Evidence for the effects of a superantigen in rheumatoid arthritis

The structural basis of T cell activation by superantigens

Superantigens (SAGs) are a class of immunostimulatory and disease-causing proteins of bacterial or viral origin with the ability to activate large fractions (5-20%) of the T cell population. Activation requires simultaneous interaction of the SAG with the V beta domain of the T cell receptor (TCR) and with major histocompatibility complex (MHC) class II molecules on the surface of an antigen-presenting cell. Recent advances in knowledge of the three-dimensional structure of bacterial SAGs, and of their complexes with MHC class II molecules and the TCR beta chain, provide a framework for understanding the molecular basis of T cell activation by these potent mitogens. These structures along with those of TCR-peptide/MHC complexes reveal how SAGs circumvent the normal mechanism for T cell activation by peptide/MHC and how they stimulate T cells expressing TCR beta chains from a number of different families, resulting in polyclonal T cell activation. The crystal structures also provide insights into the basis for the specificity of different SAGs for particular TCR beta chains, and for the observed influence of the TCR alpha chain on SAG reactivity. These studies open the way to the design of SAG variants with altered binding properties for TCR and MHC for use as tools in dissecting structure-activity relationships in this system.

The effect of staphylococcal enterotoxin B on thyrocyte HLA molecule expression

Microbial superantigens have been implicated in the pathogenesis of human autoimmune diseases. In autoimmune glands, thyrocytes inappropriately express HLA-DR molecules and these cells may function as antigen presenting cells (APC) We studied the effect in vitro of staphylococcal enterotoxin B (SEB) on HLA molecule expression on thyrocytes obtained from autoimmune and non-autoimmune glands by immunofluorescence. HLA class I and class II upregulation could be detected by FACS analysis on thyrocytes. Anti-IFN-gamma neutralizing antibodies markedly affect both class I and class II upregulation on thyrocytes. FRTL5 cells were not responsive to SEB. Similarly, a human thyroid cell strain maintained in culture in a conditioned medium was not induced to express HLA products by SEB stimulation. The addition of autologous intrathyroidal lymphocytes caused reestablishment of the SEB effect.

Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome

The exfoliative (epidermolytic) toxins of Staphylococcus aureus are the causative agents of the staphylococcal scalded-skin syndrome (SSSS), a blistering skin disorder that predominantly affects children. Clinical features of SSSS vary along a spectrum, ranging from a few localized blisters to generalized exfoliation covering almost the entire body. The toxins act specifically at the zona granulosa of the epidermis to produce the characteristic exfoliation, although the mechanism by which this is achieved is still poorly understood. Despite the availability of antibiotics, SSSS carries a significant mortality rate, particularly among neonates with secondary complications of epidermal loss and among adults with underlying diseases. The aim of this article is to provide a comprehensive review of the literature spanning more than a century and to cover all aspects of the disease. The epidemiology, clinical features, potential complications, risk factors, susceptibility, diagnosis, differential diagnoses, investigations currently available, treatment options, and preventive measures are all discussed in detail. Recent crystallographic data on the toxins has provided us with a clearer and more defined approach to studying the disease. Understanding their mode of action has important implications in future treatment and prevention of SSSS and other diseases, and knowledge of their specific site of action may provide a useful tool for physiologists, dermatologists, and pharmacologists.

Molecular fingerprinting reveals non-overlapping T cell oligoclonality between an inflamed site and peripheral blood

We have demonstrated a stable expansion of CD8+ T cells in the peripheral blood of a child with chronic arthritis. The expanded TCRBV family (TCRBV14) was enriched for CD57hiCD28- T cells. Sequencing of the TCRBV14 amplification products showed a TCR sequence which contributed 32% of the total TCR in the CD8+TCRBV14 population. Using the modified heteroduplex technique, the CD8+TCRBV14 cells showed a clonal pattern and these bands were restricted to the CD28- population. This method also detected multiple other clones within the CD8+ population but few in the CD4+ cells. The dominant TCRBV14+ clone was not detectable in synovial fluid T cells from two inflamed joints by CDR3 length analysis or heteroduplex probing, suggesting that this long-lived clone is excluded from inflammatory sites. Synovial fluid T cells showed an unexpected discordance of the CD28 and CD57 phenotype compared to peripheral blood mononuclear cells. T cells from both inflamed joints both showed marked oligoclonality in all TCR families and had almost identical heteroduplex patterns. Taken together these data suggest that some clones are actively excluded from inflamed sites in juvenile chronic arthritis, yet the pattern of restricted T cell expansion is shared between sites of inflammation.

An analysis of T cell antigen receptor variable beta genes during the clinical course of patients with chronic hepatitis B

BACKGROUND

The degree of hepatocyte injury in patients with chronic hepatitis B appears consistent with the number of T cells that respond to hepatitis B virus-related antigens.

METHODS

By using a polymerase chain reaction (PCR)-based approach, we monitored a ratio of the T cell antigen receptor (TcR) variable (V) beta gene families against a total TcR V beta gene expression in the peripheral T cells obtained from five patients and four healthy controls.

RESULTS

In the healthy controls, there was no significant change in the ratios at an interval of four or eight weeks. In contrast, several TcR V beta families showed the significant changes in the ratios of their gene expression during the follow-up period in all patients. No common highly fluctuated TcR V beta, however, was found among the patients. Furthermore, there was no correlation between their changes and serum levels of alanine aminotransferase.

CONCLUSIONS

These findings suggest that the skewing of the TcR family with multiclone is the result of T-cell responses to viral antigens in peripheral blood.

Selection of hprt mutant T cells as surrogates for dividing cells reveals a restricted T cell receptor BV repertoire in insulin-dependent diabetes mellitus

T cells with somatically acquired mutations in the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene were isolated from patients with insulin-dependent diabetes mellitus (IDDM) as representatives of populations potentially enriched for in vivo activated T cells. TCRB gene V region usage among mutant isolates from individual IDDM patients, but not from normal controls, showed a pronounced preference for BV14 and, to a lesser extent, BV6. Wild-type (nonmutant) isolates did not show such preferences. Extensive in vivo clonal expansions of the BV14 expressing mutant T cells from IDDM patients were revealed by sequence identity of TCRB chain junctional regions. These data support restricted TCRB gene usage in T cell populations enriched for in vivo activated clones in patients with IDDM.

T-cell response to proinsulin and insulin in type 1 and pretype 1 diabetes

Insulin-dependent diabetes mellitus (IDDM) results from the selective destruction of pancreatic beta cells by a T cell-mediated autoimmune process. Insulin and proinsulin are the only known beta cell-specific autoantigens. Using short-term cultures of freshly isolated peripheral blood mononuclear cells, we evaluated T-cell responses to proinsulin and to insulin in IDDM patients and individuals at risk for IDDM. A proliferative T-cell response to proinsulin was observed in only 2 of 26 recent-onset IDDM subjects and 2 of 12 long-standing IDDM subjects and was associated with a proliferative response to insulin. In contrast, 5 of 13 islet cell autoantibody-positive first-degree relatives of IDDM patients showed a proliferative response to proinsulin alone, 3 of 13 to insulin alone, and 1 of 13 to both insulin and proinsulin. Overall, 9 of 13 ICA-positive first-degree relatives responded to either proinsulin or insulin. We observed an inverse relationship between antiinsulin antibodies and T-cell responses to insulin in ICA-positive first-degree relatives but not in long-standing IDDM patients. Our data indicate that proinsulin is a major antigen in IDDM and, further, illustrate the difference between the autoimmune response to insulin and the immune response to exogenous insulin.

T cell receptor gene in synovial tissues of rheumatoid arthritis

Rheumatoid arthritis is a chronic and destructive autoimmune joint disease characterized by inflammation of synovial tissue of unknown aetiology. Studies on TCR genes expressed by infiltrating T cells in synovial tissues have attempted to identify mechanism and specificity of the recruitment. T cell infiltrate in rheumatoid arthritis appears to be an association of a polyclonal non specific infiltrate with dominant clones or clonotypes. T cell repertoire in synovial tissue is biased compared to peripheral blood but no TCR V gene can be identified as commonly over-used. Comparison of motifs found in the CDR3 region of dominant clones from different studies has currently failed to identified a commonly motif. The fact that a number of dominant clones or clonotypes is present in different joints and at different times of the disease suggests a selective expansion of T lymphocytes in rheumatoid arthritis synovial membrane. Further investigations are needed to characterize the specificity of these dominant clonotypes.

T cell receptor repertoire in rheumatoid arthritis

CD4+ T cells are a major component of the inflammatory infiltrate in rheumatoid synovitis. Within synovial lesions, clonal CD4+ T cell populations are detectable, supporting the notion of an antigen specific recognition even in the joint. In general, the clonal size of individual T cell clones is small and does not lead to a marked distortion of the synovial T cell receptor (TCR) repertoire. Comparison of TCR sequences derived from different patients has not provided evidence for common sequences. Either multiple antigens are recognized or the TCR repertoire is sufficiently plastic with a multitude of different TCR structures responding to the same antigen(s). However, within one individual, the repertoire of clonal T cell populations is restricted. Identical T cell clones can be identified in different joints and at different timepoints of the disease, emphasizing that the spectrum of antigens recognized is conserved over time and that the T cell response pattern is not subject to evolution. Characterization of antigens involved in the latter stages of the disease may thus provide critical information on disease-initiating events. Recent data have led to the new concept that the role of T cells in rheumatoid arthritis (RA) is not limited to synovial inflammation. Evidence has been provided that the premorbid TCR repertoires of RA patients and normal controls can be distinguished. The T cell repertoire in RA patients is prone to recognize certain microbial products and autoantigens. The selection of this response pattern can only partially be attributed to the disease associated HLA-DRB1 alleles. Additional factors common in RA patients but not in HLA-DR matched control individuals seem to be important in shaping the TCR repertoire. Furthermore, the repertoire of mature T cells in RA patients is characterized by oligoclonality which involves T cells in the peripheral blood compartment. Possibly, these clonal T cell populations react to widespread autoantigens, raising the possibility that RA patients have a defect in controlling peripheral tolerance and an anomaly of lymphoproliferation. In contrast to joint residing CD4+ T cells, expanded clonotypes isolated from the blood of different patients have been described to share TCR beta chain structures. How these characteristic features of the global TCR repertoire in RA patients translate into mechanisms of disease remains to be elucidated.

Specific Vβ T Cell Subsets Are Associated with Cat and Birch Pollen Allergy in Humans

Cognate interaction between TCRs and MHC class II molecules plays an important role in initiating the allergen-specific immune response. Therefore, we analyzed the TCR distribution of human PBLs of 56 atopic and nonatopic (NA) individuals, including 4 monozygotic twin pairs, from two extended and four nuclear families. The expression of 23 Vβ and 3 Vα elements was analyzed. The blood samples of symptomatic birch pollen-sensitized individuals that were taken ≤6 wk after the birch pollen season (n = 8) showed a significantly higher frequency of Vβ16.1+ and Vβ20.1+ T cells compared with the blood samples of birch pollen-sensitized individuals that were obtained out of allergen season (n = 10) or from NA individuals (p < 0.0005 and p < 0.0001, respectively). Allergen-specific lymphocyte proliferation was detected in the allergic individuals, and the distribution of Vβ16.1+ and Vβ20.1+ T cells returned to normal levels after the pollen season. The frequency of these Vβ-expressing T cells correlated with the levels of allergen-specific IgE Abs. In addition, cat-sensitized individuals (n = 8) showed a significantly higher frequency of Vβ17.1-expressing T cells than did NA individuals (p < 0.005). Our results indicate restricted TCR-Vβ gene usage in cat and birch pollen allergies; we suggest that both genetic and environmental factors contribute to TCR-Vβ gene expression and to the development of a specific T cell response.

Involvement of autoimmunity against type II collagen in the development of arthritis in mice transgenic for the human T cell leukemia virus type I tax gene

We previously reported that transgenic mice carrying the human T cell leukemia virus type I (HTLV-I) env-pX region (pX-transgenic mice) develop rheumatoid-like inflammatory arthropathy, and suggested involvement of autoimmunity in the pathogenicity. In this report, to elucidate pathogenesis of the arthritis, we investigated arthritogenic antigens in the joints. The TCR beta-chain variable region (Vbeta) repertoires in the lymphatic organs were normal in transgenic mice, however, specific Vbeta-positive T cells were expanded oligoclonally in the affected joints, suggesting that specific antigens, but not superantigens, were involved in the expansion of these T cells. These expanded T cells had the same TCR as those of lymph node T cells reactive to type II collagen (IIC). Moreover, these mice were susceptible to IIC-induced arthritis and oligoclonal T cells of the same Vbeta specificity as that found in spontaneously developed arthritic joint accumulated in the arthritic joints after immunization with IIC. These observations show that endogenous IIC is one of the arthritogenic antigens in the joint, suggesting tolerance break to this antigen in pX-transgenic mice.

Conserved T-cell receptor beta chain CDR3 sequences in IgA nephropathy biopsies

BACKGROUND

We have previously reported that both alpha beta and gamma delta T cells are involved in the progression of IgA nephropathy (IgAN) to renal failure. To determine whether the T-cells seen in the interstitium represent a generalized inflammatory response or whether they are proliferating oligoclonally in response to a particular antigen, we analyzed the TCR Vbeta gene usage by T cells infiltrating renal biopsies from patients with IgAN.

METHODS

Fourteen IgAN patients were divided by clinical criteria into stable and progressive groups (7 in each group). Reverse transcription-polymerase chain reaction (RT-PCR) and cloning were used to characterize the expression of TCR Vbeta families in renal biopsies and in peripheral blood lymphocytes.

RESULTS

TCR Vbeta8 was significantly and preferentially expressed in most IgAN kidney biopsies compared with peripheral blood lymphocytes from both IgAN patients and healthy controls (P < 0.001). TCR Vbeta8 expression was more marked in progressive biopsies than in stable biopsies (P < 0.05). Spectratyping of Vbeta8 RT-PCR products from T cells infiltrating the kidney showed an intense spectratype band at the shortest range of amplified CDR3s in the renal biopsies of four patients. Analysis of nucleotide and deduced amino acid sequences of Vbeta8 PCR products derived from intense spectratype bands from these renal biopsies revealed a high concordance across the CDR3 region. A conserved amino acid (leucine) at the first position of the nongermline-encoded nucleotides and diversity (ND) junction of Vbeta8 was found at a frequency of 95% in multiple sequences obtained from the renal biopsies of all four patients examined.

CONCLUSIONS

The preferential use of Vbeta8 with marked similarities in the CDR3 region by some renal infiltrating T cells suggests clonal expansion of T cells in the kidneys of some IgAN patients. Conserved amino acids in the TCR CDR3 hypervariable region may contribute to the recognition of a particular antigen or set of antigens.

TCR-Vbeta usage in the thymus and blood of myasthenia gravis patients

In myasthenia gravis (MG) the muscle acetylcholine receptor (AChR) is the target of an autoimmune response. The anti-AChR response may originate in the thymus, which is abnormal in most MG patients and contains anti-AChR T and B cells. Microbial superantigens (sAg) may trigger autoimmune responses and in this study we sought clues as to whether sAg play a role in the pathogenesis of MG. We investigated the frequency of use of the different TCR Vbeta families by the thymus and blood T cells in MG patients and in control subjects, using a multi-primer PCR assay. Identical TCR-Vbeta usage was found in the thymi of MG patients and controls, except Vbeta2, which showed a small increase in MG patients' thymi. Blood T cells of MG patients used Vbeta4, Vbeta6, Vbeta15, Vbeta16 and Vbeta24 significantly more than those of the controls. Vbeta4 and Vbeta6 are the gene families most frequently used by anti-AChR CD4(+) cells in MG patients. Blood T cells from MG patients used Vbeta12, Vbeta14, Vbeta17 and Vbeta18 significantly less than controls. MG patients used Vbeta4 and Vbeta6 significantly more in the blood than in the thymus, while the opposite occurred for Vbeta7, Vbeta12 and Vbeta14. Controls used Vbeta17 more and Vbeta24 less in the blood than in the thymus. The preferential expansion of Vbeta4 and Vbeta6 in MG patients might reflect the immunodominance of certain AChR epitopes, or the action of a sAg outside the thymus. The minimal differences in the TCR-Vbeta usage in the blood and thymus of control subjects might be due to expansion of T cell clones specific for common antigens. Identical Vbeta usage in the thymi of MG patients and controls does not support an important role of the thymus as the location of anti-AChR sensitization when MG is clinically evident. The differences observed in the Vbeta usage in blood and thymi of MG patients are likely to be due to preferential Vbeta usage by the anti-AChR T cells in the blood.

Three-dimensional structure of the complex between a T cell receptor beta chain and the superantigen staphylococcal enterotoxin B

Superantigens (SAGs) are a class of immunostimulatory proteins of bacterial or viral origin that activate T cells by binding to the V beta domain of the T cell antigen receptor (TCR). The three-dimensional structure of the complex between a TCR beta chain (mouse V beta8.2) and the SAG staphylococcal enterotoxin B (SEB) at 2.4 A resolution reveals why SEB recognizes only certain V beta families, as well as why only certain SAGs bind mouse V beta8.2. Models of the TCR-SEB-peptide/MHC class II complex indicate that V alpha interacts with the MHC beta chain in the TCR-SAG-MHC complex. The extent of the interaction is variable and is largely determined by the geometry of V alpha/V beta domain association. This variability can account for the preferential expression of certain V alpha regions among T cells reactive with SEB.

Oligoclonal T cells in human cancer

Many solid tumors are characterised by the infiltration of lymphocytes and their presence has been correlated with a more favourable prognosis. These tumor-infiltrating lymphocytes (TIL), have been shown to possess specific cytolytic reactivity towards autologous tumours, thus suggesting that tumour cells may express antigens capable of eliciting an immune response. Expression of such tumour-associated antigens (TAA) in combination with appropriate accessory signals would lead to the in vivo accumulation of T cells with anti-tumour specificity. Analysis of the composition of the specific T-cell receptor (TCR) of TIL could thus provide information on the nature of the antigen(s) recognised by TIL. In this review, different aspects of the presence of clonal T cells in patients with cancer are discussed.

Pristane-induced arthritis in mice. V. Susceptibility to pristane-induced arthritis is determined by the genetic regulation of the T cell repertoire

OBJECTIVE

Pristane-induced arthritis (PIA) is an experimental seropositive arthritis that is characterized by serologic and cellular immune abnormalities and is dependent on the presence of a competent CD4+ T cell population. We examined the regulation of PIA by genes of the major histocompatibility complex (MHC) and the Mls-1 loci to determine whether the selection of the T cells that infiltrate arthritic joints is a critical factor in disease susceptibility.

METHODS

Genetic regulation of PIA was investigated using F1 hybrid and congenic strain analysis to determine the influence of MHC and Mls-1 genes. The T cell receptor Vbeta phenotypes of lymph node cells and T cells infiltrating arthritic joints were examined with 2-color flow cytometry and reverse transcription-polymerase chain reaction techniques.

RESULTS

F1 hybrid offspring from 2 major PIA-susceptible strains (DBA/1 x BALB/c) were resistant to the induction of arthritis because of the interaction between genes of the MHC and the Mls-1 loci, which modified the T cell repertoire. This conclusion was supported by the observed resistance to PIA in BALB/ c-Mls-1a mice, where T cells expressing the Vbeta8.1 and Vbeta6 phenotypes were absent. The receptor phenotype of T cells infiltrating arthritic joints in DBA/1 mice was markedly skewed toward Vbeta8.1 and Vbeta6 compared with the population observed in lymph nodes from either PIA or normal control DBA/1 mice.

CONCLUSION

The data support the hypothesis that PIA is a T cell-mediated disease. While pristane causes a polyclonal T cell expansion that gives rise to lymphadenopathy, the development of arthritis in susceptible strains of mice occurs due to the preservation of specific T cell subsets with the capacity to infiltrate synovial joints.

T cell receptor peptide vaccination in rheumatoid arthritis: a placebo-controlled trial using a combination of Vbeta3, Vbeta14, and Vbeta17 peptides

OBJECTIVE

Restricted T cell receptor (TCR) gene usage has been demonstrated in animal models of autoimmune disease and has resulted in the successful use of TCR peptide therapy in animal studies. This clinical trial was undertaken to determine the safety and efficacy of a combination of Vbeta3, Vbeta14, and Vbeta17 TCR peptides in Freund's incomplete adjuvant (IFA) in patients with rheumatoid arthritis (RA).

METHODS

A double-blind, placebo-controlled, multicenter, phase II clinical trial was undertaken using IR501 therapeutic vaccine, which consists of a combination of 3 peptides derived from TCRs (Vbeta3, Vbeta14, and Vbeta17) in IFA. A total of 99 patients with active RA received either 90 microg (n = 31) or 300 microg (n = 35) of IR501 or IFA alone (n = 33) as a control. The study medication and placebo were administered as a single intramuscular injection (1 ml) at weeks 0, 4, 8, and 20.

RESULTS

Treatment with IR501 was safe and well tolerated. None of the patients discontinued the trial because of treatment-related adverse events. Efficacy was measured according to the American College of Rheumatology 20% improvement criteria. Using these criteria, patients in both IR501 dosage groups showed improvement in disease activity. In the most conservative analysis used to evaluate efficacy, an intent-to-treat analysis including all patients who enrolled, the 90-microg dosage group showed a statistically significant improvement compared with control patients at the 20-week time point after the third injection. Trends toward improvement were shown in both the 90-microg and the 300-microg dosage groups at week 24 after the fourth injection.

CONCLUSION

IR501 therapeutic vaccine therapy was safe and well tolerated, immunogenic, and demonstrated clinical improvement in RA patients. Additional clinical trials are planned to confirm and extend these observations.

A functional link for major TCR expansions in healthy adults caused by persistent Epstein-Barr virus infection

Dramatic clonal expansions of unknown functional significance have been documented in the T cell receptor (TCR) alpha beta peripheral blood repertoires of apparently healthy adults. In this study, we provide evidence that persistent infection with the ubiquitous Epstein-Barr virus (EBV) causes major distortions within the memory repertoire of healthy virus carriers. Using complementarity determining region 3 (CDR3) length analysis to measure repertoire diversity, dominant expansions that dramatically skewed the entire TCRBV6 blood repertoire towards oligoclonality were enriched in the CD8(+)CD45RO+CD45RA- subset of HLA B8(+) healthy virus carriers. Evidence of phenotypic heterogeneity between individuals was also observed for these expansions based on their variable coexpression of CD45RO and CD45RA. TCR junctional region sequencing revealed that these expansions were clonal and that they represented commonly selected HLA B8-restricted memory cytotoxic T cells that recognize the immunodominant latent EBV epitope, FLRGRAYGL. Furthermore, the functional identity of these virus-specific CD8(+) T cells was confirmed by their FLRGRAYGL-specific cytotoxicity. Therefore, the functional significance of dramatic clonal expansions in healthy adults can be linked in some cases to virus-specific CD8(+) T cells that play an essential role in immunosurveillance. This first identified link for expansions in the circulation of healthy adults strongly implies that restricted-memory TCR responses to environmental antigens play a pivotal role in expansion development, which should have an important impact on studies interpreting TCR expansion patterns in health and disease.

Selective Accumulation of Related CD4+ T Cell Clones in the Synovial Fluid of Patients with Rheumatoid Arthritis

The role of T cells in the pathogenesis of rheumatoid arthritis (RA), especially in the perpetuation of advanced disease, remains unclear. Previous studies have focused on the TCR repertoire of synovial T cells in an attempt to determine whether the pattern of expression is characteristic of Ag-stimulated populations. However, the results of past studies have been conflicting. In the present work, we have undertaken an extensive analysis of the TCRs expressed by CD4+ T cells freshly isolated from synovial fluid of different joints and blood in three patients with established RA. Despite marked heterogeneity of synovial TCR expression, the results showed that 20 to 30% of the TCR β-chain gene (TCRB) sequences found in one joint were also expressed in a second joint, but not in peripheral blood T cells of the same individual. Analysis of expressed TCRB complementarity-determining region 3 sequences showed the presence of multiple expanded clonal populations that were not predicted by quantitation of β-chain variable region (Vβ) expression by immunofluorescence staining. These studies also demonstrated sets of related, but different, complementarity-determining region 3 nucleotide sequences that encoded identical or highly homologous β-chain amino acid sequences. Analysis of matching T cell clones derived from the joint by limiting dilution culture confirmed coexpression of highly homologous TCR α-chain gene (TCRA) and TCRB sequences. Together, these studies suggest that a significant proportion of synovial CD4+ T cells has been selected and expanded by conventional Ag(s) in this disease.

Localization of a T-cell epitope of superantigen toxic shock syndrome toxin 1 to residues 125 to 158

Toxic shock syndrome toxin 1 (TSST-1) is a member of the staphylococcal enterotoxin superantigen family. So far, little is known about T-cell epitopes on superantigens. In this study, we developed an improved method for localizing T-cell epitopes on superantigens that involved synthetic peptides plus costimulation by CD28 or phorbol myristate acetate. Using this method, we localized a T-cell epitope to a 34-residue region, TSST-1 (residues 125 to 158), which possessed only two of four TSST-1-targeted beta-chain variable element (Vbeta) specificities of T-cell receptors in humans and mice, human Vbeta2 and murine Vbeta15.

Epithelial ion transport and barrier abnormalities evoked by superantigen-activated immune cells are inhibited by interleukin-10 but not interleukin-4

Many studies have indicated an association between bacteria and the severity of enteric secretory or inflammatory disorders. We previously showed that monolayers of human T84 epithelial cells display altered ion transport and permeability after coculture with Staphylococcus aureus enterotoxin B (SEB, a model superantigen)-activated immune cells, where interferon-gamma and tumor necrosis factor-alpha were key mediators in the pathophysiology. Here we examined whether the regulatory Th2-type cytokines, interleukin (IL)-10 and IL-4, could prevent these epithelial irregularities. T84 monolayers were cocultured with human peripheral blood mononuclear cells (PBMC) or T cell-enriched, monocyte-depleted PBMC (T + B cells) +/- SEB for 20 hr in the presence or absence of IL-10 or IL-4. Subsequently, T84 monolayers were mounted in Ussing chambers and ion transport (short-circuit current (Isc) and DeltaIsc evoked by forskolin) and permeability (ion resistance and probe fluxes) were assessed. IL-10 dose-dependently inhibited the increased T84 permeability and the reduced responsiveness to forskolin that were evoked by coculture with SEB-activated PBMC or T + B cells. Similar changes in T84 function occurred in response to conditioned medium from SEB-activated immune cells; however, addition of IL-10 to the conditioned medium did not prevent the changes in epithelial function. In contrast, when PBMC were stimulated with SEB in the presence of IL-10, the subsequent conditioned medium was less effective in evoking altered epithelial function. These data suggest that the affect of IL-10 was due to effects on the immune cells and not directly on the epithelium. In contrast to IL-10, IL-4 did not ameliorate any of the immune-mediated changes in T84 function. We conclude that IL-10 can reduce the epithelial functional changes caused by SEB-activated immune cells and this data adds further support for IL-10 immunotherapy in the treatment of intestinal secretory or inflammatory disorders.

T-cell receptor Vbeta gene expression in experimental lupus nephritis

A limited T-cell receptor (TCR) Vbeta repertoire employed by autoreactive T cells may be related to the development and course of autoimmune diseases. Vbeta repertoire skewing has been observed not only in man, but also in animal models of several human autoimmune diseases, such as MRL-lpr mice, which spontaneously develop a systemic lupus erythematosus (SLE)-like disease. Murine chronic graft-versus-host disease (GVHD) is an inducible model for SLE, involving direct interaction between donor T cells and recipient B cells. It is not known whether Vbeta-specific T-cell subsets are pathogenically involved in this model. Retroviral superantigens such as Mls-1 are known to have a profound impact on the TCR Vbeta repertoire in mice. Restriction of the peripheral TCR repertoire may result from intrathymic expression of Mls-1, which causes deletion of T cells expressing Vbeta6, -7, -8.1, or -9. Mls-1 incompatibility between donor and recipient can be used to determine the involvement of these TCR Vbeta families in GVHD. In the present study we induced GVHD in several strain combinations to investigate TCR Vbeta gene expression during GVHD, and the effect of Mls-1 incompatibility on the TCR Vbeta repertoire. TCR Vbeta gene expression was determined using an RNase protection assay. Our results indicate that T cells expressing the Vbeta2 or Vbeta16 chain play an important pathogenetic role, while T cells bearing the Vbeta1 or Vbeta6 chain may be related to self-limitation of the lupus-like disease in this model.

CD4+ T-cell-mediated cytotoxicity against staphylococcal enterotoxin B-pulsed synovial cells

Apoptosis of synovial cells in rheumatoid arthritis (RA) synovium determined in vivo is suggested to counteract the overgrowth of synovium. Immunohistological examination has revealed the infiltration of activated CD4+ T cells, which express Fas ligand (FasL), in RA synovium. The presence of a putative antigen (Ag) of autoimmune disorders in a target organ may induce the activation of specific T cells in the inflammatory region such as RA synovium. We examined the possible role of CD4+ T cells activated by synovial cells in a staphylococcal enterotoxin B (SEB)-dependent manner, inducing synovial cell apoptosis. Synovial cells were cultured with or without interferon-gamma (IFN-gamma) and further incubated with CD4+ T cells in the presence of SEB. After the cocultivation, both the cytotoxicity and FasL expression of CD4+ T cells were investigated. Constitutive Fas expression was detected on both unstimulated and IFN-gamma-stimulated synovial cells. CD4+ T cells did not kill SEB-pulsed unstimulated synovial cells efficiently. In contrast, when CD4+ T cells were incubated with IFN-gamma-stimulated synovial cells with SEB whose human leucocyte antigen (HLA)-DR and -DQ expression was markedly induced, significant cytotoxicity by these cells against synovial cells was detected. The addition of anti-HLA-DR and -DQ monoclonal antibodies (mAbs) or human Fas chimeric protein (hFas-Fc) reduced this cytotoxicity. FasL expression of CD4+ T cells cocultured with IFN-gamma-stimulated synovial cells with SEB was significantly induced. Furthermore, the addition of mAbs against CD54, CD58 and CD106 inhibited both the cytotoxicity and FasL expression of CD4+ T cells induced by IFN-gamma-stimulated synovial cells in the presence of SEB, indicating the importance of costimulatory molecules on synovial cells in activating CD4+ T cells. Our results suggest that CD4+ T cells are activated by synovial cells by an SEB-dependent manner and express FasL, inducing Fas-mediated apoptosis of the latter cells. These phenomena may regulate the overgrowth of synovial cells in RA synovium.

Idiopathic dilated cardiomyopathy: a superantigen-driven autoimmune disease

BACKGROUND

Many cases of idiopathic dilated cardiomyopathy (IDC) result from an inflammatory myocarditis. The specific immunological mechanisms are not yet defined. Various autoimmune diseases are associated with superantigen-triggered immune responses, resulting in massive T-cell activation and tissue damage. We studied 3 cases in a search for evidence that such a phenomenon is also implicated in IDC.

METHODS AND RESULTS

Myocardial, lymph node, and thymic tissue samples were obtained from IDC patients who were undergoing heart transplantation. Infiltrating immune-cell phenotypes and gene expression of T-cell receptor (TCR) alpha- and beta-chain variable (Valpha and Vbeta) regions were analyzed by immunostaining and polymerase chain reaction. Similar technical approaches were used to assay the tissues for the presence of coxsackievirus B (CVB). In all the specimens analyzed, an overexpression of the TCR Vbeta3, Vbeta7, and Vbeta13.1 gene families was detected among the infiltrating T cells. These tissues were also found to be CVB3-positive. In vitro exposure of peripheral blood mononuclear cells to lysates of cells infected with CVB3 was capable of stimulating expansion of the same TCR Vbeta families. The TCR Valpha repertoire was never found to be skewed.

CONCLUSIONS

A superantigen-mediated immune response is involved in human heart disease. CVB3 may directly or indirectly trigger this response, suggesting a possible mechanistic link between CVB infection and myocarditis development progressing to IDC.

Modulation of disease by superantigens

Increasing evidence suggests that bacterial and viral superantigens are involved in immune-mediated disease. Studies using an animal model for multiple sclerosis show that superantigens can induce relapses and bring into play autoreactive T cells with restricted usage of T cell receptor V beta families that may be indirectly involved in the initial episode of disease. This may also involve epitope spreading. Superantigens have also been implicated in other autoimmune diseases such as rheumatoid arthritis and psoriasis. Superantigens encoded by viruses such as mouse mammary tumor virus play an important role in disease progression.

T-cell receptor peptide vaccination in the treatment of rheumatoid arthritis

In several human T-cell-mediated autoimmune diseases and animal models of such illnesses, T-cell receptors (TCR) specific for antigens that initiate or perpetuate the disease share a limited number of variable region determinants. Vaccinations with peptides derived from over-represented TCRs are effective treatment for some of these disorders. RA is a chronic inflammatory disease in which there is prominent T-cell infiltration in the synovial lining layer. TCR V beta 3, V beta 14, and V beta 17 have been found to be over-represented among IL-2 receptor-positive T-cells from patients with RA. A phase II clinical trial in RA, using a combination of three peptides derived from V beta 3, V beta 14, and V beta 17, has yielded promising results. Larger clinical efficacy and safety studies must be performed to determine if TCR peptide vaccination will become a viable treatment alternative for patients with RA.

Interleukin 6 plays a key role in the development of antigen-induced arthritis

To investigate the direct role of interleukin (IL) 6 in the development of rheumatoid arthritis, IL-6-deficient (IL-6 -/-) mice were backcrossed for eight generations into C57BL/6 mice, a strain of mice with a genetic background of susceptibility for antigen-induced arthritis (AIA). Both histological and immunological comparisons were made between IL-6-deficient (IL-6 -/-) mice and wild-type (IL-6 +/+) littermates after the induction of AIA. Although all IL-6 +/+ mice developed severe arthritis, only mild arthritis was observed in IL-6 -/- mice. Safranin O staining demonstrated that articular cartilage was well preserved in IL-6 -/- mice, whereas it was destroyed completely in IL-6 +/+ mice. In addition, comparable mRNA expression for both IL-1beta and tumor necrosis factor alpha, but not for IL-6, was detected in the inflamed joints of IL-6 -/- mice, suggesting that IL-6 may play a more crucial role in cartilage destruction than either IL-1beta or tumor necrosis factor alpha. In immunological comparisons, both antigen-specific in vitro proliferative response in lymph node cells and in vivo antibody production were elicited in IL-6 -/- mice, but they were reduced to less than half of that found in IL-6 +/+ mice. Lymph node cells of IL-6 -/- mice produced many more Th2 cytokines than did IL-6 +/+ mice with either antigen-specific or nonspecific stimulation in in vitro culture. Taken together, these results indicate that IL-6 may play a key role in the development of AIA at the inductive as well as the effector phase, and the blockade of IL-6 is possibly beneficial in the treatment of rheumatoid arthritis.

Skewed TCRV beta repertoire in human thymus persists after thymic emigration: influence of genomic imposition, thymic maturation and environmental challenge on human TCRV beta usage in vivo

In order to investigate the mechanisms involved in originating a diverse TCR repertoire in human peripheral blood we analyzed TCRV beta surface expression in different T cell subsets of unrelated individuals. The relative frequencies of 11 distinct V beta chains were determined for immature double positive (DP) as well as for mature CD4 single positive (4SP) and CD8 single positive (8SP) thymocytes, respectively. By comparing these data with expression in peripheral blood T lymphocytes of the same donors we were able to show that usage of TCRV beta in peripheral T cells is significantly (p < 0.001) depending on the pattern in mature SP thymocytes whereas the frequency of TCRV beta families in immature DP thymocytes has no impact (p > 0.2). No association with distinct HLA-haplotypes was observed. Preferential usage of V beta-families in either CD4- or CD8-positive peripheral T cells also correlates with the status in mature thymic precursors (p < 0.001). Altogether, this first combined study of TCR frequencies within different stages of human T cell ontogeny indicates that TCRV beta repertoire is determined mainly through selectional processes within the thymus. Since neither genomically imposed expression nor modulating events in the periphery seem to have strong influence on the relative expression of TCRV beta chains these findings have to be considered in future studies of human diseases.

CD4+ T cells mediate superantigen-induced abnormalities in murine jejunal ion transport

The immunomodulatory properties of bacterial superantigens (SAgs) have been defined, yet comparatively little is known of how SAgs may affect enteric physiology. Staphylococcus aureus enterotoxin B (SEB) was used to examine the ability of SAgs to alter epithelial ion transport. BALB/c mice, severe combined immunodeficient (SCID, lack T cells) mice, or SCID mice reconstituted with lymphocytes or CD4+ T cells received SEB intraperitoneally, and jejunal segments were examined in Ussing chambers; controls received saline only. Baseline short-circuit current (Isc, indicates net ion transport) and Isc responses evoked by electrical nerve stimulation, histamine, carbachol, or forskolin were recorded. Serum levels of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) were measured. SEB-treated BALB/c mice showed elevated serum IL-2 and IFN-gamma levels, and jejunal segments displayed a time- and dose-dependent increase in baseline Isc compared with controls. Conversely, evoked ion secretion was selectively reduced in jejunum from SEB-treated mice. Elevated cytokine levels and changes in jejunal Isc were not observed in SEB-treated SCID mice. In contrast, SCID mice reconstituted with T cells were responsive to SEB challenge as shown by increased cytokine production and altered jejunal Isc responses that were similar to those observed in jejunum from SEB-treated BALB/c mice. We conclude that exposure to a model bacterial SAg causes distinct changes in epithelial physiology and that these events can be mediated by CD4+ T cells.

T cell receptor (TCR) Vbeta gene usage in bronchoalveolar lavage and peripheral blood T cells from asthmatic and normal subjects

T cells are thought to play an important regulatory role in asthma, but little is known about the T cell repertoire of the human lung or whether asthma is associated with any specific repertoire changes. Flow cytometry and MoAbs to TCR VB (TCRBV) families were used to quantify bronchoalveolar lavage (BAL) and blood T cells from normal and atopic individuals. Clonality was then assessed by polymerase chain reaction (PCR) amplification of cDNA and gene scanning using consensus and family-specific TCRBV primers and confirmed by sequence analysis. In addition, blood and BAL T cell populations were studied pre- and post-allergen challenge in four patients with allergic asthma. The majority of TCRBV families detected in blood by MoAb staining were also represented in BAL. While differences between BAL and blood populations were evident in each individual studied, these differences were not consistent between individuals or between CD4+ and CD8+ T cell subpopulations. These results are in broad agreement with other published studies, but in contrast to previous work we found a consistent difference between TCRBV7 family usage in blood and BAL in all individuals studied, and a consistently increased proportion of CD4+ BAL T cells bearing BV5S2/3 in asthmatics only. After allergen challenge, the pattern of TCRBV gene usage was largely unchanged as judged by flow cytometry. Gene scanning of PCR products generated from consensus VB primers revealed polyclonal lymphocyte populations in blood and BAL from all seven atopic individuals: in one normal tested polyclonal populations were found in blood and oligoclonal populations in BAL. Selected families amplified with family-specific primers BV5S2/3, BV6 and BV7 (chosen because of their predominance in BAL compared with blood) were more variable and revealed predominant polyclonal populations in blood and polyclonal or oligoclonal populations in BAL. In one asthmatic patient a clonal BV5S2 family was found in BAL. Following allergen challenge there were no significant changes in polyclonality/oligoclonality/clonality in three cases, but in one case a clonal BV5S2 population was found after challenge, that had not been evident beforehand. The lung T cell repertoire is thus broadly representative of blood T cells, but shows population differences that may result from response to persistent exposure to airborne antigens common to normal and atopic individuals. Oligoclonal TCRBV family expansion appears to be primarily lung-specific but independent of atopic asthma, although our challenge data in one case support the concept that clonal populations may follow local allergen challenge. These data are consistent with selection and amplification of specific T cell families in the lung in response to local antigenic exposure.

CD95 (Fas)-Based, Superantigen-Dependent, CD4+ T Cell-Mediated Down-Regulation of Human In Vitro Immunoglobulin Responses

Naturally occurring microbial superantigens (SAg) have been implicated in several human idiopathic disorders, and a compelling argument for the role of SAg in autoantibody-associated disorders, such as systemic lupus erythematosus, has been proposed. To test the effects of SAg on human in vitro Ig responses, CD4+ T cell + B cell cultures were stimulated with graded doses of staphylococcal enterotoxin B (SEB). Ig-secreting cell (IgSC) responses were very weak in CD4+ T cell + B cell cultures stimulated with SEB at the optimal mitogenic concentration (high dose SEB; 100 ng/ml) but were strong in parallel cultures stimulated with low dose SEB (0.01 ng/ml). High dose SEB actually enhanced B cell differentiation in the presence of CD4+ T cell soluble helper factors as long as the B cells were prevented from physically contacting the CD4+ T cells. However, when cell-cell contact between CD4+ T cells and B cells was permitted, high dose, but not low dose, SEB promoted increased CD4+ T cell-mediated B cell apoptosis with resulting decreases in viable CD20+ B cells and IgSC. High dose, but not low dose, SEB triggered increased levels of soluble CD95 ligand, and down-regulation of IgSC responses and incremental apoptosis of activated B cells were prevented by antagonist anti-CD95 mAb. This strongly suggests that CD4+ T cell-mediated CD95-based killing of activated B cells plays a major role in controlling SEB-driven IgSC responses. Defects in SAg-based down-regulation may contribute to autoimmune disorders such as SLE.

The arthritogenic properties of microbial antigens. Their implications in disease states

The sharing of antigenic determinants between host and microbe is a common event and new microbial-tissue cross-reactions are being recognized each year. Almost every human organ has been implicated as a possible target. The purpose of this article is to examine the arthritogenic properties of these microbial antigens and to explore the mechanisms by which they induce pathologic damage and disease.

Changes in murine jejunal morphology evoked by the bacterial superantigen Staphylococcus aureus enterotoxin B are mediated by CD4+ T cells

Bacterial superantigens (SAgs) are potent T-cell stimuli that have been implicated in the pathophysiology of autoimmune and inflammatory disease. We used Staphylococcus aureus enterotoxin B (SEB) as a model SAg to assess the effects of SAg exposure on gut form and cellularity. BALB/c, SCID (lacking T cells) and T-cell-reconstituted SCID mice were treated with SEB (5 or 100 microg intraperitoneally), and segments of the mid-jejunum were removed 4, 12, or 48 h later and processed for histochemical or immunocytochemical analysis of gut morphology and major histocompatibility complex class II (MHC II) expression and the enumeration of CD3+ T cells and goblet cells. Control mice received saline only. SEB treatment of BALB/c mice caused a time- and dose-dependent enteropathy that was characterized by reduced villus height, increased crypt depth, and a significant increase in MHC II expression. An increase in the number of CD3+ T cells was observed 48 h after exposure to 100 microg of SEB. Enteric structural alterations were not apparent in SEB-treated SCID mice compared to saline-treated SCID mice. In contrast, SEB challenge of SCID mice reconstituted with a mixed lymphocyte population or purified murine CD4+ T cells resulted in enteric histopathological changes reminiscent of those observed in SEB-treated BALB/c mice. These findings implicate CD4+ T cells in this SEB-induced enteropathy. Our results show that SAg immune activation causes significant changes in jejunal villus-crypt architecture and cellularity that are likely to impact on normal physiological processes. We speculate that the elevated MHC II expression and increased number of T cells could allow for enhanced immune responsiveness to other SAgs or environmental antigens.

Rheumatic fever. The relationships between host, microbe, and genetics

Acute rheumatic fever is a delayed, nonsuppurative sequela of a pharyngeal infection with the group A streptococcus. The onset of the disease is usually characterized by an acute febrile illness; however, there may be chronic involvement of the heart and/or central nervous system. The article explores the relationship between the initial infection and host-microbial interactions that may be operative in disease pathogenesis.

Cyclosporin A and FK-506 inhibit development of superantigen-potentiated collagen-induced arthritis in mice

1. Staphylococcal enterotoxine B (SEB; superantigen) accelerated the onset of arthritis in mice preimmunized with type II collagen (SEB-potentiated collagen-induced arthritis). Cyclosporin A and FK-506 inhibited the induction and development of clinical signs and histopathological changes of SEB-potentiated collagen-induced arthritis in mice. 2. Simultaneously, both cyclosporin A and FK-506 inhibited the development of humoral and cellular immunity to type II collagen. 3. The expression of IL-2 receptor (CD25) by SEB on splenocyte T cells from collagen-preimmunized mice was inhibited by both agents in ex vivo experimentation.

TCRBV14S1 and rheumatoid arthritis revisited: abnormalities in the percentage of transcribed TCRBV14S1 family genes in PBMC from rheumatoid arthritis patients

The purpose of this study was to identify Vbeta gene families that are associated with rheumatoid arthritis (RA). A PCR-based assay was used to compare the Vbeta repertoire of unstimulated PBMC from 18 RA patients and 18 matched controls. The influence of an HLA-DRB1-binding peptide (HA307-319) on the Vbeta repertoire of PBMC in culture was compared in 11 RA patients and 10 controls. There was a larger variance in the percentage of BV14S1 transcripts in unstimulated PBMC from RA patients than from controls (p = 0.0003). The mean percentage of BV14S1 transcripts was higher in RA patients when prednisone-treated RA patients were excluded from the analysis (p = 0.0006). In vitro stimulation with the HA307-319 peptide increased the percentage of BV14S1 transcripts in PBMC from RA patients (+ 1.5 +/- 0.4%, p < 0.005) but not controls (+ 0.3 +/- 0.2%, ns), and the difference between RA patients and controls was significant (p = 0.03). In conclusion, there is an association between RA and the BV14S1 gene family in New Zealand patients.

Development of rheumatoid arthritis after treatment of large granular lymphocyte leukemia with deoxycoformycin

The association of T-cell large granular lymphocyte (LGL) leukemia and rheumatoid arthritis is well described and it is now recognized that these patients and patients with Felty's syndrome represent different aspects of a single disease process. Most patients have rheumatoid arthritis at the time of diagnosis of LGL leukemia. This is the first detailed report of the development of rheumatoid arthritis after the diagnosis and treatment of LGL leukemia as well as the first report of rheumatoid arthritis that occurred in association with deoxycoformycin treatment. It is likely that the beneficial sustained normalization of neutrophil counts as a result of deoxycoformycin treatment played a significant role in the development of this complication. Hematological improvement occurred despite molecular genetic evidence of persistence of the abnormal T-cell clone. The role of the clonally expanded T cells in the pathogenesis of neutropenia and rheumatoid arthritis is discussed.

Comparative sequence analysis of the human T cell receptor beta chain in juvenile rheumatoid arthritis and juvenile spondylarthropathies: evidence for antigenic selection of T cells in the synovium

OBJECTIVE

To identify features of the T cell receptors (TCRs) present on clonally expanded T cells in the joints of patients with similar types of childhood rheumatic disease. Vbeta8 and Vbeta20 TCRs were selected as prototypic for polyarticular juvenile rheumatoid arthritis (JRA) and pauciarticular/juvenile spondylarthropathy (SpA), respectively.

METHODS

The portion of the TCR beta chain involved in antigen recognition in the synovial tissue, synovial fluid, and peripheral blood from patients with JRA and juvenile SpA was cloned and sequenced. The frequency of expanded clonotypes, size of expansions, the Jbeta region, and sequence motifs were determined for >2,000 sequences.

RESULTS

The majority of Vbeta20 and Vbeta8 clonal expansions were found in the joint rather than the peripheral blood. While instances of both Vbeta8 and Vbeta20 clonal expansion were detected in all disease types, the features of these expanded clonotypes were specific for disease type and Vbeta family. For example, Vbeta20 clonal expansion was characterized by many small expanded clonotypes in samples from patients with pauciarticular JRA and juvenile SpA while single large Vbeta8-specific expansions were found only in patients with polyarticular disease. Motifs specific to individual patients were identified, and for Vbeta20 clonotypes, a motif was found in synovial tissue samples.

CONCLUSION

Identification of common TCR features in oligoclonal expansions within individual patients and between patients with the same type of JRA suggests the recognition of a common or limited group of antigens in these diseases.

Biased T-cell antigen receptor repertoire in Lyme arthritis

A common concern with many autoimmune diseases of unknown etiology is the extent to which tissue T-lymphocyte infiltrates, versus a nonspecific infiltrate, reflect a response to the causative agent. Lyme arthritis can histologically resemble rheumatoid synovitis, particularly the prominent infiltration by T lymphocytes. This has raised speculation about whether Lyme synovitis represents an ongoing response to the causative spirochete, Borrelia burgdorferi, or rather a self-perpetuating autoimmune reaction. In an effort to answer this question, the present study examined the repertoire of infiltrating T cells in synovial fluid from nine Lyme arthritis patients, before and after stimulation with B. burgdorferi. Using a highly sensitive and consistent quantitative PCR technique, a comparison of the T-cell antigen receptor (TCR) beta-chain variable (Vbeta) repertoires of the peripheral blood and synovial fluid showed a statistically significant increase in expression of Vbeta2 and Vbeta6 in the latter. This is remarkably similar to our previous findings in studies of rheumatoid arthritis and to other reports on psoriatic skin lesions. However, stimulation of synovial fluid T cells with B. burgdorferi provoked active proliferation but not a statistically significant increase in expression of any TCR Vbeta, including Vbeta2 and Vbeta6. Collectively, the findings suggest that the skewing of the TCR repertoire of fresh synovial fluid in Lyme arthritis may represent more a synovium-tropic or nonspecific inflammatory response, similar to that occurring in rheumatoid arthritis or psoriasis, rather than a specific Borrelia reaction.

Structural motifs in rheumatoid T-cell receptors

The linkage of rheumatoid arthritis (RA) to HLA-DR haplotypes, high levels of HLA-DR expression, and T-cell infiltration in the joints, indicate a central role for the interaction of T-cell receptors (TCR) with antigen (Ag) + major histocompatibility complex (MHC) complexes in pathogenesis. Receptor analysis in RA has uncovered a restricted heterogeneity of TCR transcripts, suggesting an antigen-driven response. We analyzed the sequence and structural features of RA-associated TCRs in light of the recently published TCR crystal structures. The surface-exposed residues of the third complementarity-determining region (CDR3s) showed preferential use of certain amino acid residues when sequences derived from synovial fluid or tissue were compared with those derived from peripheral blood, particularly for alpha chains. Sequence alignment of oligoclonal synovial TCR CDR3s revealed groupings with similar CDR3 lengths and amino acid compositions, which suggests shared antigen recognition. Given the limitations of analyzing TCR sequences without knowing their structures, we developed several in vivo-activated synovial-tissue Vbeta17 + RA T-cell clones. Two Vbeta17/V alpha7 clones with different CDR3 sequences were analyzed by molecular modeling. Although distinct topologic features were seen, a central patch of residues with similar chemical and geometric characteristics was present in both. Electrostatic maps revealed similar binding surfaces of both alpha domains and central patches, with differences in the beta domains. This suggests that an alpha-domain-focused binding trajectory would allow shared antigen recognition by these TCRs. These studies support recognition of a limited diversity of Ag + MHC complexes by synovial RA TCRs.

T cell receptor clonotypes in skin lesions from patients with systemic lupus erythematosus

Systemic lupus erythematosus is an autoimmune disease characterized by the presence of autoantibodies and by lymphocytic infiltration into lesions at several sites such as skin, kidney, and other organs. Immunohistologic studies have clarified that the majority of lymphocytes in the skin are CD4+ alphabeta T cells. In the present work, to clarify the pathologic role of T cells in the skin of systemic lupus erythematosus patients, we analyzed T cell receptor (TCR) clonotypes of T cells infiltrating into skin lesions. TCR Vbeta gene transcripts from T cells from discoid lesions of the skin and peripheral blood lymphocytes of four systemic lupus erythematosus patients were amplified by reverse transcriptase polymerase chain reaction. Southern blot analysis of polymerase chain reaction product demonstrated the heterogeneous TCR Vbeta repertoire of T cells in the skin of systemic lupus erythematosus. Single-strand conformation polymorphism analysis showed several distinct bands for smears of most TCR Vbeta genes from T cells infiltrating the skin, whereas smears with few bands were found for all TCR Vbeta genes from peripheral blood lymphocytes of the same patients. The number of bands encoding each TCR Vbeta gene from the skin was significantly higher compared with peripheral blood lymphocytes. Sequencing analysis showed a Leucine-X-Glycine amino acid motif at position 96-98 in the CDR3 region at the frequency of 23-24% in skin-accumulated T cells from two patients, whereas the frequency of this motif in peripheral T cells was only 0-3%, indicating limited T cell epitopes. In conclusion, T cells infiltrating into the skin of systemic lupus erythematosus patients might recognize restricted T cell epitopes on autoantigens and trigger the autoimmune reaction in skin lesions.

Limited T cell receptor Vbeta-chain repertoire of liver-infiltrating T cells in autoimmune hepatitis

BACKGROUND/AIMS

To characterize the cellular immune reactions in autoimmune hepatitis, the T cell receptor repertoire of liver-infiltrating and circulating T cells was studied.

METHODS

Nucleic acids of liver-tissue and peripheral blood-derived T cells from 12 patients with untreated autoimmune hepatitis, four patients with chronic hepatitis C and three patients with toxic liver injury were extracted and analysed using a semiquantitative RT-PCR with a panel of T cell receptor Vbeta family specific primers. After agarose gel electrophoresis, the distribution of T cell receptor (TCR) Vbeta molecules was assessed by densitometry. Furthermore, results were compared to the TCR Vbeta distribution of 10 healthy blood donors.

RESULTS

Four of 12 patients with untreated autoimmune hepatitis but no patients with chronic hepatitis C and toxic liver injury showed a significant overexpression of TCR Vbeta3 (17.8% +/- 2.6% vs. 9.3% +/- 4.6%; p = 0.01) and three an overexpression of Vbeta13.1 (14.6% +/- 2.3% vs. 6.6% +/- 3.5%; p = 0.02) molecules compared to the TCR Vbeta-distribution in healthy blood donors. In addition, Vbeta3+ T cells were found enriched in the liver tissue compared to autologous peripheral blood in three autoimmune hepatitis patients (15.3% +/- 7.0% vs. 5.2% +/- 3.1%; L/B ratio: 2.9), while Vbeta13.1+ T cells were enriched in the liver tissue from one of three patients with overexpression.

CONCLUSIONS

In autoimmune hepatitis a disease specific compartmentalisation of TCR Vbeta3+ T cells was observed in the liver tissues. Although their specificity was unknown, this might indicate that these infiltrating T cells could have relevance for abnormal immunoregulation.

Cell biology of autoimmune diseases

Autoimmune diseases such as insulin-dependent diabetes mellitus, rheumatoid arthritis, and multiple sclerosis are common in the western world and are often devastating diseases which pose serious health problems. The key feature of such diseases is the development and persistence of inflammatory processes in the apparent absence of pathogens, leading to chronic breakdown of selected tissues. To date, no comprehensive explanation can be given for the onset or persistence of autoimmunity. As a rule, the chronic activation of helper T lymphocytes reactive against self proteins appears to be crucial for fueling the destructive autoimmune process, but why this occurs remains to be established. In this review, we present an overview on the rules that govern activation of T lymphocytes and on the factors that control it. The contribution of both genetic and environmental factors are discussed, clarifying that most autoimmune disease are of multifactorial origin. Special emphasis is given to the contribution of infectious events and the role of stress proteins in the process. In attempts to dissect the mechanisms involved in autoimmunity and to develop ways of blocking disease, experimental animal models are widely employed. We describe the various experimental models that exist for the study of multiple sclerosis, diabetes, and other autoimmune diseases and on the experience that has been gained in such models with experimental therapies to block the activation of self-reactive T lymphocytes. The lessons that can be drawn from these studies provide hope that continued efforts will lead to the successful development of antigen-specific strategies which block the development of autoimmunity also in humans.