Seroreactivity to an Envelope Protein of Human T-Cell Leukemia/Lymphoma Virus in Patients With CD3− (Natural Killer) Lymphoproliferative Disease of Granular Lymphocytes

Mature T-Cell leukemias: Challenges in Diagnosis

T-cell clones can frequently be identified in peripheral blood. It can be difficult to appreciate whether these are benign and transient or whether they signify a clonal disorder. We review factors that aid in understanding the relevance of T-cell clones. Conversely, obvious pathological T-cell clones can be detected in blood, but there is uncertainty in how to categorize this clonal T cell population, thus, we adopt a multidisciplinary review of the clinical features, diagnostic material and radiology before making the diagnosis. In this review we shall discuss some of these challenges faced when diagnosing mature T-cell leukemias.

Lack of Viral Load Within Chronic Lymphoproliferative Disorder of Natural Killer Cells: What Is Outside the Leukemic Clone?

Large granular lymphocyte leukemias (LGLL) are sustained by proliferating cytotoxic T cells or NK cells, as happens in Chronic Lymphoproliferative Disorder of Natural Killer cells (CLPD-NK), whose etiology is only partly understood. Different hypotheses have been proposed on the original events triggering NK cell hyperactivation and transformation, including a role of viral agents. In this perspective, we revise the lines of evidence that suggested a pathogenetic role in LGLL of the exposure to retroviruses and that identified Epstein Barr Virus (EBV) in other NK cell leukemias and lymphomas and focus on the contrasting data about the importance of viral agents in CLPD-NK. EBV was detected in aggressive NK leukemias but not in the indolent CLPD-NK, where seroreactivity against HTLV-1 retrovirus envelope BA21 protein antigens has been reported in patients, although lacking clear evidence of HTLV infection. We next present original results of whole exome sequencing data analysis that failed to identify viral sequences in CLPD-NK. We recently demonstrated that proliferating NK cells of patients harbor several somatic lesions likely contributing to sustain NK cell proliferation. Thus, we explore whether "neoantigens" similar to the BA21 antigen could be generated by aberrancies present in the leukemic clone. In light of the literature and new data, we evaluated the intriguing hypothesis that NK cell activation can be caused by retroviral agents located outside the hematopoietic compartment and on the possible mechanisms involved with the prospects of immunotherapy-based approaches to limit the growth of NK cells in CLPD-NK disease.

CD8-positive cutaneous lymphoproliferation associated with large granular lymphocyte leukemia in a patient with X-linked agammaglobulinemia

Patients with primary immunodeficiency are at increased risk for malignancy, especially hematologic neoplasms. This paper reports a unique case of a 47-year-old man with X-linked agammaglobulinemia who presented with progressive asymptomatic violaceous papules and plaques on his face, hands, and trunk for 1 year. Skin biopsies revealed deep, nodular infiltrates of histiocytes and CD8-positive lymphocytes, with a CD4:CD8 ratio of 1:10. Laboratory studies showed cytopenias. Flow cytometry in the skin, blood, and bone marrow (BM) showed a CD3+/CD8+/CD57+ large granular lymphocyte population. BM biopsy showed 30% involvement with these atypical T-cells. T-cell gene rearrangement studies of skin, blood, and BM revealed identical T-cell clones. He was diagnosed with T-large granular lymphocyte leukemia (T-LGLL) with an associated CD8+ cutaneous lymphoproliferation. Skin involvement was suspected to represent infiltration by T-LGLL. However, co-existence of two lymphoproliferative disorders (LPDs), T-LGLL and CD8+ granulomatous LPD, remains a possibility. In general, cutaneous infiltrates associated with LGLL are rare and poorly understood. It has been suggested that they are markers of poor prognosis. Our case report describes skin, blood, and BM findings in an immunosuppressed patient with T-LGLL in detail. These findings have not yet been reported and their significance requires further investigation.

A Stab in the Back: An Unusual Case of Cutaneous Neural Infiltration as a Manifestation of Chronic Lymphoproliferative Disorder of Natural Killer Cells

Chronic lymphoproliferative disorder of natural killer cells (CLPDNK) is a rare heterogenous indolent disorder comprising a persistent peripheral blood cell count of more than ≥2 × 10/L natural killer cells for over 6 months. We report an unusual case of cutaneous neural infiltration as a manifestation of CLPDNK. A 52-year-old woman with a background of CLPDNK was referred to dermatology with a painful rash primarily affecting her back. Skin biopsies revealed a neurotropic atypical lymphoid infiltration. Results of immunohistochemistry studies showed CD8, CD56, granzyme B, perforin positivity, and CD3 negativity in keeping with an atypical neurotropic lymphoid infiltrate consistent with cutaneous involvement by the patient's known CLPDNK. Cutaneous lesions and peripheral neuropathy in patients with CLPDNK have been reported; however, the involvement of cutaneous peripheral nerves as described in our case has not been reported before.

Dysfunction of immune system in the development of large granular lymphocyte leukemia

OBJECTIVES

Large granular lymphocyte (LGL) leukemia is a rare type of lymphoproliferative disease caused by clonal antigenic stimulation of T cells and natural killer (NK) cells.

METHODS

In this review, we focus on the current knowledge of the immunological dysfunctions associated with LGL leukemia and the associated disorders coexistent with this disease. Novel therapeutic options targeting known molecular mechanisms are also discussed.

RESULTS AND DISCUSSION

The pathogenesis of LGL leukemia involves the accumulation of gene mutations, dysregulated signaling pathways and immunological dysfunction. Mounting evidence indicated that dysregulated survival signaling pathways may be responsible for the immunological dysfunction in LGL leukemia including decreased numbers of neutrophils, dysregulated signal transduction of NK cells, abnormal B-cells, aberrant CD8+ T cells, as well as autoimmune and hematological abnormalities.

CONCLUSION

A better understanding of the immune dysregulation triggered by LGL leukemia will be beneficial to explore the pathogenesis and potential therapeutic targets for this disease.

Emergence of a STAT3 mutated NK clone in LGL leukemia

Large granular lymphocyte (LGL) leukemia is a chronic clonal lymphoproliferative disorder. Here, a T-LGL leukemia patient developed NK-LGL leukemia with residual leukemic T-LGL. TCRVβ usage and CDR3 sequence drifts were observed with disease progression. A STAT3 S614R mutation was identified in NK but not T-cells in the mixed leukemic stage. Multiple, non-dominant T-cell clones with distinct STAT3 mutations were present throughout. Our results suggest that T and NK-LGL leukemia may share common pathogenesis mechanisms and that STAT3 mutation alone is insufficient to bring about clonal expansion. Mutational and immunological monitoring may provide diagnostic and therapeutic significance in LGL leukemia.

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Coexistence of NK and T cell clones in LGL leukemia.

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Demonstration for the first time of a shift from T-LGL to NK type of LGL leukemia.

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Emergence of a dominant STAT3-mutated clone in NK cells during disease progression.

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Presence of additional STAT3-mutated clones that fail to become dominant over time.

Pathophysiologic mechanisms and management of neutropenia associated with large granular lymphocytic leukemia

Large granular lymphocyte (LGL) syndrome includes a spectrum of clonal T cell and natural killer cell chronic lymphoproliferative disorders. These conditions are thought to arise from chronic antigenic stimulation, while the long-term survival of the abnormal LGLs appears to be sustained by resistance to apoptosis and/or impaired survival signaling. T-cell LGL (T-LGL) leukemia is the most common LGL disorder in the Western world. Despite its indolent course, the disease is often associated with neutropenia, the pathogenesis of which is multifactorial, comprising both humoral and cytotoxic mechanisms. This article addresses the pathogenesis of T-LGL leukemia and natural killer cell chronic lymphoproliferative disorder, as well as that of T-LGL leukemia-associated neutropenia. Furthermore, as symptomatic neutropenia represents an indication for initiating treatment, available therapeutic options are also discussed.

State of the art in natural killer cell malignancies

The recently updated World Health Organization (WHO) classification of tumors of hematopoietic and lymphoid tissues, published in 2008, has made great advances in revising the disorders previously included in the pool of natural killer (NK) cell tumors. Although NK cell neoplasms represent a relatively rare group of diseases, accounting for <5% of all lymphoid neoplasms, they include very distinctive conditions both clinically and pathologically. This family of diseases includes the most indolent clinical forms, such as the provisional new entry of chronic lymphoproliferative disorder of NK cells (CLPD-NK) in the WHO classification, as well as one of the most fatal diseases recognized in medical oncology, aggressive NK cell leukemia (ANKL), which is characterized by a prognosis of weeks, or even days. In addition, some disorders previously identified as blastic NK cell lymphoma within the NK cell system have been more properly defined and included in the blastic plasmacytoid dentritic cell neoplasms, although rare cases of bona fide immature NK lymphoid tumors (now classified as NK cell lymphoblastic leukemia/lymphoma) have been reported in the literature. This paper focuses on recent concepts and progress in morphology, pathogenesis, clinicopathological features, treatment approaches, and outcomes of NK cell malignancies.

How I treat LGL leukemia

Large granular lymphocyte (LGL) leukemia is characterized by a clonal expansion of either CD3(+) cytotoxic T or CD3(-) NK cells. Prominent clinical features of T-LGL leukemia include neutropenia, anemia and rheumatoid arthritis (RA). The terminal effector memory phenotype (CD3(+)/CD45RA(+)/CD62L(-)CD57(+)) of T-LGL suggests a pivotal chronic antigen-driven immune response. LGL survival is then promoted by platelet-derived growth factor and interleukin-15, resulting in global dysregulation of apoptosis and resistance to normal pathways of activation-induced cell death. These pathogenic features explain why treatment of T-LGL leukemia is based on immunosuppressive therapy. The majority of these patients eventually need treatment because of severe or symptomatic neutropenia, anemia, or RA. No standard therapy has been established because of the absence of large prospective trials. The authors use low-dose methotrexate initially for T-LGL leukemia patients with neutropenia and/or RA. We recommend either methotrexate or oral cyclophosphamide as initial therapy for anemia. If treatment is not successful, patients are switched to either the other agent or cyclosporine. The majority of patients experience an indolent clinical course. Deaths infrequently occur because of infections related to severe neutropenia. As there are no curative therapeutic modalities for T-LGL leukemia, new treatment options are needed.

Platelet-derived growth factor mediates survival of leukemic large granular lymphocytes via an autocrine regulatory pathway

Large granular lymphocyte (LGL) leukemia results from chronic expansion of cytotoxic T cells or natural killer (NK) cells. Apoptotic resistance resulting from constitutive activation of survival signaling pathways is a fundamental pathogenic mechanism. Recent network modeling analyses identified platelet-derived growth factor (PDGF) as a key master switch in controlling these survival pathways in T-cell LGL leukemia. Here we show that an autocrine PDGF regulatory loop mediates survival of leukemic LGLs of both T- and NK-cell origin. We found high levels of circulating PDGF-BB in platelet-poor plasma samples from LGL leukemia patients. Production of PDGF-BB by leukemic LGLs was demonstrated by immunocytochemical staining. Leukemic cells expressed much higher levels of PDGFR-beta transcripts than purified normal CD8(+) T cells or NK cells. We observed that phosphatidylinositol-3-kinase (PI3 kinase), Src family kinase (SFK), and downstream protein kinase B (PKB)/AKT pathways were constitutively activated in both T- and NK-LGL leukemia. Pharmacologic blockade of these pathways led to apoptosis of leukemic LGLs. Neutralizing antibody to PDGF-BB inhibited PKB/AKT phosphorylation induced by LGL leukemia sera. These results suggest that targeting of PDGF-BB, a pivotal regulator for the long-term survival of leukemic LGLs, may be an important therapeutic strategy.

Analysis of NK cell/DC interaction in NK-type lymphoproliferative disease of granular lymphocytes (LDGL): role of DNAM-1 and NKp30

OBJECTIVE

Natural killer (NK) cells and dendritic cells (DC) can give rise to reciprocal functional interactions resulting in promotion of DC maturation, killing of immature DC (iDC), and proliferation of NK cells. In this study, we analyze whether, in NK-lymphoproliferative disease of granular lymphocytes (LDGL) patients, this function could be altered and contribute to the persistence of the disease.

MATERIALS AND METHODS

Freshly isolated peripheral blood NK granular lymphocytes (GL) and NK cell lines derived from 13 different NK-LDGL patients were analyzed in coculture experiments to evaluate their ability to interact with monocyte-derived DCs (Mo-DC).

RESULTS

As compared to NK cells isolated from healthy donors, NK-GLs displayed, in most cases, a reduced capability of promoting Mo-DC maturation and of killing iDC. These findings could be explained, at least in part, by the low expression levels of NKp30: an activating receptor involved in the molecular interactions occurring between NK cells and DC. We also show that, in the presence of DC-derived cytokines such as interleukin-12, in both patients and healthy individuals, DNAM-1 can cooperate with NKp30 to induce NK cells to kill DC, release tumor necrosis factor-alpha, and promote DC maturation. This contribution, however, is not sufficient to compensate for the defect in patients' NK cells.

CONCLUSION

Besides expanding knowledge of the molecular basis of the NK/DC cross-talk, our study demonstrates that NK cells from NK-LDGL patients are impaired in their ability to interact with Mo-DC. The possible relationship between such abnormal NK cell/DC interactions and chronic NK cell proliferation are discussed.

Short communication: Absence of evidence of HTLV-3 and HTLV-4 in patients with large granular lymphocyte (LGL) leukemia

Clonal disorders of large granular lymphocytes (LGL) result in leukemia due to the expansion of a discrete subset of either CD3(+) T cells or natural killer (NK) cells. It has been hypothesized that a viral antigen acts as the initial stimulus causing the expansion of these cells. The possible involvement of human T cell lymphotropic virus types 1 and 2 (HTLV-1 and HTLV-2) in this disease has been studied but no conclusive evidence has linked either virus with LGL leukemia. In this study, we examined whether HTLV-3 or HTLV-4, two newly identified HTLV groups discovered in Central Africa in primate hunters, is involved in LGL leukemia. We developed two specific real-time PCR quantitative assays that are highly sensitive, capable of detecting 10 copies of HTLV-3 or HTLV-4 pol sequences in a background of 1 microg of DNA from human peripheral blood lymphocytes (PBL). We tested PBL DNA samples from 40 LGL leukemia patients in the United States and found that all samples were negative for HTLV-3 or HTLV-4 infection. These results suggest that HTLV-3 and HTLV-4 are not the causative agent of LGL leukemia.

Progress in understanding and managing natural killer-cell malignancies

The World Health Organization classification of haematolymphoid tumours recognizes three categories of natural killer (NK)-cell neoplasms: blastic NK-cell lymphoma, aggressive NK-cell leukaemia, and extranodal NK/T-cell lymphoma, nasal-type. Recent studies indicate that CD4+CD56+ blastic NK-cell lymphoma is of plasmacytoid dendritic cell origin, and true tumours of precursor NK-cell origin may be present mainly in the CD4-CD56+ subset. Myeloid/NK-cell precursor acute leukaemia may also develop from precursor NK cells. However, because the developmental pathway of normal NK cells is not well understood, tumours of precursor NK-cell origin are not clearly identified. Among mature NK-cell tumours, extranodal NK/T-cell lymphoma is relatively common in Asia and Latin America. In localized disease, chemoradiotherapy seems to be promising, and in advanced disease, new combination chemotherapies are under active investigation. Aggressive NK-cell leukaemia is rare and has a poor prognosis. Because NK-cell neoplasms are rare and difficult to manage, rigorous studies are required for their understanding and management.

Diseases of large granular lymphocytes

BACKGROUND

Clonal diseases of large granular lymphocytes (LGLs) are rare lymphoproliferative malignancies that arise from either mature T-cell (CD3+) or natural killer (NK)-cell (CD3-) lineages. They manifest a distinct biologic behavior that ranges from indolent to very aggressive.

METHODS

We discuss four distinct diseases involving LGLs: indolent T-cell LGL leukemia, aggressive T-cell LGL leukemia, chronic NK-cell leukemia, and aggressive NK-cell leukemia. Furthermore, we present an up-to-date systematic review of therapies for each entity.

RESULTS

Sustained LGLs, characteristic immunophenotype, clonal origin of leukemic cells, and clinical presentation are the most important features that distinguish indolent from aggressive subtypes of LGL leukemia and guide the selection of therapy. Patients with symptomatic indolent T-cell or NK-cell LGL leukemia are usually treated with immunosuppressive therapies in contrast to aggressive T-cell and NK-cell LGL leukemia, which require intensive chemotherapy induction regimens. Novel targeted therapies using monoclonal antibodies against receptors, including CD2, CD52, the beta subunit of the interleukin-2 receptor, and small molecules such as tipifarnib, are undergoing evaluation in clinical trials.

CONCLUSIONS

Future scientific advances focusing on the delineation of molecular pathogenic mechanisms and the development of new targeted therapies for each distinct LGL leukemia entity should lead to improved outcomes of patients with these disorders.

Innate versus Adaptive Immunity: A Paradigm Past Its Prime?

Studies in tumor immunology have relied upon the classic paradigm of distinct innate and adaptive parts of the immune system. However, recent advances in immunology suggest that this division may be overly simplistic, with emerging evidence of a breakdown in conventional hallmarks of each system. Here, we provide an overview of this area and discuss how the concept of a continuum of immune cell populations suggests novel areas of investigation in cancer research.

Conformation-specific antibodies targeting the trimer-of-hairpins motif of the human T-cell leukemia virus type 1 transmembrane glycoprotein recognize the viral envelope but fail to neutralize viral entry

Human T-cell leukemia virus type 1 (HTLV-1) entry into cells is dependent upon the viral envelope glycoprotein-catalyzed fusion of the viral and cellular membranes. Following receptor activation of the envelope, the transmembrane glycoprotein (TM) is thought to undergo a series of fusogenic conformational transitions through a rod-like prehairpin intermediate to a compact trimer-of-hairpins structure. Importantly, synthetic peptides that interfere with the conformational changes of TM are potent inhibitors of membrane fusion and HTLV-1 entry, suggesting that TM is a valid target for antiviral therapy. To assess the utility of TM as a vaccine target and to explore further the function of TM in HTLV-1 pathogenesis, we have begun to examine the immunological properties of TM. Here we demonstrate that a recombinant trimer-of-hairpins form of the TM ectodomain is strongly immunogenic. Monoclonal antibodies raised against the TM immunogen specifically bind to trimeric forms of TM, including structures thought to be important for membrane fusion. Importantly, these antibodies recognize the envelope on virally infected cells but, surprisingly, fail to neutralize envelope-mediated membrane fusion or infection by pseudotyped viral particles. Our data imply that, even in the absence of overt membrane fusion, there are multiple forms of TM on virally infected cells and that some of these display fusion-associated structures. Finally, we demonstrate that many of the antibodies possess the ability to recruit complement to TM, suggesting that envelope-derived immunogens capable of eliciting a combination of neutralizing and complement-fixing antibodies would be of value as subunit vaccines for intervention in HTLV infections.

Genotypic evaluation of killer immunoglobulin-like receptors in NK-type lymphoproliferative disease of granular lymphocytes

Using polymerase chain reaction (PCR)-based sequence-specific primers, the killer immunoglobulin-like receptor (KIR) genotypes of 35 patients with natural killer (NK)-type lymphoproliferative disease of granular lymphocytes and of 50 normal subjects were investigated to evaluate whether genes coding for activating KIRs were more frequently detected in patients with NK-lymphoproliferative disease of granular lymphocytes (LDGL). Genotype frequency indicated that the most frequently found gene content was eight genes in controls and 14 in patients (P<0.05). The KIR genotype analysis revealed that patient and, surprisingly, control KIR genotypes preferentially consisted of type B haplotypes characterized by the presence of multiple-activating KIRs. Evidence was also provided that the same KIR genotype was shared by a variable number of patients. Interestingly, the recurrent genotypes observed in the patient group were not found in controls. Concerning inhibitory genes, KIR2DL5a and 2DL5b were more frequently detected in patients than in controls (P<0.01), likely representing a discrete feature of the genetic repertoire of the patients. KIR gene repertoire analysis in patients suggests that the susceptibility to NK-LDGL might be related to the presence of activating KIR genes and supports the concept that these receptors may be involved in the priming of granular lymphocytes (GL) proliferation. Population analysis might disclose a genetic background predisposing to this disease.

Large Granular Lymphocyte Leukemia

Clonal disorders of large granular lymphocytes (LGLs) represent a spectrum of biologically distinct lymphoproliferative diseases originating either from mature T cells (CD3+) or natural killer (NK) cells (CD3-). Both subtypes, T-cell and NK-cell LGL leukemia, can manifest as indolent or aggressive disorders. The majority of patients with T-cell LGL leukemia have a clinically indolent course with a median survival time >10 years. Immunosuppressive therapy with low-dose methotrexate, cyclophosphamide, or cyclosporine A can control symptoms and cytopenias in more than 50% of patients, but this approach is not curative. Several cases of an aggressive variant (CD3+ CD56+) of T-cell LGL leukemia with a poor prognosis have also been reported. Aggressive NK-cell LGL leukemia is usually a rapidly progressive disorder associated with Epstein-Barr virus (EBV), with a higher prevalence in Asia and South America. This disease is usually refractory to conventional chemotherapy, with a median survival time of 2 months. Chronic NK-cell leukemia/lymphocytosis is a rare EBV-negative disorder with an indolent clinical course. The malignant origin of this subtype is uncertain because clonality is difficult to determine in LGLs of NK-cell origin.

Phenotypic and functional analyses of dendritic cells in patients with lymphoproliferative disease of granular lymphocytes (LDGL)

We investigated whether dendritic cells (DCs) play a role in favoring granular lymphocyte (GL) proliferation in patients with lymphoproliferative disease of granular lymphocytes (LDGL). The presence of in vivo circulating DCs was studied in 11 patients (5 CD3+ and 6 CD3- LDGL). Autologous immature (iDCs) and mature (mDCs) DCs generated in vitro were studied for stimulatory activity on cell proliferation of CD3+ and CD3- GLs. The topographic organization of GLs and DCs was also studied in bone marrow (BM) biopsies. Peripheral blood (PB) CD3- GLs from patients showed significant proliferative activity in the presence of iDCs and mDCs. Conversely, monoclonal CD3+ GLs were unresponsive to autologous and allogeneic PB DCs. Analysis of BM biopsies demonstrated a topographic distribution of DCs and GLs that indicates contact between the 2 cell types. On functional assays, DCs obtained from BM were more efficient than PB DCs in stimulating CD3- GLs, and surprisingly, a low but definite stimulatory effect was demonstrated also on CD3+ GLs. The putative contact between DCs and GLs in the BM and, more crucial, the proliferative response of discrete GL populations to DC stimulation suggest the presence of a specific antigen within BM DCs, providing evidence for a role of DCs in the pathogenesis of LDGL.

ERK couples chronic survival of NK cells to constitutively activated Ras in lymphoproliferative disease of granular lymphocytes (LDGL)

Chronic NK lymphoproliferative disease of large granular lymphocytes (LDGL) is characterized by the expansion of activated CD3-, CD16+ or CD56+ lymphocytes. The mechanism of survival of NK cells from LDGL patients is unknown but may be related to antigenic stimulation. There is currently no standard effective therapy for LDGL, and the disease is characteristically resistant to standard forms of chemotherapy. We found evidence of constitutive activation of extracellular-regulated kinase (ERK) in NK cells from 13/13 patients with NK-LDGL (one patient with aggressive and 12 patients with chronic disease). Ablation of ERK activity by inhibitors or a dominant-negative form of MEK, the upstream activator of ERK, reduced the survival of patient NK cells. Ras was also constitutively active in patient NK cells, and exposure of cells to the Ras inhibitor FTI2153 or to dominant-negative-Ras resulted not only in ERK inhibition but also in enhanced apoptosis in both the presence and absence of anti-Fas. Therefore, we conclude that a constitutively active Ras/MEK/ERK pathway contributes to the accumulation of NK cells in patients with NK-LDGL. These findings suggest that strategies to inhibit this signaling pathway may be useful for the treatment of the NK type of LDGL.

Characterization of HTLV envelope seroreactivity in large granular lymphocyte leukemia

T-cell large granular lymphocyte (T-LGL) leukemia is a rare chronic lymphoproliferative disorder of unknown etiology. We have previously reported that patients with T-LGL leukemia were seroreactive against BA21, a 34 amino acid peptide derived from HTLV-I envelope protein p21. We tested sera from 70 patients with T-LGL leukemia and found that 21/70 (30%) of them were seroreactive against fusion peptide GST-BA21. In control group of healthy blood donors 3/30 (10%) were seroreactive. We synthesized a set of overlapping peptides derived from BA21 and tested them against sera from patients. Only a single peptide (p21 env 417-430) showed reactivity. We then generated multiple fusion peptides consisting of 5-14 amino acid residues derived from this peptide and tested them against patient and control sera. Shortest peptide giving positive seroreactivity was octapeptide P8 (p21 env 418-425). Competitive Western blot assay with use of fusion peptides revealed that the minimal HTLV-I epitope responsible for seroreactivity found in patients with T-LGL leukemia is a decapeptide PP10 (p21 env 417-426). Protein Bank (NCBI) search did not reveal any significant homology between PP10 epitope and known human proteins. These results further define the epitope responsible for HTLV env seroreactivity observed in LGL leukemia.

Clinicobiological, immunophenotypic, and molecular characteristics of monoclonal CD56-/+dim chronic natural killer cell large granular lymphocytosis

Indolent natural killer (NK) cell lymphoproliferative disorders include a heterogeneous group of patients in whom persistent expansions of mature, typically CD56(+), NK cells in the absence of any clonal marker are present in the peripheral blood. In the present study we report on the clinical, hematological, immunophenotypic, serological, and molecular features of a series of 26 patients with chronic large granular NK cell lymphocytosis, whose NK cells were either CD56(-) or expressed very low levels of CD56 (CD56(-/+dim) NK cells), in the context of an aberrant activation-related mature phenotype and proved to be monoclonal using the human androgen receptor gene polymerase chain reaction-based assay. As normal CD56(+) NK cells, CD56(-/+dim) NK cells were granzyme B(+), CD3(-), TCRalphabeta/gammadelta(-), CD5(-), CD28(-), CD11a(+bright), CD45RA(+bright), CD122(+), and CD25(-) and they showed variable and heterogeneous expression of both CD8 and CD57. Nevertheless, they displayed several unusual immunophenotypic features. Accordingly, besides being CD56(-/+dim), they were CD11b(-/+dim) (heterogeneous), CD7(-/+dim) (heterogeneous), CD2(+) (homogeneous), CD11c(+bright) (homogeneous), and CD38(-/+dim) (heterogeneous). Moreover, CD56(-/+dim) NK cells heterogeneously expressed HLA-DR. In that concerning the expression of killer receptors, CD56(-/+dim) NK cells showed bright and homogeneous CD94 expression, and dim and heterogeneous reactivity for CD161, whereas CD158a and NKB1 expression was variable. From the functional point of view, CD56(-/+dim) showed a typical Th1 pattern of cytokine production (interferon-gamma(+), tumor necrosis factor-alpha(+)). From the clinical point of view, these patients usually had an indolent clinical course, progression into a massive lymphocytosis with lung infiltration leading to death being observed in only one case. Despite this, they frequently had associated cytopenias as well as neoplastic diseases and/or viral infections. In summary, we describe a unique and homogeneous group of monoclonal chronic large granular NK cell lymphocytosis with an aberrant activation-related CD56(-/+dim)/CD11b(-/+dim) phenotype and an indolent clinical course, whose main clinical features are related to concomitant diseases.

Dysregulated NK receptor expression in patients with lymphoproliferative disease of granular lymphocytes

The natural killer (NK) type of lymphoproliferative disease of granular lymphocytes (LDGL) is associated with the expansion of CD3-, CD16+, and/or CD56+ lymphocytes. We have examined the repertoire of NK receptors expressed on these cells and delineated the functional activity. We found skewed NK receptor expression on patient NK cells. Reactivity to a single anti-killer cell immunoglobulin-like receptor (anti-KIR) antibody was noted in 7 of 13 patients. LDGL patients variably expressed NKp30, NKp44, and NKp46 RNA. In contrast, CD94 and its inhibitory heterodimerization partner NKG2A were homogenously expressed at high levels on these NK cells. Interestingly, these patients expressed a large number of activating KIR receptors by genotype analysis. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that lower than normal levels of RNA of the inhibitory KIR was present in some patients in contrast to normal NK cells. Consistent with a high level of activating receptors, we found the NK-LDGL cells have potent cytolytic function in both direct and redirected cytotoxicity assays. These results demonstrate that patients with NK-LDGL have an increased activating-to-inhibitory KIR ratio. This altered ratio might induce inappropriate lysis or cytokine production and impact the disease pathogenesis. (Blood. 2004;103:3431-3439)

The raft marker GM1 identifies functional subsets of granular lymphocytes in patients with CD3+ lymphoproliferative disease of granular lymphocytes

The raft marker GM1 is expressed at very low levels at the plasma membrane of resting T cells (GM1dull). In vitro T-cell activation induces synthesis of this lipid, which is then expressed at very high levels (GM1bright) at the membrane of activated/effector cells. By flow cytometry and confocal microscopy, we analyzed the expression and organization of GM1 in a series of 15 patients with CD3+ lymphoproliferative disease of granular lymphocytes (LDGL). We found that GM1bright GL were detectable in fresh blood samples obtained in all LDGL patients, although the range of brightly stained cells was extremely variable. This distinctive in vivo pattern has never been shown in T lymphocytes from healthy individuals or in patients with different chronic T or B lymphoproliferative disorders or active infectious diseases. The low number of cycling cells detected in LDGL patients was always included within the GM1bright GL population. Interestingly, GM1bright GL were demonstrated to contain a higher amount of IFN-gamma as compared to GM1dull GL. These findings allow to distinguish subsets of GL at different levels of activation within the monoclonal CD3+ population. The GM1bright GL subset is likely to be responsible for the renewing of GL and thus for maintaining chronic proliferation.

B lineage-specific regulation of V(D)J recombinase activity is established in common lymphoid progenitors

Expression of V(D)J recombinase activity in developing lymphocytes is absolutely required for initiation of V(D)J recombination at antigen receptor loci. However, little is known about when during hematopoietic development the V(D)J recombinase is first active, nor is it known what elements activate the recombinase in multipotent hematopoietic progenitors. Using mice that express a fluorescent transgenic V(D)J recombination reporter, we show that the V(D)J recombinase is active as early as common lymphoid progenitors (CLPs) but not in the upstream progenitors that retain myeloid lineage potential. Evidence of this recombinase activity is detectable in all four progeny lineages (B, T, and NK, and DC), and rag2 levels are the highest in progenitor subsets immediately downstream of the CLP. By single cell PCR, we demonstrate that V(D)J rearrangements are detectable at IgH loci in ∼5% of splenic natural killer cells. Finally, we show that recombinase activity in CLPs is largely controlled by the Erag enhancer. As activity of the Erag enhancer is restricted to the B cell lineage, this provides the first molecular evidence for establishment of a lineage-specific transcription program in multipotent progenitors.

Expression and function of KIR and natural cytotoxicity receptors in NK-type lymphoproliferative diseases of granular lymphocytes

Using monoclonal antibodies (mAbs) specific for different natural killer (NK) receptors, we studied the lymphocyte population from 18 patients with NK-type lymphoproliferative disease of granular lymphocytes (LDGL). The analysis of both resting and cultured NK cell populations demonstrated that these patients are frequently characterized by NK cells displaying a homogeneous staining with given anti-killer Ig-like receptor (anti-KIR) mAb (11 of 18 patients). In most patients NK cells were characterized by the CD94/NKG2A+ phenotype, whereas only a minor fraction of the cases expressed CD94/NKG2C. In 7 of these patients we could also assess the function of the various NK receptors. Remarkably those KIR molecules that, in each patient, homogeneously marked the NK cell expansion were found to display an activating function as determined by cross-linking with specific anti-KIR mAb. The KIR genotype analysis performed in 13 of 18 cases revealed that in NK-type LDGL certain activating KIRs, as well as certain infrequent KIR genotypes, were detected with higher frequencies as compared to previously analyzed healthy donors. Moreover, most KIR genotypes included multiple genes coding for activating KIRs. The analysis of non-HLA-specific triggering receptors indicated that the natural cytotoxicity receptors (NKp46, NKp30) were expressed at significantly low levels in freshly drawn NK cells from most patients analyzed. However, in most instances the expression of NKp46 and NKp30 could be up-regulated on culture in interleukin 2. Our data indicate that in NK-LDGL the expanded subset is frequently characterized by the expression of a given activating KIR, suggesting a direct role for these molecules in the pathogenetic mechanisms of this disorder.

Natural killer receptors in patients with lymphoproliferative diseases of granular lymphocytes

The most relevant criterion for recognizing chronic granular lymphocyte (GL) proliferations, defined as lymphoproliferative disease of GL (LDGL), has been historically based on the number of the proliferating cells displaying typical GL morphology. With the extensive development of immunological and molecular techniques, two major groups of LDGL have been recognized, one belonging to the T-cell and the other to the NK cell lineage. The recent definition of a series of receptors of NK cells (NKR) and the identification of the specific targets recognized has expanded our knowledge of the properties of these cells and the discrimination between functional reactive and pathological proliferations. Some of these receptors are expressed by GL of T-cell lineage, suggesting a possible involvement in the genesis of GL proliferation. Following an extensive description of NKR in humans, this review will summarize the recent data on phenotypic and functional characteristics of NKR expressed by proliferating GL in patients with LDGL, discussing their role in this disorder.

Clinical features of large granular lymphocyte leukemia

The spectrum of large granular lymphocyte (LGL) proliferations consists of four distinct entities: reactive/transient LGL expansion, chronic LGL lymphocytosis, classical indolent LGL leukemia, and aggressive LGL leukemia. LGL leukemias are classified as lymphoid malignancies. They are divided into CD3(+)/T-cell LGL (85% of cases) and CD3(-)/natural killer (NK) cell LGL leukemia (15% of cases). Recent progress in the comprehension of the leukemogenesis has shown a dysregulation of survival signals in leukemic cells. Identification of LGL expansion has been improved using T-cell receptor (TCR)beta/gamma polymerase chain reaction (PCR) analysis and a combination of Vbeta and killer cell immunoglobulin-like receptor (KIR)-specific monoclonal antibodies. LGL leukemias are characterized by a clonal LGL infiltration of the bone marrow, spleen, and liver. Monoclonality is recognized by phenotypic, molecular, and karyotypic analysis. T-LGL leukemias affect the elderly and display a relatively indolent behavior. Approximately 60% to 70% of patients are symptomatic: recurrent infections secondary to chronic neutropenia, anemia, and autoimmune disease such as rheumatoid arthritis are the main clinical manifestations. Long-lasting remission can be obtained with low-dose methotrexate, cyclosporine A, or cyclophosphamide. Conversely, NK LGL leukemias behave aggressively, and most patients do not respond to chemotherapy.

Survival signals in leukemic large granular lymphocytes

The central hypothesis of our laboratory research program in large granular lymphocyte (LGL) leukemia is that leukemic LGL represent antigen-driven cytotoxic T lymphocytes (CTL) with characteristics of dysregulated apoptosis. The clinical features of LGL leukemia highlight the association of autoimmune diseases such as rheumatoid arthritis with the T-cell form of LGL leukemia. We therefore used LGL leukemia as a model disease of dysregulated apoptosis leading to both malignant and autoimmune diseases. Here, we review our understanding of survival signals activated in leukemic LGL in the context of knowledge concerning apoptotic pathways in activated normal lymphocytes.

Functional inhibitory human leucocyte antigen class I receptors on natural killer (NK) cells in patients with chronic NK lymphocytosis

Chronic natural killer (NK) lymphocytosis is a rare disorder characterized by an indolent clinical course. Despite high NK cell numbers, many patients present with only mild clinical symptoms, and are often asymptomatic. NK cells are equipped with a range of receptors that bind human leucocyte antigen (HLA)-class I molecules. The killer immunoglobulin-like receptors (KIR, CD158) bind groups of HLA alleles, the CD94/NKG2 receptors bind HLA-E, and the CD85j (ILT2, LIR-1) receptor binds to the relatively non-polymorphic alpha3 domain of HLA molecules. Inhibitory HLA class I receptors silence NK cells against cells expressing normal levels of HLA class I. Analysis of NK cells in six patients with chronic NK lymphocytosis revealed a high level of the inhibitory CD94/NKG2A receptor on all NK cells. In four patients, KIR were absent, in one patient a single KIR was expressed in the absence of self-ligand, and in one patient CD85j and multiple KIR were expressed. Cytotoxicity assays demonstrated that all HLA class I receptors were functional. The ability of monoclonal antibodies to block the receptors and allow killing of autologous target cells established that both receptor and ligand expression were adequate for inhibitory function. We propose that the silent behaviour of NK cells in patients with chronic NK lymphocytosis is due to effective inhibitory HLA class I receptors.

T-gamma large granular lymphocyte leukemia associated with amegakaryocytic thrombocytopenic purpura, Sjögren's syndrome, and polyglandular autoimmune syndrome type II, with subsequent development of pure red cell aplasia

We present a female patient with T-gamma LGL leukemia, who was followed for the last 20 years. Over these years she developed several autoimmune disorders, including Sjögren's syndrome, Hashimoto's thyroiditis, premature ovarian failure (compatible with type II autoimmune polyglandular syndrome), amegakaryocytic thrombocytopenic purpura, and finally pure red cell aplasia. PCR analysis confirmed rearrangement for TCR gamma. This case emphasizes the complex association of LGL leukemia with autoimmune disorders.

[Large granular lymphocyte proliferations. Clinical and pathogenic aspects]

INTRODUCTION

The clinical course, biological features, and recent data on the pathogenesis of large granular lymphocyte (LGL) leukemia are reviewed.

CURRENT KNOWLEDGE AND KEY POINTS

Clonal diseases of LGL disorders can arise from a CD3+, CD57+ T-cell lineage, which are the most frequent, or from a CD3-, CD56+ NK-cell lineage. The diagnosis of LGL leukemia is suspected on the basis of a persistent excess of LGL, usually with neutropenia and splenomegaly. It is assessed by immunophenotypic and molecular studies of T-cell receptor clonality (southern blot, PCR). Association with autoimmune diseases (rheumatoid arthritis, erythroblastopenia, etc.) is a main feature of chronic LGL proliferation. Questions about a viral agent (HTLV1?), facilitation of clonal expansion by cytokines (IL-12, IL-15), and the defective Fas apoptotic pathway are discussed. Treatment of symptomatic LGL proliferations is based on immunosuppressive agents (principally methotrexate and cyclophosphamide).

FUTURE PROSPECT AND PROJECTS

The epidemiology, prognosis factors, therapeutics and the pathogenesis of LGL leukemia are unknown. We proposed the creation of a French register of LGL expansions to explore these different aspects.

Canine large granular lymphocyte leukemia and its derived cell line produce infectious retroviral particles

We describe a case of large granular lymphocyte (LGL) leukemia in a dog that we followed over a period of 2 years. Analysis of a hematological profile revealed lymphocytosis (19,500 lymphocytes per microliter; reference values, 1,000-4,800 lymphocytes per microliter), with a majority of LGL on the blood smear. LGL is defined as a lymphoid subset comprising 10% of peripheral blood mononuclear cells and corresponding to either CD3- CD8- NK cells or CD3+ CD8+ T cells. The cells are characterized by abundant basophilic cytoplasm containing distinct granules of variable size and number. The characteristic phenotype of our leukemic LGL is of a cytotoxic T cell, CD3+ and CD8+. A new cell line, DLC 02, was established from the peripheral lymphocytes of the leukemic dog. Particles with type C retroviral morphology were found in ultrathin sections of DLC 02 cell pellets. These particles were found to have a sucrose gradient density of 1.17 g/liter and a reverse transcriptase activity with an Mn2+ preference, suggesting that they correspond to a mammalian type C oncovirus.

Lack of BLV and PTLV DNA sequences in the majority of patients with large granular lymphocyte leukaemia

The primate T-cell lymphoma/leukaemia viruses (PTLV) and bovine leukaemia virus (BLV) comprise a unique genus of retroviruses, infection with which induces seroreactivity in the host against conserved epitopes in their p24 gag and gp21 env cognate proteins. Herein, we have confirmed this serocrossreactivity. Patients with large granular lymphocyte (LGL) leukaemia have frequent seroreactivity to the p24 and gp21 env proteins of human T-cell lymphoma/leukaemia virus I (HTLV-I), one of the species in the genus. However, only a small minority of patients are actually infected with prototypic HTLV-I or HTLV-II, another species within the group. In an attempt to determine whether LGL leukaemia might be associated with other members of the PTLV/BLV genus, we examined the peripheral blood mononuclear cell DNA of 22 HTLV p24 and/or gp21 seropositive LGL leukaemia patients via PCR using degenerate and specific primer pair/probe systems capable of detecting all known members of the PTLV/BLV genus. None of the samples was positive. These data indicate that although HTLV-II may be associated with some cases of LGL leukaemia most patients are not infected with a PTLV or BLV virus.

Current concepts: large granular lymphocyte leukemia

Clonal diseases of large granular lymphocyte (LGL) disorders can arise from a CD3+ T-cell lineage or from a CD3- NK-cell lineage. CD3+ LGL leukemia is the most frequent form of LGL leukemia. T-LGL leukemia usually affects elderly people. Approximately 60% of patients are symptomatic; recurrent infections secondary to chonic neutropenia, anemia, and rheumatoid arthrititis are the main clinical manifestations. The most common phenotype is CD3+, alphabeta+, CD8+, CD57+. Clonality is detected by clonal rearrangement of the T-cell receptor gene. NK-cell LGL proliferative disorders include NK LGL leukemia which is a very aggressive disease and NK chronic lymphocytosis. Serologic findings show frequent reactivity to the BA21 epitope of HTLV-I env p21e, suggesting that a cellular or retroviral protein with homology to BA21 may be important in pathogenesis of these diseases. Clonal expansion may be facilitated by IL12 and IL15 cytokines expressed by leukemic LGL, and also by a defective Fas (CD95) apoptotic pathway. Leukemic LGL constitutively express Fas and Fas-Ligand but they are resistant to Fas-induced apotosis. Neutropenia could be due to soluble Fas-Ligand which is highly secreted in the patient's sera. Clinical and molecular remission can be obtained with oral low-dose methotrexate. Leukemic LGL express a multi-drug resistance phenotype (PgP+/LRP+) that could partly explain the chemoresistance observed in aggressive cases. It is suggested that LGL leukemia can serve as a useful model of dysregulated apoptosis as an underlying mechanism for both malignancy and autoimmune disease.

Large granular lymphocyte leukaemia occurring after renal transplantation

Post-transplantation lymphoproliferative disorders (PTLD) are a clinicopathologically heterogeneous group of lymphoid proliferations. The majority are of B-cell origin and associated with Epstein-Barr virus (EBV) infection. In contrast, the development of T-cell PTLD is much less common and EBV does not appear to be involved in pathogenesis. In this report we describe three patients who developed large granular lymphocyte (LGL) leukaemia after renal transplantation. These patients had clonal expansion of CD3+, CD8+, CD57+, CD56- LGL. We were unable to detect CMV antigen or find evidence for EBV or human T-cell leukaemia/lymphoma virus genome in the LGL from these patients. These data show that LGL leukaemia should be included as one of the types of T-cell proliferations which can occur post transplant.

Large granular lymphocytic leukemia: an overview

Large granular lymphocytes are killer cells that differentiate into natural killer and T-cell types. Neoplastic proliferation of the lineages probably involves different etiologies, producing leukemias with distinct clinical presentations and prognoses. T-large granular lymphocytic leukemia has prominent autoimmune features and may occur in association with other autoimmune diseases, particularly rheumatoid arthritis.

Epitope mapping of HTLV envelope seroreactivity in LGL leukaemia

Sera from approximately 50% of patients with large granular lymphocyte (LGL) leukaemia react with a recombinant human T-cell leukaemia/lymphoma virus (HTLV) transmembrane envelope protein, p21e. Two immunodominant epitopes within env p21e have been defined by reactivity against recombinant proteins GD21 and BA21. In this study sera from 41 patients with LGL leukaemia were examined for reactivity against these recombinant HTLV env proteins. Overall, 21/41 (51%) sera reacted to p21e. Only two sera reacted to GD21. The predominant immunoreactivity against p21e was directed against the BA21 epitope, with 19/41 (46%) sera being BA21 positive. Seroconversion to BA21 protein was also documented. PCR analyses confirmed the low incidence of protypical HTLV sequences (2/41, 5%). These data document an association between BA21 seroreactivity and LGL leukaemia. This finding raises the possibility that such BA21 seroreactivity could be due to cross-reactivity to a cellular or retroviral antigen sharing some amino acid homology with the transmembrane glycoprotein of HTLV.

Large Granular Lymphocyte Leukemia

BACKGROUND: Clonal diseases of large granular lymphocyte (LGL) disorders can arise from a CD3+ T-cell lineage or from a CD3- NK-cell lineage. CD3+ LGL leukemia is the most frequent form of LGL leukemia and is a distinct entity by FAB and REAL classifications. METHODS: The clinical course, biological features, and recent data on pathogenesis of CD3+ LGL leukemia are reviewed. The spectrum of differential diagnosis is described. RESULTS: T-LGL leukemia affects elderly people. Approximately 60% of patients are symptomatic; recurrent infections secondary to chronic neutropenia, anemia, and rheumatoid arthritis are the main clinical features. The most common phenotype is CD3+, CD8+, CD57+. Clonality is detected by clonal rearrangement of the T-cell receptor gene. Clinical and molecular remission can be obtained with oral low-dose methotrexate. Serologic findings show frequent reactivity to the BA21 epitope of HTLV-I env p21e, suggesting that a cellular or retroviral protein with homology to BA21 may be important in pathogenesis. Clonal expansion may be facilitated by IL-12 and IL-15 lymphokines. Constitutive expression of Fas ligand by leukemic LGLs support the hypothesis that leukemic cells arise from antigen-activated cytotoxic T cells. Leukemic LGLs express a multidrug-resistance phenotype that could partly explain the chemoresistance observed in aggressive cases. CONCLUSIONS: CD3+ LGL leukemia is a distinct lymphoproliferative T-cell disorder with specific clinicobiological aspects. The clinical spectrum of LGL proliferations is wide and immunophenotypic, and genotypic studies are needed to establish the diagnosis.