EWI-2 modulates lymphocyte integrin alpha4beta1 functions

The most prominent cell-surface integrin alpha4beta1 partner, a 70-kDa protein, was isolated from MOLT-4 T leukemia cells, using anti-alpha4beta1 integrin antibody-coated beads. By mass spectrometry, this protein was identified as EWI-2, a previously described cell-surface partner for tetraspanin proteins CD9 and CD81. Wild-type EWI-2 overexpression had no effect on MOLT-4 cell tethering and adhesion strengthening on the alpha4beta1 ligand, vascular cell adhesion molecule-1 (VCAM-1), in shear flow assays. However, EWI-2 markedly impaired spreading and ruffling on VCAM-1. In contrast, a mutant EWI-2 molecule, with a different cytoplasmic tail, neither impaired cell spreading nor associated with alpha4beta1 and CD81. The endogenous wild-type EWI-2-CD81-alpha4beta1 complex was fully soluble, and highly specific as seen by the absence of other MOLT-4 cell-surface proteins. Also, it was relatively small in size (0.5 x 10(6) Da to 4 x 10(6) Da), as estimated by size exclusion chromatography. Overexpression of EWI-2 in MOLT-4 cells caused reorganization of cell-surface CD81, increased the extent of CD81-CD81, CD81-alpha4beta1, and alpha4beta1-alpha4beta1 associations, and increased the apparent size of CD81-alpha4beta1 complexes. We suggest that EWI-2-dependent reorganization of alpha4beta1-CD81 complexes on the cell surface is responsible for EWI-2 effects on integrin-dependent morphology and motility functions.

DNA methylation and expression of major histocompatibility complex class I and class II transactivator genes in human developmental tumor cells and in T cell malignancies

Major histocompatibility complex (MHC) class I and class II molecules play essential roles in the immune response by virtue of their ability to present peptides to T lymphocytes. Given their central role in adaptive immunity, the genes encoding these peptide-presenting molecules are regulated in a tight fashion to meet with local requirements for an adequate immune response. In contrast to MHC class I gene products, which are expressed on almost all nucleated cells, constitutive expression of MHC class II molecules is found in specialized antigen presenting cells of the immune system only. Transcription of both MHC class I and class II genes can be induced by immune regulators and upon cell activation. Transcription of MHC class I genes is mediated by a set of conserved cis acting regulatory elements in their promoters. Of these regulatory elements, MHC class II promoters share the SXY-module. Essential for activation of MHC class II promoters is the class II transactivator (CIITA), which acts through protein/protein interactions with regulatory factors bound to the SXY module. In this review, we discuss the role of DNA methylation in relation to altered expression of MHC class I and CIITA genes as observed in malignancies and in development.

[Study on blocking the tumor immune escape by Fas ligand pathway]

The expression of Fas ligand (FasL) on the membrane of many kinds of leukemia or solid tumor cells played an important role in the immune escape of tumor cells. This study was aimed to know if the soluble Fas (sFas), expressed by adenovirus, could block the immune escape of tumor cells by FasL pathway. The two recombinant adenoviral vectors, AdsFas with murine soluble Fas gene and AdEGFP with enhanced GFP protein gene, were constructed by homologous recombination between two plasmids in Escherichia coli with the AdEasy adenovirus vector system. The viruses were propagated and purified by two times ultracentrifugation. Their titres were detected by plaque assays. The expressed protein was evaluated by Western blot analysis. Then the tumor EL4 cells were infected with AdsFas and AdEGFP respectively. The apoptosis ratio of the target cells-YAC-1 cells induced by EL4 cells was respectively detected by (3)H-thymidine ((3)H-TdR) labeling. The results showed that the recombinant adenoviral vectors AdsFas and AdEGFP were successfully obtained. The titres of viruses purified by two times ultracentrifugation were up to 10(11) pfu/ml by plaque assays. The sFas protein was highly expressed in the target cells by Western blot analysis. After the EL4 cells were transfected with the adenoviruses AdsFas, the apoptosis rate of YAC-1 cells in the sFas transfection group (respectively 6%, 7% and 9% when the effector:target (E:T) was 3:1, 10:1 and 30:1) was obviously lower than that in the control group (respectively 28%, 37% and 45%), P < 0.01. But when the EL4 cells were transfected with AdEGFP, the apoptosis rate of YAC-1 cells (respectively 30%, 36% and 48%) was similar to the control group, P > 0.05. In conclusion, the transfer of sFas by adenovirus could inhibit the apoptosis of Fas(+) cells-YAC-1 cells induced by tumor EL4 cells. It showed that the transduction of sFas could block the effect of the immune escape of EL4 cells through FasL in vitro. These results thus provide a new direction to find a way to treat tumors.

Adult T-biphenotypic acute leukaemia: clinical and biological features and outcome

Biphenotypic acute leukaemia with T-lymphoid and myeloid markers is rare and poorly documented. In the Leucemie Aigue Lymphoblastique de l'Adulte (LALA) prospective trial (LALA 94) of treatment for adult acute lymphoblastic leukaemia (ALL), seven patients (0.86%) had T-biphenotypic forms. The clinical and biological characteristics and outcome of these seven patients are reported here. The patients' median age was 35 years. At diagnosis, all had a tumoural syndrome and five had a mediastinal mass. In all the cases, leukaemic cells expressed myeloid and lymphoid markers. Two patients (28%) entered complete remission (CR) after induction chemotherapy. Four of the five remaining and assessable patients entered CR after designed salvage chemotherapy with mitoxantrone and high-dose cytosine arabinoside. Three patients are currently in CR. Three patients died, from treatment toxicity in two cases and progressive disease in one case. One patient relapsed 6 months after allogeneic bone marrow transplantation and is still alive. Thus, biphenotypic T-acute leukaemia is clinically frequently associated with mediastinal involvement and the response to conventional chemotherapy used in ALL is poor. However, sustained CR can be achieved by salvage chemotherapy combining an intercalating agent with high-dose cytosine arabinoside, as used in acute myeloid leukaemia.

TCR Vβ repertoire analysis in CD56+ CD16dim/− T-cell large granular lymphocyte leukaemia: association with CD4 single and CD4/CD8 double positive phenotypes

We report 10 patients with T-cell large granular lymphocyte (LGL) leukaemia: four patients had CD16+ CD56- LGL lymphocytes (typical for LGL leukaemia), and six patients had CD56+ CD16(dim/-) LGL lymphocytes (atypical). Among the CD56+ CD(dim/-) patients, LGL lymphocytes were CD4+ CD8- in one patient, CD4/CD8 double positive (DP) in three, and CD4- CD8+ in two. The CD4+ CD8dim DP cells expressed a CD8alphaalpha homodimer. T-cell receptor (TCR) Vbeta complementarity-determining region 3 (CDR3) size distribution analysis and direct sequencing identified at least 1 in-frame clonal TCR Vbeta transcript in each patient; three patients had two or three different clonal sequences. To determine whether these transcripts were translated into cell surface TCR, we performed flow cytometric analysis using Vbeta monoclonal antibodies (mAbs). A single Vbeta protein was identified in patients, even those with multiple in-frame transcripts. Previous and present results suggest that CD56+ CD16(dim/-) LGL leukaemia is more common than previously thought, and is associated with unusual phenotypes. When assessed using only molecular techniques, the monoclonal status of this disease may be misinterpreted as oligoclonal; thus, flow cytometric analysis using Vbeta mAb is quite useful. Because mAbs do not cover the entire Vbeta repertoire, assessing clonality using a combination of molecular methods and mAbs is preferable.

A neutralizing monoclonal antibody (mAb A24) directed against the transferrin receptor induces apoptosis of tumor T lymphocytes from ATL patients

Adult T-cell leukemia/lymphoma (ATL) is an aggressive lymphoid proliferative disease that exists under diverse clinical forms ranging from chronic to acute. Although leukemic cells from patients with ATL exhibit an intrinsic resistance to chemotherapy, monoclonal antibodies directed against CD25 (interleukin 2 receptor alpha [IL-2Ralpha] antibody) have been used as specific therapeutic agents. However, significant clinical results with these antibodies have been demonstrated only in chronic forms of ATL. In contrast to resting T cells, human T-cell lymphotropic virus type 1 (HTLV-1)-infected cells constitutively express high levels of surface transferrin receptor (TfR). Herein, we report the characterization of a new monoclonal antibody (mAb A24) directed against the human TfR and the evaluation of its capacity to block the proliferation of ATL cells ex vivo. We determined that A24 binds TfR with an equilibrium constant (K'd) of 2.7 nM and competes with transferrin for binding to TfR. A24 also inhibited [55Fe]-transferrin uptake in activated T cells and blocked T-cell proliferation. Moreover, A24 reduced and impaired TfR expression and recycling, respectively. Most important, we showed that A24 blocked the ex vivo proliferation of malignant T cells from both acute and chronic forms of ATL, through induction of programmed cell death. Therefore efficient therapeutic tools to treat acute forms of ATL might be derived from A24.

HLA-DR4 predicts haematological response to cyclosporine in T-large granular lymphocyte lymphoproliferative disorders

T-cell large granular lymphocytic lymphoproliferative disease (T-LGL) is often associated with life-threatening cytopenias. Twenty-five subjects with anaemia and/or neutropenia caused by T-LGL were treated with cyclosporin A (CSA) 5-10 mg/kg/d for at least 3 months. Eighteen patients survived between 35 and 77 months after starting treatment. Fourteen patients [56%; 95% confidence interval (CI) 35-76%] responded to CSA with sustained improvement in the neutrophil count or transfusion independence. Seven had complete normalization of blood counts, and four achieved a durable response only after the addition of erythropoietin. Sustained response required continued low-dose CSA. In a multivariate analysis, HLA-DR4 was highly predictive of CSA responsiveness (odds ratio 18; 95% CI 1.8-184). T-LGL subtype, LGL counts after therapy, lymphocytic marrow infiltration and bone marrow cellularity did not significantly affect the probability of response. We conclude that CSA is effective in inducing haematological responses in HLA-DR4-positive patients and that T-LGL is likely to have an immune pathogenesis.

Immunoprofiling of cell lines derived from natural killer-cell and natural killer-like T-cell leukemia-lymphoma

T-cells and natural killer (NK)-cells can be distinguished by their immunophenotype and molecular biological studies though there is overlap in T- and NK-cell antigen expression, function, and malignant diseases. The relatively new cell type of NKT-cells (also termed NK-like T-cells) represents a subpopulation of T-cells that share some characteristics with NK-cells. T- and NKT-cells have their T-cell receptor (TCR) genes rearranged while NK-cells are identified molecularly and immunologically by the absence of TCR gene rearrangements and TCR protein and lack of certain surface antigens. Various continuous malignant cell lines have been derived from patients with T-cell, NK- and NKT-cell neoplasms. These cell lines possess several traits typical of the respective diseases. Characterization of these cell lines which was the objective of this study will facilitate future studies of cell biology and therapeutics for which cell lines are indispensable models. In view of the imprecision of morphological criteria alone, we analyzed a series of seven NK-cell, five NKT-cell and five T-cell lines using functional and immunophenotypic tools. All T-cell lines were negative for the presence of azurophilic granules, NK activity and Epstein-Barr virus (EBV). In contrast, 7/7 NK-cell and 4/5 NKT-cell lines displayed the azurophilic granules but only three of these combined twelve NK/NKT-cell lines showed significant NK activity which may be explained by the functional immaturity of the cells. EBV was found in 5/7 NK-cell and in 1/5 NKT-cell lines. As expected, T-cell lines were commonly positive for T-cell surface antigens and negative for NK-cell markers, and NK-cell lines vice versa; nevertheless, a number of immunomarkers were shared between T- and NK-cell lines. NKT-cell lines express T-cell, NK-cell and markers shared between T- and NK-cells. Sets of markers distinctive for the three types of cell lines are presented. The composite data gained on the present panels of cell lines allow for the operational definition of typical NK- and NKT-cell line profiles. Such cell lines will prove invaluable as informative models for studies of normal and neoplastic NK- and NKT-cell biology.

2-deoxycoformycin in the treatment of T-large granular lymphocyte leukemia

A 52-year-old woman presented to our clinic for investigation of agranulocytosis and mild lymphocytosis. A diagnosis of T-large granular lymphocyte leukemia was made, based on immunophenotyping findings of the peripheral blood lymphocytes (CD3, CD8, CD16, CD57). Flow cytometric analysis of TCR-Vbeta repertoire showed single Vbeta9 expression on peripheral T-cells. Clonality was also demonstrated with PCR analysis which revealed clonal rearrangement of TCRgamma-chain gene. Granulocyte-macrophage colony-stimulating factor (G-CSF) (G-CSF), cyclosporine, methylprednisolone and oral methotrexate failed to correct the neutropenia. Finally, treatment with 2-deoxycoformycin (DCF) was successful and resulted in complete correction of the neutrophil count. Flow cytometric analysis of TCR-Vbeta repertoire proved to be an effective method to assess the therapeutic response to various treatments and to evaluate residual disease.

Update in the pathologic features of mature B-cell and T/NK-cell leukemias

Modern diagnosis of mature B- and T-cell leukemias requires integration of morphologic, immunophenotypic, and molecular genetic features. This integrative approach has allowed more precise definitions of specific disease entities. This in turn provides better information for clinicians to select proper therapy and determine prognosis. The characteristic pathologic features of these disorders are reviewed.

TCRalphabeta+/CD4+ large granular lymphocytosis: a new clonal T-cell lymphoproliferative disorder

Large granular lymphocyte (LGL) leukemia is a well-recognized disease of mature T-CD8(+) or less frequently natural killer cells; in contrast, monoclonal expansions of CD4(+) T-LGL have only been sporadically reported in the literature. In the present article we have explored throughout a period of 56 months the incidence of monoclonal expansions of CD4(+) T-LGL in a population of 2.2 million inhabitants and analyzed the immunophenotype and the pattern of cytokine production of clonal CD4(+) T cells of a series of 34 consecutive cases. Like CD8(+) T-LGL leukemias, CD4(+) T-LGL leukemia patients have an indolent disease; however, in contrast to CD8(+) T-LGL leukemias, they do not show cytopenias and autoimmune phenomena and they frequently have associated neoplasias, which is usually determining the clinical course of the disease. Monoclonal CD4(+) T-LGLshowed expression of TCRalphabeta, variable levels of CD8 (CD8(-/+dim)) and a homogeneous typical cytotoxic (granzyme B(+), CD56(+), CD57(+), CD11b(+/-)) and activated/memory T cell (CD2(+bright), CD7(-/+dim), CD11a(+bright), CD28(-), CD62L(-) HLA-DR(+)) immunophenotype. In addition, they exhibited a Th1 pattern of cytokine production [interferon-gamma(++), tumor necrosis factor-alpha(++), interleukin (IL-2)(-/+), IL-4(-), IL-10(-), IL-13(-)]. Phenotypic analysis of the TCR-Vbeta repertoire revealed large monoclonal TCR-Vbeta expansions; only a restricted number of TCR-Vbeta families were represented in the 34 cases analyzed. These findings suggest that monoclonal TCRalphabeta(+)/CD4(+)/NKa(+)/CD8(-/+dim) T-LGL represent a subgroup of monoclonal LGL lymphoproliferative disorders different from both CD8(+) T-LGL and natural killer cell-type LGL leukemias. Longer follow-up periods are necessary to determine the exact significance of this clonal disorder.

[Molecular design and construction of IL6D24-PE40KDEL, a novel recombinant interleukin6-pseudomonas exotoxin fusion protein, having targeted cytotoxicity for leukemias expressing interleukin6 receptors]

OBJECTIVE

A novel recombinant interleukin6-Pseudomonas exotoxin fusion protein, having targeted cytotoxicity for leukemic cells highly expressing IL6R has been molecularly designed and constructed in this study.

METHODS

Firstly, REDLK at C-terminus of Pseudomonas exotoxin PE40 was replaced with KDEL using point mutagenesis technology. Secondly, a cDNA encoding interleukin-6 devoid of N-terminal 24 amino acids [IL6D24] was fused to 5' terminus of PE40KDEL DNA by the method of gene splicing by overlap extension, which could generate recombinant IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL fusion genes. Thirdly, recombinant fusion genes IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL were ligated into the EcoR I and Sma I cloning sites in the pBV220 plasmids respectively and then transformed into E.coli HB101 cells. The expressed recombinant exotoxin fusion proteins were purified to electrophoresis purity by Mono Q column chromatography. Its selectively killing was tested by the MTS colorimetric method using both U937 and CEM cells lines.

RESULTS

Recombinant exotoxin fusion proteins IL6D24-PE40KDEL was expressed as a form of inclusion bodies at higher level of 40% approximately of total proteins in bacterial cells. Western blot showed that the purified products could react specifically with IL6 monoclonal antibody and PEA antiserum, respectively. IL6D24-PE40KDEL was selectively cytotoxic to U937 cells expressing IL6R-positive with ID50 of 250 ng/ml, and but not CEM cells expressing IL6R-negative.

CONCLUSIONS

Two novel recombinant interleukin6-Pseudomonas exotoxin fusion proteins IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL have been successfully constructed and they can selectively kill the leukemic cells expressing highly IL6R.

T-cell large granular lymphocyte leukemia is characterized by massive TCRBV-restricted clonal CD8 expansion and a generalized overexpression of the effector cell marker CD57

INTRODUCTION

Large granular lymphocyte leukemia (LGL) is a clonal lymphoproliferative disease of CD8+ T cells expressing the CD57 activation marker. It is, however, unknown whether the CD57+ population represents the LGL clone or not. We previously demonstrated that the clone can be found in both CD8+CD57+ and CD8+CD57- cells, indicating that the LGL clone also resides in the CD57- fraction.

MATERIALS AND METHODS

Here, we quantified the extent of the clonal CD8 expansion in LGL using T-cell receptor Vbeta (TCRBV)-specific monoclonal antibodies, and determined whether the CD4 population also contained skews. Furthermore, dominant TCRBV populations were assessed for clonal status using T-cell receptor-gamma (TCRG) PCR on genomic DNA.

RESULTS

We show that the dominant TCRBV in LGL contains CD57+ and CD57- cells. Molecular analysis of CD8+CD57+ and CD8+CD57- subfractions of the dominant TCRBV by TCRG PCR demonstrates that indeed both fractions are clonal, and that the clone is absent from the dominant TCRBV-negative population. Furthermore, we show that CD57 overexpression is not restricted to the LGL clone, but a general phenomenon in CD8 cells of LGL patients.

CONCLUSION

We therefore conclude that the primary characteristic of LGL is a clonal expansion of CD8 cells, with a concomitant upregulation of CD57 on this clone and uninvolved cells.

B cell apoptosis accelerates the onset of murine lupus

To investigate whether the increased rate of lymphocyte apoptosis in systemic lupus erythematosus is involved in the onset of the disease, apoptotic or necrotic T or B lymphocytes from various cell lines were injected intraperitoneally into pre-autoimmune (NZBxNZW)F1 mice (BW) and non-autoimmune BALB/c mice. The intraperitoneal production of cytokines and chemokines, the specific T cell response in the spleen, and the production of anti-histone and anti-dsDNA Ab were investigated. The onset of the disease was characterized by creatinine levels and evaluation of glomerular IgG deposits. In BW, but not in BALB/c mice, injection of apoptotic and not necrotic cells up-regulated IL-6 and IL-10 in resident macrophages. Administration of apoptotic cells augmented the number of Th2 and B lymphocytes recruited in the peritoneal cavity. Only the treatment with apoptotic B cells promoted a systemic Th2 autoimmune response to H2 histones, associated with earlier occurrence of high levels of anti-dsDNA autoantibodies, higher creatinine levels and more numerous glomerular IgG deposits than in BW controls not injected with apoptotic B cells. In genetically susceptible mice exposure to apoptotic of B, but not T, lymphocytes can elicit a Th2 response to H2 histones that helps B cell production of anti-dsDNA Ab and finally triggers the onset of lupus.

Application of the molecular analysis of the T-cell receptor repertoire in the study of immune-mediated hematologic diseases

The basis for the vast recognition spectrum of the T-cell receptor (TCR) can be determined by the rearrangement and recombination of the variable, diversity and joining regions of the variable portions of beta (B) and alpha (A) chains as well as their recombination and modification. Analysis of the TCR rearrangement has been routinely used to detect clonality for the diagnosis of lymphoid malignancies. However, molecular analysis of the TCR repertoire can be a powerful tool in the study of T-cell responses to pathogens and in autoimmune diseases. The concept of the oligoclonality in the context of cellular immune responses is based on the presence of immunodominant T-cell clones within distinct T-cell subpopulations used for analysis. Under normal circumstances, a limited number of clones undergo periodic expansions in reaction to foreign antigens. Under pathologic conditions, though, the derailment of immune regulation allows expansions of specific and potentially pathogenic T-cell clones. For example, large granular lymphocyte (LGL) leukemia illustrates an extreme expansion of a single T-cell clone associated with a distinct autoimmune pathology, which suggests an exaggerated clonal response to a specific antigenic target. In immune-mediated bone marrow failure syndromes, clonal rearrangement of the TCR cannot be detected in unseparated blood or marrow. Nevertheless, individual T-cell clones can significantly expand and may allow for demonstration of oligoclonality in selected T-cell populations. These subpopulations are defined, for example, by a specific beta (B)-chain usage or other phenotypic markers. Given the diversity of the TCR recognition spectrum, the task of identifying immunodominant clonotypes derived from unique complementarity determining region-3 (CDR3) sequences is very complex. However, expanded T-cell clones likely represent immunodominant responses which can be detected on the molecular level using analysis of the individual TCR VB-chain representation, CDR3 size fragment skewing, and determination of the frequency of individual clonotypic sequences. In the future, TCR VB clonotypes may be applied as a diagnostic tool, analogous to serologic markers. As an investigative tool in hematology, molecular analysis of the TCR utilization pattern and the detection of immunodominant clonotypes represents a novel approach in the study of immune-mediated hematologic diseases, such as aplastic anemia (AA), some forms of myelodysplasia (MDS), anti-leukemic immune surveillance, graft-versus-leukemia effects and graft-versus-host disease (GvHD).

Bcl11a is essential for normal lymphoid development

Bcl11a (also called Evi9) functions as a myeloid or B cell proto-oncogene in mice and humans, respectively. Here we show that Bcl11a is essential for postnatal development and normal lymphopoiesis. Bcl11a mutant embryos lack B cells and have alterations in several types of T cells. Phenotypic and expression studies show that Bcl11a functions upstream of the transcription factors Ebf1 and Pax5 in the B cell pathway. Transplantation studies show that these defects in Bcl11a mutant mice are intrinsic to fetal liver precursor cells. Mice transplanted with Bcl11a-deficient cells died from T cell leukemia derived from the host. Thus, Bcl11a may also function as a non-autonomous T cell tumor suppressor gene.

Preferential expansion of Vgamma9-JgammaP/Vdelta2-Jdelta3 gammadelta T cells in nasal T-cell lymphoma and chronic active Epstein-Barr virus infection

We recently established an Epstein-Barr virus (EBV)-positive gammadelta T-cell line from a nasal T/natural killer (NK)-cell lymphoma (Nagata H, Konno A, Kimura N, Zhang Y, Kimura M, Demachi A, Sekine T, Yamamoto K, Shimizu N: Characterization of novel natural killer (NK)-cell and gammadelta T-cell lines established from primary lesions of nasal T/NK-cell lymphomas associated with the Epstein-Barr virus. Blood 2001, 97:708-713). Subsequently, we established two novel EBV-positive gammadelta T-cell lines from the peripheral blood of patients with chronic active EBV infection. Analysis of the terminal repeat of EBV showed that the three cell lines consisted of monoclonal populations, and flow cytometry showed that they had a common phenotype of gammadelta T cells: CD3(+) CD4(-) CD8(-) CD16(-) CD19(-) CD56(+) CD57(-) HLA-DR(+) T-cell receptor (TCR) alphabeta(-) TCR gammadelta(+). Analysis for the expression of TCR by flow cytometry showed that all three cell lines were Vgamma9(+)/Vdelta2(+), but negative for VgammaI, Vdelta1, or Vdelta3 TCR. Southern blot analysis for TCR genes showed that the three cell lines had a common rearrangement of Vgamma9-JgammaP and Jdelta3 genes. Polymerase chain reaction and sequence analysis of the junction between Vdelta and Jdelta genes revealed that the Jdelta3 genes were rearranged with the Vdelta2 genes. In contrast, none of the EBV-negative gammadelta T-cell lines, Molt-14, Peer, or Loucy, which were analyzed for controls, had Vgamma9 or Vdelta2 TCR, or a rearrangement of Jdelta3 genes. These results indicated that Vgamma9-JgammaP/Vdelta2-Jdelta3(+) gammadelta T cells were preferentially affected by EBV and expanded in patients with nasal gammadelta T-cell lymphoma and chronic active EBV infection. Jdelta3(+) gammadelta T cells are known to be a very minor population in gammadelta T cells of peripheral blood, whereas Vgamma9-JgammaP/Vdelta2-Jdelta1(+) cells are the major population. The close association of EBV with this particular gammadelta T-cell population may provide a key to the etiology of EBV-positive lymphoproliferative diseases.

Natural killer resistance of a drug-resistant leukemia cell line, mediated by up-regulation of HLA class I expression

BACKGROUND AND OBJECTIVES

Drug-resistant leukemia cells may exhibit cross-resistance towards immunological effector mechanisms by alterations of apoptosis pathways. This is particularly relevant in allogeneic bone marrow transplantation for leukemia, where the graft-versus-leukemia effect acts on cells pretreated with cytostatic drugs. Here, we clarify the mechanism underlying cross-resistance of drug-resistant variants of the T-leukemia cell line CEM towards natural killer cells.

DESIGN AND METHODS

We determined the sensitivity of different CEM sublines to natural killer (NK) cytotoxicity, and separately analyzed the components of the killing machinery by detection of granzyme B-induced caspase cleavage and HLA class I-dependent recognition mechanisms. Furthermore, we studied regulation of HLA class I expression comparing CEM with other cell lines.

RESULTS

We found that CEM cells resistant to cytostatic drugs or CD95 were cross-resistant towards NK cells from a variety of donors. Granzyme B-induced caspase and PARP cleavage in the sensitive and resistant cells were comparable, indicating that downstream apoptosis pathways were not altered in the drug-resistant cells. HLA class I molecules were upregulated in the resistant cells, inhibiting NK cells at the level of killer/target recognition. HLA class I upregulation was not found in other leukemia cell lines.

INTERPRETATION AND CONCLUSIONS

This is the first description of HLA class I-mediated NK cross-resistance in drug-resistant cells. This finding may have a clinical impact since it may be considered as a possible reason for resistance to a graft-versus-leukemia approach in allogeneic bone marrow transplantation

Monoclonal T-cell expansions in asymptomatic individuals and in patients with large granular leukemia consist of cytotoxic effector T cells expressing the activating CD94:NKG2C/E and NKD2D killer cell receptors

We have analyzed the phenotype, cytokine profile, and mitotic history (telomere length) of monoclonal T-cell expansions in 5 CD3(+) T-cell large granular lymphocyte (TLGL) leukemia patients by fluorescence activated cell sorting (FACS) and single-cell polymerase chain reaction (PCR). We confirm that the common phenotype of TLGL leukemia is CD3(+)CD8(+)CD45RA(+)CD27(-)CD94(+)(CD57(+)). Interestingly, the C-type lectin-like type killer cell receptor CD94 was invariably associated with the activating form of its signal-transducing molecule NKG2. Furthermore, when judged by criteria such as interferon gamma (IFN-gamma)/tumor necrosis factor (TNF) production, expression of granzyme, FasL, and NKG2D, the TLGL cells had all the features of a cytotoxic effector T cell. Telomere shortening in TLGL cells was in the normal range for CD8(+) T cells, indicating that they had not divided significantly more than chronically stimulated CD8(+) T cells in healthy individuals. In 25 of 27 controls, cells with a TLGL phenotype occurred at low (1%-3%) frequencies. However, in the other 2 individuals (ages 28-36 years), large stable (> 3 years) monoclonal expansions of CD3(+)CD8(+)CD45RA(+)CD27(-)CD57(+)CD94(+) NKG2C(+) were found which rendered these controls phenotypically indistinguishable from TLGL leukemia patients. We believe that the TLGL clonopathy, rather than being of a neoplastic nature, is more likely an extreme manifestation of the large and stable clonal size characteristic of CD8(+) effector cells. Such a TLGL clone consisting of cells without any particular pathologic trait might exist in a considerable number of individuals. Clinical symptoms may occur in individuals in whom the TLGL clone encounters antigen and is triggered to produce large amounts of effector molecules that dysregulate the immune system, which could manifest itself as autoimmunity or as a FasL-mediated neutropenia.

Notch signalling at the crossroads of T cell development and leukemogenesis

Members of the Notch family (e.g. Notch1 and Notch3) have been recently described to play a critical role in T cell development and their constitutive activation has been related to T cell leukaemia in both animal models and human disease. Nevertheless, whether they act as redundant molecules, by affecting the same molecular mechanisms, or play distinct roles in T cell differentiation and/or leukemogenesis is not clear. Altered Notch signalling impairs the developmentally-regulated interplay between pre-TCR signalling, NFkappaB and E2A activities, thus identifying the crucial role of Notch receptors at the cross-roads of disrupted lymphoid differentiation and neoplastic transformation.

Demonstration of aberrant T-cell and natural killer-cell antigen expression in all cases of granular lymphocytic leukaemia

The diagnosis of granular lymphocytic leukaemia (GLL) requires the presence of an immunophenotypically distinct T-cell (T-GLL) or natural killer-cell (NK-GLL) population. Flow cytometric immunophenotyping was performed on 21 T-GLL patients, 11 NK-GLL patients and 20 normal control subjects using antibodies to T and NK cell-associated antigens in order to accurately identify the distinguishing features of T-GLL and NK-GLL. The NK antigens evaluated included: CD16, CD57, CD94, CD161, and the killing inhibitory receptors (KIRs) CD158a, CD158b and CD158e (p70). Abnormal T-antigen expression was present in all T-GLL patients. CD57 was frequently expressed in T-GLL, however, one-third of patients showed partial CD57 expression similar to that seen in T cells from normal control subjects. Ten T-GLL were KIR positive; all expressed a single KIR isoform. All NK-GLL showed a distinctive, abnormal immunophenotype. Four NK-GLL expressed a single KIR isoform; the remaining seven patients lacked all tested KIRs, which is also a distinct, abnormal finding. Immunoperoxidase staining of bone marrow biopsy specimens from NK-GLL patients with antibodies to CD8, TIA-1 and granzyme B revealed the disease-specific distinctive staining patterns previously found in T-GLL. These studies delineate the unique immunophenotypic features diagnostic of T-GLL and provide strong evidence that NK-GLL, like T-GLL, represents a clonal lymphoproliferative disorder.

Use of a chimeric synthetic peptide from the core p19 protein and the envelope gp46 glycoprotein in the immunodiagnosis of HTLV-II virus infection

A chimeric synthetic peptide incorporating immunodominant epitope of the p19 gag protein (116-134) and the gp46 env protein (178-200) of HTLV-II virus, separated by two glycine residues, was synthesized by conventional solid-phase peptide synthesis. The antigenic activity of this peptide was evaluated by Ultramicro Enzyme-linked immunosorbent assay (UMELISA) by using panels of anti-HTLV-II positive sera (n = 9), anti-HTLV-I/II positive sera (n = 2), HTLV-positive (untypeable) serum samples (n = 1),and anti-HTLV-I positive sera (n = 14), while specificity was evaluated with samples from healthy blood donors (n = 20). The efficacy of the chimeric peptide in solid-phase immunoassays was compared with the monomeric peptides. Data demonstrated that the chimeric peptide was the most reactive because it detected antibodies to virus efficiently. This may be related to peptide adsorption to the solid surface and epitope accessibility to the antibodies. The results indicate that chimeric peptide as coating antigen is very useful for the immunodiagnosis of HTLV-II infection.

Lymphoid disorders other than common acute lymphoblastic leukemia: background

The cytogenetic abnormalities that are found in chronic lymphoid malignancies (and in acute leukemias deriving from relatively mature cells) fall mainly into two groups according to whether the malignant cells are of B-lineage or T-lineage. In most of the B-lineage cases. there is some abnormality of the IgH gene which is located at 14q32 or, less frequently, the other immunoglobulin genes located at 2p12 and 22q11. In the T-lineage cases, there is often some abnormality involving the T-cell receptor loci, most frequently those at 14q11. Other abnormalities occur, but few have a close association with a particular disease type, and so do not often contribute to determining a precise diagnosis. This lack of specificity is due partly to deficiencies in our understanding of the biological relationships between different lymphoid disorders, and also to the various classifications that have been used. As a consequence, there has to be some doubt about the diagnosis assigned to many of the cases in published cytogenetic studies. It is also difficult to combine data from series that have used different classification systems. The present unsatisfactory situation greatly limits the clinical usefulness of cytogenetic studies and there is a real need to unravel the complexities of this large family of malignancies.