Tap gene associations in UK caucasoids

The authors determined the allele frequencies of the TAP1 and TAP2 transporter genes in a healthy UK Caucasoid population by ARMS-PCR. TAP1A was the most frequent TAP1 allele by far, being present in 76% of subjects. TAP1 alleles could not be assigned in 24% of subjects, since the combinations TAP1A/1b and TAP1C/1D cannot be separated. TAP2A was the most frequent TAP2 alleles (75% of subjects) followed by TAP2B (43%), TAP2C (11%), TAP2D (8%) and TAP2E (6%). The authors also identified an individual with a previously undescribed TAP2 allele, TAP2H (isoleucine at amino acid [aa] 379, alanine at aa 565, alanine at aa 665). It was not possible to assign unequivocally TAP2 alleles in 15 individuals (9%) as TAP2A/D and TAP2C/E cannot be distinguished from each other. To address this problem a separate study of families of rheumatoid arthritis (RA) patients selected for this ambiguity were studied. In all five informative families, TAP2A/2D was confirmed as the combination present. In the population studied no evidence was found for linkage disequilibrium between TAP1 and TAP2 or between the TAP genes and HLA-DP. There was no evidence for extensive linkage disequilibrium between the TAP genes and HLA-DQR, although TAP2B was associated with DRI (delta = 0.056, corrected P < 0.01) and TAP2D with DR4 (delta = 0.018). In the RA families studied, TAP2D was found on DRB1*0401-bearing haplotypes.

Increased levels of sCD23 in rheumatoid arthritis are related to disease status

The low affinity receptor for IgE (Fc epsilon RII, CD23) is involved in many aspects of T and B cell regulation. In the current study, serum levels of sCD23 were measured in monozygotic (MZ) twins discordant for rheumatoid arthritis (RA) to examine whether an increased level of sCD23 in RA is, at least in part, genetically determined. Paired analysis showed significantly elevated sCD23 levels in affected twins when compared with their unaffected co-twins (p < 0.01). There was no significant difference in sCD23 in the unaffected twins compared with normal controls. Higher levels of sCD23 were found in males compared to females in both affected and unaffected twins. Soluble CD23 showed a significant increase with age in RA affected twins (p = 0.013), but no association with disease duration (p = 0.87). There was no significant variation in sCD23 level with HLA-DR phenotype. We conclude that elevations in serum sCD23 in patients with RA are primarily disease related.

"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.

HLA-DP does not contribute towards susceptibility to systemic lupus erythematosus

OBJECTIVES

To determine whether HLA-DP genes are involved in determining susceptibility to systemic lupus erythematosus (SLE).

METHODS

HLA-DPA1 and DPB1 genes were amplified by PCR of DNA samples from a panel of patients with SLE and normal controls. Amplified DNA was blotted on to nylon filters and probed with sequence-specific oligonucleotide (SSO) probes.

RESULTS

No DPA1 or DPB1 allele was significantly associated with SLE, or with any immunological or clinical subset of SLE. Evidence was found for only limited linkage disequilibrium between HLA-DP and HLA-DQ/DR variants, and none between HLA-DP and the TAP2 gene.

CONCLUSIONS

These data indicate that HLA-DP genes do not contribute towards determining susceptibility to SLE.

Influence of previous exposure to human parvovirus B19 infection in explaining susceptibility to rheumatoid arthritis: an analysis of disease discordant twin pairs

OBJECTIVES

To assess the association between exposure to parvovirus B19 and susceptibility to rheumatoid arthritis (RA).

METHODS

One hundred and fifty five twin pairs (76 monozygotic (MZ) and 79 dizygotic (DZ)), discordant for RA, were tested for the presence of IgG antiparvovirus antibodies using ELISA. The data obtained were analysed using conditional logistic regression, from which odds ratios and 95% confidence intervals were calculated.

RESULTS

Overall, there was no association between exposure to parvovirus and RA (OR = 1.2, 95% CI: 0.7-1.7). However, in two subgroups there was a suggestion of an association. These were: (1) pairs where the affected twin was rheumatoid factor (RF) seronegative (OR = 2.0, 95% CI: 0.9-12.4) and (2) in opposite-sexed twin pairs where the affected twin was female (OR = 3.0, 95% CI: 0.9-11.6).

CONCLUSION

Previous exposure to parvovirus infection did not explain disease susceptibility in both MZ and DZ discordant pairs with rheumatoid arthritis. This infection, however, might be relevant in some subgroups.

[Idiotypic T-lymphocyte receptor in animal and human autoimmune diseases]

Animal models have demonstrated that the T-cell repertoire is restricted when the response to defined autoantigens is studied. Anti-V beta specific monoclonal antibodies or specific V beta-derived peptides can be used to manipulate autoreactive T-cells to either prevent or treat established experimental disease in animals. In some animal models of arthritis, inherited differences in the TCR repertoire can protect against the development of experimental autoimmune disease. Human studies have generally given conflicting results with regard to the role of the TCR complexes as susceptibility loci for disease. This may be due to the heterogeneity present in the human population and/or in the diseases studied. In some diseases, where there is convincing evidence for putative autoantigens (multiple sclerosis) or distinct immunodysfunctional pathology (hypergammaglobulinaemic primary Sjögren's syndrome), restricted TCR repertoires and germline TCR susceptibility loci can be discerned. Recent evidence suggests that autoimmune disease may eventually be mapped to regulatory regions of the TCR V genes rather than the allelic differences in coding region structure. This may have implications for the future therapy of autoimmune rheumatic disease.

Polymorphisms of the TAP2 transporter gene in systemic lupus erythematosus

OBJECTIVES

To determine whether the TAP2 transporter gene, which lies between HLA-DP and HLA-DQ, is involved in determining susceptibility to systemic lupus erythematosus (SLE).

METHODS

TAP2 types were determined by ARMS-PCR in 89 white patients with SLE and 156 control subjects.

RESULTS

No particular TAP2 dimorphism or allele was associated with SLE or with any clinical/immunological subgroup of SLE. Furthermore, there was no evidence for significant linkage disequilibrium between TAP2 and HLA-DQ/DR in SLE.

CONCLUSIONS

These data suggest that TAP2 is not a disease susceptibility gene for SLE and that the disease-predisposing haplotypes do not extend as far as TAP2. This indicates that any HLA-DP association with SLE must be independent of other class II (DQ/DR) associations.

Antibodies to major histocompatibility complex class II inhibit proliferation, but increase production of soluble CD23 in lymphoblastoid B-cell lines

Class II major histocompatibility complex (MHC) proteins bind and present peptide antigens to T cells. Moreover, their function as signal transduction molecules has recently been emphasized. Here we used Epstein-Barr virus (EBV)-transformed B-cell lines (B-LCL) in experiments to investigate the changes induced by binding of specific antibodies to HLA-DR molecules. Binding of the antibodies induced, in an allele-specific manner, striking non-cytotoxic inhibition of B-LCL proliferation. This inhibition was associated with an increase in shedding of soluble CD23. These findings provide further evidence for the function of MHC class II proteins as signal transduction molecules which may be important in B-cell activation.

Twin concordance rates for rheumatoid arthritis: results from a nationwide study

We report the concordance rate for RA in a nationwide study of 91 monozygotic (MZ) and 112 dizygotic (DZ) pairs. Twin pairs were recruited from both a national media campaign and a 2-month prospective inquiry of all UK rheumatologists. Disease status was established following a structured clinical and serological appraisal, together with radiological assessment where necessary. Zygosity was confirmed using DNA fingerprinting. In all, 14 (15.4%) of the MZ and four (3.6%) of the DZ pairs were disease concordant (risk ratio: 4.3 95% CI 1.5 to 12.6). There was no difference in the concordance between the media and clinical derived twins. Further the excess MZ concordance persisted after adjusting for age, age at disease onset, sex and rheumatoid factor status. Analysing the data in relation to the timing of disease onset in the first affected twin showed that subsequent disease risk in the initially unaffected co-twins of the MZ affected probands increased with increasing duration of follow-up. We conclude that the overall MZ concordance at 15% is lower than the 30% figure normally quoted from a study some 30 years ago and sets a ceiling at the potential genetic contribution to disease susceptibility.

The expressed T cell receptor V gene repertoire of rheumatoid arthritis monozygotic twins: rapid analysis by anchored polymerase chain reaction and enzyme-linked immunosorbent assay

Because of heterogeneity in the outbred human population, it has been difficult to determine the genetic factors that influence the expressed T cell receptor (TcR) repertoire in autoimmune diseases. To overcome this problem, we have developed a combination of anchored polymerase chain reaction (APCR) and enzyme-linked immunosorbent assay (ELISA) that can accurately assess TcR V gene frequencies in numerous clinical samples. The results are independent of amplification efficiency, and V gene usage can be readily analyzed with an ELISA plate reader and associated software. Using this method, the TcR V beta gene repertoires in peripheral lymphocytes from nine sets of identical twins, normal, concordant or discordant for rheumatoid arthritis (RA), were studied. The TcR V beta results were compared with TcR V gamma frequencies in the same specimens as determined by APCR-ELISA and cDNA sequence analysis. The results showed a marked similarity in the TcR V beta gene repertoires between identical twins, compared to unrelated subjects (p < 0.05) whether or not they were concordant or discordant for RA. In contrast, the TcR V gamma gene repertoires in the monozygotic twins differed as much as in controls. The data imply that (a) the human TcR V beta gene repertoire in peripheral blood is genetically controlled, whereas (b) the TcR V gamma gene repertoire is primarily influenced by environmental stimuli, and (c) RA causes no consistent change in TcR V beta repertoire of peripheral blood. The APCR-ELISA method, in the context of large-scale family and population studies, should facilitate a more precise delineation of the genetic factors that regulate human TcR V beta expression.

Lack of association of increased antibody levels to mycobacterial hsp65 with rheumatoid arthritis: results from a study of disease discordant twin pairs

OBJECTIVES

To investigate the role of humoral immunity to mycobacterial hsp65 in the aetiology of rheumatoid arthritis.

METHODS

Levels of IgG antibodies to recombinant mycobacterial hsp65 were measured by enzyme linked immunosorbent assay (ELISA) in serum samples of 152 twin pairs discordant for RA and in serum samples from 62 normal blood donors.

RESULTS

No significant differences between antibody levels in the subjects with RA compared either with their unaffected twins or with a group of normal blood donors was observed. In the monozygotic twins there was a strong but negative association between levels of antibody to hsp65 and disease status. Zygosity, sex, and HLA status did not significantly affect levels of antibody to hsp65.

CONCLUSION

Previous reports of an association between hsp65 and RA were not confirmed.

An identical twin pair discordant for rheumatoid arthritis and ankylosing spondylitis

Both rheumatoid arthritis (RA) and ankylosing spondylitis (AS) have an increased familial occurrence and each disease is associated with the inheritance of specific HLA antigens. We report a pair of identical twin brothers with discordant disease phenotypes: one developed AS at the age of 26, and the other developed RA at the age of 55. The twins possessed both of the disease susceptibility antigens HLA B27 and DR4. Differences in the twins' environmental exposure are discussed.

Multiplex ARMS-RFLP: a simple and rapid method for HLA-DR4 subtyping

We have developed a simple and rapid non-radioactive technique for HLA-DR4 subtyping. A multiplex ARMS-RFLP (Amplification Refractory Mutation System--Restriction Fragment Length Polymorphism) system allows HLA-DR4 subtyping by analysis of the products of two multiplex ARMS reaction mixtures. For some cases, restriction enzyme digests (Hae II and/or SacII) of the products are analysed. The technique relies on the fact that an ARMS primer with a mismatch at its 3'-end with respect to the template will not be elongated under PCR conditions. Hence, by designing ARMS primers such that different HLA-DR4 alleles yield PCR products of different lengths, only two reactions, each using a mixture of different ARMS primers, are sufficient to type all of the known HLA-DR4 alleles. This system can distinguish between HLA-DR4 'homozygotes' and 'heterozygotes' since every HLA-DR4 allele can be detected. The ARMS conditions were optimized using DNA from cell lines. This technique has now been used to type a panel of rheumatoid arthritis patients and controls.

HLA-DPA1 and HLA-DPB1 in rheumatoid arthritis and its subsets

The aim of this study was to examine the relationship between HLA-DP and susceptibility to articular and extra-articular features (Felty's syndrome and vasculitis) of rheumatoid arthritis (RA). The possible association of DP types with severity of articular disease was also analysed. No statistically significant associations were observed between HLA-DP alleles and articular or extra-articular features of RA, or to the severity of the arthritis when p was corrected for the number of alleles tested.

Divergent T cell receptor gamma repertoires in rheumatoid arthritis monozygotic twins

OBJECTIVE

To determine if the expressed T cell receptor (TCR) gamma repertoire is altered in rheumatoid arthritis (RA).

METHODS

Peripheral blood lymphocytes were collected from monozygotic twins who were either concordant or discordant for RA, or from a normal twin pair. TCR gamma-specific complementary DNA libraries were constructed using the anchored polymerase chain reaction. Gene usage was analyzed by plaque hybridization and sequencing.

RESULTS

The expressed TCR V gamma repertoires both in RA patients and normal subjects were extremely diverse. Monozygotic twins who were concordant for RA expressed very different frequencies of TCR V gamma genes.

CONCLUSION

RA does not lead to a specific clonal expansion or deletion of TCR V gamma genes in peripheral blood.

Unusual DQA-DR haplotypes in rheumatoid vasculitis

DQA and DQB variants and HLA haplotypes were defined in Caucasian subjects with rheumatoid arthritis (RA), in a rheumatoid subset characterized clinically by extra-articular features of major vasculitis, and in controls. DQ variants were defined using a panel of sequence specific oligonucleotide probes. In RA subjects without extra-articular features the frequency of DQB*0301 was significantly increased but this was secondary to the main association with DR4. In rheumatoid vasculitis by contrast, DQB*0302 rather than DQB*0301 was increased in frequency, in addition to an increase of C4A null alleles. Family studies showed that DR4 negative haplotypes had an increased frequency of unusual DR-DQA combinations as compared to other rheumatoid subsets. These findings are in keeping with the concept that genes within the MHC other than DR4 have a disease-modifying role in rheumatoid subsets. HLA haplotypes were defined in a family where the proband has RA and Felty's syndrome and an affected sister has rheumatoid vasculitis. These siblings share a DR4 bearing haplotype typing for DQB*0301, and the sister with rheumatoid vasculitis has a DR4 negative haplotype carrying a C4A null allele and an unusual DR-DQA combination.

Regulation of the mature human T cell receptor gamma repertoire by biased V-J gene rearrangement

To delineate how gene rearrangement influences the expressed human gamma delta T cell repertoire, we generated T cell receptor gamma (TCR gamma) V domain-specific cDNA libraries from the peripheral lymphocytes of eight donors and sequenced a total of 232 TCR gamma gene transcripts. The libraries consisted of both in-frame and out-of-frame rearranged TCR gamma genes. The in-frame TCR gamma gene transcripts were used to determine the diversity of functional T cells, whereas the out-of-frame transcripts, primarily derived from alpha beta T cells, were used to assess the frequencies of TCR V gamma-J gamma rearrangements in progenitor T lymphocytes. The results showed that both sets of transcripts exhibited strikingly restricted V gamma-J gamma combinations. Only 11 of 40 potential V gamma-J gamma rearrangements were common ( > or = 3% of total). The pattern of gene usage in the functional and nonfunctional transcripts was similar and did not differ markedly among donors. The only exception was the predominance of V gamma 9-JP in potentially functional transcripts from seven of eight individuals. These results show that V gamma-J gamma rearrangement is nonrandom and suggest that the diversity of TCR gamma genes in the functional gamma delta T cell repertoire partly depends upon preferentially rearranged V gamma-J gamma gene combinations. However, the expansion of V gamma 9/V gamma 2 T cells in adult peripheral blood can only be explained by antigenic selection of relatively rare V gamma 9-JP recombinants.

An abnormal T cell repertoire in hypergammaglobulinaemic primary Sjögren's syndrome

T cell antigen specificity is determined by the products of the genes which encode the variable regions of their receptors. Of the T cell receptor (TCR) variable region gene products examined, only V beta 6.7a TCR-positive lymphocytes were reduced in primary Sjögren's syndrome patients with IgG1 hypergammaglobulinaemia compared with an age-, sex- and HLA-matched control population. The levels of V beta 6.7a T cells were also significantly reduced when these patients were compared with an age- and sex-matched but HLA-unmatched control group and non-tissue typed normal people of both sexes. Since published studies show no such abnormality in rheumatoid arthritis, systemic lupus erythematosus or other autoimmune diseases, this abnormality may reflect a pathogenic process specific to primary Sjögren's syndrome.

Is rheumatoid arthritis in Indians associated with HLA antigens sharing a DR beta 1 epitope?

HLA class II antigens were identified in a group of 44 patients with rheumatoid arthritis (RA) originating largely from the north or northeast of the Indian subcontinent and resident now in east London. Compared with 67 locally typed east London Asian controls, the prevalence of three HLA-DR antigens was raised in the patients: DR1 18.2% v 6.0% chi 2 = 3.99, DR4 20.5% v 11.9% chi 2 = 1.48, and DRw10 27.3% v 8.9% chi 2 = 6.56. These differences were also found when the patients with RA were compared with a larger control group of 110 northern Indians: DR1 18.2% v 7.2% chi 2 = 4.02, DR4 20.5% v 7.2% chi 2 = 5.56, and DRw10 27.3% v 8.1% chi 2 = 9.7. Twenty five (57%) of the patients expressed at least one of these antigens. All patients were also characterised for HLA-Dw types by mixed lymphocyte culture typing. The prevalence of the HLA-DR4 associated Dw types in the patients was: Dw4 2.3%, Dw10 0%, Dw14 11.4%, and Dw15 6.8%. The DR beta 1 chains of DR1 and DRw10 together with the Dw types of DR4 other than Dw10 share amino acid residues in a region of the third hypervariable region considered to be critical in antigen presentation. It is concluded that RA in Indians is associated with these HLA antigens, and data from this study support the hypothesis of a cross reactive epitope common to HLA specificities associated with RA.

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.

Autoimmune thyroid disease and thyroid autoantibodies in rheumatoid arthritis patients and their families

All 504 available members from 58 multicase rheumatoid arthritis (RA) families were interviewed and examined for the presence or history of autoimmune thyroid disease and were tested serologically for thyroid autoantibodies. The serological data were compared with those from a major population survey which used the same assay methods. Overall, 6% had thyroid disease with a fivefold female excess. Thyroglobulin antibodies were present in 5% of males and 11% of females and thyroid microsomal antibodies in 5% of males and 15% of females. These rates were all significantly greater than published rates for the general population. The differences persisted after analysing separately by age group. The results confirm the suggestions by others that there may be a common genetic link between RA and autoimmune thyroid disease.

Evidence for similarity in testosterone levels in haplotype identical brothers

An analysis of 89 male sibling pairs from multicase rheumatoid arthritis families demonstrated an association between HLA and serum testosterone levels. In sibling pairs that were haplotype identical, the mean inter-pair difference in testosterone level expressed as a log ratio was significantly less than sibling pairs sharing neither haplotype (p = 0.03). This difference was independent of the RA status of the pairs. These results suggest the presence of a gene(s) controlling testosterone levels linked to the Major Histocompatibility Complex (MHC) on chromosome 6. These findings may aid understanding of the roles of HLA antigens and sex hormones in the susceptibility to RA and other autoimmune disease.

Failure to find disease similarity in sibling pairs with rheumatoid arthritis

Clinical and laboratory measures of disease expression were compared within and between 33 families with two or more affected siblings with rheumatoid arthritis (RA). None of the variables studied--age and calendar year of disease onset, pattern of joint involvement, the presence of rheumatoid nodules, Sjögren's syndrome, a positive latex or antinuclear antibody (ANA) titre--showed a greater concordance within the families than between them. The families were then divided into those in which the affected sibling pairs were and were not HLA identical. Such a division did not alter the conclusion, with the possible exception of a positive latex titre. These results suggest that genetic or unique environmental factors within families may have only a limited role in explaining disease heterogeneity in RA. Conversely, the absence of homogeneity within the families justifies their use in genetic linkage studies and the extrapolation of results obtained from affected siblings to the commoner sporadic disease.

HLA polymorphisms in Nigerians

The HLA class I and class II phenotypes of a panel of 114 unrelated Nigerians have been determined. The panel was tested for all the known class I antigens and comparisons of the HLA-A and -B frequencies with those of other African Negroid populations revealed some differences. Only limited comparisons could be made for the HLA-DR and -D frequencies as these are not available for any well-defined African Negroid population. The data concerning the class II antigens of this panel are the most interesting. Half of the DRw11-positive panel members are DQw3 negative and DQw1 positive. In addition, there is dissociation of some HLA-D and -DR specificities, a number of panel members are positive for an HLA-D specificity and are negative for the corresponding HLA-DR specificity. Our results show the value of population studies in the investigation of the relationship between the different HLA class II antigens.

Properdin Factor B (Bf) Polymorphism in Saudi Arabs

The distribution of properdin factor B (Bf) phenotypes and the gene frequencies were investigated in 918 Saudi Arabs. A high frequency of the 'rare' allele BFS0.7 was observed BfS0.7 = 0.1514). The frequencies of the common Bf alleles (BfS = 0.5174, BfF = 0.3213) are outside the corresponding ranges of BfS, BfF gene frequencies found in European Caucasoids.