (OR 6.94; 95% CI 1.10 to 43.88) compared with rheumatoid factor-negative children, after adjusting for age, sex and maternal education. In HLA-DR4-positive children, there were no significantly associated risk factors for rheumatoid factor positivity.

CONCLUSIONS

Risk factors for rheumatoid factor positivity in children vary by HLA-DR4 genotype. In HLA-DR4-negative children, breast feeding may decrease the risk, and environmental tobacco smoke may increase the risk, of autoimmunity.

The immune response to citrullinated proteins in patients with rheumatoid arthritis

This article reviews data concerning the applicability of anti-citrullinated peptide antibodies in the diagnosis, estimation of prognosis, and follow-up of patients with rheumatoid arthritis (RA). The production of anti-citrullinated peptide antibodies is closely associated with the presence of the HLA-DRB1 shared epitope, a known risk factor for development of RA, and the production may be influenced by environmental factors such as tobacco smoking. Patients who harbor this antibody from the early stage of their disease develop more severe erosive disease than patients with RA who lack the antibody. The anti-citrullinated peptide antibody level may be a reflection of disease activity, at least in the early phase of the disease. The antibody can sometimes be found several years before the onset of clinical symptoms of RA, which may represent an open window for preventive measures to be taken.

Linkage proof for PTPN22, a rheumatoid arthritis susceptibility gene and a human autoimmunity gene

The tyrosine phosphatase PTPN22 allele 1858T has been associated with rheumatoid arthritis (RA) and other autoimmune diseases. RA is the most frequent of those multifactorial diseases. The RA association was usually restricted to serum rheumatoid factor positive disease (RF+). No interaction was shown with HLA-DRB1, the first RA gene. Many case-control studies replicated the RA association, showing an allele frequency increase of approximately 5% on average and large variations of population allele frequencies (2.1-15.5%). In multifactorial diseases, the final proof for a new susceptibility allele is provided by departure from Mendel's law (50% transmission from heterozygous parents). For PTPN22-1858T allele, convincing linkage proof was available only for type 1 diabetes. We aimed at providing this proof for RA. We analyzed 1,395 West European Caucasian individuals from 465 "trio" families. We replicated evidence for linkage, demonstrating departure from Mendel's law in this subset of early RA onset patients. We estimated the overtransmission of the 1858T allele in RF+ families: T = 63%, P < 0.0007. The 1858T allele frequency increased from 11.0% in controls to 17.4% in RF+ RA for the French Caucasian population and the susceptibility genotype (1858T/T or T/C) from 20.2% to 31.6% [odds ratio (OR) = 1.8 (1.2-2.8)]. In conclusion, we provided the linkage proof for the PTPN22-1858T allele and RF+ RA. With diabetes and RA, PTPN22 is therefore a "linkage-proven" autoimmunity gene. PTPN22 accounting for approximately 1% of the RA familial aggregation, many new genes could be expected that are as many leads to definitive therapy for autoimmune diseases.

Systemic rheumatoid vasculitis: a review

OBJECTIVES

To review the most recent information on the incidence, clinical course, pathology, pathogenesis, diagnosis, and treatment of rheumatoid vasculitis (RV), including the still scanty data on the use of biologics.

METHODS

PubMed and MEDLINE databases (1950-2006) were searched for the key words "vasculitis" and "rheumatoid arthritis"; and "rheumatoid arthritis" and "extra-articular manifestations." All relevant articles in English and French were reviewed. Additional words used in follow-up research include "anti-TNF," "rituximab," "IL-1 receptor antagonists," and "CTLA-4 Ig," all in conjunction with "vasculitis." Pertinent secondary references were also retrieved.

RESULTS

RV is an inflammatory condition of the small- and medium-sized vessels that affects a subset of patients with established rheumatoid arthritis (RA) (approximately 1 to approximately 5%). It has a vast array of clinical manifestations with a predilection for the skin (peripheral gangrene, deep cutaneous ulcers) and the peripheral nervous system (mononeuritis multiplex). Because of the lack of specific signs and symptoms, the diagnosis relies on the exclusion of other causes of similar lesions (diabetes, atherosclerosis, drug reactions, infection, neoplasias) and, ideally, on the histopathological demonstration of necrotizing vasculitis. Despite the availability of a host of promising new drugs for the treatment of RA, no clinical trials have tested their efficacy in RV; therefore, its management remains largely empirical.

CONCLUSIONS

Although RV has apparently been decreasing over the last 2 decades, possibly as a consequence of the more energetic approach to the management of RA currently used, it remains an important complication of RA that needs to be promptly recognized and treated.

Genetics of autoimmune diseases--disorders of immune homeostasis

In the past few years, our extensive knowledge of the mammalian immune system and our increasing ability to understand the genetic causes of complex human disease have opened a window onto the pathways that lead to autoimmune disorders. In addition to the well-established role of genetic variation that affects the major histocompatibility complex, a number of rare and common variants that affect a range of immunological pathways are now known to have important influences on the phenotypic diversity that is seen among autoimmune diseases. Recent studies have also highlighted a previously unanticipated interplay between the innate and adaptive immune system, providing a new direction for research in this field.

Biologic therapies in rheumatology: lessons learned, future directions

During the past decade biologic therapies such as monoclonal antibodies and fusion proteins have revolutionized the management of rheumatic disease. By targeting key cytokines and immune cells biologics have provided more specific therapeutic interventions with less immunosuppression. Clinical use, however, has revealed that their theoretical simplicity hides a more complex reality. Efficacy, toxicity and even pharmacodynamic effects can deviate from those predicted, as poignantly illustrated by the catastrophic effects witnessed during the first-into-human administration of TGN1412. This review summarizes lessons gleaned from practical experience and discusses how these can inform future discovery and development of new biologic therapies for rheumatology.

Association of smoking with the constitution of the anti–cyclic citrullinated peptide response in the absence of HLA–DRB1 shared epitope alleles

OBJECTIVE

Smoking is a risk factor for anti-cyclic citrullinated peptide (anti-CCP) antibody-positive rheumatoid arthritis (RA) in patients with HLA-DRB1 shared epitope (SE) alleles. It is unknown whether smoking influences not only the presence of these antibodies, but also other characteristics of the anti-CCP response, such as isotype usage. The aim of this study was to determine the influence of smoking on anti-CCP isotypes in RA patients, and to determine whether this influence is observed in the presence and/or absence of SE alleles.

METHODS

IgA, IgM, and IgG subclasses of anti-CCP antibodies were measured by enzyme-linked immunosorbent assay in serum obtained at the first visit to the Leiden Early Arthritis Clinic from 216 patients with anti-CCP-positive RA whose smoking habits were also assessed. HLA genotyping data were available for 202 of these patients.

RESULTS

IgA and IgM anti-CCP were more frequent in RA patients who were smokers than in those who were nonsmokers (odds ratio 2.8 and 1.8, respectively). In addition, levels of all isotypes of anti-CCP, except IgG3, were significantly higher (P < 0.05) in smokers. The number of anti-CCP isotypes was higher in smokers compared with nonsmokers, both in SE-negative RA (P = 0.04) and in SE-positive RA (P = 0.07).

CONCLUSION

Patients with anti-CCP-positive RA who have a current or former tobacco exposure display a more extensive anti-CCP isotype usage in general, and IgA and IgM in particular, compared with patients with anti-CCP-positive RA who have never smoked. In contrast to its influence on the incidence of anti-CCP positivity, the influence of tobacco exposure on the constitution of the anti-CCP response is significant in SE-negative RA. These findings suggest a differential effect of tobacco exposure on the induction as compared with the propagation of the anti-CCP antibody response.

Biologic treatment of rheumatoid arthritis and the risk of malignancy: Analyses from a large US observational study

OBJECTIVE

Induction of malignancy is a major concern when rheumatoid arthritis (RA) is treated with biologic therapy. A meta-analysis of RA biologic clinical trials found a general increased risk of malignancy, but this risk was not found in a large observational study. We undertook this study to assess the risk of malignancy among biologic-treated patients in a large US observational database.

METHODS

We studied incident cases of cancer among 13,001 patients during approximately 49,000 patient-years of observation in the years 1998-2005. Cancer rates were compared with population rates using the US National Cancer Institute SEER (Surveillance, Epidemiology, and End-Results) database. Assessment of the risk of biologic therapy utilized conditional logistic regression to calculate odds ratios (ORs) as estimates of the relative risk, further adjusted for 6 confounders: age, sex, education level, smoking history, RA severity, and prednisone use.

RESULTS

Biologic exposure was 49%. There were 623 incident cases of nonmelanotic skin cancer and 537 other cancers. The standardized incidence ratios and 95% confidence intervals (95% CIs) compared with SEER data were as follows: all cancers 1.0 (1.0-1.1), breast 0.8 (0.6-0.9), colon 0.5 (0.4-0.6), lung 1.2 (1.0-1.4), lymphoma 1.7 (1.3-2.2). Biologics were associated with an increased risk of nonmelanotic skin cancer (OR 1.5, 95% CI 1.2-1.8) and melanoma (OR 2.3, 95% CI 0.9-5.4). No other malignancy was associated with biologic use; the OR (overall risk) of any cancer was 1.0 (95% CI 0.8-1.2).

CONCLUSION

Biologic therapy is associated with increased risk for skin cancers, but not for solid tumors or lymphoproliferative malignancies. These associations were consistent across different biologic therapies.

Smoking as a trigger for inflammatory rheumatic diseases

PURPOSE OF REVIEW

This review has two purposes: to describe the known effects of cigarette smoking on the development of inflammatory rheumatic diseases, in particular rheumatoid arthritis and systemic lupus erythematosus, and to review recent research aimed at understanding the mechanisms by which smoking may interact with genes and immunity in triggering these diseases.

RECENT FINDINGS

Large case-control studies as well as cohort studies have demonstrated that cigarette smoking is a risk factor for RF positive and anti-citrulline antibody with rheumatoid arthritis and that the risk diminishes only several years after cessation of smoking. Evidence exists that smoking is a risk factor also for systemic lupus erythematosus, and that the risk may be related to the presence of anti-dsDNA antibodies. Mechanistic studies are reviewed that suggest that smoking can trigger specific and potentially disease-inducing immune reactions against citrullinated proteins in rheumatoid arthritis, and dsDNA in systemic lupus erythematosus, and it is suggested that the genetic context determines which immune reactions may be triggered by smoking.

SUMMARY

Counselling against smoking should be mandatory in rheumatological practice both to patients and to their relatives. Studies on the mechanisms whereby smoking triggers rheumatoid arthritis and systemic lupus erythematosus may provide fundamental new knowledge about the cause and molecular pathogenesis of these diseases.

Recent advances in the genetics of rheumatoid arthritis

Recent progress in defining the role of genetic factors in rheumatoid arthritis (RA) has been remarkable. Anticyclic citrullinated peptide (anti-CCP) antibody-positive disease appears to be immunogenetically distinct from anti-CCP-negative disease, with the former subgroup primarily responsible for association and linkage with the HLA-DRB1 shared epitope (SE). There is preliminary evidence that non-HLA genes contribute differentially to anti-CCP-positive and negative disease. The phenotypic differences evident in anti-CCP-positive and negative disease suggest a need to reclassify RA based on the presence or absence of this autoantibody. Some recent work also suggests marked interactions between cigarette smoking, anti-CCP antibodies, and the SE, though these relationships may vary across populations. Lastly, a recent single nucleotide polymorphism-based genome-wide linkage analysis of multicase RA families revealed novel genomic regions that likely contain genes that predispose to RA or more specific phenotypes.

Metabolic disorders in patients with psoriasis and psoriatic arthritis

Psoriasis is one of the common complex disorders in Western world, affecting 2% to 3% of the population. Recent studies indicate that psoriasis is associated with an increased risk of comorbidity and mortality compared to the general population. It appears that patients with psoriasis have a higher prevalence of metabolic disorders such as diabetes, hypertension, obesity, and hyperlipidemia, as well as a higher frequency of cigarette smoking. These concomitant diseases can complicate the treatment of psoriasis. Even though the etiology of these associations is elusive, physicians should be aware of them and take active steps to reduce the risk profiles of patients with psoriasis and psoriatic arthritis, in order to lessen mortality and comorbidity.

Influence of male sex on disease phenotype in familial rheumatoid arthritis

OBJECTIVE

To examine sex differences in clinical, demographic, and genetic characteristics among a large cohort of patients with familial rheumatoid arthritis (RA).

METHODS

We studied 1,004 affected members of 467 Caucasian multicase RA families recruited from the North American Rheumatoid Arthritis Consortium. Standardized information about demographic and clinical characteristics was collected from all patients. Affected individuals also underwent radiography of the hands and were genotyped for markers in the HLA region. Sex differences were assessed using contingency table analysis (for categorical variables) and Student's t-tests for (continuous variables), and by multivariate logistic and linear regression analysis.

RESULTS

Male patients had a significantly later onset of RA, were more likely to be seropositive for RF, and had significantly higher titers of anti-cyclic citrullinated peptide (anti-CCP) antibodies compared with female patients, even after adjustment for covariates in multivariate analyses. Male patients were also significantly more likely to have a history of smoking and to be HLA-DRB1 shared epitope (SE) positive. Interestingly, female patients with an affected male sibling had significantly higher titers of anti-CCP antibodies and were more likely to be SE positive compared with female patients without affected male siblings. Multivariate analyses indicated that the presence of the SE did not fully explain the increased anti-CCP antibody titers observed in these families.

CONCLUSION

Sex has an important influence on the disease phenotype in RA, including the age at disease onset and autoantibody production. Furthermore, families with affected male members are characterized by higher titers of autoantibodies, particularly anti-CCP antibodies. Our results indicate that these findings are not fully explained by differences in exposure to tobacco smoke, presence of the HLA-DRB1 SE, or other HLA region genetic variation. Thus, other genetic or nongenetic factors also contribute to sex differences in the RA phenotype.

Mechanisms of disease: Genetic susceptibility and environmental triggers in the development of rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex disease in which environmental agents are thought to interact with genetic factors that influence susceptibility. This interaction triggers immunologic events that eventually result in the clinical signs of arthritis. Knowledge of the chain of etiological events that lead to the development of RA is incomplete. In this review, we describe the experimental approaches that are used to address the issue of gene-environment interactions in the etiology of RA, and discuss relevant examples of such interactions. We focus on how smoking, the best-known environmental risk factor for RA, interacts with HLA-DR shared epitope genes, the main genetic risk factors for RA, and result in a high risk of RA in individuals exposed to both of these risk factors. From these and other related findings, we can begin to define the distinct environmental risk factors (such as smoking) that in certain genetic contexts (for example, the presence of HLA-DR shared epitope alleles) can trigger immune reactions (such as autoantibodies to citrullinated peptides) many years before onset of RA, and consider how these immune reactions might contribute to clinical symptoms in a subset of affected patients. Increased knowledge about these and other events involved in the development of RA should enable the design of new tools for suppressing RA pathogenesis before the onset of disease.

Genes, environment and immunity in the development of rheumatoid arthritis

The combined role of genes, environment and immunity in the development of rheumatoid arthritis (RA) has been the subject of recent investigations. New data support a gene-environment interaction between smoking and the MHC class II HLA-DRB1 shared epitope (SE) genes in anti-citrulline antibody (anti-CP(+)) RA but not in anti-CP(-) disease. These data from genetic epidemiology, together with information on citrullination in the lungs of smokers, have prompted the formulation of a new etiological hypothesis for anti-CP(+) RA, suggesting that smoking in the context of HLA-DR SE might trigger immunity to citrulline-modified proteins and that this immunity, after several years, might cause arthritis.

What does the immunogenetic basis of rheumatoid arthritis teach us about the immunobiology of the disease?

Rheumatoid arthritis is a chronic inflammatory autoimmune disease in which, although the exact etiology is unknown, the contribution from genetic factors is approximately 60%. major histocompatibility complex alleles make the largest contribution to this genetic effect. The remainder is probably made up of an, as yet undefined, number of genes ( approximately 50-200) with low disease penetrance. Recent advances in genetic technology are now enabling us to start to identify some of these more moderate risk-conferring candidate genes. Evidence from functional studies of such genes is beginning to provide insight into the exact nature of the pathways and processes involved in disease susceptibility and expression. In this review, we will discuss how a growing number of genetic polymorphisms might underpin the immunological and molecular anomalies characteristic of rheumatoid arthritis. Specifically, we will focus on one particular pathway, T-cell activation, with an emphasis on the genetic polymorphism that influences antigen presentation and recognition in antigen-presenting cells, as well as those genes that influence the thresholds of antigen-receptor signaling in T lymphocytes.

Prediction models for rheumatoid arthritis during diagnostic investigation: evaluation of combinations of rheumatoid factor, anti-citrullinated protein/peptide antibodies and the human leucocyte antigen-shared epitope

OBJECTIVES

To calculate the probabilities for rheumatoid arthritis in a consecutive cohort of patients during diagnostic investigation. Different logistic regression models evaluating the value of human leucocyte antigen (HLA)-shared epitope determination and testing for rheumatoid factor and anti-citrullinated protein/peptide antibodies (ACPA) were fitted.

METHODS

1003 consecutive patients were included in the study, presenting a new diagnostic problem for which rheumatoid arthritis was included in the differential diagnosis. All patients were tested for ACPA, rheumatoid factor and HLA-shared epitope.

RESULTS

After 1 year, diagnoses were established: 153 patients had definite rheumatoid arthritis and 629 patients had rheumatoid arthritis excluded. Rheumatoid factor, used as a continuous marker, is useful in evaluating the probability for rheumatoid arthritis. Combined rheumatoid factor and shared epitope testing may provide additional predictive information, but combined ACPA and rheumatoid factor testing is superior. The redundancy of shared epitope testing in a model that includes ACPA testing can be explained by the high association between ACPA and shared epitope both in patients with rheumatoid arthritis and in those with non-rheumatoid arthritis. The value of rheumatoid factor testing increased if patients presented with at least one swollen joint at baseline.

CONCLUSION

Valid probabilities for rheumatoid arthritis during routine diagnostic investigation were calculated, and showed that the potential additional value of shared epitope testing disappears when ACPA testing is available. Combined rheumatoid factor and ACPA testing is useful, especially when rheumatoid factor is considered as a continuous parameter reflecting an increasing probability for rheumatoid arthritis at higher rheumatoid factor titres. The value of (continuous) rheumatoid factor testing increases when the a priori chance is higher.

From ubiquitous antigens to joint-specific inflammation: could local vascular permeability be the missing link?

The mechanisms underlying organ-specific autoimmune diseases are incompletely understood. In particular, it is still unclear how autoantibodies, often against ubiquitous antigens, can cause pathology preferentially in certain tissues. Recently, Binstadt and colleagues, using observations in the K/BxN murine arthritis model, suggested novel pathways underlying the site-specific localization of inflammation driven by immune complexes. In this commentary, we discuss these findings, the problems related to their general applicability and the implications for future research.

Validation of the reshaped shared epitope HLA-DRB1 classification in rheumatoid arthritis

Recently, we proposed a classification of HLA-DRB1 alleles that reshapes the shared epitope hypothesis in rheumatoid arthritis (RA); according to this model, RA is associated with the RAA shared epitope sequence (72–74 positions) and the association is modulated by the amino acids at positions 70 and 71, resulting in six genotypes with different RA risks. This was the first model to take into account the association between the HLA-DRB1 gene and RA, and linkage data for that gene. In the present study we tested this classification for validity in an independent sample. A new sample of the same size and population (100 RA French Caucasian families) was genotyped for the HLA-DRB1 gene. The alleles were grouped as proposed in the new classification: S₁ alleles for the sequences A-RAA or E-RAA; S₂ for Q or D-K-RAA; S_3D for D-R-RAA; S_3P for Q or R-R-RAA; and X alleles for no RAA sequence. Transmission of the alleles was investigated. Genotype odds ratio (OR) calculations were performed through conditional logistic regression, and we tested the homogeneity of these ORs with those of the 100 first trio families (one case and both parents) previously reported. As previously observed, the S₂ and S_3P alleles were significantly over-transmitted and the S₁, S_3D and X alleles were under-transmitted. The latter were grouped as L alleles, resulting in the same three-allele classification. The risk hierarchy of the six derived genotypes was the same: (by decreasing OR and with L/L being the reference genotype) S₂/S_3P, S₂/S₂, S_3P/S_3P, S₂/L and S_3P/L. The homogeneity test between the ORs of the initial and the replication samples revealed no significant differences. The new classification was therefore considered validated, and both samples were pooled to provide improved estimates of RA risk genotypes from the highest (S₂/S_3P [OR 22.2, 95% confidence interval 9.9–49.7]) to the lowest (S_3P/L [OR 4.4, 95% confidence interval 2.3–8.4]).

HLA and RA revisited: citrullinated food for the SE hypothesis, the DR6 effect, and NIMA

An obvious way to unravel the apparently complex association between human leukocyte antigen (HLA) and rheumatoid arthritis (RA) is to reduce the heterogeneity of this multifactorial disease. Recently we have discovered that shared epitope (SE)-positive HLA-DRB1 alleles are exclusively associated with a subgroup of RA patients that test positive for auto-antibodies against cyclic citrullinated peptides. Further studies suggested that SE-positive alleles are classical immune response genes for the development of these antibodies. On the basis of these and other data we formulated a two-hit model for the pathogenesis of RA which incorporates a novel "citrullinated" SE hypothesis. About 5 years ago Zanelli et al. reported that HLA-DR6 (*1301 and *1302) and some other DR alleles that share the DERAA-sequence on amino acids 70-74 of their third hypervariable region are associated with protection from (severe) RA. Recently we corroborated these data in a large prospective cohort study and demonstrated that protection was observed both in the presence and in the absence of a SE susceptibility allele on the other haplotype. Finally we review the state of the art of the association of noninherited maternal HLA antigens with both susceptibility to and protection from RA.

Citrullination: a posttranslational modification in health and disease

Posttranslational modifications are chemical changes to proteins that take place after synthesis. One such modification, peptidylarginine to peptidylcitrulline conversion, catalysed by peptidylarginine deiminases, has recently received significant interest in biomedicine. Introduction of citrulline dramatically changes the structure and function of proteins. It has been implicated in several physiological and pathological processes. Physiological processes include epithelial terminal differentiation, gene expression regulation, and apoptosis. Rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease are examples of human diseases where protein citrullination involvement has been demonstrated. In this review, we discuss our current understanding on the importance of protein deimination in these processes. We describe the enzymes catalyzing the reaction, as well as their known protein substrates. We review the citrullinated peptide epitopes that are proposed as disease markers, specifically recognized in certain human autoimmune disorders. The potential autopathogenic role of citrullinated epitopes is also discussed.

Citrullination is an inflammation-dependent process

OBJECTIVES

To study the presence of citrullinated proteins in inflammatory conditions and in clinically non-affected tissues of controls.

METHODS

Synovial biopsy specimens from 19 patients with rheumatoid arthritis and 10 healthy controls were investigated by immunohistochemistry. Additionally, muscle tissue from 5 patients with polymyositis and from 7 healthy controls, intestinal tissue from macroscopically affected and non-affected areas from 10 patients with inflammatory bowel disease (IBD) and tonsil tissues from 4 chronically inflamed tonsils were studied.

RESULTS

Citrullinated proteins were present in all synovial biopsy specimens from patients with rheumatoid arthritis, whereas only three of 10 healthy synovial biopsy specimens showed scarce amounts of citrullination. Citrullination was also present in all myositis-affected muscles, whereas it was absent in the muscle tissues of controls. All tonsil biopsy specimens studied were positive for citrulline. Even though more frequently detected in the macroscopically affected colonic areas, no marked difference was observed in the pattern or extent of citrullination between the macroscopically affected and non-affected intestinal IBD tissues.

CONCLUSION

Citrullination is present in a wide range of inflammatory tissues, suggesting that this process is inflammation dependent rather than disease dependent.

Activation of nitric oxide signaling by the rheumatoid arthritis shared epitope

OBJECTIVE

Susceptibility to rheumatoid arthritis (RA) is closely associated with HLA-DRB1 alleles encoding a shared epitope (SE) in positions 70-74 of the HLA-DRbeta chain. The mechanistic basis for this association is unknown. Given the proposed pathogenic role of nitric oxide (NO) in RA, this study was undertaken to examine whether the SE can trigger NO signaling events.

METHODS

The intracellular levels of NO were measured with the fluorescent NO probe 4,5-diaminofluorescein diacetate and by the 2,3-diaminonaphthalene method. NO synthase activity was determined by measuring the rate of conversion of radioactive arginine to citrulline. Levels of cGMP were measured with a commercial enzyme-linked immunosorbent assay, and the cytolytic activity of T cells was measured using a standard (51)Cr release assay.

RESULTS

Lymphoblastoid B cell lines carrying SE-positive HLA-DR alleles displayed a higher rate of spontaneous NO production compared with SE-negative cells. L cell transfectants expressing SE-positive DR molecules on their surface also generated higher levels of NO. Tetrameric HLA-DR molecules containing a DRbeta-chain encoded by the SE-positive DRB1*0401 allele stimulated fibroblast cells to produce higher levels of NO compared with cells stimulated with a control HLA-DR tetramer. Multimeric hepatitis B core proteins engineered to express region 65-79 encoded by the DRB1*0401 allele, but not the same region encoded by the control allele DRB1*0402, stimulated NO production in fibroblasts. Similarly, synthetic 15-mer peptides corresponding to the region 65-79 encoded by SE-positive alleles triggered increased NO levels when incubated with class II major histocompatibility complex-negative cells. The signaling pathway was found to involve NO synthase activation, followed by increased production of cGMP. SE-triggered increased NO levels inhibited cytolytic elimination of target cells.

CONCLUSION

The SE can trigger NO-mediated signaling events in opposite cells, and may thereby contribute to RA pathogenesis.

Association between occupational exposure to mineral oil and rheumatoid arthritis: results from the Swedish EIRA case-control study

The aim of the present study was to investigate the association between exposure to mineral oil and the risk of developing rheumatoid arthritis (RA), and in addition to perform a separate analysis on the major subphenotypes for the disease; namely, rheumatoid factor (RF)-positive RA, RF-negative RA, anticitrulline-positive RA and anticitrulline-negative RA, respectively. A population-based case–control study of incident cases of RA was performed among the population aged 18–70 years in a defined area of Sweden during May 1996–December 2003. A case was defined as an individual from the study base who for the first time received a diagnosis of RA according to the American College of Rheumatology criteria of 1987. Controls were randomly selected from the study base with consideration taken for age, gender and residential area. Cases (n = 1,419) and controls (n = 1,674) answered an extensive questionnaire regarding lifestyle factors and occupational exposures, including different types of mineral oils. Sera from cases and controls were investigated for RF and anticitrulline antibodies.

Among men, exposure to any mineral oil was associated with a 30% increased relative risk of developing RA (relative risk = 1.3, 95% confidence interval = 1.0–1.7). When cases were subdivided into RF-positive RA and RF-negative RA, an increased risk was only observed for RF-positive RA (relative risk = 1.4, 95% confidence interval 1.0–2.0). When RA cases were subdivided according to the presence of anticitrulline antibodies, an increased risk associated with exposure to any mineral oil was observed only for anticitrulline-positive RA (relative risk = 1.6, 95% confidence interval = 1.1–2.2). Analysis of the interaction between oil exposure and the presence of HLA-DR shared epitope genes regarding the incidence of RA indicated that the increased risk associated with exposure to mineral oil was not related to the presence of shared epitope genotypes.

In conclusion, our study shows that exposure to mineral oil is associated with an increased risk to develop RF-positive RA and anticitrulline-positive RA, respectively. The findings are of particular interest since the same mineral oils can induce polyarthritis in rats.

Does a positive anti-CCP test identify a distinct arthritis entity?

The introduction of tests recognizing 'anti-citrullinated protein antibodies' (ACPA) has caused a revolution in rheumatology. Immunization against citrullinated proteins is a feature almost unique for rheumatoid arthritis, although ACPA may occur long before the onset of symptoms. Even if the presence of ACPA does not seem to reveal a distinct arthritis phenotype at symptom onset, it predicts an aggressive disease course with unfavourable outcome. Despite the very high diagnostic specificity for rheumatoid arthritis, ACPA-positivity does not always accord with a traditional diagnosis of rheumatoid arthritis at clinical presentation. However, even when these patients are judged to suffer from mild undifferentiated arthritis, they call for follow-up and special attention by rheumatologists.