Significance of circulating T-cell clones in Sézary syndrome

Abstract

Identification of malignant Sé zary cells by T-cell receptor (TCR) clonality studies is routinely used for the diagnosis of Sé zary syndrome, but T-cell clones expressed in a single patient have never been accurately characterized. We previously reported that CD158k expression delineates Sé zary syndrome malignant cells, and, more recently, we identified vimentin at the surface membranes of Sé zary cells and normal activated lymphocytes. In the present study, T-cell clones from 13 patients with Sé zary syndrome were identified by immunoscopy and further characterized in the blood according to their TCR V␤, CD158k, and vimentin cell-surface expression. We found in most patients a unique malignant T-cell clone that coexpressed CD158k and vimentin and that, when patients were tested, was also present in the skin. However, in some patients we detected the presence of a nonmalignant circulating clone expressing high amounts of vimentin and lacking IntroductionSézary syndrome (SS) is an erythrodermic, aggressive, cutaneous T-cell lymphoma characterized by a malignant T-cell clone that localizes in the blood and skin. In the absence of a specific marker for malignant Sézary cells, a diagnosis of SS relies on the circulating Sézary cell count and on the molecular detection of a circulating T-cell clone. Given that the cytomorphology of Sézary cells is not specific to SS, 1,2 identification of a specific marker of malignant Sézary cells has been a challenging issue. Besides a T-cell memory phenotype, CD4 ϩ CD45RO ϩ , Sézary cells were shown to lack CD26 3-5 and to have diminished CD3 expression, 6 whereas the loss of CD7 3,7 appears not to be a specific feature of the malignant T-cell clone. 5,8 More recently, it has been shown that Sézary cells specifically overexpress T-plastin, which, however, cannot be used as a cell-surface marker because it is located in the cytoskeleton, in association with actin. 9 New markers of Sézary cells were described, including KIR3DL2/CD158k, the first positive cell-surface marker of Sézary cells. In patients with SS, KIR3DL2/CD158k is dimly expressed by circulating and cutaneous CD4 ϩ lymphocytes. [10][11][12] In healthy persons, CD158k is absent in CD4 ϩ lymphocytes, and only minor subsets of T CD8 ϩ and natural killer (NK) lymphocytes express high amount of this antigen. 13 SC5 monoclonal antibody (mAb) was shown to react with an unknown cell-surface antigen expressed by normal activated lymphocytes and Sézary cells, whereas it failed to stain most circulating T lymphocytes in healthy individuals. 14 We found that SC5 mAb specifically recognizes vimentin (VIM) at the cell surface of viable activated T lymphocytes and is effectively expressed by Sézary cells. 15 The finding of an expanded T-cell clone in the blood of patients with SS is commonly considered to be a diagnostic marker. TCR V␤ phenotyping with specific mAbs may identify a "clonotypic" lymphocyte subset as an expanded population bearing a single TCR V␤ chain, which may be of diagnostic value. 3,[16][17][18] This approach, h...

Th1 Response and Cytotoxicity Genes Are Down-Regulated in Cutaneous T-Cell Lymphoma

“…KIR3DL2 may be because only about half of the expanded T-cell clones express CD158k and that CD158k expression is heterogeneous even within the malignant clones (31). Taking together, our data provide evidence for the down-regulation of several cytotoxicity-associated genes in Sezary syndrome.…”

Flow cytometric detection of peripheral blood involvement by mycosis fungoides and Sézary syndrome using T-cell receptor Vβ chain antibodies and its application in blood staging

“…These findings agree with earlier observations that loss or dim expression of CD7 and CD26 can be found in patients with benign inflammatory dermatoses 17,34,35 and other reactive conditions, 14 and aberrant dim CD3 can be observed non-neoplastic T cells. 29 Similarly, T-cell receptor gene rearrangements have been detected in samples of patients without clinical or histologic evidence of lymphoma or evidence of T-cell clonality shown by other methods. In this study group, Vb flow cytometric clonality assessment correlated with PCR testing for T-cell receptor gene rearrangements in 86% of cases, but flow cytometric Vb analysis had 100% specificity vs 77% for PCR.…”

“…Subsequently, several studies validated and expanded the use of flow cytometry to assess T-cell receptor Vb in T-cell malignancies. 13,25,[27][28][29][30] Morice et al 30 studied 29 T-cell lymphoproliferative disorders by flow cytometric Vb analysis, including 10 cases of cutaneous T-cell lymphoma, and showed a good correlation with molecular methods. This group expanded their study to include 11 Sézary syndrome and 6 mycosis fungoides cases, and showed that Vb analysis by flow cytometry was helpful for assessing clonality and quantifying the peripheral blood tumor burden.…”

Use of PLS3, Twist, CD158k/KIR3DL2, and NKp46 gene expression combination for reliable Sézary syndrome diagnosis

“…[1][2][3][4][5] Besides PLS3, several other molecular SS-restricted markers, including the transcription factor Twist, 6 have been identified by gene expression analysis on whole peripheral blood mononuclear cells. We also previously reported SS malignant cells characterization by their membrane expression of CD158k/ KIR3DL2 [7][8][9] and CD335/NKp46. 10 Here we investigated whether PLS3, Twist, KIR3DL2, and NKp46 gene expression profiling by quantitative PCR (qRT-PCR) can be used for an efficient molecular SS diagnosis.…”