Clonal drift demonstrates unexpected dynamics of the T-cell repertoire in T-large granular lymphocyte leukemia

Chronic lymphoproliferative disorder of natural killer cells-related neurolymphomatosis with severe autonomic dysfunction: a case report

BACKGROUND

Chronic lymphoproliferative disorder of natural killer cells (CLPD-NK) is a rare disease characterized by a persistent increase in NK cells in peripheral blood and is generally asymptomatic. If present, symptoms may include fatigue, B symptoms (fever, night sweats, and unintentional weight loss), autoimmune-associated diseases, splenomegaly, and infection due to neutropenia. Peripheral neuropathy, however, is uncommon with an incidence of 3%. Neurolymphomatosis is a neurological manifestation of non-Hodgkin lymphoma and leukemia in which neurotropic neoplastic cells infiltrate the nerves. Moreover, neurolymphomatosis caused by CLPD-NK is extremely rare, with even fewer cases of autonomic dysfunction. We report a case of neurolymphomatosis associated with CLPD-NK and developed autonomic dysfunction, including orthostatic hypotension and gastrointestinal symptoms.

CASE PRESENTATION

The patient was a 61-year-old male who was referred to our hospital for leukocytosis. He was diagnosed with CLPD-NK; however, was untreated since he had no hepatosplenomegaly, and other systemic symptoms. He later developed numbness in his lower extremities. Cerebral spinal fluid examination revealed a markedly elevated protein level of 140 mg/dL, and contrast-enhanced magnetic resonance imaging showed bilateral L4 and 5 nerve roots with enlargement and contrast effect. An immune-mediated polyradiculoneuropathy was suspected, and he was treated with intravenous methylprednisolone and immunoglobulin followed by oral prednisolone and cyclosporine. Although his symptoms were relieved by the immunotherapy, significant autonomic dysfunction, including intractable diarrhea, decreased sweating, and orthostatic hypotension, appeared. Additionally, tests for onconeuronal antibodies, ganglionic nicotinic acetylcholine receptor (gAChR) antibody, NF155, CNTN1, Caspr1 antibody, and anti-ganglioside antibodies were all negative. A sural nerve biopsy revealed lymphocytic infiltration, and immunohistochemical staining of lymphocytes confirmed the infiltration of NK and T cells. Therefore, a diagnosis of neurolymphomatosis caused by CLPD-NK was made, and chemotherapy led to partial symptom improvement.

CONCLUSIONS

We experienced a case of pathologically diagnosed neurolymphomatosis with autonomic dysfunction associated with CLPD-NK. In cases of subacute to chronic autonomic dysfunction, paraneoplastic neuropathy, amyloidosis, and autoimmune autonomic ganglionopathy are considered; however neurolymphomatosis caused by CLPD-NK, an important cause of autonomic dysfunction, is not. In difficult to make diagnosis, aggressive nerve biopsy is required.

Extrinsic and intrinsic drivers of natural killer cell clonality

Clonal expansion of antigen-specific lymphocytes is the fundamental mechanism enabling potent adaptive immune responses and the generation of immune memory. Accompanied by pronounced epigenetic remodeling, the massive proliferation of individual cells generates a critical mass of effectors for the control of acute infections, as well as a pool of memory cells protecting against future pathogen encounters. Classically associated with the adaptive immune system, recent work has demonstrated that innate immune memory to human cytomegalovirus (CMV) infection is stably maintained as large clonal expansions of natural killer (NK) cells, raising questions on the mechanisms for clonal selection and expansion in the absence of re-arranged antigen receptors. Here, we discuss clonal NK cell memory in the context of the mechanisms underlying clonal competition of adaptive lymphocytes and propose alternative selection mechanisms that might decide on the clonal success of their innate counterparts. We propose that the integration of external cues with cell-intrinsic sources of heterogeneity, such as variegated receptor expression, transcriptional states, and somatic variants, compose a bottleneck for clonal selection, contributing to the large size of memory NK cell clones.

T-Large Granular Lymphocytic Leukemia with Hepatosplenic T-Cell Lymphoma? A Rare Case of Simultaneous Neoplastic T-Cell Clones Highlighted by Flow Cytometry and Review of Literature

Lymphoproliferative diseases are a heterogeneous set of malignant clonal proliferations of lymphocytes. Despite well-established diagnostic criteria, the diagnosis remains difficult due to their variety in clinical presentation and immunophenotypic profile. Lymphoid T-cell disorders are less common than B-cell entities, and the lack of a clear immunophenotypic characteristic makes their identification hard. Flow cytometry turned out to be a useful tool in diagnosing T-cell disorders and to resolve complicated cases, especially if the number of analyzable neoplastic cells is small. We present a case of a 55-year-old man with simultaneous lymphoproliferative neoplastic T-cell clones, one αβ and the other γδ, identified and characterized by flow cytometry (FC), exploiting the variable expression intensity of specific markers. However, the patient's rapid decline made it impossible to define a differential diagnosis in order to confirm the identity of the γδ clone, which remains uncertain. This case is added to the few other cases already documented in the literature, characterized by the co-existence of T-large granular lymphocytic leukemia (T-LGLL)-αβ and T-LGLL-γδ/Hepatosplenic T-cell lymphoma (HSTCL). Our case underlines the key role of sensitive diagnostic tools in the assessment of potential relationship between the diagnosis, prognosis, and treatment in the two pathologies.

Context-dependent T-cell Receptor Gene Repertoire Profiles in Proliferations of T Large Granular Lymphocytes

T cell large granular lymphocyte (T-LGL) lymphoproliferations constitute a disease spectrum ranging from poly/oligo to monoclonal. Boundaries within this spectrum of proliferations are not well established. T-LGL lymphoproliferations co-occur with a wide variety of other diseases ranging from autoimmune disorders, solid tumors, hematological malignancies, post solid organ, and hematopoietic stem cell transplantation, and can therefore arise as a consequence of a wide variety of antigenic triggers. Persistence of a dominant malignant T-LGL clone is established through continuous STAT3 activation. Using next-generation sequencing, we profiled a cohort of 27 well-established patients with T-LGL lymphoproliferations, aiming to identify the subclonal architecture of the T-cell receptor beta (TRB) chain gene repertoire. Moreover, we searched for associations between TRB gene repertoire patterns and clinical manifestations, with the ultimate objective of discriminating between T-LGL lymphoproliferations developing in different clinical contexts and/or displaying distinct clinical presentation. Altogether, our data demonstrates that the TRB gene repertoire of patients with T-LGL lymphoproliferations is context-dependent, displaying distinct clonal architectures in different settings. Our results also highlight that there are monoclonal T-LGL cells with or without STAT3 mutations that cause symptoms such as neutropenia on one end of a spectrum and reactive oligoclonal T-LGL lymphoproliferations on the other. Longitudinal analysis revealed temporal clonal dynamics and showed that T-LGL cells might arise as an epiphenomenon when co-occurring with other malignancies, possibly reactive toward tumor antigens.

Monoclonal B-cell lymphocytosis, monoclonal gammopathy of undetermined significance, and T-cell clones of uncertain significance: are these premalignant conditions sharing a common identity?

Monoclonal B-cell lymphocytosis, monoclonal gammopathy of undetermined significance, and T-cell clones of uncertain significance are three premalignant conditions characterised by the presence of small clonal cell expansions in individuals without symptoms or signs that distinguish the related overt malignancies (chronic lymphocytic leukaemia, multiple myeloma, and T-cell large granular lymphocytic leukaemia). As most individuals with these precursor states never progress to malignancies, considerable interest has arisen in comprehending the steps involved in the progression to malignancy, providing more accurate models to investigate potential mechanisms of early blood cancer identification, prevention, and, possibly, intervention. Single-cell technologies and recent progress in high-throughput sequencing and multiomics approaches have contributed to a better definition of the pathophysiological mechanisms of these premalignant conditions, moving our knowledge in the field forward. In this Viewpoint, we analyse the seemingly shared biological trajectories in these precursor haematological malignancies in search of common pathogenetic events. In particular, we address the issue of interactions between expanding clones and their immune ecosystem, offering new clues that might prompt innovative ideas and inspire further investigations to understand the cellular and molecular dynamics entailing progression into overt malignant disease. The relationships between the non-leukaemic microenvironmental cells and the leukaemic counterpart, and the primary drivers of their initial clonal expansion, represent shared biologies that suggest a common identity among the premalignant conditions considered in this Viewpoint.

New approaches to idiopathic neutropenia in the era of clonal hematopoiesis

Isolated chronic idiopathic neutropenia (CIN) is a rare disease with multiple contributing etiologies that must be ruled out before establishing a diagnosis. We studied clinical and molecular data of 238 consecutive adult patients with CIN. Autoimmune neutropenia was present in 28% of our cohort. In contrast, T cell-mediated neutropenia was the main underlying pathological mechanism among patients with T cell expansions, such as T-cell large granular lymphocytic leukemia (T-LGL) and T cell clonopathy of undetermined significance, found in 37% and 8% of cases, respectively. Patients with neutropenia also had hypogammaglobulinemia (6%) and/or monoclonal gammopathy of undetermined significance (5%). NGS application has further broadened the spectrum of causes of CIN by including manifestations of clonal hematopoiesis, present in 12% of cases. TET2 (3%), TP53 (2%), and IDH1/IDH2 (2%) mutations were the most commonly found and were enriched in cases with T-LGL. We show that these clinico-molecular associations can be simultaneously present, complicating a proper diagnostic distinction within the broader entity of seemingly idiopathic neutropenia of autoimmune origin. Identification of etiologic culprits may also guide rational selection of therapies.

T-cell clonality testing for the diagnosis of T-cell large granular lymphocytic leukemia: Are we identifying pathology or incidental clones?

INTRODUCTION

T-cell clonality testing by T-cell receptor (TCR) gene rearrangement is key to the diagnosis of T-cell lymphoproliferative disorders such as T-cell large granular lymphocytic (T-LGL) leukemia. Benign clonal T-cell expansions, however, are commonly found in patients without identifiable disease, a condition referred to as T-cell clones of uncertain significance (T-CUS). In practice, T-cell clonality testing is performed for a range of reasons and results are often challenging to interpret given the overlap between benign and malignant clonal T-cell proliferations and uncertainties in the management of T-CUS.

METHODS

We conducted a 5-year retrospective cohort study of 211 consecutive patients who underwent PCR-based T-cell clonality testing for suspected T-LGL leukemia at our institution to characterize the use of T-cell clonality testing and its impact on patient management.

RESULTS

Overall, 46.4% (n = 98) of individuals tested had a clonal T-cell population identified. Patients with a monoclonal T-cell population were more likely to be older, have rheumatoid arthritis and have higher lymphocyte counts compared to patients with polyclonal populations. The majority of patients eventually diagnosed and treated for T-LGL leukemia had rheumatoid arthritis and lower neutrophil counts compared to untreated patients with monoclonal T-cell populations. A diagnosis of T-LGL leukemia was made in only a minority of patients (n = 48, 22.7%), and only a small proportion were treated (n = 17, 8.1%).

CONCLUSION

Our study suggests that T-cell clonality testing most commonly identifies incidental T-cell clones with only a minority of patients receiving a diagnosis of T-LGL leukemia and fewer requiring active treatment. These finding indicate an opportunity to improve utilization of T-cell clonality testing in clinical practice to better target patients where the results of testing would impact clinical management.

All that glitters is not LGL Leukemia

LGL disorders are rare hematological neoplasias with remarkable phenotypic, genotypic and clinical heterogeneity. Despite these constraints, many achievements have been recently accomplished in understanding the aberrant pathways involved in the LGL leukemogenesis. In particular, compelling evidence implicates STAT signaling as a crucial player of the abnormal cell survival. As interest increases in mapping hematological malignancies by molecular genetics, the relevance of STAT gene mutations in LGL disorders has emerged thanks to their association with discrete clinical features. STAT3 and STAT5b mutations are recognized as the most common gain-of-function genetic lesions up to now identified in T-LGL leukemia (T-LGLL) and are actually regarded as the hallmark of this disorder, also contributing to further refine its subclassification. However, from a clinical perspective, the relationships between T-LGLL and other borderline and overlapping conditions, including reactive cell expansions, clonal hematopoiesis of indeterminate potential (CHIP) and unrelated clonopathies are not fully established, sometimes making the diagnosis of T cell malignancy challenging. In this review specifically focused on the topic of clonality of T-LGL disorders we will discuss the rationale of the appropriate steps to aid in distinguishing LGLL from its mimics, also attempting to provide new clues to stimulate further investigations designed to move this field forward.

LGL Clonal Expansion and Unexplained Cytopenia: Two Clues Don't Make an Evidence

Clonal expansions of large granular lymphocytes (LGL) have been reported in a wide spectrum of conditions, with LGL leukemia (LGLL) being the most extreme. However, the boundaries between LGLL and LGL clones are often subtle, and both conditions can be detected in several clinical scenarios, particularly in patients with cytopenias. The intricate overlap of LGL clonal expansion with other disease entities characterized by unexplained cytopenias makes their classification challenging. Indeed, precisely assigning whether cytopenias might be related to inadequate hematopoiesis (i.e., LGL as a marginal finding) rather than immune-mediated mechanisms (i.e., LGLL) is far from being an easy task. As LGL clones acquire different pathogenetic roles and relevance according to their diverse clinical settings, their detection in the landscape of bone marrow failures and myeloid neoplasms has recently raised growing clinical interest. In this regard, the current availability of different diagnostic techniques, including next generation sequencing, shed light on the relationship between LGL clones and cytopenias, paving the way towards a better disease classification for precision medicine treatments. Herein, we discuss the clinical relevance of LGL clones in the diagnostic algorithm to be followed in patients presenting with cytopenias, offering a foundation for rational management approaches.

Single-cell RNA sequencing coupled to TCR profiling of large granular lymphocyte leukemia T cells

T-cell large granular lymphocyte leukemia (T-LGLL) is a lymphoproliferative disease and bone marrow failure syndrome which responds to immunosuppressive therapies. We show single-cell TCR coupled with RNA sequencing of CD3+ T cells from 13 patients, sampled before and after alemtuzumab treatments. Effector memory T cells and loss of T cell receptor (TCR) repertoire diversity are prevalent in T-LGLL. Shared TCRA and TCRB clonotypes are absent. Deregulation of cell survival and apoptosis gene programs, and marked downregulation of apoptosis genes in CD8+ clones, are prominent features of T-LGLL cells. Apoptosis genes are upregulated after alemtuzumab treatment, especially in responders than non-responders; baseline expression levels of apoptosis genes are predictive of hematologic response. Alemtuzumab does not attenuate TCR clonality, and TCR diversity is further skewed after treatment. Inferences made from analysis of single cell data inform understanding of the pathophysiologic mechanisms of clonal expansion and persistence in T-LGLL.

Large Granular Lymphocytic Leukemia: Current State of Diagnosis, Pathogenesis and Treatment

PURPOSE OF REVIEW

This manuscript aims at updating the knowledge on the clinico-biological characteristics, pathogenesis, and the diagnostic challenges of T-LGLL and CLPD-NK disorders and reviews the advances in the management and treatment of these patients.

RECENT FINDINGS

It has been shown that clonal large granular lymphocyte (LGL) expansions arise from chronic antigenic stimulation, leading to resistance to apoptosis. All the above findings have facilitated the diagnosis of LGLL and provided insights in the pathogenesis of the disease. At present, there is no standard first-line therapy for the disease. Immunosuppressive agents are the treatment routinely used in clinical practice. However, these agents have a limited capacity to eradicate the LGL clone and induce long-lasting remission. Advances in the knowledge of pathogenesis have made it possible to explore new therapeutic targets with promising results. Since LGLL is a rare disease, international efforts are needed to carry on prospective clinical trials with new potentially active drugs that could include a large number of patients.

Large granular lymphocytic leukemia: a brief review

LGL leukemia is a rare chronic lymphoproliferative disorder of cytotoxic lymphocytes which can be immunophenotypically either T cell or NK cell-derived. According to the World Health Organization classification, it can be divided into three subtypes: chronic T-cell leukemia and chronic natural killer cell lymphocytosis, and aggressive natural killer cell LGL leukemia. Clonal proliferation of large granular lymphocytes can be because of stimulation of various molecular pathways namely JAK-STAT3 pathway, FAS/FAS-L pathway, RAS-RAF-1-MEK1-ERK pathway, PI3K/AKT pathway, NF-KB pathway, and Sphingolipid Rheostat pathways. The most common clinical features presenting with this leukemia are neutropenia, anemia, thrombocytopenia. This leukemia is also associated with various autoimmune conditions. It usually has an indolent course except for the aggressive NK cell LGL leukemia. The cause of death in the indolent cases was mostly due to infectious complications related to the neutropenia associated with the disease. The rarity of the disease coupled with the availability of only a handful of clinical trials has been a hindrance to the development of a specific treatment. Most of the cases are managed with immunomodulators. The advances in the knowledge of molecular pathways associated with the disease have brought few targeted therapies into the limelight. We discuss here the evolution, epidemiology, demographic profile, pathophysiology, differential diagnosis, the available treatment options along with the survival and prognostic variables which may help us in better understanding and better management of the disease and hopefully, paving the way for a targeted clinical approach.

Spectrum of Kidney Disorders Associated with T-Cell Immunoclones

Large granular T-cell leukemia is a clonal hematological condition often associated with autoimmune disorders. Whether small-sized T-cell clones that are otherwise asymptomatic can promote immune kidney disorders remains elusive. In this monocentric retrospective cohort in a tertiary referral center in France, we reviewed characteristics of 29 patients with T-cell clone proliferation and autoimmune kidney disorders. Next-generation sequencing of the T-cell receptor of circulating T-cells was performed in a subset of patients. The T-cell clones were detected owing to systematic screening (mean count 0.32 × 10⁹/L, range 0.13–3.7). Strikingly, a common phenotype of acute interstitial nephropathy was observed in 22 patients (median estimated glomerular filtration rate at presentation of 22 mL/min/1.73 m² (range 0–56)). Kidney biopsies showed polymorphic inflammatory cell infiltration (predominantly CD3⁺ T-cells, most of them demonstrating positive phospho-STAT3 staining) and non-necrotic granuloma in six cases. Immune-mediated glomerulopathy only or in combination with acute interstitial nephropathy was identified in eight patients. Next-generation sequencing (n = 13) identified a major T-cell clone representing more than 1% of the T-cell population in all but two patients. None had a mutation of STAT3. Twenty patients (69%) had two or more extra-kidney autoimmune diseases. Acute interstitial nephropathies were controlled with corticosteroids, cyclosporin A, or tofacitinib. Thus, we showed that small-sized T-cell clones (i.e., without lymphocytosis) undetectable without specific screening are associated with various immune kidney disorders, including a previously unrecognized phenotype characterized by severe inflammatory kidney fibrosis and lymphocytic JAK/STAT activation.

High-Sensitive TRBC1-Based Flow Cytometric Assessment of T-Cell Clonality in Tαβ-Large Granular Lymphocytic Leukemia

Simple Summary

TRBC1 expression analysis by flow cytometry (FCM) has been recently proved to be a useful, simple and fast approach to assessing Tαβ-cell clonality. The aim of this study was to validate the utility of this assay specifically for the diagnosis of T-cell clonality of T-large granular lymphocytic leukemias (T-LGLL), as more mature polyclonal Tαβ large granular lymphocytes (Tαβ-LGL) show broader TRBC1⁺/TRBC1⁻ ratios vs. total Tαβ cells. Our results showed that a TRBC1-FCM assay is also a fast and easy method for detecting T-cell clonality in T-LGLL based on altered (increased or decreased) percentages of TRBC1⁺ Tαβ cells of LGL expansions (i.e., with lymphocytosis) suspected of T-LGLL, whereas in the absence of lymphocytosis (or in TαβCD4-LGLL), the detection of increased absolute cell-counts of more precisely defined subpopulations of T-LGL expressing individual TCRVβ families is required.

Abstract

Flow cytometric (FCM) analysis of the constant region 1 of the T-cell receptor β chain (TRBC1) expression for assessing Tαβ-cell clonality has been recently validated. However, its utility for the diagnosis of clonality of T-large granular lymphocytic leukemia (T-LGLL) needs to be confirmed, since more mature Tαβ cells (i.e., T-LGL normal-counterpart) show broader TRBC1⁺/TRBC1⁻ ratios vs. total Tαβ cells. We compared the distribution and absolute counts of TRBC1⁺ and TRBC1⁻ Tαβ-LGL in blood containing polyclonal (n = 25) vs. clonal (n = 29) LGL. Overall, polyclonal TRBC1⁺ or TRBC1⁻ Tαβ-LGL ranged between 0.36 and 571 cells/μL (3.2–91% TRBC1⁺ cells), whereas the clonal LGL cases showed between 51 and 11,678 cells/μL (<0.9% or >96% TRBC1⁺ cells). Among the distinct TCRVβ families, the CD28⁻ effector-memory and terminal-effector polyclonal Tαβ cells ranged between 0 and 25 TRBC1⁺ or TRBC1⁻ cells/μL and between 0 and 100% TRBC1⁺ cells, while clonal LGL ranged between 32 and 5515 TRBC1⁺ or TRBC1⁻ cells/μL, representing <1.6% or >98% TRBC1⁺ cells. Our data support the utility of the TRBC1-FCM assay for detecting T-cell clonality in expansions of Tαβ-LGL suspected of T-LGLL based on altered percentages of TRBC1⁺ Tαβ cells. However, in the absence of lymphocytosis or in the case of TαβCD4-LGL expansion, the detection of increased absolute cell counts by the TRBC1-FCM assay for more accurately defined subpopulations of Tαβ-LGL-expressing individual TCRVβ families, allows the detection of T-cell clonality, even in the absence of phenotypic aberrations.

Infectious Agents and Bone Marrow Failure: A Causal or a Casual Connection?

Acquired bone marrow failure (BMF) syndromes are considered immune-mediated disorders because hematological recovery after immunosuppressive therapies is the strongest indirect evidence of the involvement of immune cells in marrow failure development. Among pathophysiology hypotheses, immune derangement after chronic antigen exposure or cross-reactivity between viral particles and cellular components are the most accepted; however, epitopes against whom these lymphocytes are directed to remain unknown. In this study, we showed that BMF-associated immunodominant clones, namely the most represented T cells carrying an antigen-specific T-cell receptor (TCR) sequence in a random pool, were frequently associated with those described in various infectious diseases, such as cytomegalovirus (CMV) and Mycobacterium tuberculosis infection. We hypothesize that these pathogens might elicit an autoimmune response triggered by cross-reactivity between pathogen-related components and proteins or might be expanded as an unspecific response to a global immune dysregulation during BMF. However, those frequent intracellular pathogens might not only be passengers in marrow failure development, while playing a central role in starting the autoimmune response against hematopoietic stem cells.

The Value of Flow Cytometry Clonality in Large Granular Lymphocyte Leukemia

Simple Summary

Large granular lymphocyte (LGL) leukemia, a lymphoproliferative disease, is characterized by an increased frequency of large-sized lymphocytes with typical expression of T-cell receptor (TCR) αβ, CD3, CD8, CD16, CD45RA, and CD57, and with the expansion of one to three subfamilies of the TCR variable β chain reflecting gene rearrangements. Molecular analysis remains the gold standard for confirmation of TCR clonality; however, flow cytometry is time and labor saving, and can be associated with simultaneous investigation of other surface markers. Moreover, Vβ usage by flow cytometry can be employed for monitoring clonal kinetics during treatment and follow-up of LGL leukemia patients.

Abstract

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative disorder of mature T or NK cells frequently associated with autoimmune disorders and other hematological conditions, such as myelodysplastic syndromes. Immunophenotype of LGL cells is similar to that of effector memory CD8⁺ T cells with T-cell receptor (TCR) clonality defined by molecular and/or flow cytometric analysis. Vβ usage by flow cytometry can identify clonal TCR rearrangements at the protein level, and is fast, sensitive, and almost always available in every Hematology Center. Moreover, Vβ usage can be associated with immunophenotypic characterization of LGL clone in a multiparametric staining, and clonal kinetics can be easily monitored during treatment and follow-up. Finally, Vβ usage by flow cytometry might identify LGL clones silently underlying other hematological conditions, and routine characterization of Vβ skewing might identify recurrent TCR rearrangements that might trigger aberrant immune responses during hematological or autoimmune conditions.

Single-Antibody Evaluation of T-Cell Receptor β Constant Chain Monotypia by Flow Cytometry Facilitates the Diagnosis of T-Cell Large Granular Lymphocytic Leukemia

OBJECTIVES

The diagnosis of T-cell large granular lymphocytic leukemia (T-LGLL) is challenging because of overlapping immunophenotypic features with reactive T cells and limitations of T-cell clonality assays. We studied whether adding an antibody against T-cell receptor β constant region 1 (TRBC1) to a comprehensive flow cytometry panel could facilitate the diagnosis of T-LGLL.

METHODS

We added TRBC1 antibody to the standard T-cell and natural killer (NK) cell panel to assess T-cell clonality in 56 T-LGLLs and 34 reactive lymphocytoses. In addition, 20 chronic lymphoproliferative disorder of NK cells (CLPD-NKs) and 10 reactive NK-cell lymphocytoses were analyzed.

RESULTS

Clonal T cells were detected in all available T-LGLLs by monotypic TRBC1 expression and clonal/equivocal T-cell receptor gene rearrangement (TCGR) studies, compared with only 27% of T-LGLLs by killer-cell immunoglobulin-like receptor (KIR) restriction. Overall, 85% of T-LGLLs had a blood tumor burden greater than 500 cells/µL. Thirty-four reactive cases showed polytypic TRBC1 expression, except for 5 that revealed small T-cell clones of uncertain significance. All CLPD-NKs showed expected clonal KIR expression and negative TRBC1 expression.

CONCLUSIONS

Addition of TRBC1 antibody to the routine flow cytometry assay could replace the TCGR molecular study and KIR flow cytometric analysis to assess clonality, simplifying the diagnosis of T-LGLL.

How I manage acquired pure red cell aplasia in adults

Pure red cell aplasia (PRCA) is a rare hematological disorder with multiple etiologies. The multifaceted nature of this disease is emphasized by the variety of concomitant clinical features. Classic idiopathic presentation aside, prompt recognition of pathogenetic clues is important because of their diagnostic and therapeutic implications. As a consequence, treatment of PRCA is diverse and strictly dependent on the presented clinical scenario. Here, we propose a series of clinical vignettes that showcase instructive representative situations derived from our routine clinical practice. Using these illustrative clinical cases, we review the diagnostic workup needed for a precise diagnosis and the currently available therapeutic options, discussing their applications in regard to the various PRCA-associated conditions and individual patients' characteristics. Finally, we propose a treatment algorithm that may offer guidance for personalized therapeutic recommendations.

Bone Marrow Failure Syndromes, Overlapping Diseases with a Common Cytokine Signature

Bone marrow failure (BMF) syndromes are a heterogenous group of non-malignant hematologic diseases characterized by single- or multi-lineage cytopenia(s) with either inherited or acquired pathogenesis. Aberrant T or B cells or innate immune responses are variously involved in the pathophysiology of BMF, and hematological improvement after standard immunosuppressive or anti-complement therapies is the main indirect evidence of the central role of the immune system in BMF development. As part of this immune derangement, pro-inflammatory cytokines play an important role in shaping the immune responses and in sustaining inflammation during marrow failure. In this review, we summarize current knowledge of cytokine signatures in BMF syndromes.

Noncanonical effector functions of the T-memory-like T-PLL cell are shaped by cooperative TCL1A and TCR signaling

T-cell prolymphocytic leukemia (T-PLL) is a poor-prognostic neoplasm. Differentiation stage and immune-effector functions of the underlying tumor cell are insufficiently characterized. Constitutive activation of the T-cell leukemia 1A (TCL1A) oncogene distinguishes the (pre)leukemic cell from regular postthymic T cells. We assessed activation-response patterns of the T-PLL lymphocyte and interrogated the modulatory impact by TCL1A. Immunophenotypic and gene expression profiles revealed a unique spectrum of memory-type differentiation of T-PLL with predominant central-memory stages and frequent noncanonical patterns. Virtually all T-PLL expressed a T-cell receptor (TCR) and/or CD28-coreceptor without overrepresentation of specific TCR clonotypes. The highly activated leukemic cells also revealed losses of negative-regulatory TCR coreceptors (eg, CTLA4). TCR stimulation of T-PLL cells evoked higher-than-normal cell-cycle transition and profiles of cytokine release that resembled those of normal memory T cells. More activated phenotypes and higher TCL1A correlated with inferior clinical outcomes. TCL1A was linked to the marked resistance of T-PLL to activation- and FAS-induced cell death. Enforced TCL1A enhanced phospho-activation of TCR kinases, second-messenger generation, and JAK/STAT or NFAT transcriptional responses. This reduced the input thresholds for IL-2 secretion in a sensitizer-like fashion. Mice of TCL1A-initiated protracted T-PLL development resembled such features. When equipped with epitope-defined TCRs or chimeric antigen receptors, these Lckpr-hTCL1Atg T cells gained a leukemogenic growth advantage in scenarios of receptor stimulation. Overall, we propose a model of T-PLL pathogenesis in which TCL1A enhances TCR signals and drives the accumulation of death-resistant memory-type cells that use amplified low-level stimulatory input, and whose loss of negative coregulators additionally maintains their activated state. Treatment rationales are provided by combined interception in TCR and survival signaling.

STAT3 and STAT5B Mutations in T/NK-Cell Chronic Lymphoproliferative Disorders of Large Granular Lymphocytes (LGL): Association with Disease Features

Simple Summary

STAT3 and STAT5B mutations have been identified in a subset of T and NK large granular lymphocytic leukemia (T/NK-LGLL). The aim of our study was to evaluate the frequency and type of these mutations in all different subtypes of T/NK-LGL expansions (n = 100 patients), as well as to analyze its association with biological and clinical features of the disease. We show for the first time that STAT3/5B mutations were present in all different T/NK-cell LGLL categories here studied; further, STAT3 mutations were associated with overall reduced counts of almost all normal residual populations of immune cells in blood, together with a shorter time-to-therapy vs. wild type T/NK-LGLL. These findings contribute to support the utility of the STAT3 mutation analysis for diagnostic and prognostic purposes in LGLL.

Abstract

STAT3 and STAT5B (STAT3/STAT5B) mutations are the most common mutations in T-cell large granular lymphocytic leukemia (T-LGLL) and chronic lymphoproliferative disorders of NK cells (CLPD-NK), but their clinical impact remains unknown. We investigated the frequency and type of STAT3/STAT5B mutations in FACS-sorted populations of expanded T/NK-LGL from 100 (82 clonal; 6 oligoclonal; 12 polyclonal) patients, and its relationship with disease features. Seventeen non-LGL T-CLPD patients and 628 age-matched healthy donors were analyzed as controls. STAT3 (n = 30) and STAT5B (n = 1) mutations were detected in 28/82 clonal T/NK-LGLL patients (34%), while absent (0/18, 0%) among oligoclonal/polyclonal LGL-lymphocytosis. Mutations were found across all diagnostic subgroups: TCD8⁺-LGLL, 36%; CLPD-NK, 38%; TCD4⁺-LGLL, 7%; Tαβ⁺DP-LGLL, 100%; Tαβ⁺DN-LGLL, 50%; Tγδ⁺-LGLL, 44%. STAT3-mutated T-LGLL/CLPD-NK showed overall reduced (p < 0.05) blood counts of most normal leukocyte subsets, with a higher rate (vs. nonmutated LGLL) of neutropenia (p = 0.04), severe neutropenia (p = 0.02), and cases requiring treatment (p = 0.0001), together with a shorter time-to-therapy (p = 0.0001), particularly in non-Y640F STAT3-mutated patients. These findings confirm and extend on previous observations about the high prevalence of STAT3 mutations across different subtypes of LGLL, and its association with a more marked decrease of all major blood-cell subsets and a shortened time-to-therapy.

Rituximab for rheumatoid arthritis-associated large granular lymphocytic leukemia, a retrospective case series

OBJECTIVES

To assess the efficacy and tolerance profile of rituximab in rheumatoid arthritis (RA)-associated large granular lymphocyte leukemia (LGLL).

METHODS

Multicenter retrospective case series. Inclusion criteria were RA defined by the ACR/EULAR 2010 criteria and LGLL defined by absolute LGL count ≥ 0.3 × 10⁹/L with evidence of an expanded clonal LGL population (flow cytometry, TCR-γ polymerase chain reaction, or Stat3 mutation).

RESULTS

Fourteen patients (10 women, mean age 55.2 ± 14.2 years) included; 13 were seropositive for anti-cyclic citrullinated peptides (n = 11) or rheumatoid factor (n = 10). LGLL diagnosis was made 9.5 [IQR: 3.25;15.5] years after RA diagnosis. Thirteen patients had T-LGLL. Rituximab was the first-line therapy for LGLL for 4 patients. Previous treatment lines included methotrexate (n = 7), cyclophosphamide (n = 2), cyclosporin A (n = 1), or granulocyte colony-stimulating factor (n = 4). Rituximab was used in monotherapy (n = 8) or associated to methotrexate (n = 3), granulocyte colony-stimulating factor (n = 2), or alkylating agents (n = 1). The number of rituximab cycles ranged from 1 to 11 (median 6), with high heterogeneity in dosing regimens. Median duration response after rituximab initiation was 35 [IQR: 23.5;41] months. The overall response rate was 100%: 8 patients experienced complete response (normalization of blood count and LGL ≤ 0.3 × 10⁹/L) and 6 experienced partial responses (improvement in blood counts without complete normalization). The tolerance profile was good, with no infectious complications.

CONCLUSION

rituximab appears as a valuable therapeutic option for RA-associated LGLL.

Advances in the Diagnosis and Treatment of Large Granular Lymphocytic Leukemia

PURPOSE OF REVIEW

The past decade in LGL leukemia research has seen increased pairing of clinical data with molecular markers, shedding new insights on LGL leukemia pathogenesis and heterogeneity. This review summarizes the current standard of care of LGL leukemia, updates from clinical trials, and our congruent improved understanding of LGL pathogenesis.

RECENT FINDINGS

Various clinical reports have identified associations between stem, bone marrow, and solid organ transplants and incidence of LGL leukemia. There is also a potential for underdiagnosis of LGL leukemia within the rheumatoid arthritis patient population, emphasizing our need for continued study. Preliminary results from the BNZ-1 clinical trial, which targets IL-15 along with IL-2 and IL-9 signaling pathways, show some evidence of clinical response. With advances in our understanding of LGL pathogenesis from both the bench and the clinic, exciting avenues for investigations lie ahead for LGL leukemia.

Subclonal STAT3 mutations solidify clonal dominance

T large granular lymphocyte leukemia (T-LGLL) is a clonal lymphoproliferative disorder that can arise in the context of pathologic or physiologic cytotoxic T-cell (CTL) responses. STAT3 mutations are often absent in typical T-LGLL, suggesting that in a significant fraction of patients, antigen-driven expansion alone can maintain LGL clone persistence. We set out to determine the relationship between activating STAT3 hits and CTL clonal selection at presentation and in response to therapy. Thus, a group of patients with T-LGLL were serially subjected to deep next-generation sequencing (NGS) of the T-cell receptor (TCR) Vβ complementarity-determining region 3 (CDR3) and STAT3 to recapitulate clonal hierarchy and dynamics. The results of this complex analysis demonstrate that STAT3 mutations produce either a sweeping or linear subclone within a monoclonal CTL population either early or during the course of disease. Therapy can extinguish a LGL clone, silence it, or adapt mechanisms to escape elimination. LGL clones can persist on elimination of STAT3 subclones, and alternate STAT3-negative CTL clones can replace therapy-sensitive CTL clones. LGL clones can evolve and are fueled by a nonextinguished antigenic drive. STAT3 mutations can accelerate this process or render CTL clones semiautonomous and not reliant on physiologic stimulation.

Mixed-phenotype large granular lymphocytic leukemia: a rare subtype in the large granular lymphocytic leukemia spectrum

Large granular lymphocytic leukemia (LGLL) is a chronic proliferation of cytotoxic lymphocytes in which more than 70% of patients develop cytopenia(s) requiring therapy. LGLL includes T-cell LGLL and chronic lymphoproliferative disorder of natural killer (NK) cells. The neoplastic cells in LGLL usually exhibit a single immunophenotype in a patient, with CD8-positive/αβ T-cell type being the most common, followed by NK-cell, γδ T-cell, and CD4-positive/αβ T-cell types. We investigated a total of 220 LGLL cases and identified 12 mixed-phenotype LGLLs (5%): 7 cases with coexistent αβ T-cell and NK-cell clones and 5 with coexistent αβ and γδ T-cell clones. With a median follow-up of 48 months, the clinicopathological characteristics of these patients seemed similar to those of typical LGLL patients. Treatment was instituted in 9 patients, and 5 patients (55%) attained complete hematologic response or partial response. The therapeutic response rate of this cohort is comparable to the reported overall response rate of 40% to 60% in typical LGLL patients. Three patients who did not receive any treatment had progressive or persistent cytopenias. Interestingly, inverted proportions of 2 clones at disease recurrence were identified in 4 patients (36%) and stable clonal proportions in 7 patients (64%). Mixed-phenotype LGLL is rare, and this study underscores the importance of recognizing this rare type of LGLL in patients who may benefit from LGLL treatment.

Divergent roles for antigenic drive in the aetiology of primary versus dasatinib-associated CD8+ TCR-Vβ+ expansions

CD8+ T-cell expansions are the primary manifestation of T-cell large granular lymphocytic leukemia (T-LGLL), which is frequently accompanied by neutropenia and rheumatoid arthritis, and also occur as a secondary phenomenon in leukemia patients treated with dasatinib, notably in association with various drug-induced side-effects. However, the mechanisms that underlie the genesis and maintenance of expanded CD8+ T-cell receptor (TCR)-Vβ+ populations in these patient groups have yet to be fully defined. In this study, we performed a comprehensive phenotypic and clonotypic assessment of expanded (TCR-Vβ+) and residual (TCR-Vβ-) CD8+ T-cell populations in T-LGLL and dasatinib-treated chronic myelogenous leukemia (CML) patients. The dominant CD8+ TCR-Vβ+ expansions in T-LGLL patients were largely monoclonal and highly differentiated, whereas the dominant CD8+ TCR-Vβ+ expansions in dasatinib-treated CML patients were oligoclonal or polyclonal, and displayed a broad range of memory phenotypes. These contrasting features suggest divergent roles for antigenic drive in the immunopathogenesis of primary versus dasatinib-associated CD8+ TCR-Vβ+ expansions.

Deep sequencing and flow cytometric characterization of expanded effector memory CD8+CD57+ T cells frequently reveals T-cell receptor Vβ oligoclonality and CDR3 homology in acquired aplastic anemia

Oligoclonal expansion of CD8⁺ CD28⁻ lymphocytes has been considered indirect evidence for a pathogenic immune response in acquired aplastic anemia. A subset of CD8⁺ CD28⁻ cells with CD57 expression, termed effector memory cells, is expanded in several immune-mediated diseases and may have a role in immune surveillance. We hypothesized that effector memory CD8⁺CD28⁻CD57⁺ cells may drive aberrant oligoclonal expansion in aplastic anemia. We found CD8⁺CD57⁺ cells frequently expanded in the blood of aplastic anemia patients, with oligoclonal characteristics by flow cytometric Vβ usage analysis: skewing in 1–5 Vβ families and frequencies of immunodominant clones ranging from 1.98% to 66.5%. Oligoclonal characteristics were also observed in total CD8⁺ cells from aplastic anemia patients with CD8⁺CD57⁺ cell expansion by T-cell receptor deep sequencing, as well as the presence of 1–3 immunodominant clones. Oligoclonality was confirmed by T-cell receptor repertoire deep sequencing of enriched CD8⁺CD57⁺ cells, which also showed decreased diversity compared to total CD4⁺ and CD8⁺ cell pools. From analysis of complementarity-determining region 3 sequences in the CD8⁺ cell pool, a total of 29 sequences were shared between patients and controls, but these sequences were highly expressed in aplastic anemia subjects and also present in their immunodominant clones. In summary, expansion of effector memory CD8⁺ T cells is frequent in aplastic anemia and mirrors Vβ oligoclonal expansion. Flow cytometric Vβ usage analysis combined with deep sequencing technologies allows high resolution characterization of the T-cell receptor repertoire, and might represent a useful tool in the diagnosis and periodic evaluation of aplastic anemia patients. (Registered at clinicaltrials.gov identifiers: 00001620, 01623167, 00001397, 00071045, 00081523, 00961064)

Clinical features and treatment outcomes in large granular lymphocytic leukemia (LGLL)

Large granular lymphocytic leukemia (LGLL) represents a clonal/oligoclonal lymphoproliferation of cytotoxic T and natural killer cells often associated with STAT3 mutations. When symptomatic, due to mostly anemia and neutropenia, therapy choices are often empirically-based, because only few clinical trials and systematic studies have been performed. Incorporating new molecular and flow cytometry parameters, we identified 204 patients fulfilling uniform criteria for LGLL diagnoses and analyzed clinical course with median follow-up of 36 months, including responses to treatments. While selection of initial treatment was dictated by clinical features, the initial responses, as well as overall responses to methotrexate (MTX), cyclosporine (CsA), and cyclophosphamide (CTX), were similar at 40-50% across drugs. Sequential use of these drugs resulted in responses in most cases: only 10-20% required salvage therapies such as ATG, Campath, tofacitinib, splenectomy or abatacept. MTX yielded the most durable responses. STAT3-mutated patients required therapy more frequently and had better overall survival.

Dysregulated signaling, proliferation and apoptosis impact on the pathogenesis of TCRγδ+ T cell large granular lymphocyte leukemia

TCRγδ+ T-LGL leukemia is a rare form of chronic mature T cell disorders in elderly, which is generally characterized by a persistently enlarged CD3+CD57+TCRγδ+ large granular lymphocyte population in the peripheral blood with a monoclonal phenotype. Clinically, the disease is heterogeneous, most patients being largely asymptomatic, although neutropenia, fatigue and B symptoms and underlying diseases such as autoimmune diseases or malignancies are also often observed. The etiology of TCRγδ+ T-LGL proliferations is largely unknown. Here, we aimed to investigate underlying molecular mechanisms of these rare proliferations by performing gene expression profiling of TCRγδ+ T-LGL versus normal TCRγδ+ T cell subsets. From our initial microarray dataset we observed that TCRγδ+ T-LGL leukemia forms a separate group when compared with different healthy control TCRγδ+ T cell subsets, correlating best with the healthy TemRA subset. The lowest correlation was seen with the naive subset. Based on specific comparison between healthy control cells and TCRγδ+ T-LGL leukemia cells we observed up-regulation of survival, proliferation and hematopoietic system related genes, with a remarkable down-regulation of apoptotic pathway genes. RQ-PCR validation of important genes representative for the dataset, including apoptosis (XIAP, CASP1, BCLAF1 and CFLAR), proliferation/development (ID3) and inflammation (CD28, CCR7, CX3CR1 and IFNG) processes largely confirmed the dysregulation in proliferation and apoptosis. Based on these expression data we conclude that TCRγδ+ T-LGL leukemia is likely the result of an underlying aberrant molecular mechanisms leading to increased proliferation and reduced apoptosis.

Large granular lymphocytic leukemia. Current diagnostic and therapeutic approaches and novel treatment options

INTRODUCTION

Large granular lymphocytic leukemia (LGLL) is a low grade lymphoproliferative disorder characterized by the clonal proliferation of large granular lymphocytes (LGL) and recognised by the WHO. The diagnosis and management of these patients is challenging due to the limited information from prospective studies. Guidelines for front-line therapy have not been established. The prognosis is favourable with median overall survivals greater than 10 years. Areas covered: This manuscript is a review of the clinical features, diagnosis, pathogenesis and, in particular, the various available therapeutic options for this rare lymphoid leukemia. A systematic literature search using electronic PubMed database has been carried out. Expert commentary: A watch and wait strategy without therapeutic intervention is recommended in asymptomatic patients. The immunomodulators methotrexate, cyclophosphamide and cyclosporin are the most commonly used drugs in the routine practice with responses ranging from 50 to 65% and without evidence of cross-resistance among them. Purine analogs such as 2´deoxycoformycin and fludarabine alone or in combination may be indicated in patients with bulky and/or widespread disease. Trials using monoclonal antibodies such as Alemtuzumab and agents targeting the disrupted JAK/STAT pathway in LGLL such as JAK-3 inhibitors are promising particularly in a relapse setting.

LGL leukemia: from pathogenesis to treatment

Large granular lymphocyte (LGL) leukemia has been recognized by the World Health Organization classifications amongst mature T-cell and natural killer (NK) cell neoplasms. There are 3 categories: chronic T-cell leukemia and NK-cell lymphocytosis, which are similarly indolent diseases characterized by cytopenias and autoimmune conditions as opposed to aggressive NK-cell LGL leukemia. Clonal LGL expansion arise from chronic antigenic stimulation, which promotes dysregulation of apoptosis, mainly due to constitutive activation of survival pathways including Jak/Stat, MapK, phosphatidylinositol 3-kinase-Akt, Ras-Raf-1, MEK1/extracellular signal-regulated kinase, sphingolipid, and nuclear factor-κB. Socs3 downregulation may also contribute to Stat3 activation. Interleukin 15 plays a key role in activation of leukemic LGL. Several somatic mutations including Stat3, Stat5b, and tumor necrosis factor alpha-induced protein 3 have been demonstrated recently in LGL leukemia. Because these mutations are present in less than half of the patients, they cannot completely explain LGL leukemogenesis. A better mechanistic understanding of leukemic LGL survival will allow future consideration of a more targeted therapeutic approach than the current practice of immunosuppressive therapy.

Imaging tumour cell heterogeneity following cell transplantation into optically clear immune-deficient zebrafish

Cancers contain a wide diversity of cell types that are defined by differentiation states, genetic mutations and altered epigenetic programmes that impart functional diversity to individual cells. Elevated tumour cell heterogeneity is linked with progression, therapy resistance and relapse. Yet, imaging of tumour cell heterogeneity and the hallmarks of cancer has been a technical and biological challenge. Here we develop optically clear immune-compromised rag2^E450fs(casper) zebrafish for optimized cell transplantation and direct visualization of fluorescently labelled cancer cells at single-cell resolution. Tumour engraftment permits dynamic imaging of neovascularization, niche partitioning of tumour-propagating cells in embryonal rhabdomyosarcoma, emergence of clonal dominance in T-cell acute lymphoblastic leukaemia and tumour evolution resulting in elevated growth and metastasis in BRAF^V600E-driven melanoma. Cell transplantation approaches using optically clear immune-compromised zebrafish provide unique opportunities to uncover biology underlying cancer and to dynamically visualize cancer processes at single-cell resolution in vivo.

Direct visualisation of heterogeneous cell populations in live animals has been challenging. Here, the authors optimize cell transplantation into optically clear immune-deficient zebrafish, and use intravital imaging to track and to assess functional diversity of individual cancer cells in vivo.

Clinicopathologic, Immunophenotypic, Cytogenetic, and Molecular Features of γδ T-Cell Large Granular Lymphocytic Leukemia: An Analysis of 14 Patients Suggests Biologic Differences With αβ T-Cell Large Granular Lymphocytic Leukemia. [corrected]

OBJECTIVES

T-cell large granular lymphocytic (T-LGL) leukemia is a rare disorder in which the neoplastic cells usually express the αβ T-cell receptor (TCR). To determine the significance of γδ TCR expression in this leukemia, we compared the clinicopathologic, immunophenotypic, and genetic features of patients with T-LGL leukemia expressing γδ TCR or αβ TCR.

METHODS

We used the World Health Organization classification criteria to confirm the diagnosis. All patients were diagnosed and treated at our institution.

RESULTS

We identified 14 patients with γδ T-LGL leukemia, 11 men and three women; six (43%) patients had a history of rheumatoid arthritis, 10 (71%) had neutropenia, four (29%) had thrombocytopenia, and three (21%) had anemia. Eight (67%) of 12 patients had a CD4-/CD8- phenotype, and four (33%) had a CD4-/CD8+ phenotype. The median overall survival was 62 months. Patients with γδ T-LGL leukemia were more likely to have rheumatoid arthritis (P = .04), lower absolute neutrophil count (P = .04), lower platelet count (P = .004), and a higher frequency of the CD4-/CD8- phenotype (P < .0001). However, there was no significant difference in overall survival between the two groups (P = .64).

CONCLUSIONS

Although patients with γδ and αβ T-LGL leukemia show some different clinical or phenotypic features, overall survival is similar, suggesting that γδ TCR expression does not carry prognostic significance.

Spectrum of Clonal Large Granular Lymphocytes (LGLs) of αβ T Cells: T-Cell Clones of Undetermined Significance, T-Cell LGL Leukemias, and T-Cell Immunoclones

OBJECTIVES

Clones of T-cell large granular lymphocytes (LGLTs) were detected by flow cytometry. Disease associations are described.

METHODS

Flow cytometry on blood or marrow detected clonal LGLTs by analyzing variable regions of the T-cell receptor β chain.

RESULTS

LGLT clones were detected in 20% (54/264) of tested patients. The clone sizes were less than 2.0 × 10(9)/L in the blood in 73% and less than 10% of marrow space in 94%. Blood counts showed cytopenias. Clinical associations included B-cell clones, myeloid neoplasms, nonneoplastic disorders of blood or marrow, transplants, systemic immune disorders, carcinomas, or hypothyroidism. Twelve patients had LGLT leukemia. Most (76%) had small LGLT clones with limited impact on the clinical management.

CONCLUSIONS

Most of the LGLT clones detected by flow cytometry were small and did not change the clinical management. We propose the following terminology: T-cell clones of undetermined significance, LGLT leukemias, and T-cell immunoclones.

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.

Discrimination of T-cell subsets and T-cell receptor repertoire distribution

Flow cytometry-based analysis of T-cell receptor (TCR) repertoires is an essential tool for the detection of clonal T-cell expansions in physiologic and pathologic conditions. Individual T-cell subsets can be investigated based on their surface properties. The aims of our study were to provide reference values for various disease settings and delineate the contribution of individual TCR repertoires to the human T-cell differentiation pathway. We analyzed blood of 66 healthy subjects aged 0 (cord blood) to 72 years. Lymphocyte subpopulations and TCR repertoires were simultaneously explored using antibodies specific to CD3, CD4, CD8, CD45RA, CCR7, CD27, CD57 and a set of 25 antibodies detecting human TCR-Vβ chains. Statistical analysis included Wilcoxon, paired t and ANOVA tests. Initially, TCR expansion values were calculated based on the analysis of TCR-Vβ distribution on CD4+ and CD8+ T cells. We then established gating strategies and an algorithm for data analysis allowing for discrimination of T-cell subsets and TCR distribution. Dominant TCR expansions were present within effector as opposed to central/effector memory or naive cells, e.g., median TCR-Vβ expansion rate was highest on CD45RA+/CCR7- effector CD4+/8+ cells (eight and 11-fold, respectively). Remarkably, TCR expansions were missing (0) or very low (0.5) on CD4+ and CD8+ central memory population, respectively. No significant gender-related variability of TCR repertoires was identified, and significant impact of chronic cytomegalovirus infection was shown. Our results serve as reference for future studies elucidating clonal TCR dominance of T-cell subsets.

The analysis of clonal diversity and therapy responses using STAT3 mutations as a molecular marker in large granular lymphocytic leukemia

T-cell large granular lymphocytic leukemia and chronic lymphoproliferative disorder of natural killer cells are intriguing entities between benign and malignant lymphoproliferation. The molecular pathogenesis has partly been uncovered by the recent discovery of somatic activating STAT3 and STAT5b mutations. Here we show that 43% (75/174) of patients with T-cell large granular lymphocytic leukemia and 18% (7/39) with chronic lymphoproliferative disorder of natural killer cells harbor STAT3 mutations when analyzed by quantitative deep amplicon sequencing. Surprisingly, 17% of the STAT3-mutated patients carried multiple STAT3 mutations, which were located in different lymphocyte clones. The size of the mutated clone correlated well with the degree of clonal expansion of the T-cell repertoire analyzed by T-cell receptor beta chain deep sequencing. The analysis of sequential samples suggested that current immunosuppressive therapy is not able to reduce the level of the mutated clone in most cases, thus warranting the search for novel targeted therapies. Our findings imply that the clonal landscape of large granular lymphocytic leukemia is more complex than considered before, and a substantial number of patients have multiple lymphocyte subclones harboring different STAT3 mutations, thus mimicking the situation in acute leukemia.

Detection of monoclonal T populations in patients with KIR-restricted chronic lymphoproliferative disorder of NK cells

The etiology of chronic large granular lymphocyte proliferations is largely unknown. Although these disorders are characterized by the expansion of different cell types (T and natural killer) with specific genetic features and abnormalities, several lines of evidence suggest a common pathogenetic mechanism. According to this interpretation, we speculated that in patients with natural killer-type chronic lymphoproliferative disorder, together with natural killer cells, also T lymphocytes undergo a persistent antigenic pressure, possibly resulting in an ultimate clonal T-cell selection. To strengthen this hypothesis, we evaluated whether clonal T-cell populations were detectable in 48 patients with killer immunoglobulin-like receptor-restricted natural killer-type chronic lymphoproliferative disorder. At diagnosis, in half of the patients studied, we found a clearly defined clonal T-cell population, despite the fact that all cases presented with a well-characterized natural killer disorder. Follow-up analysis confirmed that the TCR gamma rearrangements were stable over the time period evaluated; furthermore, in 7 patients we demonstrated the appearance of a clonal T subset that progressively matures, leading to a switch between killer immunoglobulin-like receptor-restricted natural killer-type disorder to a monoclonal T-cell large granular lymphocytic leukemia. Our results support the hypothesis that a common mechanism is involved in the pathogenesis of these disorders.

Patterns of somatically acquired amplifications and deletions in apparently normal tissues of ovarian cancer patients

Little is understood about the occurrence of somatic genomic alterations in normal tissues and their significance in the context of disease. Here, we identified potential somatic copy number alterations (pSCNAs) in apparently normal ovarian tissue and peripheral blood of 423 ovarian cancer patients. There were, on average, two to four pSCNAs per sample detectable at a tissue-level resolution, although some individuals had orders of magnitude more. Accordingly, we estimated the lower bound of the rate of pSCNAs per cell division. Older individuals and BRCA mutation carriers had more pSCNAs than others. pSCNAs significantly overlapped with Alu and G-quadruplexes, and the affected genes were enriched for signaling and regulation. Some of the amplification/deletion hotspots in pan-cancer genomes were hot spots of pSCNAs in normal tissues as well, suggesting that those regions might be inherently unstable. Prevalence of pSCNA in peripheral blood predicted survival, implying that mutations in normal tissues might have consequences for cancer patients.

T-cell receptor signaling in peripheral T-cell lymphoma - a review of patterns of alterations in a central growth regulatory pathway

T-cell receptor (TCR) signaling is pivotal in T-cell development and function. In peripheral T-cell lymphomas/leukemias (PTCL/L), histogenesis, transforming events, epidemiology, and clinical presentation are also closely linked to TCR-mediated influences. After reviewing the physiology of normal TCR signaling and cellular responses, we describe here the association of subgroups of PTCL/L with specific patterns of TCR activation as relevant tumor-initiating and/or tumor-sustaining programs. We identify PTCL/L with a functionally intact TCR machinery in which stimulation is possibly incited by exogenous antigens or autoantigens. Distinct from these are tumors with autonomous oncogenic signaling by dysregulated TCR components uncoupled from extrinsic receptor input. A further subset is characterized by transforming events that activate molecules acting as substitutes for TCR signaling, but triggering similar downstream cascades. We finally discuss the consequences of such a functional model for TCR-targeted therapeutic strategies including those that are being tested in the clinic and those that still require further development.

STAT3 gene mutations and their association with pure red cell aplasia in large granular lymphocyte leukemia

Large granular lymphocyte leukemia (LGL L) has been morphologically characterized as a group of lymphoproliferative diseases that include T-cell large granular lymphocytic leukemia (T-LGL L) and chronic lymphoproliferative disorders of natural killer cells (CLPD-NK). We investigated mutations in the Src homology 2 (SH2) domain of the signal transducer and activator of transcription 3 (STAT3) gene in Asian cohorts of T-LGL L and CLPD-NK (n = 42 and 11, respectively). Two mutations, Y640F and D661Y, were identified using direct sequencing or allele-specific (AS) PCR. Y640F and D661Y mutations were found in seven and 18 patients, respectively. Two patients were positive for both mutations. Frequencies of STAT3 mutations in T-LGL L and CLPD-NK were 47.6% and 27.2%, respectively. Pure red cell aplasia (PRCA) was associated with the mutations (P = 0.005). The mutations were persistently found at stable levels in some patients after more than 5 years using AS-quantitative PCR. The results of the present study indicate that the SH2 domain of the STAT3 gene is frequently mutated in Asian T-LGL L and CLPD-NK, and that PRCA is closely correlated with the mutations.

Lack of common TCRA and TCRB clonotypes in CD8(+)/TCRαβ(+) T-cell large granular lymphocyte leukemia: a review on the role of antigenic selection in the immunopathogenesis of CD8(+) T-LGL

Clonal CD8⁺/T-cell receptor (TCR)αβ⁺ T-cell large granular lymphocyte (T-LGL) proliferations constitute the most common subtype of T-LGL leukemia. Although the etiology of T-LGL leukemia is largely unknown, it has been hypothesized that chronic antigenic stimulation contributes to the pathogenesis of this disorder. In the present study, we explored the association between expanded TCR-Vβ and TCR-Vα clonotypes in a cohort of 26 CD8⁺/TCRαβ⁺ T-LGL leukemia patients, in conjunction with the HLA-ABC genotype, to find indications for common antigenic stimuli. In addition, we applied purpose-built sophisticated computational tools for an in-depth evaluation of clustering of TCRβ (TCRB) complementarity determining region 3 (CDR3) amino-acid LGL clonotypes. We observed a lack of clear TCRA and TCRB CDR3 homology in CD8⁺/TCRαβ⁺ T-LGL, with only low level similarity between small numbers of cases. This is in strong contrast to the homology that is seen in CD4⁺/TCRαβ⁺ T-LGL and TCRγδ⁺ T-LGL and thus underlines the idea that the LGL types have different etiopathogenesis. The heterogeneity of clonal CD8⁺/TCRαβ⁺ T-LGL proliferations might in fact suggest that multiple pathogens or autoantigens are involved.

Are T-LGL Leukemia and NK-Chronic Lymphoproliferative Disorder really two distinct diseases?

Mature Large Granular lymphocytes (LGL) disorders include a spectrum of conditions, ranging from polyclonal to clonal indolent and/or overt leukemic LGL proliferations. Most cases are represented by clonal expansions of TCRα/β+ LGL displaying a CD8+ phenotype with expression of cytotoxic T-cell antigens (CD57, CD16, TIA-1, perforin and granzyme B). Proliferations of CD3-CD16+ NK cells with a restricted patter of NK receptors are less common, usually comprising 15% of the cases. Main features are cytopenias, splenomegaly and autoimmune phenomena. Morphology, immunophenotyping and molecular analyses are crucial to establish a correct diagnosis of disease. According to the 2008 WHO classification, two separate entities account for the majority of cases, T-LGL leukemia and Chronic Lymphoproliferative Disease of NK cell (this latter still provisional). Although these disorders are characterized by the expansion of different cells types i.e. T and NK cells, with specific genetic features and abnormalities, compelling evidence supports the hypothesis that a common pathogenic mechanism would be involved in both disorders. As a matter of fact, a foreign antigen driven clonal selection is considered the initial step in the mechanism ultimately leading to generation of both conditions. In this chapter we will discuss recent advances on the pathogenesis of chronic T and NK disorders of granular lymphocytes, challenging the current WHO classification on the opportunity to separate T and NK disorders, which are likely to represent two sides of the same coin.

Distinguishing T-cell Large Granular Lymphocytic Leukemia from Reactive Conditions: Laboratory Tools and Challenges in Their Use

This article focuses on the challenges of diagnosing T-cell large granular leukemia and distinguishing it from benign reactive conditions, as well as more aggressive neoplasms of cytotoxic lymphocytes. No single laboratory method is sufficient to make the diagnosis, but instead a combination of flow cytometry, genetic studies, and bone marrow immunohistochemistry must be used.

Familial CD3+ T large granular lymphocyte leukemia: evidence that genetic predisposition and antigen selection promote clonal cytotoxic T-cell responses

CD3+ T-large granular lymphocyte (T-LGL) proliferations often present with cytopenias and splenomegaly and are linked to autoimmunity, especially rheumatoid arthritis and Felty's syndrome. We report here the intra-family occurrence of T-LGL leukemia in a father and son, both presenting with cytopenias and splenomegaly. Both patients carried the HLA-DRB1*04 allele, strongly associated with rheumatoid arthritis and Felty's syndrome, exhibited distinctive histopathological features suggestive of immune-mediated suppression of hematopoiesis and expressed a remarkably skewed T-cell receptor beta chain gene repertoire with overtime evolution (clonal drift). Immunoinformatics analysis and comparisons with clonotype sequences from various entities revealed (quasi)identities between (i) father and son, and (ii) father or son and patients with autoimmune disorders, T-LGL leukemia or chronic idiopathic neutropenia. Altogether, our results further corroborate antigen selection in the ontogeny of T-LGL leukemia and point to the interplay between genetics and the (micro)environment in shaping the outcome of cytotoxic T cell responses.

Deep sequencing of the T-cell receptor repertoire in CD8+ T-large granular lymphocyte leukemia identifies signature landscapes

New massively parallel sequencing technology enables, through deep sequencing of rearranged T-cell receptor (TCR) Vβ complementarity-determining region 3 (CDR3) regions, a previously inaccessible level of TCR repertoire analysis. The CDR3 repertoire diversity reflects clonal composition, the potential antigenic recognition spectrum, and the quantity of available T-cell responses. In this context, T-large granular lymphocyte (T-LGL) leukemia is a chronic clonal lymphoproliferation of cytotoxic T cells often associated with autoimmune diseases and various cytopenias. Using CD8(+) T-LGL leukemia as a model disease, we set out to evaluate and compare the TCR deep-sequencing spectra of both patients and healthy controls to better understand how TCR deep sequencing could be used in the diagnosis and monitoring of not only T-LGL leukemia but also reactive processes such as autoimmune disease and infection. Our data demonstrate, with high resolution, significantly decreased diversity of the T-cell repertoire in CD8(+) T-LGL leukemia and suggest that many T-LGL clonotypes may be private to the disease and may not be present in the general public, even at the basal level.