Synergy between T cell receptor beta gene polymorphism and HLA-DR4 in susceptibility to rheumatoid arthritis

T-cell receptor BV gene segment polymorphisms in healthy elderly individuals from the south of Brazil

The ageing of the immune system (immunosenescence) is believed to be involved in both morbidity and mortality in elderly humans due to a higher incidence of infections, autoimmune diseases, cancers and other pathological situations. As any specific immune response involves recognition of antigens by T cells, the ability to develop a given immune response is also dependent on the T-cell repertoire available at a given time point. Different T-cell receptor beta variable segment (BV) (TCRBV) gene segment alleles have been associated with diseases in various human populations. In the present work we analysed the allelic frequencies of four biallelic polymorphisms in TCRBV gene segments (TCRBV3S1, TCRBV13S5, TCRBV13S6 and TCRBV18) in healthy elderly human subjects (80 years old or more) from the south of Brazil, where life expectancies reach similar levels to those observed in developed countries. Except for allele 2 of the TCRBV13S6 polymorphism, which was more frequent in elderly than in young individuals (P = 0.0105), there were no differences in allele or genotype frequencies between young and elderly individuals. The data suggest that there is no direct correlation between the TCRBV3S1, TCRBV13S5 and TCRBV18 polymorphisms analysed and healthy senescence in this particular group of elderly individuals. The higher frequency of TCRBV13S6 allele 2 in healthy elderly individuals should be confirmed in other samples to establish the significance of this finding.

T-cell receptor bias in patients with allergic bronchopulmonary aspergillosis

CD4(+) Th2 helper cell mediated immune responses have been shown to play a crucial role in the pathogenesis of ABPA. HLA and TCR are the candidate genes, which can influence the specificity of these responses. We have previously established a strong association of HLA DR2/5 in ABPA susceptibility. The study was designed to determine whether allergen specific T cell express a limited usage of T cell receptor (TCR) Vbeta gene repertoire in ABPA and to find an association of susceptible HLA-DR determinants with the identified TCR gene segments. TCR Vbeta typing was performed on antigen specific T cell lines from 14 ABPA and 12 nonABPA patients. The majority of ABPA patients (86%) expressed allergen specific T cells with Vbeta13 genes indicating its role in susceptibility, whereas in nonABPA controls, Vbeta1 genes T cell repertoires were predominantly expressed. The unrestricted pattern of Vbeta gene amplification seen before antigen stimulation suggests an oligoclonal expansion of a specific T cell population in response to the allergen Asp f 1 in ABPA and nonABPA patients. The increased usage of Vbeta13 in ABPA and Vbeta1 in nonABPA indicates their importance in susceptibility and resistance, respectively.

Rheumatoid arthritis in African Colombians from Quibdo

OBJECTIVES

Little data is available on the prevalence and incidence of rheumatoid arthritis (RA) or the genetic and environmental factors that influence RA risk and severity in non-Caucasian populations. The prevalence of RA in Caucasians and some Native American populations is 1% or more; in contrast, low prevalences of RA have been reported in some African populations. We determined the hospital incidence (HI) and period prevalence (PP) of RA in African Colombians in Quibdo, Colombia, by using data collected at the Hospital San Francisco de Asis, a primary-to-tertiary care center. Genetic and immunologic studies of factors that influence RA risk and severity, such as HLA genes, immunoglobulin-A (IgA) rheumatoid factor (RF), and antikeratin antibodies (AKA) were performed. African Colombians with RA also were compared with Mestizo RA patients from Medellín, Colombia.

METHODS

To determine the HI, all the outpatient charts for 1995 were reviewed (n = 3,044). PP during 1996 (Jan-Dec) was assessed by stratified sampling of all African Colombians aged 18 or more having arthralgia. Participants completed a survey and a pretested standard questionnaire, had hands and feet X-rays, and provided a blood sample. Total and IgA RF were measured by turbidimetry and ELISA, respectively; AKA were assessed by indirect immunofluorescence on rat esophagus. HLA-DRB1 and DQB1 alleles were determined by polymerase chain reaction technique with primers of specific sequence and by reverse dot blot.

RESULTS

The HI was 0.65 cases per 1,000 person years. There were 321 individuals with arthralgia (0.3%; 95% CI, 0.28-0.3), 18 of whom fulfilled the American College of Rheumatology criteria for RA (PP in the general population, 0.01%; 95% CI, 0.008-0.02). Lower erosion scores were seen in African Colombian patients compared to Mestizos (n = 56), although duration of disease was similar in each group. No association between any HLA allele and RA risk or RA severity or between autoantibodies and RA severity was observed in African Colombians. Comparisons showed no significant differences between African Colombians and Mestizo patients in the presence of RF (total and IgA), AKA, age at onset, extra-articular manifestations, formal education level, and history of malaria.

CONCLUSIONS

These results suggest that RA in African Colombian patients from Quibdo is rare, may be less severe in terms of radiographic damage than in Colombian Mestizo patients, and lacks association to HLA-DRB1 and DQB1 alleles. Additionally, RF (total and IgA) and AKA are not markers of progression and activity of the disease in this population.

Potential biologic agents for treating rheumatoid arthritis

The encouraging clinical results observed in trials using anti-TNF therapy clearly warrant further studies to determine whether TNF inhibitors are capable of modifying the destructive component of this disease in long-term follow-up studies as well as to assess the safety of long-term use (see the article by Keystone in this issue). It is also reasonable to propose that interfering with the cytokine cascade earlier in the course of disease may be of even greater therapeutic benefit. As the pathogenetic mechanisms in RA are more clearly defined, especially in early disease and in those individuals destined to develop severe disease, the potential of other biologic agents to specifically inhibit these critical pathways may provide better treatments for our patients. Many potential targets in the immune-mediated process of RA are currently being rigorously evaluated in clinical trials. Use of combinations of biologic therapies, perhaps in human patients with RA, should be of considerable interest in future trials.

The genetics of rheumatoid arthritis: influences on susceptibility, severity, and treatment response

There has been an explosion of knowledge of genetic variations among different populations and the influence of genetics on complex diseases such as rheumatoid arthritis (RA). Although class II major histocompatibility complex (MHC) alleles are important contributors, there are likely multiple other genes that modulate the disease phenotype. Genetic markers may allow prediction of response to particular treatments. Given the recent approval of tumor necrosis factors (TNF) inhibitors and the large number of biologic agents currently undergoing clinical trials, pharmacogenetic markers may prove to be clinically useful.

CD4 TCRBV CDR3 analysis in prevalent SLE cases from two ethnic groups

We examined CD4+ T cell TCRBV-CDR3 transcripts from 19 lupus patients and 16 controls to test the hypothesis that CD4+ TCRBV-CDR3 expression in SLE differs from normals. Within the disease group we also performed exploratory analyses to determine the association between risk of oligoclonality and HLA-DRB specificities and the duration of the CDR3 patterns. Oligoclonal patterns consistent with CDR3 restriction were three times more likely in SLE than in controls (OR = 3.7). TCRBV1, BV4, BV5.1, BV7, BV9, BV18 and BV22 gene segment CDR3 patterns of oligoclonality were seen exclusively among lupus patients. HLA-DRB3 increased the risk of oligoclonal expression in SLE. In four patients studied over time, the pattern of TCRBV-CDR3 expression was stable in a second sample obtained 6-14 months later. The increased frequency of CD4+ T cell TCRBV-CDR3 oligoclonal expression in SLE when compared to controls and the persistence of these patterns are consistent with an expanded pool of autoreactive CD4 T cells in SLE which recognize peptides derived from autoantigens. The association of HLA-DRB3 genes with increased risk of CDR3 oligoclonality among the SLE subjects is compatible with the hypothesis that molecules encoded by HLA-DRB3 may facilitate autoantigen recognition by CD4 T cells.

Genetics of rheumatoid arthritis: confronting complexity

The genetic basis for rheumatoid arthritis (RA) is likely to be extremely complex. Even the role of MHC genes remains to be fully defined, and may involve interactive genetic effects. The difficulty of precisely defining the clinical phenotype, as well as underlying genetic heterogeneity, complicates the problem. In addition, stochastic genetic or physiologic events may contribute to the low penetrance of susceptibility genes. This situation parallels developing paradigms for other autoimmune disorders, in which many different genes each appear to contribute a small amount to overall risk for disease, and where severity and specific phenotypic subtypes are subject to genetic effects. The completion of the human genome project, along with advances in informatics, will be required to reach a deeper understanding of RA. It is likely that this will involve an iterative and interactive process between several different scientific disciplines.

A linkage study across the T cell receptor A and T cell receptor B loci in families with rheumatoid arthritis

OBJECTIVE

To examine whether the T cell receptor (TCR) A or TCRB loci exhibit linkage with disease in multiplex rheumatoid arthritis (RA) families.

METHODS

A linkage study was performed in 184 RA families from the UK Arthritis and Rheumatism Council Repository, each containing at least 1 affected sibpair. The microsatellites D14S50, TCRA, and D14S64 spanning the TCRA locus and D7S509, Vbeta6.7, and D7S688 spanning the TCRB locus were used as DNA markers. The subjects were genotyped using a semiautomated polymerase chain reaction-based method. Two-point and multipoint linkage analyses were performed.

RESULTS

Nonparametric single-marker likelihood odds (LOD) scores were 0.49 (P = 0.07) for D14S50, 0.65 (P = 0.04) for TCRA, 0.07 (P = 0.29) for D14S64, 0.01 (P = 0.43) for D7S509, 0.0 (P = 0.50) for Vbeta6.7, and 0.0 (P = 0.50) for D7S688. By multipoint analysis, there was no evidence of linkage at TCRB (LOD score 0), and the maximum LOD score at the TCRA locus was 0.37 (at D14S50). The presence of a susceptibility locus (LOD score < -2.0) was excluded, with lambda > or = 1.8 at TCRA and > or = 1.4 at TCRB.

CONCLUSION

These linkage studies provide no significant evidence of a major germline-encoded TCRA or TCRB component of susceptibility to RA.

Lack of linkage between anti-nuclear antibody or clinical features of systemic lupus erythematosus (SLE) and TCR-A/Vbeta loci in families of subjects with SLE

The role of the TCR-A and TCR-Vbeta genes in the genetic predisposition to SLE expression and anti-nuclear antibody (ANA) production were examined by linkage analysis in eighteen multiplex and forty-three simplex SLE families. All subjects were Caucasian. A significantly increased prevalence of positive ANAs in first-degree relatives of SLE patients from multiplex families was noticed compared to that of simplex families. Linkage between TCR-A/Vbeta genes and SLE expression and ANA production were analysed by affected sib-pair method. Results showed that the haplotypes identical by descent sharing TCR-A and TCR-Vbeta genes in the affected sib-pairs was not different from that expected (P = 0.93 and P = 0.74, respectively). There was no linkage between ANA positivity and TCR-A and TCR-Vbeta genes in ANA positive sib-pairs from both multiplex and simplex families. This study suggests that germline TCR-A and TCR-Vbeta gene loci confer no susceptibility to ANA and SLE expression.