High resolution linkage and association mapping identifies a novel rheumatoid arthritis susceptibility locus homologous to one linked to two rat models of inflammatory arthritis

Rheumatoid arthritis (RA) is an oligogenic autoimmune disease but, to date, linkage and association to major histocompatibility complex (MHC) has been the only consistent finding in genetic studies. However, MHC is estimated to contribute only 30-40% of the total genetic component to disease susceptibility. Studies in animal models of inflammatory arthritis have identified a number of putative vulnerability loci but the homologous regions in the human genome have not previously been investigated as candidate RA susceptibility loci. We have investigated linkage to five regions homologous to those identified in animal models of inflammatory arthritis in RA affected sibling pair (ASP) families. Linkage to 17q22 syntenic to a susceptibility locus common to two experimental rat models was detected in 200 RA ASP families and replicated in a further 100 RA ASP families. Linkage to additional markers mapping to the area has refined the extent of linkage to a 4 cM region. Association to one of the markers (D17S807) was demonstrated in this cohort using extensions of the transmission disequilibrium test. Association to two 2-marker haplotypes including this marker was detected in an independent cohort of single-case RA families, thus narrowing the region harbouring the aetiological mutation to approximately 1 cM. This is the first time that an arthritis susceptibility locus mapped in experimental animal models of disease has been used to identify a novel RA susceptibility locus in humans. The difficult task of identifying a disease mutation from a linkage result should, in this case at least, be facilitated by the combined use of animal and human based investigations.

Nomenclature for factors of the dog major histocompatibility system (DLA), 2000: second report of the ISAG DLA Nomenclature Committee

The International Society for Animal Genetics (ISAG) Dog Leukocyte Antigen (DLA) Nomenclature Committee met during the "Comparative Evolution of the Mammalian major Histocompatibility Complex (MHC)" meeting in Manchester, UK on 10 September 2000. The main points discussed were the naming of class I genes and alleles, and the inclusion of alleles from other canidae.

A novel 5'-flanking region polymorphism of macrophage migration inhibitory factor is associated with systemic-onset juvenile idiopathic arthritis

OBJECTIVE

To determine if polymorphisms of the macrophage migration inhibitory factor (MIF) gene are associated with systemic-onset juvenile idiopathic arthritis (JIA).

METHODS

Denaturing high-performance liquid chromatography was used to screen for the MIF gene in 32 healthy Caucasian subjects. One hundred seventeen UK Caucasian patients with systemic-onset JIA and 172 unrelated healthy UK Caucasian controls were genotyped for a single-nucleotide polymorphism (SNP) identified in the 5'-flanking region of the gene, using polymerase chain reaction-restriction fragment length analysis.

RESULTS

A G-to-C transition was identified at position -173 of the MIF gene. The presence of a C at -173 creates an activator protein 4 transcription factor binding site. Allele and genotype frequencies differed significantly between the patients and controls for the MIF-173 polymorphism. Individuals possessing a MIF-173*C allele have an increased risk of systemic-onset JIA (36.8% versus 20.3%) (odds ratio 2.3, 95% confidence interval 1.34-3.86; P = 0.0005).

CONCLUSION

This is the first report of a SNP in the MIF gene. This polymorphism is associated with systemic-onset JIA.

Two novel polymorphisms in the human transforming growth factor beta 2 gene

We have identified two novel polymorphisms in the transforming growth factor beta 2 (TGFbeta2) gene; an insertion in the 5'-untranslated region (5'UTR) and a single nucleotide polymorphism (SNP) in exon 1. A 895-bp fragment was analysed covering part of the 5'UTR and exon 1. Single-strand conformation polymorphism (SSCP) analysis of polymerase chain reaction (PCR) products was performed to detect sequence variations. This was followed by the sequencing of samples demonstrating distinct banding patterns. A 4-bp insertion (ACAA) in the 5'UTR and a SNP (G > A) within exon 1 was identified. The 5'UTR polymorphism was found to be common in three Caucasian populations from Spain, Turkey and the UK. Exon 1 polymorphism is rare and results in an R to H amino acid substitution in codon 91. Both polymorphisms may prove useful for investigating possible associations of TGFbeta2 with disease.

What is the natural history of rheumatoid arthritis?

Inflammatory polyarthritis can be a self-limiting disease, develop into rheumatoid arthritis (RA) or differentiate into another form of chronic arthritis. It remains a clinical and scientific challenge to understand the relationship between these phenotypes, determine their aetiologies and predict the course and outcome for individual patients. Even patients labelled as having RA show a wide spectrum of clinical phenotypes. Disease definition is a major problem in studying the aetiology of RA as currently used classification criteria were derived using patients with established disease. RA is thought to result from the combination of genetic susceptibility and exposure to an appropriate environmental trigger. The genetic component is probably oligogenic. The association with HLA has been known for over 25 years. RA is now thought to be associated with a conserved sequence of amino acids in a number of HLA-DRB1 alleles, called the RA shared epitope. However, the shared epitope appears to be associated with RA chronicity and severity more than with susceptibility. Other potential RA susceptibility genes include IL-1, aromatase, corticotropin-releasing hormone and a region on the X chromosome. Hormonal and reproductive factors also influence RA susceptibility and severity. RA is more common in women than men, especially before the menopause. Men may be protected by hormonal factors and require a stronger genetic component to develop disease. Although infectious triggers of RA have long been suspected, no definitive evidence has been obtained. Previous blood transfusion, smoking and obesity are also possible risk factors. Chronicity and remission are important aspects of the natural history of early RA. Although we can identify patients at risk of adverse prognosis with some accuracy, we remain unable to predict remission. Functional disability and radiological damage are the most studied outcomes in RA. Radiological damage often occurs early in the course of RA, but patients may show erosion for the first time several years after symptom onset. Many studies have demonstrated a relationship between HLA and features of severe RA in established patients. This appears to be related to gene dosage.

Nomenclature for factors of the dog major histocompatibility system (DLA), 2000: Second report of the ISAG DLA Nomenclature Committee

The ISAG DLA Nomenclature Committee met during the "Comparative Evolution of the Mammalian MHC" meeting in Manchester, England on 10th September 2000. The main points discussed were the naming of class I genes and alleles, and the inclusion of alleles from other canidae.

Independent association of rheumatoid factor and the HLA-DRB1 shared epitope with radiographic outcome in rheumatoid arthritis

OBJECTIVE

Findings of a recent study suggested that HLA-DRB1 alleles encoding the rheumatoid arthritis (RA) "shared epitope" (SE) were not predictive of erosive damage at 2 years in patients with early inflammatory arthritis who were rheumatoid factor (RF) positive, but were predictive in those who were RF negative. The present study was undertaken to determine whether RF status was also important in the association between the SE and radiographic outcome in patients with longstanding RA.

METHODS

The association between radiographic outcome, HLA-DRBI, and RF status was examined in 299 RA patients with established disease (5-30 years). Radiographic outcome was measured by scoring radiographs of the hands and feet using the standard radiographs of Larsen. HLA-DRB1 typing was performed using polymerase chain reaction methodology. Results were stratified by RF status and analyzed by multiple regression.

RESULTS

An association between radiographic severity and the SE was found in RF-, but not RF+, patients. RF- patients carrying an SE allele had higher Larsen scores than RF- patients lacking the SE, although there was no association with SE dosage. The mean Larsen score was significantly higher in RF+ patients than in RF- patients, but there were no differences between RF+ patients with 0, 1, or 2 SE alleles. Multiple regression analysis confirmed independent associations of RF and SE positivity with radiographic outcome. No significant associations were found between RF and the SE, or RF and individual SE alleles.

CONCLUSION

Our data indicate that RF and the SE are independently associated with radiographic outcome in RA. In RF+ patients with longstanding RA, there is no apparent association between the presence of the SE and radiographic damage. However, in RF-patients, although radiographic outcome is generally less severe, there is an association between severity and presence of the SE.

Lack of association between intercellular adhesion molecule-1 gene polymorphisms and giant cell arteritis

OBJECTIVE

Studies have shown an association between HLA-DRB1*04 and giant cell arteritis (GCA). Intercellular adhesion molecule-1 (ICAM-1) gene polymorphisms were reported to contribute susceptibility to GCA in Italian patients where susceptibility to GCA is not associated with HLA-DRB1*04 alleles. ICAM-1 is also highly expressed within inflammatory infiltrates of the blood vessels of GCA patients. To investigate the clinical implications of ICAM-1 polymorphisms in GCA, we examined their potential association and influence in the development of visual ischemic complications in a series of patients with GCA from Northwest Spain where GCA susceptibility is associated with HLA-DRB1*04.

METHODS

Fifty-eight biopsy proven GCA and 129 ethnically matched controls were studied. Patients and controls were genotyped for ICAM-1 polymorphism at codons 241 and 469 by PCR-RFLP.

RESULTS

The distribution of the alleles and genotypes for each ICAM- polymorphism did not show significant differences between GCA patients and controls. Although visual manifestations were significantly more likely to occur in men than women (OR 5.2, p = 0.018), allele and genotype frequencies of ICAM-1 polymorphisms in patients with GCA were not associated with development of visual complications or anemia. Visual complications in GCA were primarily associated with carriage of an HLA-DRB1*04 allele. No evidence was found for interaction between HLA-DRB1*04 and ICAM-1 polymorphism.

CONCLUSION

ICAM-1 polymorphisms are not genetic risk factors for the susceptibility and severity of GCA in Northwest Spain.

HLA-DRB1*01 association with Henoch-Schönlein purpura in patients from northwest Spain

OBJECTIVE

To examine the HLA-DRB1 phenotypes of patients with Henoch-Schönlein purpura (HSP) and determine if associations exist with disease susceptibility, clinical heterogeneity, or severe systemic complications.

METHODS

A retrospective study was performed on an unselected population of patients from Northwest Spain with HSP classified according to proposed criteria. Patients were included in this study if they had at least one year of followup. Fifty Caucasian patients (25 women), 11 of them older than 20 years, were studied. Patients and ethnically matched controls were HLA-DRB1 genotyped from DNA using molecular based methods.

RESULTS

During the course of the disease, renal manifestations, especially hematuria, and severe gastrointestinal (GI) manifestations (bowel angina or GI bleeding) were observed in more than 60% of the patients. Twenty percent of patients had persistent renal involvement (renal sequelae). Patients with HSP had a significantly higher frequency of the HLA-DRB1*01 phenotype compared to matched controls. The HLA-DRB1*07 phenotype was also significantly reduced compared with controls. Patients with severe GI manifestations or with persistent renal involvement did not exhibit any specific HLA-DRB1 association other than the underlying association with HLA-DRB1*01.

CONCLUSION

HSP in a population from Northwest Spain is significantly associated with HLA-DRB1*01.

Polymorphism at codon 469 of the intercellular adhesion molecule-1 locus is associated with protection against severe gastrointestinal complications in Henoch-Schönlein purpura

OBJECTIVE

Henoch-Schonlein purpura (HSP) is a small sized vasculitis affecting mainly children. Intercellular adhesion molecule-1 (ICAM-1) gene polymorphisms have recently been implicated in the susceptibility to some vasculitides. To further investigate the clinical implication of ICAM-1 polymorphisms in HSP, we examined their potential association and influence in the development of severe complications in an unselected series of patients with HSP.

METHODS

Fifty-two patients, of which 41 were children, were diagnosed with HSP using classification criteria of Michel, et al at the Hospital Xeral-Calde (Lugo, Spain); 129 ethnically matched controls were included. Patients had at least one year of followup. Patients and controls were genotyped by allelic oligonucleotide techniques for ICAM-I polymorphism at codon 241 and 469.

RESULTS

The frequency distribution of the alleles and genotypes for each ICAM-1 polymorphism did not show significant differences between HSP patients and controls. Also, no differences between patients with or without renal manifestations were found. However, the frequency of the codon 469 K/E genotype was significantly decreased in patients without severe gastrointestinal manifestations compared to those with them (22.29 vs 65%, OR 0.1, p = 0.02, after correction for age, sex, and disease duration). None of the 11 adults exhibited the R/G genotype at codon 241 compared with 7 of 41 children (OR 0.0, 95% CI 0.0-2.9, p = 0.14). Patients with the R/G genotype were associated with low incidence of renal manifestations and none developed permanent renal involvement (renal sequelae); however, this finding did not achieve statistical significance.

CONCLUSION

ICAM-1 polymorphisms alone are not associated with development of HSP, but patients not carrying the codon 469 K/E genotype are at decreased risk of developing severe gastrointestinal complications. The R/G polymorphism at codon 241 may reduce the risk of renal sequelae in the development of HSP in adulthood.

Novel IFN-alpha receptor promoter polymorphisms

We have identified two single nucleotide polymorphisms and one dinucleotide microsatellite within the promoter region of the interferon-alpha receptor gene (IFNAR, GenBank accession number X60459). Allele frequencies in a Caucasian population were established using PCR-RFLP for the two SNPs and semi-automated genotyping for the microsatellite.

HLA-DRB1 and disease outcome in multiple sclerosis

The association between susceptibility to multiple sclerosis (MS) and the class II MHC allele HLA-DRB1*15 is well established although a possible relationship between this allele and outcome in MS is less clear. HLA-DRB1 typing was performed on 375 unrelated white patients with clinically definite MS and on 367 healthy controls. Putative associations of the gene with outcome were examined by dividing patients into two groups: those with an EDSS of 0-5.5 (mild/moderate disease) and those with an EDSS of 6-10 (severe disease). In order to minimise the effects of disease variability patients with a disease duration of at least 10 years or 15 years were examined. As subsidiary HLA-DRB1*03 and HLA-DRB1*04 associations have been previously reported, the effect of these alleles was also examined. As expected, HLA-DRB1*15 was found more frequently in patients than in controls (P < 0.000001). HLA-DRB1*15 positive patients had a significantly earlier age at onset than HLA-DRB1*15 negative patients. No significant associations were noted between HLA-DRB1*15 and outcome in the total patient group or in patients with a disease duration of 10 years or longer. In patients with a disease duration of at least 15 years HLA-DRB1*15 negative status was associated with a worse prognosis, although this did not remain significant after correction for multiple testing. It is thus likely that the contribution of HLA in MS is primarily towards onset and initial triggering mechanisms rather than influencing disease progression, chronicity and severity.

Cytokine gene polymorphisms and susceptibility to juvenile idiopathic arthritis. British Paediatric Rheumatology Study Group

OBJECTIVE

To investigate the involvement of candidate cytokine genes in the pathogenesis of juvenile idiopathic arthritis (JIA).

METHODS

Single nucleotide polymorphisms and intragenic microsatellite markers within 8 candidate cytokine genes (interleukin-1alpha [IL-1alpha], IL-2, IL-4, IL-6, IL-10, interferon-alpha1 [IFNA1], interferon-gamma [IFNG], and interferon regulatory factor 1 [IRF-1]) were investigated in 417 Caucasian patients with clinically characterized JIA and a panel of 276 unrelated, healthy Caucasian controls, all from the United Kingdom.

RESULTS

A novel 3'-untranslated region (3'UTR) polymorphism in IRF-1 was found to be associated with susceptibility to JIA (corrected P = 0.002). No significant association with IL-1alpha, IL-2, IL-4, IL-6, IL-10, IFNA1, or IFNG was observed.

CONCLUSION

An association between JIA and a previously unreported 3'UTR polymorphism of IRF-1 was observed. This association was not found to be specific to any particular JIA subgroup. This suggests that IRF-1 may contribute to a common pathogenesis shared by all JIA patients, regardless of clinical phenotype. This is most likely to be a genetic contribution to the chronic inflammatory process that underlies JIA pathology.

HLA-DRB1 alleles encoding an aspartic acid at position 70 protect against development of rheumatoid arthritis

OBJECTIVE

To determine whether the association between rheumatoid arthritis (RA) and HLA-DRB1 is influenced by the amino acid residue encoded at position 70 (beta70) of the third hypervariable region (HVR3) of the HLA-DRbeta chain.

METHODS

The frequencies of HLA-DRB1 alleles encoding different amino acid residues at beta70 were compared between patients with RA and controls in a population from the UK and in a confirmatory population from northwestern Spain. HLA-DRB1 typing was done by polymerase chain reaction methods on 476 clinic based patients with RA and 180 healthy controls from Staffordshire and Cheshire in the UK, and on 179 clinic patients and 145 controls from Lugo, Spain. Associations were investigated using chi-square analyses and regression analyses. The extended Mantel-Haenszel procedure was used for trend analysis.

RESULTS

Carriage of 2 shared epitope (SE)+ alleles encoding a glutamine at beta70 (Q70SE+/Q70SE+) was associated with the greatest risk of RA in the UK and Spanish population (odds ratios 7.93 and 4.66, respectively), while possession of 2 SE- alleles encoding an aspartic acid at beta70 (D70SE-D70SE-) was associated with the lowest risk (OR 0.23 and 0.34, respectively). In individuals carrying one SE+ allele and an accompanying D70SE- allele there was no increased risk of developing RA [OR 0.93 (UK) and 1.30 (Spain)]. Possession of D70SE- was more strongly protective than possession of Q70SE. Analysis of trend indicated that the strength of association of different DRB1 genotypes with RA could be ranked in order (from Q70SE+/Q70SE+ to D70SE-/D70SE-) according to which amino acid residues were encoded at beta70, and whether or not they formed part of a SE sequence. The severity of radiographic damage could not be ranked in the same fashion.

CONCLUSION

The amino acid residue at position 70 of the HVR3 in HLA-DRbeta molecules influences susceptibility to RA. The strength of the association of DRB1 genotypes with RA is dependent not only on SE status, but also on which amino acid residues are encoded at beta70 of the DRB1 alleles. Presence of an aspartic acid residue at beta70 protects against development of RA. However, the severity of erosive damage does not appear to be associated with the amino acid substitution at 1370.

Association between rheumatoid arthritis and polymorphism of tumor necrosis factor receptor II, but not tumor necrosis factor receptor I, in Caucasians

OBJECTIVE

Tumor necrosis factor (TNF) is a powerful mediator of inflammation in rheumatoid arthritis (RA). In vivo, its acute effects are limited by binding to soluble receptors (TNFR), suggesting that TNFR genes could be important candidate risk factors. The present study was undertaken to investigate association of polymorphisms of TNFRI and TNFRII with RA in subjects in the UK.

METHODS

Unrelated Caucasian RA patients (n = 291) and healthy Caucasian controls (n = 143) were genotyped for A/G polymorphism in exon 1 of TNFRI. From this sample, 240 of the patients and 137 controls were also typed for a single-nucleotide polymorphism (SNP) in exon 6 of the TNFRII gene. In followup studies, DNA samples from UK Caucasian RA patients with a positive family history (n = 149) and UK Caucasian patients with sporadic RA (n = 208) were also typed for the exon 6 TNFRII polymorphism.

RESULTS

TNFRI polymorphism was not associated with RA (odds ratio [OR] for GG genotype 0.93, 95% confidence interval [95% CI] 0.54-1.60). For TNFRII, in the initial study group, patients with RA were significantly more likely to be positive for both the G allele and GG genotype than were controls (OR for GG genotype 2.55, 95% CI 1.11-5.86). The association appeared to be confined to those with a family history of RA. This finding was replicated in an independent cohort of patients with familial RA.

CONCLUSION

The results of this study provide evidence of association between an SNP in the TNFRII gene and RA, the strongest association being observed in patients with a family history. No evidence of association between RA and TNFRI was demonstrated.

Linkage of rheumatoid arthritis to insulin-dependent diabetes mellitus loci: evidence supporting a hypothesis for the existence of common autoimmune susceptibility loci

OBJECTIVE

To seek potential autoimmune disease susceptibility loci by testing for linkage and linkage disequilibrium between insulin-dependent diabetes mellitus (IDDM) susceptibility loci and rheumatoid arthritis (RA).

METHODS

Five IDDM susceptibility loci map to 2 chromosomal regions, chromosome 2q31-34 (IDDM7, 12, and 13) and chromosome 6q25-27 (IDDM5 and 8). Microsatellite markers within these regions were genotyped in 255 RA families, by fluorescence-based genotyping technology. Evidence for linkage disequilibrium was assessed using the extended transmission disequilibrium test (ETDT) program.

RESULTS

With the ETDT, we found evidence for linkage disequilibrium of the marker D6S446, at IDDM8, with RA (P < 0.0001). There was additional evidence for linkage disequilibrium with 2 markers at IDDMS (D6S311 and D6S440) (P = 0.016 and P = 0.017, respectively). There was no evidence for significant linkage disequilibrium of RA with any markers at IDDM7, 12, or 13.

CONCLUSION

These results support the hypothesis that there are autoimmune disease genes at IDDM5 and IDDM8.

Chemokine RANTES promoter polymorphism affects risk of both HIV infection and disease progression in the Multicenter AIDS Cohort Study

OBJECTIVE

To examine whether polymorphism in the RANTES gene is associated with HIV disease outcome.

DESIGN

RANTES, a ligand of the major HIV co-receptor, CCR5, is known to block HIV-CCR5 interactions. Recently, two single nucleotide polymorphisms in the RANTES gene promoter region, designated -403G/A and -28C/G, have been described. Both polymorphisms can affect in-vitro promoter activity, and the RANTES -403A, -28G haplotype has been associated with a slower CD4 cell count decline rate in a Japanese cohort.

METHODS

We compared RANTES compound genotype frequencies between HIV-positive and exposed-uninfected participants of the Multicenter AIDS Cohort Study (MACS) and rates of progression to AIDS for MACS seroconverters.

RESULTS

We found that the two most common RANTES promoter compound genotypes, G1 (-403G/G, -28C/C) found in 67% of Caucasians, and G4 (-403G/A, -28C/C) found in 23% of Caucasians, were associated with altered risk of HIV transmission and progression, particularly in individuals who lacked the protective CCR5 mutation, CCR5delta32. In this study, individuals with a G4 compound genotype were more likely to acquire HIV than individuals with a G1 compound genotype (OR 1.72, P = 0.016) and the risk increased when individuals possessing CCR5delta32 were omitted from consideration (OR 2.13, P = 0.005). Among seroconverters lacking CCR5delta32, those who had the G4 compound genotype progressed significantly slower to AIDS-1993 than those with the G1 compound genotype (median time to AIDS 7.6 versus 5.4 years; RH 0.65; P = 0.007).

CONCLUSIONS

These data implicate the RANTES-403A allele as a risk factor for HIV transmission and as a protective factor for HIV progression.

Association of markers for TGFbeta3, TGFbeta2 and TIMP1 with systemic sclerosis

OBJECTIVES

To investigate whether six microsatellite markers known to map closely to genes involved in fibrosis are associated with systemic sclerosis (SSc).

METHODS

Markers mapping to TGFbeta1, TGFbeta2, TGFbeta3, PDGFB, TIMP1 and COL5A2 were genotyped and allele frequency distributions compared in 191 patients and 196 controls. As TIMP1 maps to the X chromosome, male and females were analysed separately. Markers associated with SSc were further investigated according to whether patients had limited (lcSSc) or diffuse (dcSSc) cutaneous fibrosis.

RESULTS

Associations were found between SSc and markers for TGFbeta3 (chi(2)=17.3, df=8, P=0.02), TGFbeta2 (chi(2)=25.2, df=13, P=0.02) and TIMP1 (with male SSc, chi(2)=11.9, df=5, P=0.03), between lcSSc and the TGFss2 marker (chi(2)=25.6, df=13, P=0.02), and between dcSSc and TGFbeta3 marker (chi(2)=27.1, df=8, P=0.001). Between lcSSc and dcSSc patients, the allele frequency distribution differed only for the TGFbeta3 marker (chi(2)=16.5, df=6, P=0.01).

CONCLUSION

These associations indicate a possible role for TGFbeta3, TGFbeta2 and TIMP1 in genetic susceptibility to SSc and for TGFbeta3 in determining the degree of cutaneous fibrosis.

The -403 G-->A promoter polymorphism in the RANTES gene is associated with atopy and asthma

Asthma is a complex inflammatory condition often associated with bronchial hyperreactivity and atopy. Genetic and environmental factors are implicated and several candidate genes have been implicated. Of these, the chemokine RANTES is responsible for the recruitment of inflammatory cells such as eosinophils and T-lymphocytes. We have recently identified a polymorphism within the RANTES promoter (-403 G-->A) and have examined its role, using a PCR-RFLP assay, in the development of atopy and asthma in 201 Caucasian subjects. Atopic status was determined using skin prick testing and serum IgE levels. Severity of airway dysfunction was assessed using spirometric measurement (FEV1) and methacholine challenge (PC20). The -403 A allele was associated with an increased susceptibility to both atopy and asthma. Thus, the proportion of subjects carrying this allele was higher in each of atopic non-asthmatics, non-atopic asthmatics and atopic asthmatics compared with non-atopic, non-asthmatic controls. In particular, this allele was associated with skin test positivity but not IgE level. Homozygosity for the -403 A allele conferred a 6.5-fold increased risk of moderate/severe airway obstruction (FEV1 < or = 80% predicted), a marker for established asthma. Our data, whilst preliminary, indicate that the association of RANTES genotype with both atopy and asthma reflect independent effects, suggesting different mechanisms for the role of this chemokine in atopy and development of airway obstruction.

Association between HLA-DRB1*15 and secondary Sjögren's syndrome in patients with rheumatoid arthritis

OBJECTIVE

To examine the relationship between HLA-DRB1 alleles and the clinical expression of the secondary form of Sjogren's syndrome (SS) in patients with rheumatoid arthritis (RA).

METHODS

Typing of HLA-DRB1 alleles was carried out by molecular based techniques on DNA obtained from a population of patients with RA from Lugo in northwestern Spain. Patients were diagnosed according to the 1987 American College of Rheumatology criteria for RA, and comprised 137 seropositive and 42 seronegative individuals. Secondary SS was defined by xerostomia and keratoconjunctivitis sicca, supported by ophthalmologic examination. Patients were compared with 145 ethnically matched controls.

RESULTS

Twenty-two (12.3%) of the patients with RA also had secondary SS. The majority of these (19/22) were rheumatoid factor positive. Eleven (57.9%) of the seropositive patients with secondary SS carried an HLA-DRB1*15 allele compared with 28 (23.7%) seropositive patients without secondary SS (OR 4.4, 95% CI 1.5-13.6, pc = 0.014). In contrast, the frequency of DRB1*04 was reduced in seropositive patients with secondary SS compared to those without secondary SS, although this did not achieve significance after correction for multiple testing (OR 0.28, 95% CI 0.09-0.88, pc = 0.08). Of note, in individuals lacking the RA shared epitope (SE), DRB1*15 was found to be associated (OR 2.3, 95% CI 1.0-5.1, pc = 0.03) with RA in the absence of secondary SS. No differences were found between DRB1*15 positive and negative patients in terms of erosive disease, nodules, or rheumatoid factor positivity.

CONCLUSION

Secondary SS is associated with an increased frequency of HLA-DRB1*15 in seropositive patients with RA from northwestern Spain. HLA-DRB1*15 is also associated with RA in SE negative individuals without secondary SS, although the possibility that such patients will later develop SS cannot be ruled out. Further studies are needed to confirm whether the HLA-DRB1*15 association with secondary SS in RA is common to Spanish and other ethnic populations.

Visual manifestations of giant cell arteritis. Trends and clinical spectrum in 161 patients

Giant cell (temporal) arteritis (GCA) is the most common systemic vasculitis in Western countries. It involves large and medium-sized vessels with predisposition to the cranial arteries in the elderly. Cranial ischemic complications, in particular permanent visual loss, constitute the most feared aspects of this vasculitis. Although the use of corticosteroids and a higher physician awareness may have contributed to a decrease in the frequency of severe ischemic complications, permanent visual loss is still present in 7%-14% of patients. To investigate further the incidence, trends, and clinical spectrum of visual manifestations in patients with GCA, we examined the features of patients with biopsy-proven GCA diagnosed at the single reference hospital for a defined population in northwestern Spain during an 18-year period. Predictive factors for the development of any visual manifestation, not only permanent visual loss, were also examined. Between 1981 and 1998, 161 patients were diagnosed with biopsy-proven GCA. Visual ischemic complications were observed in 42 (26.1%), and irreversible blindness, mainly due to anterior ischemic optic neuropathy and frequently preceded by amaurosis fugax, was found in 24 (14.9%). Despite a progressive increase in the number of new cases diagnosed, there was not a significant change in the proportion of patients with visual manifestations during the study period (p = 0.37). Patients with visual ischemic complications had lower clinical and laboratory biologic markers of inflammation. Indeed, during the last years of the study, anemia was associated with a very low risk of visual complications. Also, HLA-DRB1*04-positive patients had visual manifestations more commonly. Patients with other ischemic complications developed irreversible blindness more frequently. The best predictors of any visual complication were HLA-DRB1*04 phenotype (odds ratio [OR] 7.47) and the absence of anemia at the time of admission (OR for patients with anemia = 0.07). The best predictors of irreversible blindness (permanent visual loss) were amaurosis fugax (OR 12.63) and cerebrovascular accidents (OR 26.51). The present study supports the claim that ocular ischemic complications are still frequent in biopsy-proven GCA patients from southern Europe. The presence of other ischemic complications constitutes an alarm for the development of irreversible blindness. In contrast, a higher inflammatory response may be a protective factor against the development of cranial ischemic events.

Multipoint linkage analysis of a candidate gene locus in rheumatoid arthritis demonstrates significant evidence of linkage and association with the corticotropin-releasing hormone genomic region

OBJECTIVE

Rheumatoid arthritis (RA) is the most common disabling autoimmune disease, affecting approximately 1% of the population. The disease etiology is unknown, but it involves inflammation and immune dysregulation and is influenced by genetic variation at both HLA and other, as-yet-unidentified genetic loci. Corticotropin-releasing hormone (CRH; or corticotropin-releasing factor), a primary regulator of the hypothalamic-pituitary-adrenal axis and a key element in the response to stress and inflammation, is a strong candidate gene for RA. We examined the role of DNA variation across the region containing this gene in multicase families with RA.

METHODS

We genotyped fluorescently labeled simple tandem repeat genetic markers from chromosome 8q13 in 295 families with multiple cases of RA. Singlepoint and multipoint nonparametric linkage analysis and association analysis using transmission disequilibrium testing (TDT) were also used.

RESULTS

Single-point linkage analysis using a microsatellite within 30 kb of the CRH locus (CRH.PCR at position 8q13) showed a significant excess of allele sharing in 295 United Kingdom RA families with at least 2 affected members (MapMaker/Sibs logarithm of odds [LOD] 1.4; P = 5.5x10(-3); mean identity by descent [ibd] sharing 55.9%). To provide a more detailed linkage map, a multipoint analysis was conducted with an additional 7 dinucleotide microsatellite markers (average heterozygosity 0.75) flanking the CRH locus. Significant linkage was detected over a 22-cM region between D8S285 and D8S530, with the maximum singlepoint LOD score of 1.77 at D8S1723 (MapMaker/Sibs P = 2.2x10(-3); mean ibd sharing 59.3%). Multipoint analysis showed strongest evidence for linkage at the same marker (multipoint LOD 1.78, P = 2.1x10(-3), mean ibd sharing 55.8%). TDT analysis showed significant association at the CRH locus (P = 2.6x10(-3)). CRH has a sibling relative risk of 1.14, and contributes <10% to the sibling relative risk of RA.

CONCLUSION

With the exception of HLA, this is the strongest evidence yet of a genetic locus that is both linked to and associated with RA, and provides an avenue for further genetic characterization and potentially novel therapeutic intervention.

Association of giant cell arteritis and polymyalgia rheumatica with different tumor necrosis factor microsatellite polymorphisms

OBJECTIVE

To determine whether giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are associated with different tumor necrosis factor (TNF) microsatellite polymorphisms.

METHODS

Typing of TNF microsatellite polymorphisms was carried out by molecular-based techniques on DNA obtained from a population sample of residents from Lugo, northwestern Spain. A case-control approach was used to compare 136 patients with GCA and/or PMR with 147 ethnically matched controls. The association of disease with TNF microsatellite polymorphisms was investigated using chi-square tests and multivariate logistic regression analyses.

RESULTS

Different TNF microsatellite associations were found with GCA and PMR. In patients with isolated GCA, the primary association was with TNFa2, which was independent of the GCA associations with HLA-DRB1*0401 and *0101. A negative association was found with TNFa10. In patients with isolated PMR, there was a positive association with TNFb3. This was found to be independent of the HLA-DRB1*13/*14 association in isolated PMR. TNFd4 was negatively associated with isolated PMR. Forward stepwise logistic regression analyses indicated that the strongest association with GCA was provided by the TNFa2 allele, although DRB1*0401 and *0101 were still associated. PMR was primarily associated with TNFb3. A direct comparison of TNF allele frequencies between isolated GCA and isolated PMR indicated that the main difference between these conditions occurred in the frequency of TNFa10.

CONCLUSION

GCA and PMR in individuals from northwestern Spain are associated with different TNF microsatellite polymorphisms. The primary TNF associations (TNFa2 and TNFb3) appear to influence susceptibility to these conditions independent of any HLA-DRB1 association.

Mannose binding lectin (MBL) genotype distributions with relation to serum levels in UK Caucasoids

Mannose binding lectin (MBL) gene and promoter-region polymorphisms contribute to a reduction in the levels of circulating MBL in a number of ways. Promoter polymorphisms affect the levels of MBL produced, whilst structurally encoding mutations cause non-functional protein to be assembled and subsequently degraded. MBL is important as a protein of the innate immune system in both the clearance of potential pathogens and the activation of the complement cascade. Using variations of SSP-PCR amplifications and SSO probing techniques, we have produced MBL-polymorphism haplotype and genotype profiles of a series of high-level MBL-producing, low-level MBL-producing and random individuals taken from a population of 800 UK Caucasoid controls. Structurally encoding mutant alleles were more frequent within the low-level producing cohort when compared to both high-level producers and the randomly selected sample. However, not all low-level producers could be accounted for by the possession of low-level encoding haplotypes. This may be due to the presence of additional, undetected polymorphisms governing MBL production, or another external factor that may influence the transcriptional regulation of the gene.

A novel PCR-RFLP assay for the detection of a polymorphism in the 3' of STAT6 gene

We have identified a novel single nucleotide polymorphism at position 2964 (G/A) in the 3' untranslated region of the human STAT6 gene (GeneBank Accession No. U16031). A novel PCR-RFLP method has been devised for this polymorphism using the amplification-created restriction site (ACRS) method. Allele frequencies in the UK Caucasian population were found to be 0.33 for allele A and 0.67 for allele G.

RANTES gene polymorphism in polymyalgia rheumatica, giant cell arteritis and rheumatoid arthritis

OBJECTIVE

To investigate whether a biallelic polymorphism (A or G) occurring within the promoter region of the RANTES gene (position-403) is associated with polymyalgia rheumatica (PMR), giant cell arteritis (GCA) and rheumatoid arthritis (RA).

METHODS

A PCR-RFLP method was used to genotype cases and controls for this polymorphism. 3 groups of patients were examined; these comprised GCA patients who did not exhibit features of PMR (n = 30), PMR patients who did not exhibit features of GCA (n = 53) and RA patients (n = 99). All patients and controls (n = 65) originated from the area surrounding Lugo, Galicia, NW Spain.

RESULTS

A significant increase in the frequency of allele A was found in PMR patients compared with normal controls. A marginal increase of this allele frequency was observed in RA but not in GCA patients.

CONCLUSION

This is the first report of an association of a RANTES gene polymorphisms with PMR and RA. Our data suggest a possible role for of RANTES in the development of both PMR and RA.

High serum levels of pro-matrix metalloproteinase-3 are associated with greater radiographic damage and the presence of the shared epitope in patients with rheumatoid arthritis

OBJECTIVE

To determine if there is a relationship between serum pro-matrix metalloproteinase-3 (proMMP-3) levels and radiographic damage in rheumatoid arthritis (RA), and to investigate whether high levels are associated with presence of the HLA-DRB1 shared epitope (SE).

METHODS

Serum proMMP-3 levels were measured by ELISA on 45 RA patients with early disease and 292 with established disease. Early RA was arbitrarily defined as disease duration <3 years. Clinical and laboratory measures of disease activity and severity were obtained. Radiographic damage was assessed by scoring radiographs of the hands and feet using the method of Larsen. HLA-DRB1 typing was performed by sequence-specific oligonucleotide probing. Data were analyzed by multiple regression analysis.

RESULTS

In all patients, there was a correlation (r = 0.318, p<0.0001) between serum proMMP-3 levels and Larsen scores. Other correlations were found with Health Assessment Questionnaire score (r = 0.261, p<0.0001) and C-reactive protein (CRP) (r = 0.357, p<0.0001) levels. ProMMP-3 levels were significantly higher in SE+/+ patients than in those completely lacking the SE, with the highest levels in patients carrying an HLA-DRI+/DR4+ phenotype. The greatest difference in proMMP-3 levels between SE+/+ and SE-/- patients was in those with a disease duration <3 years (381.6 vs. 71.7 ng/ml; p = 0.02).

CONCLUSION

Our data indicate that there is a significant relationship between radiographic damage and serum levels of proMMP-3. As well, higher circulating levels of proMMP-3 are found in patients positive for the SE, particularly in early RA, and this may partly explain the association between the SE and more erosive disease.

Different gene loci within the HLA-DR and TNF regions are independently associated with susceptibility and severity in Spanish rheumatoid arthritis patients

The aim of this study was to investigate whether polymorphisms in the tumor necrosis factor (TNF) and HLA-DRB1 gene regions are independently associated with rheumatoid arthritis (RA) in a population from Lugo region of northwestern Spain. RA patients (n=179) attending hospital outpatient clinics in Lugo, northwestern Spain and matched controls (n=145) were recruited. RA susceptibility in this population was predominantly associated with DRB1*0401, while erosive disease was associated with HLA-DRB1*0101 and DRB1*04. The increase in DRB1*04 was accounted for by an increase in DRB1*0404 and *0405 but not *0401 frequencies. In contrast, *0401 frequency was significantly increased in seropositive patients. The rheumatoid arthritis shared epitope (SE) was associated with increased risk for seropositive and erosive disease and this appeared to operate in a dose-dependent manner. Logistic regression analyses revealed that the TNF microsatellite markers TNFc1 and b3 were associated with RA independently of DRB1*04 and the SE. Carriage of a TNF c1 allele provided an increased risk of RA in SE-negative and SE-heterozygous individuals. TNFc1 and TNFb3 were not associated with erosive or seropositive disease. In contrast, TNF a2 was significantly associated with erosive disease which was independent of DRB1*04 and the SE. Further studies will be needed to establish why (TNFc1) polymorphism seemingly associated with low TNFalpha production, is a risk factor for RA.

Predominance of one T-cell antigen receptor BV haplotype in African populations

The human T-cell antigen receptor (TCR) is the counter-receptor for the HLA/peptide complex displayed on the surface of antigen-presenting cells. It confers antigen specificity on T lymphocytes and therefore plays a central role in pathogen recognition and host response. The most frequently used form of the TCR is a heterodimer composed of variable alpha and beta chains. We investigated allele frequencies for four variable-region gene segments of the beta chain (2S1, 3S1, 8S3, and 15S1) in 146 Caucasians and 165 Africans. The results reveal significant unexpected differences between the two populations for allele frequencies, phenotypes, genotypes, and haplotypes. Among Caucasians, there are 43 phenotypes, whereas there are 31 among the Africans studied. There are 17 haplotypes in the Caucasian sample but only 10 in Africans. This loss of diversity is largely due to the high frequency of one haplotype in the African sample which represents 65% of the informative chromosomes. At least one copy of this haplotype is present in 90% of informative individuals. As a result, 29% of Africans are homozygous for the common haplotype. Less genetic diversity at TCRBV is unexpected, since Africans usually show greater genetic diversity than other ethnic groups. For example, there are approximately twice as many HLA haplotypes in Africans compared to Caucasians. Homozygosity is also unexpected because it reduces the number of TCR variants available to recognize HLA pathogen-derived peptide complexes.

DLA-DQA1 polymorphisms in dogs defined by sequence-specific oligonucleotide probes (SSOP)

Several recent studies have identified DNA sequences for alleles of the DLA-DQA1 locus in the dog. To date, 10 DQA1 alleles have been reported. No data exists on the frequencies of these alleles within the general dog population, nor is there any indication of whether alleles are breed specific. We have addressed this issue by establishing a molecular-based sequence-specific oligonucleotide probing (SSOP) method to identify all published DQA1 alleles and have used these methods to type a large number of dogs. Oligonucleotide probes were designed to detect all the polymorphic sites in exon 2. This allowed assignment at the allele level. Three hundred and thirty dogs were typed for DQA1. All but two of the published DQA1 alleles were identified in these animals. One new allele was identified, and confirmed by DNA cloning and sequencing. This typing method provides a powerful tool for generating data that will be essential for studies investigating the genetic relationships between different breeds.

Preliminary evidence of an association of tumour necrosis factor microsatellites with increased risk of multiple basal cell carcinomas

Tumour necrosis factor alpha (TNF-alpha) appears important in ultraviolet-induced immunosuppression, suggesting that it is a susceptibility candidate for cutaneous basal cell carcinoma (BCC). We now describe data on the association between TNF microsatellite polymorphisms, first on susceptibility in 202 controls and 133 cases each having two to 30 BCCs, and secondly, within the cases, on BCC numbers. The data show that the proportions of individuals with TNF a1- and a7-containing genotypes were significantly different (P = 0. 0271, P = 0.0393, respectively) between cases and controls. Secondly, within the cases, TNF alleles d4 (P = 0.023) and d6 (P = 0.006) alone, and the TNF a2-b4-d5 haplotype (P = 0.007), were significantly associated with the number of BCC lesions. These preliminary data provide the first evidence that TNF microsatellite polymorphism may influence the pathogenesis of multiple BCC.

Nomenclature for factors of the dog major histocompatibility system (DLA), 1998: first report of the ISAG DLA Nomenclature Committee

A Nomenclature committee for Factors of the Dog Major Histocompatibility System or Dog Leukocyte Antigen (DLA) has been convened under the auspices of the International Society for Animal Genetics (ISAG) to define a sequence based nomenclature for the genes of the DLA system. The remit of this committee includes: assignment of gene names rules for naming alleles assignment of names to published alleles assignment of names to new alleles rules for acceptance of new alleles DLA Nomenclature Committee, rules for acceptance, DLA genes and alleles, sequence based nomenclature.

Genetic polymorphism of IL-12 p40 gene in immune-mediated disease

Understanding of the genetic basis of autoimmune diseases is currently incomplete. Cytokine gene polymorphisms warrant consideration as factors explaining variation in the human immune and inflammatory responses and as candidate susceptibility genes for related pathological states. Interleukin 12 (IL-12) is a key regulator of the polarisation of immune responses to T helper 1 or 2 categories and plays a role in autoimmune and infectious diseases. Using a bioinformatic strategy, we aligned cDNA and expressed sequence tag sequences to identify putative polymorphic regions of the IL-12 p40 gene. Position 1188 in the 3' untranslated region (UTR) was polymorphic with the frequency of the common allele around 80% in healthy UK Caucasoids. PCR genotyping of multiple Caucasoid groups and an African group showed significant population variation. In a case-control design, the polymorphism was not associated with rheumatoid arthritis, Felty's syndrome or large granular lymphocyte syndrome with arthritis or multiple sclerosis. A nonsignificant increase in the B allele frequency was observed in the rare large granular lymphocyte syndrome without arthritis (odds ratio 2.02 95% CI 0.95-4.3). This new genetic marker could be useful in anthropological studies and should be investigated in other autoimmune, allergic, inflammatory and infectious diseases.

Tumor necrosis factor receptor II (TNFRII) exon 6 polymorphism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that exhibits extensive clinical heterogeneity. Several studies have suggested a role for tumor necrosis factor alpha (TNFalpha) in SLE and recently, the locus encompassing the TNF receptor II (TNFRII), which is a mediator of TNF effect, was amongst the candidate loci suggested by genetic linkage studies of multi-case SLE families. Komata et al. reported an association between a polymorphism at position 196 (R allele) of TNFR II and SLE in Japanese patients. We have typed SLE patients from two different ethnic populations, Spanish and UK Caucasoids, for this polymorphism using a polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP)-based technique. No significant differences in allele or genotype frequencies were found between cases and matched controls in either population. The TNFRII 196R allele does not appear to be associated with SLE susceptibility in either Spanish or UK populations.

The influence of HLA-DRB1 alleles encoding the DERAA amino acid motif on radiological outcome in rheumatoid arthritis

OBJECTIVES

To investigate the influence of HLA-DRB1 alleles encoding the QK/RRAA shared epitope (SE) on radiological outcome in rheumatoid arthritis (RA), and to determine whether it is modulated by alleles carrying the putative rheumatoid arthritis-protective (RAP) sequence DERAA. Patients and methods. The association between erosive damage and HLA-DRB1 status was examined in 315 RA patients with a disease duration of 5-30 yr. Radiological outcome was measured by scoring X-rays of the hands and feet using the standard radiographs of Larsen (Larsen score). HLA-DRB1 typing was carried out using polymerase chain reaction methodology.

RESULTS

Patients with two alleles encoding the QK/RRAA SE had significantly higher Larsen scores than SE-negative patients (96.9 vs 83.3; P=0.04, after correction for multiple testing), with DRB1*0401/*0401 homozygotes demonstrating the greatest radiological damage (99.9). The lowest Larsen score (65.6) was observed in patients carrying the DERAA motif without an accompanying SE allele (RAP+/SE-). This was significantly lower than in patients with RAP+/SE+ (105.6; P=0.04), RAP-/SE- (88.2; P=0.05) and RAP-/SE+ (95.8; P=0.009), after correction for multiple testing. There was no evidence that the RAP sequence was modulating the effect of the SE since radiological outcome in RAP+/SE+ patients was not significantly different to that in RAP-/SE+ individuals.

CONCLUSIONS

Our data support a possible role for DRB1 alleles encoding the DERAA motif in protection against severe erosive damage in patients lacking the QK/RRAA SE, but not in patients heterozygous for the SE. This suggests that DRB1 alleles encoding the SE have a dominant influence over 'protective alleles' and are not merely 'non-protective'.

Interaction between tumor necrosis factor microsatellite polymorphisms and the HLA-DRB1 shared epitope in rheumatoid arthritis: influence on disease outcome

OBJECTIVE

To investigate whether interactions between tumor necrosis factor (TNF) microsatellite polymorphisms and the HLA-DRB1 shared epitope (SE) are associated with disease severity in rheumatoid arthritis (RA), and to determine if such associations are the same in male and female patients.

METHODS

Genotyping for the TNFa microsatellite and HLA-DRB1 was carried out on 157 RA patients with established disease (duration >5 years). Disease severity measures included radiographic damage (the Larsen method), functional assessment by the Health Assessment Questionnaire, history of joint surgery, and global appraisal of outcome by means of a visual analog scale score. The association of severity measures with TNFa microsatellite polymorphisms stratified by SE status, and the interaction between TNFa and the SE, were investigated using stratified analyses and multiple or logistic regression analyses.

RESULTS

No significant associations were observed between any single TNFa microsatellite polymorphism and disease severity, although preliminary evidence for an interaction between TNFa6 and TNFa11 was obtained. In the presence of the SE, a significantly worse outcome was associated with individuals carrying TNFa6, and a significant interaction (P = 0.04-0.006) was found between these alleles for all the outcome measures examined except history of joint surgery. In the absence of the SE, the TNFa6 allele was associated with significantly better outcome scores. When examined by sex, significant associations between the TNFa6/SE haplotype and disease outcome measures were found only in females. No statistically significant interactions were found in males, although the TNFa6/SE haplotype was still associated with the worst outcome scores.

CONCLUSION

The association of the SE with disease severity in RA is influenced by an interaction with the TNFa6 microsatellite polymorphism. This interaction appears to be acting predominantly in female patients, although the trend is similar in the smaller percentage of males carrying the TNFa6/SE haplotype.

Interleukin-10 (IL10) promoter polymorphisms and multiple sclerosis

Interleukin-10 (IL10) is an anti-inflammatory cytokine which may modulate disease expression in multiple sclerosis (MS). Three dimorphic polymorphisms within the IL10 promoter region at positions - 1082, -819 and -519 have previously been identified. The - 1082*A allele has been associated with low and the - 1082*G allele with high in vitro IL10 production. We have genotyped 185 Caucasian MS patients and 211 ethnically matched controls for each of these three dimorphisms. MS patients were stratified for severity of disease outcome. No associations were found for any IL10 promoter polymorphisms when the MS cases were compared with controls or with disease outcome with regards to disability. IL10 polymorphism does not appear to be associated with MS or to influence disease progression.

Nomenclature for factors of the dog major histocompatibility system (DLA), 1998. First report of the ISAG DLA Nomenclature Committee. International Society for Animals Genetics

A Nomenclature Committee for factors of the dog major histocompatibility system or dog leukocyte antigen (DLA) has been convened under the auspices of the International Society for Animal Genetics (ISAG) to define a sequence-based nomenclature for the genes of the DLA system. The remit of this committee includes: i) assignment of gene names; ii) rules for naming alleles; iii) assignment of names to published alleles; iv) assignment of names to new alleles; and v) rules for acceptance of new alleles.

Combined sib-TDT and TDT provide evidence for linkage of the interleukin-1 gene cluster to erosive rheumatoid arthritis

Rheumatoid arthritis (RA) is a common disease of unknown aetiology which usually causes progressive destruction of the joints. Familial aggregation, twin studies and segregation analyses suggest that there is a genetic component to RA and the HLA-DRB1 locus in the major histocompatibility complex on chromosome 6 has been shown to be linked to, and associated with, RA susceptibility. It is likely that other genes with weaker effects are also involved, which may be difficult to detect using conventional parametric and non-parametric linkage methods. We have implemented the combined sib-TDT and TDT, in addition to parametric and non-parametric linkage methods, to investigate the candidate genes of the interleukin-1 (IL-1) gene cluster on chromosome region 2q13, since IL-1 is an important cytokine in the control of the inflammatory response that is central to RA pathology. Several tightly linked IL-1 cluster markers yielded suggestive evidence for linkage in the combined TDT in those families in which affected siblings did not share two HLA-DRB1 alleles identical by descent. The evidence was significant in those with severe disease, as assessed by the presence of bone erosions. In contrast, there was no evidence of linkage using non-parametric linkage analysis, but parametric analysis revealed weak evidence of linkage when marker-trait disequilibrium was incorporated into the analysis. The data provide preliminary evidence for linkage of genes of the IL-1 cluster to RA and suggest a possible role for this region in severe erosive disease.

Linkage of a marker in intron D of the estrogen synthase locus to rheumatoid arthritis

OBJECTIVE

To test for the presence of linkage of the estrogen synthase (CYP19) locus to rheumatoid arthritis (RA) in affected sibling pair (ASP) families.

METHODS

Two data sets of RA ASPs (225 ASPs and 107 ASPs) were genotyped for a polymorphic tetranucleotide marker at the CYP19 locus using fluorescence-based semiautomated genotyping technology. Evidence of linkage was assessed by estimating allele sharing (identical by descent) in affected sibling pairs. The effect of this locus was also examined in patient subgroups stratified by sex and by age at disease onset.

RESULTS

An increase in allele sharing at the CYP19 locus was observed in the first data set of 225 ASPs (logarithm of odds [LOD] 0.8; P = 0.04). There was also an increase in allele sharing in a second data set, but this did not reach statistical significance (LOD 0.34; P = 0.1). The highest increase in allele sharing was seen in patients with an age at disease onset that was >50 years (LOD 1.1; P = 0.02).

CONCLUSION

An increase in allele sharing at the CYP19 locus has been demonstrated in 2 large samples of RA ASPs. The evidence for linkage was strongest in patients with an age at onset that was >50 years, which suggests that this locus may be a susceptibility locus for developing RA later in life. These data provide preliminary evidence that CYP19 may have a role in RA susceptibility.

The Bg/II polymorphism of the human prolactin gene lies within intron C and can be detected by PCR/RFLP

Prolactin has been shown to be active as an immunomodulatory hormone and is therefore of potential importance in disease progression and development. Any polymorphism in the gene and regulatory sequences may prove useful for disease association studies. A Bg/II polymorphism has been previously detected within the prolactin gene region. We have mapped this polymorphism to intron C and detected the base mutation that causes it. We have also developed a PCR-RFLP method to genotype individuals.