Heberden Oration, 1969. Rheumatoid arthritis--nature or nurture?

Immunosusceptibility genes in rheumatoid arthritis

The polygenic predisposition to RA is conferred particularly by disease susceptibility sequences in the HVR3 of HLA DRB1 present in those subtypes of DR4 and DR1 that are associated with RA. The aim of this study was to examine predisposing interactions between genes encoding HLA and immunoglobulin molecules. Accordingly, we compared the genetic background of 114 Australian patients with RA with that of Australian controls of similar ethnic background. We identified HLA-A, B, and DR phenotypes serologically, HLA-DR, DQ alleles, and subtypes of DR4 by DNA typing, and Gm allogenotypes and immunoglobulin switch region polymorphisms by RFLP. For the subjects with RA, we confirmed previously reported observations that included an excess of females, 71%, a high frequency of HLA types DR4 or DR1 of 77% versus controls 47%, and a high frequency of the HVR3 susceptibility sequences of 76%, with 24% homozygous, and 52% heterozygous for the sequences. We observed other genetic correlations in RA that included increases in frequencies of DR4 in males, DR1 in females, the class I specificity HLA-B27 overall but more particularly in females, 24% in females, versus 5% of controls, HLA-DQB1*0302 (DQ8) in DR4*0401-positive patients, and the Gm allogenotype 1,2,3;23 +/- ; 5,10, 15% of patients versus 4% of controls. Examination of switch region genes gave no evidence of differences in the polymorphisms distributions. Thus, the major genetic risks for RA that are conferred by female gender and the HVR3 of HLA DRB1 are modulated by interactions between gender and HLA class I and class II alleles, and the Gm allogenotype.

Cigarette smoking increases the risk of rheumatoid arthritis. Results from a nationwide study of disease-discordant twins

OBJECTIVE

To test the hypothesis that cigarette smoking is associated with susceptibility to rheumatoid arthritis (RA) by comparing smoking history between twins with RA and their unaffected co-twins.

METHODS

Interview questionnaires on smoking history were administered to 79 identical (monozygotic [MZ]) and 71 same-sex nonidentical (dizygotic, [DZ]) twin pairs who were discordant for RA, recruited from the Arthritis and Rheumatism Council Twin Study. Results were expressed as odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

Although most twin pairs were concordant for smoking history, there was a strong association between ever smoking and RA in the MZ pairs (OR 12.0, 95% CI 1.78-513), with a similar trend observed in the DZ pairs (OR 2.5, 95% CI 0.92-7.87).

CONCLUSION

The discordance in cigarette smoking history for individuals who are at presumed identical genetic risk for RA supports other data suggesting the role of smoking in disease susceptibility.

Sex influences on the penetrance of HLA shared-epitope genotypes for rheumatoid arthritis

The association between rheumatoid arthritis (RA) and HLA DRB1 alleles may arise through linkage disequilibrium with a disease locus or the direct involvement of HLA alleles in RA. In support of the latter possibility, the shared-epitope hypothesis has been postulated, stating that conformationally similar DR beta chains encoded by several DRB1 alleles confer disease susceptibility. To examine these alternative hypotheses of marker-disease association and to investigate gender differences in RA susceptibility, we analyzed the distributions of PCR-based DRB1 genotypes of 309 Caucasian RA patients and 283 Caucasian controls. Initially, the marker-association-segregation chi 2 method was used to evaluate evidence for linkage disequilibrium and the direct involvement of markers DR4 Dw4, DR4 Dw14, and DR1 in RA susceptibility. Additional shared-epitope models that grouped DRB1 alleles into five classes (*0401, *0404/*0102, *0405/*0408/*0101, *1001, and all others) and postulated relationships between genotypes and RA susceptibility were also fitted to observed genotypic distributions by the method of minimal chi 2. For females, a linkage-disequilibrium model provided a good fit to the data, as did a shared-epitope model with RA most penetrant among individuals with the *0401,*0401 genotype. For males, the best model indicated highest RA penetrance among shared-epitope compound heterozygotes. Clinically, male RA patients had more subcutaneous nodules and greater use of slowly acting antirheumatic drugs, while female RA patients had earlier disease onset. This study therefore suggests that sex-related factors influence the RA penetrance associated with DRB1 shared-epitope genotypes and that DRB1 effects on RA prognosis and pathogenesis should be considered separately for men and women.

Occurrence of rheumatoid arthritis is not increased in the first degree relatives of a population based inception cohort of inflammatory polyarthritis

OBJECTIVE

To determine the risk of rheumatoid arthritis (RA) in first degree relatives of a true population based sample of probands with inflammatory polyarthritis.

METHODS

In a case-control study, a two stage screening procedure was used to ascertain the prevalence of RA in 518 first degree relatives of 207 Norfolk Arthritis Register cases registered in 1990 and 414 first degree relatives of 180 local controls. An initial joint symptom and medical history questionnaire was followed by a physical examination, and serological and radiological evaluation of those with symptoms.

RESULTS

The prevalence of RA in the first degree relatives of all the Norfolk Arthritis Register cases was 7.7/1000, compared with 4.8/1000 in the first degree relatives of the controls, with a risk ratio of 1.6 (95% confidence interval 0.3 to 8.7). This very modest increase was also seen when the analysis was restricted to the first degree relatives of Norfolk Arthritis Register cases who satisfied the American Rheumatism Association criteria for RA: prevalence rate 7.2/1000.

CONCLUSION

There was no evidence of an important increased familial risk of RA in this community based sample. These data are compatible with others from immunogenetic studies showing only weak HLA associations with community ascertained RA.

The genotypic distribution of shared-epitope DRB1 alleles suggests a recessive mode of inheritance of the rheumatoid arthritis disease-susceptibility gene

OBJECTIVE

To test whether the genotypic distribution of rheumatoid arthritis (RA)-associated DRB1 alleles suggests that the DRB1-associated disease-susceptibility gene has a recessive or additive (dominant) mode of inheritance.

METHODS

Caucasian patients with RA and control subjects were recruited from a faculty outpatient practice. DRB1 typing was done by several DNA-based techniques: polymerase chain reaction (PCR), followed by dot-blot hybridization with sequence-specific oligonucleotides, conventional and PCR-based restriction fragment length polymorphisms (RFLPs), and a multiplex amplification-refractory mutation RFLP system. The genotypic distribution of shared-epitope DRB1 alleles was analyzed by antigen genotype frequency among patients. The analytical method postulates a linkage-disequilibrium model with a disease locus close to a marker locus and a marker allele in linkage disequilibrium with the disease-susceptibility allele. In this instance, the marker allele was defined alternatively by any DR4-group allele, by any DR4-group or DR1-group allele, by any DR4-group shared-epitope allele, by any DR4-group shared-epitope allele plus DRB1*0101, or by any shared-epitope DRB1 allele. Observed numbers were compared with those predicted for recessive mode or additive (dominant) mode of inheritance of the DRB1-associated RA disease-susceptibility gene.

RESULTS

The genotypic distribution of shared-epitope DRB1 alleles (DRB1*0401, *0404, *0405, *0408, *0101, *0102, or *1001) fit that predicted for a recessive mode of inheritance and was significantly different from that predicted for an additive (dominant) mode. When the analysis was restricted to shared-epitope DR4 alleles alone (DRB1*0401, *0404, *0405, or *0408), the observed genotype numbers fit the recessive mode best. When DR1-group alleles were added to DR4-group alleles, or alternatively, when the major shared-epitope DR1 allele (*0101) was added to DR4-group shared-epitope alleles, there was a less significant deviation from the additive mode of inheritance. The reason for this was derived by comparison of observed genotype frequencies to those expected under Hardy-Weinberg equilibrium; there was a deficit of persons with DRB1*0401, *0101 and an excess of *0101,X.

CONCLUSION

The genotypic distribution of shared-epitope DRB1 marker alleles suggests that the mode of inheritance of the DRB1-associated disease susceptibility gene must be recessive and not additive (dominant).

Hormonal and pregnancy relationships to rheumatoid arthritis: convergent effects with immunologic and microvascular systems

OBJECTIVE

To review sex hormones and rheumatoid arthritis (RA) and the interrelationships between hormonal, immunological, and vascular systems.

DATA SOURCES

Publications detailing serum sex hormone levels and their HLA interactions, steroidogenesis, pregnancy, and therapeutic uses of sex hormones in RA.

STUDY SELECTION

Controlled studies of sex hormone levels in RA patients not previously treated with glucocorticoids.

DATA EXTRACTION

Mean (+/- SD) serum levels of dehydroepiandrosterone sulfate (DHEAS), testosterone (T), and estradiol (E2).

DATA SYNTHESIS

Mean (+/- SD) levels were collated into tables for women with pre-versus postmenopausal onsets of disease and men. Data were also ordered across all study groups by increasing mean levels of the control subjects. Pooled data were summarized statistically, and major sources of variation between the studies were identified.

CONCLUSIONS

Serum DHEAS, an adrenal androgen, was impressively decreased among women with premenopausal onset of RA. One study showed such deficiency years before disease onset. Serum T was somewhat decreased in the premenopausal onset group, but could be explained by decreased peripheral conversion of the lower levels of adrenal androgens. Women with postmenopausal onset of RA had modestly decreased serum DHEAS levels overall, but no difference in serum T, compared with controls. Male RA cases had consistently decreased serum levels of T, but not of DHEAS. Serum E2 was comparable in all RA versus control groups. The complex biology of pregnancy was interpreted as an example of vital interactions between hormonal, immunological, and vascular systems, as they may relate to the physiopathology of RA. The major age, sex, and hereditable determinants of RA were compared within a composite table of estimated relative risks. Elucidation of the interacting risk factors offers promising avenues of research in this complex disease.

Genetic epidemiology of rheumatoid arthritis

We conducted family studies and segregation analyses of rheumatoid arthritis (RA) that were based on consecutive patients with RA ascertained without regard to family history or known risk factors. First-degree relatives from 135 simplex and 30 multiplex families were included in the analyses. A highly penetrant recessive major gene, with a mutant allele frequency of .005, was identified as the most parsimonious genetic risk factor. Significant evidence for heterogeneity in risk for RA was observed for proband gender but not for proband age at onset. Kaplan-Meier risk analysis demonstrated significant evidence for differences in the distribution of risk among first-degree relatives. These analyses demonstrated that both proband gender and age at onset are important risk factors but that proband gender appears to be the more important determinant of risk, with relatives of male probands having the greatest cumulative risk for RA. In addition, log-linear modeling identified proband gender, familiality (multiplex or simplex), and an interaction term between these two variables as being adequate to define the distribution of risk in families. The pattern of risk for RA among susceptible individuals and its inheritance is thus heterogeneous. For future genetic analyses, families with an excess of affected males having a young age at onset may be the most informative in identifying the putative recessive gene and its modifiers.

Changes in the blood-thymus barrier of adult rats after estradiol-treatment

The accessibility of the thymus parenchyma for relatively large Mw (+/- 150 Kd) proteins has been studied by the intravenous injection of monoclonal antibodies (mAbs) specific either for all T cells (His-17) or MHC class II molecules (His-19) in control and estradiol benzoate (EB)-treated adult Wistar rats. In controls, the transcapsular route rather than cortical capillaries seems to be involved in the entry of molecules into the thymus. By contrast, a specific staining for either T cells (His-17) or MHC class II molecules (His-19 positive cells) disappears almost completely from the thymic cortex of EB-treated rats except in the immediate subcapsular epithelial cell layer. In these rats, T cells and epithelial cells intimately associated to blood vessels from both inner cortex and corticomedullary border showed additional staining with the respective mAbs confirmed by electron microscopy. The disappearance of the transcapsular route together with the increased vascular permeability of cortical blood vessels would be related to the reinforcement of the subcapsular epithelial cell layer and to direct effects of EB on vascular endothelia, respectively. These results are discussed in relationship to the cell migration into and out of adult thymus, as suggested by the changes in intrathymic T cell subsets evaluated by flow cytometry.

HLA-linked rheumatoid arthritis

Twenty-eight pedigrees were ascertained through pairs of first-degree relatives diagnosed with rheumatoid arthritis (RA). RA was confirmed in 77 pedigree members including probands; the absence of disease was verified in an additional 261 pedigree members. Pedigree members were serologically typed for HLA. We used likelihood analysis to statistically characterize the HLA-linked RA susceptibility locus. The genetic model assumed tight linkage to HLA. The analysis supported the existence of an HLA-linked RA susceptibility locus, estimated the susceptibility allele frequency as 2.16%, and estimated the lifetime penetrance as 41% in male homozygotes and as 48% in female homozygotes. Inheritance was recessive in males and was nearly recessive in females. In addition, the analysis attributed 78% of the variance within genotypes to genetic or environmental effects shared by siblings. The genetic model inferred in this analysis is consistent with previous association, linkage, and familial aggregation studies of RA. The inferred HLA-linked RA susceptibility locus accounts for approximately one-half of familial RA, although it accounts for only approximately one-fifth of the RA in the population. Although other genes may account for the remaining familial RA, a large portion of RA cases may occur sporadically.

Epidemiology of rheumatoid arthritis

Rheumatoid arthritis remains the most important form of arthritis seen in rheumatological practice in the developed world. It presents some tantalizing epidemiological features. It is a relatively rare disease particularly in young life. It has a marked female excess in all populations studied. There are suggestions that it might be declining in incidence, though the reasons for this are unexplained. The geographical distribution of the disease is remarkably homogeneous. There is evidence of a genetic factor as witnessed by familial aggregation particularly by increased disease occurrence in identical twins; though the large majority of such twins remain disease discordant throughout life. Whilst undoubtedly one of the most important genetic factors in explaining disease occurrence is located in HLA class II, genes encoded in this region are neither necessary nor sufficient on their own for disease development. The female excess remains unexplained but it suggests a hormonal basis for disease development. Factors supporting this hypothesis include the observed protective effect of the oral contraceptive pill, the increased risk in women who are nulliparous and the increased susceptibility to disease during the first three months postpartum. This latter finding may be linked with breast feeding: women who have breast fed, particularly after their first pregnancy, have an increased risk for disease development. It is possible that this is explained by a massive increase in circulating prolactin levels.

Twin studies in rheumatic diseases

Twin studies attract both clinicians and geneticists because of the value of the twin method in helping unravel the genetic predisposition to diseases and the role of environment in their causation. In the field of rheumatology, there are many case reports on twins concordant or discordant for diseases. Interesting as such reports may be, very few generalizations can be made from them. The concordance rate among monozygotic (MZ) twins indicates the maximum level of genetic contribution. Based on studies of systematically compiled twin series, the concordance rate is about 15% for rheumatoid arthritis; the rate is probably of the same order of magnitude for systemic lupus erythematosus (SLE). The fine specificity of antinuclear antibodies of MZ twins at least one of whom is affected by SLE is very similar, despite somatic generation of immune diversity. Up to now, twin studies have provided little information on the role of environmental factors in rheumatic diseases. A notable exception is a case-control study of MZ twins discordant for smoking that reinforced the role of smoking as a cause of lumbar intervertebral disc degeneration.

Decreasing incidence and prevalence of rheumatoid arthritis in Pima Indians over a twenty-five-year period

OBJECTIVE

To evaluate temporal trends in the incidence of rheumatoid arthritis (RA).

METHODS

Incident cases of RA were identified among a population-based cohort of Pima Indians in Arizona over the period 1965-1990.

RESULTS

Among 2,894 subjects, 78 incident cases of RA were identified. The age-adjusted incidence declined by 55% in men (Ptrend = 0.225), and by 57% in women (Ptrend = 0.017) after controlling for oral contraceptive or estrogen use and for pregnancy experience. During the same period, age-adjusted prevalence rates of active RA decreased by 29% in men (Ptrend = 0.63) and by 40% in women (Ptrend = 0.02). Fewer than 17% of subjects with known RA were taking slow-acting antirheumatic drugs (SAARDs) in 1990.

CONCLUSION

The decrease in incidence and prevalence of RA in this population over such a short period implicates the involvement of an environmental factor(s), other than exogenous estrogens, in the pathogenesis of the disease. However, the possibility that the observed decrease might be explained by an increased use of SAARDs in subjects with RA cannot be excluded.

T-cell antigen receptors in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic disease of unknown etiology characterized by chronic inflammation mainly in the joints. Several lines of evidence suggest that T cells are involved in the pathogenesis of the disease. RA is associated with certain HLA-DR alleles. Studies analyzing T-cell receptor transcripts in RA have found biased or preferential usage of certain V alpha and/or V beta gene segments by T cells infiltrating the synovial membrane or extravasating into the synovial fluid compared to peripheral blood. In certain patients few T-cell antigen receptor (TCR) clones dominated the infiltrating T cells, suggesting that T cells from the synovial membrane or the synovial fluid comprise oligoclonal populations of T cells. However, other studies have found a polyclonal population of T cells. In interpreting these results the phase of the disease (early vs. late RA), the source of T cells and the limitations of the methods used in these studies should be taken into consideration. However, it appears that synovial T cells comprise oligoclonal populations of T cells and that there is a bias towards particular TCR gene segments, although a specific TCR gene segment in RA has not emerged.

"Homozygosity" for the HLA-DR shared epitope contributes the highest risk for rheumatoid arthritis concordance in identical twins

OBJECTIVE

To assess the contribution of HLA-DRB1 alleles in determining rheumatoid arthritis (RA) concordance in monozygotic twins.

METHODS

Ninety-one monozygotic twins pairs in which at least 1 twin was affected were typed for HLA-DRB1 using both serologic methods and polymerase chain reaction amplification with sequence-specific oligonucleotide hybridization. The role of DR4 and of the shared epitope in disease concordance was investigated. Relative risks (RR) with 95% confidence intervals were determined.

RESULTS

Increased concordance for RA was observed in both DR4 positive and shared epitope positive pairs (RR 3.4 and 3.7, respectively). A 5-fold risk for RA concordance was seen in twins who were "homozygous" for the shared epitope, compared with those negative for the shared epitope.

CONCLUSION

In the absence of the shared epitope, RA concordance in monozygotic twins is rare. In contrast, "homozygosity" for the shared epitope is the most important factor in determining RA concordance.

Personal experience in the treatment of seropositive rheumatoid arthritis with drugs used in combination

Drug therapy for seropositive rheumatoid arthritis (RA) is entirely empiric. Single agents often fail to control synovial inflammation adequately. Combination therapy with relatively small doses of several agents shown to be effective in controlled trials when used alone often produce sustained and marked therapeutic control. Adverse effects are frequent but probably are no greater than those associated with the use of an effective dose of a single agent. As in the treatment of malignancy or tuberculosis, the use of potent drugs in combination may prevent or delay the clonal expansion of resistant cells. If this is indeed the case in the treatment of RA, then consideration should be given to the routine use of drug combinations. It is conceivable that we do patients a disservice by using potentially valuable drugs sequentially rather than in tandem. Whatever its merits, combination drug therapy for seropositive RA is clearly a stopgap measure whose usefulness will end as more specific means of controlling joint inflammation become available.

HLA-linked susceptibility to rheumatoid arthritis. A study of forty-one multicase families from northern India

OBJECTIVE

To analyze segregation of rheumatoid arthritis (RA) with HLA-DR4 and/or other alleles in multicase RA families and to compare the segregation patterns among affected and unaffected sibs.

METHODS

Forty-one multicase families (22 multiplex and 19 simplex) of northern Indian origin were studied for HLA haplotype segregation.

RESULTS

HLA haplotype sharing among affected sibs was observed more often than expected in families in which both parents were healthy (P < 0.05). RA cosegregated with a DR4 haplotype among offspring only in multiplex families in which both parents were unaffected (P < 0.05), while in simplex families, the disease segregated with DR4 only when the allele was from the affected DR4-heterozygous parent. In DR4-negative affected sib pairs, DR1, DR6, and DR10 were inherited from healthy parents more often than expected.

CONCLUSION

Dissimilar modes of inheritance are seen among multiplex and simplex RA families. The results of segregation analysis are compatible with the hypothesis that an epitope, rather than an individual DR antigen(s), is responsible for increased risk for development of RA.

Linkage of rheumatoid arthritis with HLA

OBJECTIVE

To determine whether HLA exerts a variable influence on the predisposition of siblings of probands with clinically mild and severe rheumatoid arthritis (RA).

METHOD

Calculation of crude and adjusted odds ratios for concordance rates in sibships sharing two, one and no HLA haplotypes with a proband with clinically mild and severe RA, and HLA haplotype sharing in multiply affected sibships in the same clinical groups.

RESULTS

Compared with a reference value of 1.0 in siblings sharing no HLA haplotypes with a proband with mild RA, siblings sharing two HLA haplotypes with a severely affected proband had a sibship concordance rate odds ratio of 9.7 (95% confidence interval 2.5 to 38.2). When adjusted for age, sex, and disease duration, the odds ratio was 7.6 (1.8 to 32.4). No other sibships showed concordance rates which were significantly higher than the reference group. HLA haplotype sharing in multiply affected sibships in which the proband had severe RA deviated significantly from random (two, one, and no HLA haplotypes shared: 53.3, 40, and 6.7%, respectively; expected 25, 50, and 25%), whereas in sibships of probands with mild RA they did not (14.6, 70.8, and 14.6%).

CONCLUSIONS

In the predisposition of siblings to RA, sharing HLA haplotypes with a proband is only important if the proband has severe RA. Mild RA is not genetically linked to the HLA region.

A T cell receptor beta chain variable region polymorphism associated with radiographic progression in rheumatoid arthritis

OBJECTIVE

In rheumatoid arthritis (RA) genetic factors influence susceptibility to disease and progression. Identifying these genetic factors may give more insight into the aetiology and pathogenesis of this disease. Furthermore, if these genetic markers can predict progression in an early stage of disease, timely institution of more aggressive treatment in patients with a bad prognosis may help to prevent joint damage. Several studies have shown that HLA-DRB1 alleles are associated with RA, whereas others have indicated that genes not linked to the HLA complex are also involved. Candidates for such genes are the T cell receptor (TCR) alpha/beta genes.

METHODS

The association of a polymorphism in a TCR beta chain variable region gene (TCR-V beta 8) with both risk for RA and radiographic progression of joint disease was analysed after a three year follow up. A cohort of 118 white patients with a duration of disease shorter than one year at entry, and 110 white controls were typed for this (BamHI) TCR-V beta 8 polymorphism.

RESULTS

The distribution of the two alleles, 2.0 and 23.0 kb, was identical in patients and controls. Radiographic progression (modified Sharp method) after a three year follow up, studied in 111 patients, was significantly less in the group possessing the 2.0 kb allele (p = 0.03).

CONCLUSION

This does not confirm the reported association of the (BamHI) TCR-V beta 8 2.0 kb allele with RA. By contrast with previous findings in smaller studies, in the present study this 2.0 kb allele was protective against radiographic progression. Because well known prognostic variables in RA were corrected for, the findings indicate that the TCR-V beta 8 polymorphism studied is a new prognostic marker for this disease.

Epistatic modeling in rheumatoid arthritis: an application of the Risch theory

Rheumatoid arthritis (RA) is a disease of unknown etiology but with a presumed complex pattern of inheritance. Risch [Am J Hum Genet 46:222-228, 1990] has shown that the recurrence risk ratio, lambda R, (which is defined as the risk to type R relatives vs. the population prevalence) can be used to evaluate patterns of inheritance in genetically complex diseases. We have used the Risch theory to examine some multiple locus models of inheritance in RA. Recurrence risk ratios in MZ twins and in 1st, 2nd, and 3rd degree relatives are summarized from the literature. The limited data available supports at least a two-locus model of inheritance for RA (assuming that one locus is HLA). Better estimates of the recurrence risk ratios in RA families are required so that the Risch theory can be pursued further.

Occurrence of autoimmune diseases and relationship of autoantibody expression with HLA phenotypes in multicase rheumatoid arthritis families

Presence of autoimmune diseases and relationship of autoantibody expression with HLA association has been studied in 44 multicase rheumatoid arthritis (RA) families of Asian Indian origin. An increased prevalence of systemic lupus erythematosus (SLE) was observed in relatives (2.3%). Although HLA-DR4 segregated preferentially with seropositivity in general, no difference was observed among seropositive versus seronegative RA. On the other hand, no HLA association was observed with ANF positivity in these families. An increased frequency of DR7 in the ANF negative and RF negative group of RA patients compared to positive groups suggests that it may act as protective element for the development of autoantibodies in RA. An increased occurrence of DR4 in relatives affected with SLE was observed. While RA segregated mostly with HLA-DR4 in these families, autoimmune thyroid disease and insulin dependent diabetes mellitus (IDDM) segregated with HLA-DR3 suggesting the involvement of at least two sets of HLA-linked autoimmunity favouring susceptibility genes in the Indian population.

Effect of disease severity on rheumatoid arthritis concordance in same sexed siblings

To assess the factors in a proband with rheumatoid arthritis (RA) that might predict the occurrence of the disease in siblings, 240 same sexed sibships (190 female, 50 male) in which the proband had classical or definite RA were clinically and immunologically documented. Sibship concordance rates were consistently higher for features of severe disease in the proband, reaching statistical significance for a clinical score of disease severity (the SS index). This trend for increasing disease severity to be associated with increasing sibship concordance rates could not be accounted for by age or disease duration of the proband. These results suggest that siblings of probands with severe RA are at greater risk of developing RA than those of probands with mild disease.

Rheumatoid arthritis in twins: a study of aetiopathogenesis based on the Australian Twin Registry

The 1980 cohort of the Australian Twin Registry contains 3808 pairs of twins, 258 of whom self reported a diagnosis of rheumatoid arthritis (RA) in one or both subjects. Seventy two pairs were lost to follow up by 1990. The remaining 186 pairs received a self administered questionnaire, followed, if necessary, by telephone interviews to them, their general practitioners, and their specialists. Twenty discordant and three concordant pairs of twins were verified as having RA. The prevalence of RA in this sample was 0.40%. There was an 89% false positive rate for the self reported diagnosis of RA. Pairwise concordance percentages for RA were as follows: monozygotic 21% (95% confidence interval (CI) = 6 to 44), dizygotic 0% (95% CI = 0 to 25). It was concluded that: (a) there is a high false positive rate in self reporting RA; (b) the prevalence of RA in Australia may be less than the 0.8-1.0% often quoted; and (c) genetic factors play some part in the aetiopathogenesis of RA but do not account entirely for its determination.

Differences in t cell receptor restriction fragment length polymorphisms in patients with rheumatoid arthritis

OBJECTIVE

The purpose of this study was to determine whether a T cell receptor (TCR) polymorphism, either by itself or in combination with particular HLA polymorphism, leads to susceptibility to rheumatoid arthritis (RA).

METHODS

Eight restriction fragment length polymorphisms (RFLPs) detected with TCR gene segments were investigated in 46 individuals with RA and were compared with data from normal control subjects.

RESULTS

A statistically significant difference in the genotype frequencies of a Taq I RFLP detected with the TCR alpha constant region (C alpha) gene was noted. In addition, when the DR4+ subpopulations were examined, the allelic frequency of a 2-kb Bam HI fragment detected with a V beta 8 gene was increased in the samples from RA patients (P less than 0.0086).

CONCLUSION

The results of this study suggest that germline differences in the TCR repertoire may be associated with RA, and that there is a contributory effect of DR4+ haplotypes with certain TCR haplotypes in susceptibility to RA.

A revised estimate of twin concordance in systemic lupus erythematosus

OBJECTIVE

Based on a small clinical series and previously published case reports, concordance for systemic lupus erythematosus (SLE) among monozygous (MZ) twins has been reported to be as high as 69%. Using a larger and less biased sample, we provide another estimate of this percentage.

METHODS

We established a registry of twins with SLE, based upon self-reports and information provided by the patients' physicians. We used DNA fingerprinting to validate the reported zygosity in a sample of these twins.

RESULTS

Of 107 twin pairs meeting the American College of Rheumatology 1982 revised criteria for the diagnosis of SLE, 24% of 45 MZ pairs and 2% of 62 dizygous (DZ) pairs were concordant. The frequency distributions of diagnostic criteria and disease symptoms in the SLE patients were similar to those in other published reports of SLE patients. Zygosity was confirmed by DNA fingerprinting in a subsample of 15 self-described MZ twins and 7 self-described DZ twins. All individuals had correctly predicted their zygosity.

CONCLUSION

MZ concordance for SLE is similar to that for other autoimmune diseases and is much lower than previously believed.

Variable-constant segment genotype of immunoglobulin kappa is associated with increased risk for rheumatoid arthritis

OBJECTIVE

To further investigate the association of rheumatoid arthritis (RA) with a particular genotype identified by a restriction site polymorphism near the constant segment of immunoglobulin kappa (C kappa).

METHODS

The frequencies of genomic DNA polymorphisms detected within or near C kappa (the most C kappa-proximal variable segment [V kappa] B3 and a T lymphocyte marker [CD8A]) were determined by Southern blotting and hybridization. The frequencies of coding-region polymorphisms of C kappa (Km allotypes) were determined by amplification by polymerase chain reaction followed by restriction enzyme digestion.

RESULTS

Although the frequencies of B3, Km, and CD8A genotypes were not different between RA and normal control populations, more individuals were homozygous for both C kappa and B3 in the RA group (relative risk 2.2, P less than 0.01), especially in the DR4-negative RA subgroup (relative risk 3.9, P less than 0.001).

CONCLUSION

The homozygous genotype of an approximately 30,000-base region including the C kappa segment confers an elevated risk for RA, particularly in the DR4-negative subgroup.

HLA haplotype sharing in rheumatoid arthritis sibships: risk estimates in siblings

The distribution of the number of parental HLA haplotypes shared by sibs with rheumatoid arthritis (RA) has been used to obtain information on the genetics of the disease. Thirty-four RA sibships (25 sib-pairs, 9 sib-trios) were ascertained, all of which were HLA typed and which satisfied the 1958 American Rheumatism Association criteria for "definite" RA. These were combined with other published but nonoverlapping data from the literature; thus, 143 sib-pairs, 36 sib-trios and 4 sibquads were identified. The affected RA sibs shared two, one and zero parental HLA haplotypes in a ratio of 40: 45: 15 which was significantly different from random expectations (p less than 0.05). Risk estimates for sibs of probands for those sharing two, one and zero parental HLA haplotypes were 6.2%, 3.5% and 2.3% respectively. Risks subdivided by DR genotype of the proband are also calculated, the highest (8.7%) being for sibs sharing two haplotypes with a proband carrying at least one DR4 allele. The manuscript also considers genetic information in relatives other than siblings; an extension of the affected relative pair haplotype sharing method to second and third degree kinships is presented.

Association of rheumatoid arthritis with a dominant DR1/Dw4/Dw14 sequence motif, but not with T cell receptor beta chain gene alleles or haplotypes

HLA-DR, HLA-DQ, and T cell receptor beta (TCR beta) chain gene polymorphisms were investigated in 43 patients with rheumatoid arthritis (RA), in 10 patients with Felty's syndrome (FS), and in 5 RA multicase families. RA was found to be strongly associated with a DRB1 gene sequence motif present in DR1, DR4-Dw4, and DR4-Dw14 alleles. Ninety-three percent of RA patients were positive for at least 1 of these alleles, providing strong support for the "shared epitope hypothesis." The frequency distribution of this sequence motif suggests a dominant mode of inheritance. All 10 FS patients were DR4-Dw4 positive. Different DR-DQ associations among DR4 positive RA and FS patients indicate heterogeneity in the genetic susceptibility to these 2 disease entities. Furthermore, analyses of TCR V beta 8, V beta 11, and C beta gene polymorphisms did not support the notion of an influence of TCR beta germline allotypes on RA susceptibility.

Investigating the HLA component in rheumatoid arthritis: an additive (dominant) mode of inheritance is rejected, a recessive mode is preferred

We examined the mode of inheritance of rheumatoid arthritis (RA) and estimated the genetic contribution of the HLA-linked locus to the development of RA using data from 111 multiplex families (54 London, 57 Cleveland), and 43 randomly ascertained patients (Seattle). HLA-DR4 was present in 78 multiplex probands (70%); a further 16 probands who were negative for DR4 were positive for DR1. Both DR4 and DR1 were significantly in excess when compared to control population frequencies (P less than 0.001); an additional finding was an excess of DR7, although the numbers of probands with DR7 were small. Despite the well-established HLA association with RA, neither recessive nor additive (dominant) modes of inheritance, nor any intermediate models have been ruled out using affected sib-pair and antigen genotype frequency among patients (AGFAP) methods. However, in our study the AGFAP data for HLA-DR4 and DR1 were close to recessive expectations (P = ns) while an additive (dominant) mode of inheritance was rejected (P less than 0.001). The same results were obtained by an independent method which considered HLA-DR transmission from affected parents to their affected children. The affected sib-pair haplotype sharing method showed deviation from random expectations but did not allow discrimination between recessive and additive (dominant) modes. The effect of the HLA-linked locus on familiarity accounted for only a 1.61-fold increased risk to sibs over the population prevalence, compared to an observed value of 3.90. This indicated that there could be at least one other non-HLA locus predisposing to RA with a weight that is slightly greater than that of HLA.

Rheumatoid arthritis in identical twins: a clinical and immunogenetic study of eight concordant pairs derived from a nationwide twin panel

The nationwide Finnish Twin Cohort was linked with the national Sickness Insurance Register. Eight identical twin pairs concordant for rheumatoid arthritis (RA) fulfilling the American Rheumatism Association criteria were identified. All 16 cases were known to be seropositive. Four pairs had at least one additional first-degree relative with RA, and the prevalence of RA among all the first-class relatives was 9%. HLA-typing was performed for 15 patients representing the eight pairs; six pairs carried the DR4 allele, and three of these pairs were putative homozygotes. Nodules and Sjögren syndrome occurred fairly frequently (in 7 of 16 and 6 of 13 cases examined, respectively), but concordance within pairs was no higher than that expected by chance. The course of the disease was fulminant in one patient and in several others the disease had led to marked joint destructions. The findings pointed out to some intrapair similarity in the progression of the joint damage and in the type of complications caused by gold.

Psychoimmunology and rheumatoid arthritis: concepts and methodologies

The recent growth of knowledge about the immune-neuroendocrine network has important implications for future research into psychosomatic hypotheses about the aetiology of rheumatoid arthritis. The available evidence suggests that three phases of the aetiological process in rheumatoid arthritis need to be considered separately because of the different role that psychological and social variables may play at different points of the disease. These are the loss of immunological tolerance, the onset of joint inflammation and the long-term disease course. It is suggested that future studies will need to be prospective, include multiple sampling techniques and comparisons within patient groups if they are to elucidate the precise role of psychoneuroimmunological factors in rheumatoid arthritis.

Rheumatoid factor induction in the mouse: sex differences and the effect of the sex steroids

Female CBA mice produced a significantly higher plasma rheumatoid factor (RF) response to Salmonella typhosa lipopolysaccharide than did male mice. The peak level in females was observed on day 5-6 after injection and in males on day 7-8. Elevated RF levels continued to be detected more than 30 days later. A second injection of LPS, 38 days after the first, to assess the secondary response, had no more than an additive effect on plasma RF concentration, although the day of peak response was earlier by two days in both sexes. Administration of oestradiol-17 beta by Silastic implant brought forward the day of peak response by two days in both sexes although it reduced its amplitude considerably. Testosterone had little effect on the peak concentrations achieved in both sexes, but did produce a slower decay in plasma RF level. This investigation indicates that the sex hormones can influence the response to LPS, a polyclonal B cell activator. This may have implications for the sex differences seen in autoimmune diseases.

Immunoglobulin kappa genotype confers risk of rheumatoid arthritis among HLA-DR4 negative individuals

Because DNA polymorphisms of immunoglobulin kappa confer risk for rheumatoid arthritis (RA) and not all persons with RA have the HLA-DR4 marker, genomic polymorphisms of immunoglobulin kappa and HLA-DR beta were determined in white patients with RA. Compared with control subjects matched for DR beta genotype, the homozygous genotype of the constant segment of immunoglobulin kappa (C kappa) was more frequent in the subgroups of RA patients without the DR beta genotype corresponding to HLA-DR4 (relative risk 6.2, P less than 0.01) and patients without DR4 or DR1 (relative risk 6.7, P = 0.013), but not in the DR4+ RA subgroup. Therefore, RA may be a genetically heterogeneous disease, with HLA-DR4 marking one genetic subset and the homozygous C kappa genotype marking another.

Association of complement alleles C4AQ0 and C4B5 with rheumatoid arthritis in Japanese patients

We investigated polymorphisms of complement components C2, C4, and factor B (BF) in Japanese patients with rheumatoid arthritis (RA). The frequencies of C4AQ0 (32.1%) and C4B5 (35.9%) among RA patients were significantly higher than among healthy control subjects. C4B5 was strongly associated with HLA-Bw54, Bw59, DR4.1, and DQw4. C4AQ0 showed no association with HLA-Bw54 or Bw59, but there was weak association with HLA-DR4.1 and DQw4. The number of persons with both C4AQ0 and C4B5 was significantly higher in the RA patient group (relative risk 13.5). C2C and BFS were the most common alleles in RA patients, as well as in healthy control subjects. These data support the existence of 2 different putative susceptibility haplotypes (HLA-Bw54 or Bw59;C2C; BFS;C4A3;C4B5;DR4.1;DQw4 and C2C;BFS; C4AQ0;C4B1 or C4B2) in Japanese patients with RA.

DNA polymorphism of immunoglobulin kappa confers risk of rheumatoid arthritis

To examine the hypothesis that a hereditary factor linked to the immunoglobulin kappa constant segment (C kappa) contributes to risk of rheumatoid arthritis (RA), white persons with RA were examined for Sac I restriction site polymorphisms. RA patients were more likely to have the 5/5-kb C kappa genotype than white control subjects (relative risk 2.8, P less than 0.02). A subgroup of RA patients who were positive for serum rheumatoid factor had a relative risk of 2.4 (P less than 0.05). The subgroup without serum rheumatoid factor had an even higher relative risk of 9.7 (P less than 0.05). The results suggest that immunoglobulin kappa is an important component in the genetic predisposition toward RA.

Lupus erythematosus and rheumatoid arthritis--groups of defects in microdebridement (polygenetic defects exceeding the fault tolerance threshold--a consequence of natural defense mechanisms)

Lupus erythematosus (LE) and rheumatoid arthritis (RA) are groups of defects in microdebridement of tissue which includes removal of infectious agents and cellular debris. They are the phenotypic response to a number of polygenetic and/or induced defects. The recognized clinical patterns of these disorders are the responses to accumulated tissue debris and complications of secondary debridement mechanisms that cannot function properly due to basic defects in the debridement system. The series of events that occurs after infection or tissue damage is polygenetic and involve multiple pathways. Genetic polymorphism of this group of mechanisms increases survival against a wider variety of infections. An organism capable of bypassing or destroying a specific step in the host defense is still eliminated by the host in spite of the created defect (a fault tolerant system). However, a single mutant error of this same step creating the same defect will not disrupt the host to the point of clinical illness or death. The pathways are broad enough to bypass some mutant errors. It is the same fault tolerant system. Increased pressure on the system from infection or tissue damage or a combination of multiple genetic defects results in enough faults to exceed the threshold of fault tolerance and produce clinical patterns of disease. The large number of possible combinations of defects gives rise to marked disease variation among patients. The higher frequency of some defects or combination of defects ces subsets. Inbred strains of animals have less polymorphism and thus some strains have a greater susceptibility to infections, LE and RA. Many of the phenomena that occur in LE and RA are secondary to the basic defect of inadequate tissue debridement. Rheumatoid factor (RF) is generally a normal beneficial phenomenon of increasing particle size so that immune complexes can more readily be removed by the reticuloendothelial system. In the presence of defective microdebridement the system is overloaded and no longer effective. This results in circulating RF. There are clearly multiple basic genetic defects. For example, the known multiple genetic defects in complement in LE are relevant to the systems involved. They are important ligands for defense and debridement mechanisms. A null allele is not likely to be a secondary phenomenon. It might be in a fault tolerant site and contribute to disease in one host, and yet not contribute to disease in another host.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromosome 14 markers in rheumatoid arthritis

Phenotype frequencies for variants of the chromosome 14 markers, alpha 1 antitrypsin (protease inhibitor--Pi), and immunoglobulin heavy chain gene allotypes (Gm and Am) were examined in affected and unaffected members of multicase rheumatoid arthritis (RA) families and compared with published population data. Significantly higher frequencies of phenotypes containing Pi*Z and Pi*S were observed in unrelated index RA cases compared with UK population data. There was also a higher frequency of Pi*Z in family members without RA than in population controls but no such difference for the frequency of Pi*S. No difference in the frequency of PiM1M2 heterozygotes was seen between patients with RA and population controls. An examination of clinical data failed to show any relation between any particular feature of RA and positivity for Pi*Z or Pi*S. No significant differences in frequency of Gm phenotypes were observed between patients with RA and controls. Significant association was found, however, between Pi*Z and Gm phenotypes containing Gm(zax;g). These associations are interpreted as indicating linkage disequilibria between these alleles. No interactions between DR4 and either G1m(z), (a), or (x) allotypes were apparent in patients with RA. A significant association was seen in the index RA cases between DR4 and Pi phenotypes carrying Z or S alleles. Observations from this study provide evidence for the existence of a genetic component for RA susceptibility encoded on chromosome 14. An interactive effect of these genes with DR4 towards susceptibility appears likely.