In vitro and in vivo T cell oligoclonality following chronic stimulation with staphylococcal superantigens

Superantigens and Chronic Rhinosinusitis: Skewing of T-Cell Receptor Vβ-Distributions in Polyp-Derived CD4+ and CD8+ T Cells

Background

Recent studies have suggested that Staphylococcus aureus secrete superantigenic toxins that play a role in the etiology of chronic rhinosinusitis with nasal polyposis (CRSwNP). Twenty S. aureus superantigens (SAg's) have been identified, each of which bind the Vβ-region of the T-cell receptor (TCR) outside the peptide-binding site. Approximately 50 distinct Vβ-domains exist in the human repertoire, and distinct SAg's will bind only particular domains generating a pattern of Vβ-enrichment in lymphocytes dependent on the binding characteristics of a given toxin. The aim of this study was to analyze the pattern of Vβ-expression in polyp-derived lymphocytes from CRSwNP patients.

Methods

Polyps were harvested from 20 patients with CRSwNP and 3 patients with antrochoanal polyps. Flow cytometry was used to analyze the Vβ-repertoire of polyp-derived CD4+ and CD8+ lymphocytes. Data were analyzed in light of the known skewing associated with SAg exposure in vivo and in vitro. Skewing was defined as a percentage of Vβ-expression >2 SD of that seen in normal blood.

Results

Seven of 20 subjects exhibited skewing in Vβ-domains with strong associations with S. aureus SAg's. The three antrochoanal polyps failed to show any significant Vβ-skewing.

Conclusion

This study establishes evidence of S. aureus SAg–T-cell interactions in polyp lymphocytes of 35% of CRSwNP patients. Although these results are consistent with intranasal exposure of polyp lymphocytes to SAg's, additional study is necessary to establish the role of these toxins in disease pathogenesis.

The role of 9-O-acetylated ganglioside D3 (CD60) and {alpha}4{beta}1 (CD49d) expression in predicting the survival of patients with Sezary syndrome

BACKGROUND

Sézary syndrome is a rare and very aggressive leukemic variant of cutaneous T-cell lymphoma characterized by extensive skin involvement and a malignant circulating CD4(+) T-cell clone which homes to the skin, over-expresses CD60, and lacks CD7, CD26 and CD49d. So far prognostic markers in this disease are limited to treatment with systemic steroids, age, serum lactate dehydrogenase, and a white blood cell count of 20×10(9)/L or higher: no other biological marker with prognostic value, especially related to malignant cells, has been described.

DESIGN AND METHODS

We used flow activated cell sorting analysis to compare the distribution of the T-cell receptor-Vβ repertoire and several surface molecules (CD7, CD26, CD49d and CD60) within the circulating CD4(+) T-cell population in 62 patients with Sézary syndrome, 180 with mycosis fungoides, 6 with B-cell lymphomas, and 19 with chronic eczema. We calculated the 5-year overall survival of patients with Sézary syndrome after first hospital admission using Kaplan-Meier product-limit estimates and hazard ratios from the Cox proportional hazards model.

RESULTS

We found that both higher number of CD60(+) and lower number of CD49d(+) cells within circulating CD4(+) T cells at disease presentation were significantly associated with a lower probability of survival. An exceedingly high risk of death was observed for patients with a combination of a high proportion of CD4(+)CD60(+) cells (≥ 0.5×10(9)/L) and low proportion of CD4(+)CD49d(+) cells (<0.5×10(9)/L) (hazard ratio = 12.303, 95% confidence interval 1.5-95.9; P<0.02). In addition, a skewed usage of T-cell receptor-Vβ subfamilies was observed in the circulating T-cell clone for 61.9% of all patients with Sézary syndrome, T-cell receptor-Vβ 2 and 5.1 subfamilies being the most frequently represented (42.8%), followed by T-cell receptor-Vβ 12 and 13.1.

CONCLUSIONS

In this study we showed that up-regulation of CD60 and down-regulation of CD49d on circulating CD4(+) T cells are two useful markers for predicting a very poor outcome in patients with Sézary syndrome.

An in vitro model of T cell receptor revision in mature human CD8+ T cells

V(D)J recombination is a mechanism peculiar to the somatic rearrangement of antigen receptor genes. It requires both expression of the RAG-1 and RAG-2 recombinases and accessibility of the substrate to its recombinase and post-cleavage/DNA repair stage. TCR revision is a genetic correction mechanism that changes T cell specificity by re-activating V(D)J recombination in peripheral T cells. This process is now well described in both normal or pathological murine and human settings. Many of its features, such as the question of whether it occurs in truly mature T cells, remain to be elucidated. Its occurrence in human CD8+ T cells is also an open question. We have therefore established an in vitro model of TCR revision in mature human CD8+ T cells to determine whether down-regulation of the TCR/CD3 complex from the cell surface in the presence of IL7 as a factor favouring chromatin remodelling initiates a TCR revision pathway. Only mature CD8+ T cells carrying already-formed antigen receptors were used. CD8+ T cells treated with anti-CD3 and IL7 showed rearrangement intermediates and expressed new Vbeta-chains on their surface. Investigation of the molecular pathway thus induced disclosed up-regulation of the RAG-2 transcript, but absence of the 'canonical' RAG-1 mRNA. A surprising finding was the demonstration of alternative splice forms of this mRNA, already expressed in untreated CD8+ T cells, encoding for the full-length RAG-1 protein, which was increased three-fold in the treated cells. All the V(D)J requirements were thus fulfilled when mature human CD8+ T cells were stimulated with anti-CD3 and IL7. Induction of TCR revision in vitro in mature T cells is an easily controllable system that could be employed in further studies to elucidate the molecular pathways involved in secondary V(D)J rearrangements in peripheral cells.

A study of the factors inducing the development of childhood-onset myasthenia gravis using CDR3 spectratyping analysis of the TCR repertoire

Myasthenia gravis (MG) is an autoimmune disease. AChR-specific autologous helper T (Th) cells are essential to the pathogenesis of MG. Factors correlated with the development of childhood-onset MG are unknown. In longitudinal studies, we found TCR Vbeta 2/5.1/6/7 usage in the development or relapse phases, but not in the remission phase. We also found that TCR Vbeta 8/9/13.1/15/18/20 usage persisted. The polyclonally expanded TCR Vbeta 2/5.1/6/7 by CDR3 spectratyping was found to be associated with the development of disease. These data suggest that in patients with childhood-onset MG, stimuli such as superantigens induced by a preceding infection, which cause development of the polyclonal pattern in TCR Vbeta families, play an important role in the development of the disease.

Superantigens and chronic rhinosinusitis II: analysis of T-cell receptor V beta domains in nasal polyps

BACKGROUND

The superantigen (SAg) hypothesis of chronic rhinosinusitis (CRS) suggests that toxins within the nose stimulate massive oligoclonal expansion of T-cell populations with subsequent eosinophil recruitment and tissue inflammation. SAgs are capable of activating 1 x 10(4) more lymphocytes than conventional antigens by binding specific Vbeta-domains of the T-cell receptor (TCR). The net effect is skewing from the normal Vbeta-profile by oligoclonal expansion of specific domains. This study will assess polyp tissue for evidence of an SAg response in CRS with nasal polyps (CRSwNP).

METHODS

This study consists of a prospective analysis of 18 CRSwNP subjects undergoing sinus surgery. Flow cytometry was used to analyze the distribution of 24 specific TCR V beta-domains in lymphocytes from polyp tissue and blood. Evidence of oligoclonal expansion was tabulated for each specimen and defined as mean normative percentage + 2 SD.

RESULTS

Eighteen of 18 CRSwNP subjects showed expansion of polyp lymphocytes expressing TCRs with specific V beta-domains. The average number of V beta-clones per CRSwNP subject was seven in polyp lymphocytes but only two in blood lymphocytes.

CONCLUSION

The current results indicate that polyp lymphocytes exhibit significant oligoclonal expansion of specific V beta-domains. These data are considered diagnostic of a SAg effect. The corresponding blood profile is much less, suggesting that the nose is the primary source of stimulus. Although the trigger(s) for this expansion are unknown, these data are consistent with the hypothesis that staphylococcal toxins are central to the development of CRSwNP.

Chronic rhinosinusitis and superantigens

This article discusses the potential role of bacterial superantigens (SAgs) in chronic rhinosinusitis with nasal polyposis (CRS/NP). First, it briefly describes SAgs, focusing on how they interact with the immune system by binding to T-cell receptors (TCR) and major histocompatibility complex (MHC) class II molecules. Second, it discusses the role of SAgs in other chronic inflammatory diseases.Finally, it presents evidence for the role of SAgs in the pathogenesis and maintenance of CRS/NP focusing on current research and future considerations.

Evidence for Restricted Vβ Usage in the Leukemic Phase of Cutaneous T Cell Lymphoma

Antibodies directed against the beta chain of the T cell receptor (anti-Vbeta antibodies) are useful to identify the Vbeta repertoire of T cells in various diseases and to quantify numbers of Vbeta-bearing T cells. The goals of this study were to identify Vbeta+ cases of leukemic phase cutaneous T cell lymphoma (CTCL) and to compare the percentage of positive calls with other measures of blood tumor burden, i.e., lymphocyte subsets with a CD4+CD7- and CD4+CD26- phenotype and Sezary cell counts. Thirty-three of 49 (67%) cases of leukemic CTCL reacted with an anti-Vbeta antibody. When combined with reports from the literature, the frequency of Vbeta5 (probably Vbeta5.1) usage was relatively high when compared with Vbeta2 that is also frequently expressed by normal CD4+ T cells. The percentage of Vbeta+ cells correlated to the percentage of CD4+CD7- and CD4+CD26- cells for cases in which the neoplastic cells were deficient in expression of CD7 and CD26, respectively, but not the Sezary cell count. We hypothesize that the increased Vbeta5.1 usage in CTCL may be the result of depletion of Vbeta2 and other Vbeta-bearing T cells by staphylococcal superantigens prior to neoplastic transformation, resulting in a relative increase in the frequency of Vbeta5.1 usage in CTCL.