Large Granular Lymphocyte Leukemia

A lineage-specific STAT5BN642H mouse model to study NK-cell leukemia

ABSTRACT

Patients with T- and natural killer (NK)-cell neoplasms frequently have somatic STAT5B gain-of-function mutations. The most frequent STAT5B mutation is STAT5BN642H, which is known to drive murine T-cell leukemia, although its role in NK-cell malignancies is unclear. Introduction of the STAT5BN642H mutation into human NK-cell lines enhances their potential to induce leukemia in mice. We have generated a mouse model that enables tissue-specific expression of STAT5BN642H and have selectively expressed the mutated STAT5B in hematopoietic cells (N642Hvav/+) or exclusively in NK cells (N642HNK/NK). All N642Hvav/+ mice rapidly develop an aggressive T/NKT-cell leukemia, whereas N642HNK/NK mice display an indolent NK-large granular lymphocytic leukemia (NK-LGLL) that progresses to an aggressive leukemia with age. Samples from patients with NK-cell leukemia have a distinctive transcriptional signature driven by mutant STAT5B, which overlaps with that of murine leukemic N642HNK/NK NK cells. To our knowledge, we have generated the first reliable STAT5BN642H-driven preclinical mouse model that displays an indolent NK-LGLL progressing to aggressive NK-cell leukemia. This novel in vivo tool will enable us to explore the transition from an indolent to an aggressive disease and will thus permit the study of prevention and treatment options for NK-cell malignancies.

Clinical characteristics and treatment outcomes of Asian patients with T-cell large granular lymphocytic Leukemia: a single-center analysis of 67 cases

Large granular lymphocytic (LGL) leukemia is a clonal lymphoproliferative disorder of LGLs derived from cytotoxic T lymphocytes or natural killer cells. However, the clinical features and treatment responses are still not fully understood because of the rarity of the disease. To describe and assess a cohort of patients with T-cell large granular lymphocytic leukemia (T-LGLL). Single-center, retrospective, observational study. We retrospectively collected the clinical data of patients diagnosed with T-LGLL at Seoul National University Hospital since 2006. We included 67 patients in this study. The median age at diagnosis was 60 years. Additionally, 37 patients (55%) were symptomatic, and 25 (37%) had splenomegaly; 54 patients (81%) required treatment. Cyclophosphamide (n = 35), methotrexate (n = 25), and cyclosporin A (n = 19) were used most frequently for treatment, and their overall response rates were similar: cyclophosphamide (77%), methotrexate (64%), and cyclosporin A (63%). Splenomegaly was associated with an increased response rate to first-line therapy and a decreased complete response rate. Thrombocytopenia was associated with decreased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. In contrast, a high LGL number (> 2000/µL) in the peripheral blood smear was associated with increased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. This study describes the clinical features and treatment outcomes of patients with T-LGLL, providing valuable information for clinical decision-making regarding T-LGLL treatment.

Large granular lymphocyte lymphoma in 65 dogs (2005-2023)

Large granular lymphocyte lymphoma (LGLL) is a rare form of lymphoma in dogs. Limited information exists regarding presentation, treatment response, and outcome. The aim of this single-institute, retrospective study was to characterise clinical presentation, biologic behaviour, outcomes, and prognostic factors for dogs with LGLL. Cytologic review was also performed. Sixty-five dogs were included. The most common breed was the Labrador retriever (29.2%), and the most common presenting signs were lethargy (60.0%) and hyporexia (55.4%). The most common primary anatomic forms were hepatosplenic (32.8%) and gastrointestinal (20.7%). Twenty dogs (30.8%) had peripheral blood or bone marrow involvement. Thirty-two dogs were treated with maximum tolerated dose chemotherapy (MTDC) with a response documented in 74.1% of dogs. Dogs ≥7 years, and those with neutropenia or thrombocytopenia at diagnosis had the reduced likelihood of response to treatment. For dogs treated with MTDC median progression-free interval (PFI) was 17 days (range, 0-481), the median overall survival time (OST) 28 days (range, 3-421), and the 6-month and 1-year survival rates were 9.4% and 3.1%, respectively. On multivariable analysis, monocytosis and peripheral blood involvement were significantly associated with shorter PFI and OST. Long-term survival (≥100 days) was significantly associated with intermediate lymphocyte size on cytology. Dogs with LGLL have moderate response rates to chemotherapy but poor overall survival. Additional studies are needed to further evaluate prognostic factors and guide optimum treatment recommendations.

JAK/STAT defects and immune dysregulation, and guiding therapeutic choices

Inborn errors of immunity (IEIs) encompass a diverse spectrum of genetic disorders that disrupt the intricate mechanisms of the immune system, leading to a variety of clinical manifestations. Traditionally associated with an increased susceptibility to recurrent infections, IEIs have unveiled a broader clinical landscape, encompassing immune dysregulation disorders characterized by autoimmunity, severe allergy, lymphoproliferation, and even malignancy. This review delves into the intricate interplay between IEIs and the JAK-STAT signaling pathway, a critical regulator of immune homeostasis. Mutations within this pathway can lead to a wide array of clinical presentations, even within the same gene. This heterogeneity poses a significant challenge, necessitating individually tailored therapeutic approaches to effectively manage the diverse manifestations of these disorders. Additionally, JAK-STAT pathway defects can lead to simultaneous susceptibility to both infection and immune dysregulation. JAK inhibitors, with their ability to suppress JAK-STAT signaling, have emerged as powerful tools in controlling immune dysregulation. However, questions remain regarding the optimal selection and dosing regimens for each specific condition. Hematopoietic stem cell transplantation (HSCT) holds promise as a curative therapy for many JAK-STAT pathway disorders, but this procedure carries significant risks. The use of JAK inhibitors as a bridge to HSCT has been proposed as a potential strategy to mitigate these risks.

T-large Granular Lymphocytic Leukemia: A Rare Diagnosis in a Young Woman With Fever, Necrotic Skin Lesions and Cytopenias

T-large granular lymphocytic leukemia (T-LGLL) is a rare lymphoproliferative disorder. The diagnosis is established by identifying an abnormally high number of clonal granular T lymphocytes in the peripheral blood and eventually in the bone marrow, in cases with medullary infiltration. The majority of patients present with symptoms related to neutropenia and this condition may be associated with autoimmune diseases in up to a third of cases. The authors describe the case of a 26-year-old patient admitted with subacute high fever and bullous dermatitis with necrotic lesions with central bullae. Analytically, she presented anemia and leukopenia with severe neutropenia of 200 cells/L. Skin lesions were compatible with ecthyma and the skin biopsy revealed aspects compatible with leukocytoclastic vasculitis. The myelogram and bone biopsy revealed hypoplasia of the myeloid line and a pathological T population of CD8+, TIA-1+ and granzyme B+, which were associated with compatible flow cytometry (CD3+, T-cell receptor (TCR) Alpha-Beta+, CD5+, CD2+, with loss of CD7 antigen expression) established the diagnosis of T-LGLL. The patient had a favorable evolution, with cytopenias almost returning to normal after two months. She began follow-up at a Hematology Reference Center, remaining asymptomatic without specific treatment considering the indolent course of the disease.

Felty's syndrome

Felty's syndrome was first described in 1924 by the US-American physician Augustus Roi Felty as a triad of rheumatoid arthritis, splenomegaly and leucopenia. Even nearly 100 years later, this rare syndrome is still paralleled by diagnostic and therapeutic challenges and its pathogenesis is incompletely understood. Neutropenia with potentially life-threatening infections is the main problem and several pathomechanisms like Fas-mediated apoptosis, anti-neutrophil antibodies, anti-G-CSF antibodies, neutrophil consumption in the context of NETosis and suppression of granulopoiesis by T-LGLs have been suggested. Felty's syndrome has various differential diagnoses as splenomegaly and cytopenia are common features of different infectious diseases, malignancies and autoimmune disorders. Additionally, benign clonal T-/NK-LGL lymphocytosis is increasingly noticed in Felty's syndrome, which further complicates diagnosis. Today's treatment options are still sparse and are largely based on case reports and small case series. Methotrexate is the mainstay of therapy, followed by rituximab, but there is less evidence for alternatives in the case of adverse reactions or failure of these drugs. This article gives an updated review about Felty's syndrome including its pathogenesis and treatment options.

Effective treatment with the selective cytokine inhibitor BNZ-1 reveals the cytokine dependency of T-LGL leukemia

T-cell large granular lymphocytic leukemia (T-LGLL) is a clonal proliferation of cytotoxic T lymphocytes that can result in severe neutropenia, anemia, and bone marrow failure. Strong evidence from patients and mouse models demonstrate the critical role of interleukin-15 (IL-15) in T-LGLL pathogenesis. BNZ-1 is a pegylated peptide that selectively inhibits the binding of IL-15 and other γc cytokines to their cellular receptor complex, which has demonstrated efficacy in ex vivo T-LGLL cells and transgenic mice in preclinical studies. We conducted a phase 1/2 trial of BNZ-1 in patients with T-LGLL who had hematocytopenias (anemia or neutropenia) and required therapy. Clinical responses were assessed using hematologic parameters (improvement in hematocytopenias) based on response criteria from the Eastern Cooperative Oncology Group 5998 T-LGLL trial. BNZ-1 demonstrated clinical partial responses in 20% of patients with T-LGLL with minimal toxicity and the maximum tolerated dose was not reached. Furthermore, T-LGL leukemic cells showed significantly increased apoptosis in response to BNZ-1 treatment as early as day 2, including in clinical nonresponders, with changes that remained statistically different from baseline throughout treatment (P < .005). We report first-in-human proof that T-LGL leukemic cells are dependent on IL-15 and that intervention with IL-15 inhibition with BNZ-1 in patients with T-LGLL shows therapeutic effects, which carries important implications for the understanding of the pathogenesis of this disease. This trial was registered at www.clinicaltrials.gov as #NCT03239392.

Transient Leukemoid Reaction from T-Cell Large Granular Lymphocytes Post Autologous Stem Cell Transplant in a Patient Affected by Hodgkin Lymphoma

Monoclonal T-cell lymphocytosis has been reported in patients with concomitant autoimmune diseases, viral infections, or immunodeficiencies. Referred to as T-cell large granular lymphocytic leukemia (T-LGLL), most cases cannot identify the triggering cause. Only small case series have been reported in the literature, and no treatment consensus exists. T-cell lymphocytosis may also appear after the transplant of hematopoietic stem cells or solid organs. Rare cases have been reported in patients undergoing autologous stem cell transplant (ASCT) for hematological diseases (including multiple myeloma or non-Hodgkin's lymphoma). Here, we describe the singular case of a patient who underwent ASCT for Hodgkin's lymphoma and displayed the onset of T-LGLL with an uncommonly high number of lymphocytes in peripheral blood and their subsequent spontaneous remission.

A Comparison of the Fifth World Health Organization and the International Consensus Classifications of Mature T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are a rare subset of non-Hodgkin lymphomas that often carry significant difficulty in diagnosis and classification because of their rarity and biological complexity. Previous editions of the World Health Organization (WHO) classifications of hemopoietic neoplasms in 2001, 2008, and 2017 aimed to standardize hemopoietic neoplasm diagnosis in general. Since then, crucial clinico-pathological, immunophenotypic, and recent molecular discoveries have been made in the field of lymphomas, contributing to refining diagnostic criteria of several diseases, upgrading entities previously defined as provisional, and identifying new entities. In 2022, two different models were proposed to classify hematolymphoid neoplasms: the 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC). Of note, a common nosography is mandatory to ensure progress in health science and ensure the basis for a real precision medicine. In this article, the authors summarized the main differences with the previous fourth WHO edition and reviewed the main discrepancies between the two newest classifications, as far as PTCLs are concerned.

T-cell Large Granular Lymphocytic Leukemia and Felty Syndrome in Rheumatoid Arthritis: A Case Report

T-cell large granular lymphocytic (LGL) leukemia is characterized by a clonal proliferation of CD3+ T-cells and has been associated with rheumatoid arthritis (RA). Splenomegaly is a common finding and a majority of cases present with cytopenia. Felty syndrome (FS) is characterized by neutropenia and splenomegaly and is also classically described in the literature for its association with RA. Similarities in clinical features, pathogenesis, management, genetics, and immunologic basis of FS and T-cell LGL leukemia have led to the suggestion that they exist on the same spectrum of disease. We present a case of T-cell LGL leukemia in an RA patient with clinical features not distinguishable from features of FS.

JAKs and STATs from a Clinical Perspective: Loss-of-Function Mutations, Gain-of-Function Mutations, and Their Multidimensional Consequences

The JAK/STAT signaling pathway plays a key role in cytokine signaling and is involved in development, immunity, and tumorigenesis for nearly any cell. At first glance, the JAK/STAT signaling pathway appears to be straightforward. However, on closer examination, the factors influencing the JAK/STAT signaling activity, such as cytokine diversity, receptor profile, overlapping JAK and STAT specificity among non-redundant functions of the JAK/STAT complexes, positive regulators (e.g., cooperating transcription factors), and negative regulators (e.g., SOCS, PIAS, PTP), demonstrate the complexity of the pathway's architecture, which can be quickly disturbed by mutations. The JAK/STAT signaling pathway has been, and still is, subject of basic research and offers an enormous potential for the development of new methods of personalized medicine and thus the translation of basic molecular research into clinical practice beyond the use of JAK inhibitors. Gain-of-function and loss-of-function mutations in the three immunologically particularly relevant signal transducers STAT1, STAT3, and STAT6 as well as JAK1 and JAK3 present themselves through individual phenotypic clinical pictures. The established, traditional paradigm of loss-of-function mutations leading to immunodeficiency and gain-of-function mutation leading to autoimmunity breaks down and a more differentiated picture of disease patterns evolve. This review is intended to provide an overview of these specific syndromes from a clinical perspective and to summarize current findings on pathomechanism, symptoms, immunological features, and therapeutic options of STAT1, STAT3, STAT6, JAK1, and JAK3 loss-of-function and gain-of-function diseases.

Clonal cytopenia of undetermined significance (CCUS)-associated reversion of donor-derived, transient αβ T-cell large granular clonal lymphocytosis, emerging post-transplant in a patient with a history of γδ T-cell large granular lymphocytic leukemia

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) has revolutionized the therapy of hematolymphoid malignancies. Yet, how to best detect or predict the emergence of HSCT-related complications remain unresolved. Here, we describe a case of donor-derived, transient Alpha Beta (αβ) T-cell large granular clonal lymphocytosis and cytopenia that emerged post-HSCT in a patient with a history of gamma delta (γδ) T-cell large granular lymphocytic leukemia (T-LGLL). Clonal unrelatedness of post-transplant T-LGL lymphocytosis to the patient's pretransplant T-LGLL was first identified by T-cell receptor (TCR) PCR showing different sized fragments of rearranged gamma chains, in addition to shift from γδ to αβ TCR expression by flow cytometry analyses. Donor-derivation of the patient's post-transplant clonal lymphocytosis was confirmed by serial chimerism analyses of recipient's blood specimens demonstrating 100% donor DNA. Moreover, oncogenic DNMT3A and RUNX1 mutations were detected by next-generation sequencing (NGS) only in post-transplant specimens. Intriguingly, despite continued increase in DNMT3A and RUNX1 mutation load, the patient's clonal lymphocytosis and anemia eventually largely resolved; yet, the observed mutation profile with persistent thrombocytopenia indicated secondary clonal cytopenia of undetermined significance (CCUS) in the absence of overt morphologic evidence of myeloid neoplasm in the marrow. This case illustrates the utility of longitudinal chimerism analysis and NGS testing combined with flow cytometric immunophenotyping to evaluate emerging donor-derived hematolymphoid processes and to properly interpret partial functional engraftment. It may also support the notion that driver mutation-induced microenvironmental changes may paradoxically contribute to reestablishing tissue homeostasis.

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.

Large granular lymphocytic leukemia cured by allogeneic stem cell transplant: a case report

BACKGROUND

Large granular lymphocytic leukemia is a rare lymphocytic neoplasm that can pose a treatment challenge in patients with severe neutropenia in whom conventional therapies fail. We report one of the first cases in which allogeneic stem cell therapy was used as treatment for large granular lymphocytic leukemia. We report and discuss the case of a 42-year-old white Caucasian female who, despite multiple therapies including methotrexate, cyclophosphamide, prednisone, cyclosporine, and pentostatin, continued to show severe neutropenia and recurrent infections. The patient was treated successfully and cured by allogeneic stem cell transplant without any major complications.

CONCLUSIONS

The significant importance of this case report is the introduction of a new treatment algorithm for challenging cases of T-cell large granular lymphocytic leukemia in which standard care fails. We hope that this case report will raise awareness of the potential benefits of allogeneic stem cell transplant in the treatment of aggressive forms of T-cell large granular lymphocytic leukemia.

Pathogenesis and Treatment of T-Large Granular Lymphocytic Leukemia (T-LGLL) in the Setting of Rheumatic Disease

A complex relationship exists between rheumatic diseases and cancer. This delicate balance between chronic inflammation and malignant cell transformation in hematologic neoplasms has been observed, but is not well defined. Large Granular Lymphocyte (LGL) leukemia is at the intersection of a clonal lymphoproliferative disease, chronic inflammation, and autoimmunity. The association between rheumatoid arthritis (RA) and the spectrum of Felty’s Syndrome is well-known. Other rheumatic disorders have been reported including systemic lupus erythematosus (SLE), Sjogren’s Syndrome (SS), vasculitis, Behcet’s Disease (BD) and systemic sclerosis. The association between T-LGLL and rheumatic disease pathogenesis has been hypothesized, but has not yet been fully understood. Components of a shared pathogenesis includes chronic antigen stimulation, JAK-STAT pathway activation and overlap of various cytokines. We will summarize current knowledge on the molecular understanding between T-LGLL and rheumatic disease. There are many potential areas of research to help meet this need and lead to development of targeted therapeutic options.

Intersection Between Large Granular Lymphocyte Leukemia and Rheumatoid Arthritis

Large granular lymphocyte (LGL) leukemia, a rare hematologic malignancy, has long been associated with rheumatoid arthritis (RA), and the diseases share numerous common features. This review aims to outline the parallels and comparisons between the diseases as well as discuss the potential mechanisms for the relationship between LGL leukemia and RA. RA alone and in conjunction with LGL leukemia exhibits cytotoxic T-cell (CTL) expansions, HLA-DR4 enrichment, RA-associated autoantibodies, female bias, and unknown antigen specificity of associated T-cell expansions. Three possible mechanistic links between the pathogenesis of LGL leukemia and RA have been proposed, including LGL leukemia a) as a result of longstanding RA, b) as a consequence of RA treatment, or c) as a driver of RA. Several lines of evidence point towards LGL as a driver of RA. CTL involvement in RA pathogenesis is evidenced by citrullination and granzyme B cleavage that modifies the repertoire of self-protein antigens in target cells, particularly neutrophils, killed by the CTLs. Further investigations of the relationship between LGL leukemia and RA are warranted to better understand causal pathways and target antigens in order to improve the mechanistic understanding and to devise targeted therapeutic approaches for both disorders.

Gamma-Delta Large Granular Lymphocytic Leukemia: A Diagnostic Dilemma

We report an initial diagnostic dilemma case of a 60-year-old male who presented with worsening hemolytic anemia, thrombocytopenia, and acute kidney injury requiring hemodialysis. His presentation was initially suspected to be secondary to thrombotic thrombocytopenic purpura (TTP) and he was treated with intravenous immunoglobulin (IVIG) and plasmapheresis. Despite treatment, he failed to improve during his admission leading to further workup revealing gamma-delta T-cell large granular lymphocytic (γδ T-LGL) leukemia. In this paper, we will discuss the features, workup, and treatment of this rare malignancy.

Cytokines in the Pathogenesis of Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is a lymphoproliferative disorder of older adults characterized by the clonal expansion of cytotoxic T/natural killer cells due to constitutive pro-survival signaling. In recent years, it has become clear that cytokines and their receptors are aberrantly expressed in LGLL cells. The exact initiation process of LGLL is unknown, although several cytokine-driven mechanisms have emerged. Elevated levels of several cytokines, including interleukin-15 (IL-15) and platelet-derived growth factor (PDGF), have been described in LGLL patients. Evidence from humans and animal models has shown that cytokines may also contribute to the co-occurrence of a wide range of autoimmune diseases seen in patients with LGLL. The goal of this review is to provide a comprehensive analysis of the link between cytokines and pro-survival signaling in LGLL and to discuss the various strategies and research approaches that are being utilized to study this link. This review will also highlight the importance of cytokine-targeted therapeutics in the treatment of 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.

Case Report: Large Granular Lymphocyte Leukemia (LGLL)-A Case Series of Challenging Presentations

Large granular lymphocyte leukemia (LGLL) represents a rare group of diseases with considerable difficulties in their correct diagnostic workup and therapy. The major challenges lie in their distinction from reactive (including autoimmune) lymphoproliferations. Moreover, monoclonal LGL proliferative diseases are in fact a heterogeneous group of disorders, as recognized by the three subtypes in the current WHO classification. It distinguishes two chronic forms (the focus of this case series), namely T-LGLL and chronic lymphoproliferative disorders of Natural Killer cells (CLPD-NK) as well as aggressive NK-cell leukemia. In the clinical routine, the variable presentations and phenotypes of T-LGLL and CLPD-NK are underappreciated. The relevant differential diagnoses range from benign reactive T-cell expansions to other mature T-cell leukemias to highly aggressive γδ-lymphomas. T-LGLL or CLPD-NK patients suffer from a wide variety of symptoms often including, but not limited to, cytopenias or classical autoimmune phenomena. They receive treatments ranging from mere supportive measures (e.g. antibiotics, growth factors, transfusions) over strategies of immunosuppression up to anti-leukemic therapies. The diagnostic pitfalls range from recognition of the subtle T-cell proliferation, repeated establishment of monoclonality, assignment to a descript immunophenotypic pattern, and interpretations of molecular aberrancies. Here, we report a series of selected cases to represent the spectrum of LGLL. The purpose is to raise awareness among the scientifically or practically interested readers of the wide variety of clinical, immunological, and phenotypic features of the various forms of LGLL, e.g. of T-cell type, including its γδ forms or those of NK-lineage. We highlight the characteristics and courses of four unique cases from two academic centers, including those from a prospective nationwide LGLL registry. Each case of this instructive catalogue serves to transport a key message from the areas of (chronic inflammatory) contexts in which LGLL can arise as well as from the fields of differential diagnostics and of various treatment options. Implications for optimization in these areas are discussed.

Large Granular Lymphocyte Expansion in Myeloid Diseases and Bone Marrow Failure Syndromes: Whoever Seeks Finds

Large granular lymphocytes (LGL) are lymphoid cells characterized by either a T-cell or a natural killer phenotype whose expansion may be reactive to toxic, infectious, and neoplastic conditions, or result from clonal selection. Recently, the higher attention to LGL clones led to their detection in many clinical conditions including myeloid neoplasms and bone marrow failures. In these contexts, it is still unclear whether LGL cells actively contribute to anti-stem cell autoimmunity or are only a reaction to dysplastic/leukemic myelopoiesis. Moreover, some evidence exists about a common clonal origin of LGL and myeloid clones, including the detection of STAT3 mutations, typical of LGL, in myeloid precursors from myelodysplastic patients. In this article we reviewed available literature regarding the association of LGL clones with myeloid neoplasms (myelodysplastic syndromes, myeloproliferative neoplasms, and acute myeloid leukemias) and bone marrow failures (aplastic anemia and pure red cell aplasia, PRCA) focusing on evidence of pathogenic, clinical, and prognostic relevance. It emerged that LGL clones may be found in up to one third of patients, particularly those with PRCA, and are associated with a more cytopenic phenotype and good response to immunosuppression. Pathogenically, LGL clones seem to expand after myeloid therapies, whilst immunosuppression leading to LGL depletion may favor leukemic escape and thus requires caution.

Large Granular Lymphocytic Leukemia: From Immunopathogenesis to Treatment of Refractory Disease

Large Granular Lymphocyte Leukemia (LGLL) is a rare, chronic lymphoproliferative disorder of effector cytotoxic T-cells, and less frequently, natural killer (NK) cells. The disease is characterized by an indolent and often asymptomatic course. However, in roughly 50% of cases, treatment is required due to severe transfusion-dependent anemia, severe neutropenia, or moderate neutropenia with associated recurrent infections. LGLL represents an interesting disease process at the intersection of a physiological immune response, autoimmune disorder, and malignant (clonal) proliferation, resulting from the aberrant activation of cellular pathways promoting survival, proliferation, and evasion of apoptotic signaling. LGLL treatment primarily consists of immunosuppressive agents (methotrexate, cyclosporine, and cyclophosphamide), with a cumulative response rate of about 60% based on longitudinal expertise and retrospective studies. However, refractory cases can result in clinical scenarios characterized by transfusion-dependent anemia and severe neutropenia, which warrant further exploration of other potential targeted treatment modalities. Here, we summarize the current understanding of the immune-genomic profiles of LGLL, its pathogenesis, and current treatment options, and discuss potential novel therapeutic agents, particularly for refractory disease.

Large granular lymphocytic leukemia - A retrospective study of 319 cases

Large granular lymphocytic leukemia (LGLL) is a rare hematological malignancy that arises from cytotoxic T lymphocytes (T-LGLL) in 85% of cases and natural killer (NK) cells in the rest. A significant knowledge gap exists regarding the pathogenesis, treatment choices, and prognostic factors of LGLL. We report a cohort of 319 consecutive LGLL patients who presented to our cancer center between 2001 and 2020. A total of 295 patients with T-LGLL and 24 with chronic NK-cell lymphoproliferative disorder (CLPD-NK) were identified. The median age was 65 years (range, 17-90 years). Eighty-three patients (26.0%) had autoimmune diseases. A total of 119 patients (37.3%) had coexisting malignancies, 66 (20.7%) had solid tumors, and 59 (18.5%) had hematological malignancies. Most coexisting malignancies were diagnosed before the diagnosis of LGLL. Treatment was needed for 57% of patients. Methotrexate (MTX), cyclophosphamide (Cy), and cyclosporine A (CSA) were most used and had similar response rates between 61.5%-74.4%. Cy produced more complete responses (32.3%) compared to MTX and CSA (15.7% and 23.1%, respectively). Thrombocytopenia, splenomegaly, and female gender (after controlling for autoimmune diseases) were associated with decreased response rates to MTX, CSA, or Cy. Autoimmune diseases were associated with increased response rates. Thrombocytopenia was an independent risk factor for worse survival.

Immunodeficiency and bone marrow failure with mosaic and germline TLR8 gain of function

Inborn errors of immunity (IEI) are a genetically heterogeneous group of disorders with a broad clinical spectrum. Identification of molecular and functional bases of these disorders is important for diagnosis, treatment, and an understanding of the human immune response. We identified 6 unrelated males with neutropenia, infections, lymphoproliferation, humoral immune defects, and in some cases bone marrow failure associated with 3 different variants in the X-linked gene TLR8, encoding the endosomal Toll-like receptor 8 (TLR8). Interestingly, 5 patients had somatic variants in TLR8 with <30% mosaicism, suggesting a dominant mechanism responsible for the clinical phenotype. Mosaicism was also detected in skin-derived fibroblasts in 3 patients, demonstrating that mutations were not limited to the hematopoietic compartment. All patients had refractory chronic neutropenia, and 3 patients underwent allogeneic hematopoietic cell transplantation. All variants conferred gain of function to TLR8 protein, and immune phenotyping demonstrated a proinflammatory phenotype with activated T cells and elevated serum cytokines associated with impaired B-cell maturation. Differentiation of myeloid cells from patient-derived induced pluripotent stem cells demonstrated increased responsiveness to TLR8. Together, these findings demonstrate that gain-of-function variants in TLR8 lead to a novel childhood-onset IEI with lymphoproliferation, neutropenia, infectious susceptibility, B- and T-cell defects, and in some cases, bone marrow failure. Somatic mosaicism is a prominent molecular mechanism of this new disease.

T-Cell Large Granular Lymphocyte Leukemia in a Patient With Rheumatoid Arthritis

Large granular lymphocyte leukemia (LGL) is a clonal, lymphoproliferative disorder with an indolent disease course. T-cell LGL (T-LGL) is the most common type of LGL driven from T-cell lineage (85%). The coexistence of T-LGL with several types of autoimmune disorders, mostly rheumatoid arthritis (RA), has been reported. Felty’s syndrome (FS) is defined by splenomegaly, low neutrophil count, and destructive arthritis and is usually seen in <1% of patients with RA. About 30% to 40% of patients with FS have been reported to have an expansion of large granulated lymphocytes in the circulation. FS and T-LGL are similar in terms of clinical manifestations, response to immunosuppressive therapy, their smoldering course, and immunogenetic findings, proposing FS and T-LGL with RA might be different aspects of a single disease spectrum. In this article, we present a case with long-standing RA who had never been on DMARD (Disease Modifying Anti-Rheumatic Drugs) treatment found to have constitutional symptoms, neutropenia, and splenomegaly, and the patient was diagnosed with T-LGL.

Belinostat in Relapsed/Refractory T-Cell Large Granular Lymphocyte Leukemia

T-cell large granular lymphocyte (LGL) leukemia is a rare indolent neoplasm primarily treated with immunosuppression. Few therapies and no consensus exist for the optimal treatment of T-cell LGL leukemia refractory to immunosuppressive therapy. Here, we report a case of relapsed/refractory T-cell LGL treated with belinostat. A 57-year-old male presented with lymphocytosis and anemia and was found to have T-cell LGL, requiring frequent packed red blood cell transfusions. He was initially treated with methotrexate with no response after 7 months. He was then switched to cyclosporine and cyclophosphamide and experienced transfusion independence for 42 months before disease relapse. He was then started on belinostat with noted subsequent transfusion independence for greater than 15 months to date and decreased disease involvement on bone marrow biopsy. To our knowledge, this is the first reported case of belinostat use in relapsed/refractory T-cell LGL leukemia which resulted in a durable clinical and biologic response.

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.

[Clinical and laboratory analysis of 17 patients with γδT-cell large granular lymphocyte leukemia]

目的

比较γδT细胞大颗粒淋巴细胞白血病（γδT-LGLL）与αβT细胞大颗粒淋巴细胞白血病（αβT-LGLL）的临床及实验室特征。

方法

回顾性分析中国医学科学院血液病医院贫血诊疗中心2009年1月至2019年1月17例γδT-LGLL患者的临床及实验室结果，与同时期91例αβT-LGLL患者进行对比。

结果

17例γδT-LGLL患者中位年龄54（25~73）岁，10例就诊原因为贫血。γδT-LGLL与αβT-LGLL一致，脾大（41%和44%）较为常见，肝大（12%和5%）及淋巴结肿大（6%和8%）较为少见；两者均有较高的抗核抗体阳性率（59%和45%），较低的风湿因子阳性率（6%和10%）；两者中性粒细胞绝对值、淋巴细胞绝对值、HGB及PLT差异均无统计学意义（P值均>0.05）。γδT-LGLL患者的典型免疫分型为CD3⁺/CD4⁻/CD8⁻/CD57⁺/TCRγδ⁺，CD4⁻/CD8⁻双阴性表型显著多于αβT-LGLL患者（P<0.001）。17例γδT-LGLL患者有1例口服泼尼松治疗，3例口服环孢素A治疗，13例口服环孢素A联合泼尼松治疗，治疗4个月后2例获得完全缓解，4例获得部分缓解，总体有效率为35%。

结论

γδT-LGLL是一种少见的成熟T淋巴细胞增殖性疾病，其临床及实验室表现与αβT-LGLL相比除CD4⁻/CD8⁻双阴性表型外均无显著差异。环孢素A可作为γδT-LGLL的首选治疗药物。

Clinical features and treatment outcomes in patients with T-cell large granular lymphocytic leukemia: A single-institution experience

AIM

Large granular lymphocyte leukemia (LGLL) is a rare lymphoproliferative disorder associated with failure of hematopoiesis and autoimmune diseases. This study describes the clinical features and treatment responses of 108 patients with T-cell large granular lymphocyte leukemia (T-LGLL).

METHODS

Clinical data were collected from T-LGLL patients treated at an anemia treatment center within the hematology and blood diseases unit of a single hospital from January 2009 to April 2019.

RESULTS

The majority of patients (78 %) were symptomatic at the time of presentation. Splenomegaly was observed in 41 % of cases, while hepatomegaly and lymphadenopathy were rare (6 % and 7 %, respectively). Cyclosporine (CsA) monotherapy was used as first-line therapy for 16 patients, with an overall response rate (ORR) of 56 %. CsA in combination with steroids was administered in 83 patients, with an ORR of 48 %. Among patients experiencing relapse or resistance to first-line therapy, 10 received antithymocyte globulin (ATG) therapy, with an ORR of 50 %; an additional 9 patients received a modified regimen of high-dose cyclophosphamide (CTX) therapy, yielding an ORR of 78 %.

CONCLUSIONS

This study provides new information regarding the clinical features and therapeutic strategies for T-LGLL, which can be used to improve clinical decision making for T-LGLL patients. The data presented here indicate the CsA is an effective option for the treatment of T-LGLL, while modified regimens of high-dose CTX or ATG are safe and effective choices for patients with CsA refractory disease.

High Incidence of Clonal CD8+ T-cell Proliferation in Non-malignant Conditions May Reduce the Significance of T-cell Clonality Assay for Differential Diagnosis in Oncohematology

Polymerase chain reaction (PCR) analysis of rearranged T-cell receptor (TCR) genes is a valuable diagnostic tool for differential diagnosis of T-cell large granular lymphocytic (T-LGL) leukemia and reactive lymphocytosis. Age-related narrowing of T-cells repertoire and expansion of immune or autoimmune clones may lead to false-positive results. The objective of this study was to evaluate the specificity and positive predictive value of PCR-based clonality assessment for a differential diagnostics of T-LGL leukemia. Rearrangements of TCRG and TCRB genes using the BIOMED-2 protocol were assessed in healthy individuals including the elderly (n = 62) and patients with rheumatic diseases (n = 14), transitory reactive CD8+ lymphocytosis (n = 17), and T-LGL leukemia (n = 42). Monoclonal TCRG/TCRB rearrangements in blood were identified in 11.3%/4.8% (7/3 of 62) of healthy individuals; 21.4%/14.3% (3/2 of 14) of patients with rheumatic diseases, and 17.6%/11.8% (3/2 of 17) of patients with reactive lymphocytosis. Immunomagnetic selection of lymphocytes in healthy individuals (31 of 33) revealed that clonal T-cells belong to CD8+ and CD57+ population. No clonal Vβ-Jβ TCRB rearrangements were found in the control group, only Dβ-Jβ TCRB and TCRG. Given the high detectability (96.7%) of Vβ-Jβ TCRB monoclonal rearrangements in patients with αβ-T-LGL leukemia, this marker had the greatest specificity and positive predictive value (100%; 99.2%). The presence of clonal CD8+CD57+ cells in blood is common for healthy individuals and patients with reactive conditions and may not associate with any malignancy. Different specificity of TCRG/ Dβ-Jβ TRB/ Vβ-Jβ TCRB PCR reactions should be taken into account for T-cell clonality data interpretation.

Pathophysiologic Mechanisms And Management Of Large Granular Lymphocytic Leukemia Associated Pure Red Cell Aplasia

Large granular lymphocytic leukemia (LGLL) is a chronic clonal lymphoproliferative disease of mature T or NK cells, and produces a variety of hematological abnormalities. Pure red cell aplasia (PRCA) is a rare haematological disease and is one of the most common complications of LGLL. LGLL-associated PRCA may represent a relatively indolent type and may be more common than reported, but its natural history and clinical course have not been well described. The ethnic origin of the patients is an important consideration in determining the relationship between PRCA and LGLL. Guidelines and progresses for management of LGLL-associated PRCA rely on accumulation of empirical experiences, integrative analyses of several cases and clinical trials. The purpose of this review is to evaluate occurrence, possible mechanisms, diagnosis, clinical features, treatments and outcomes of LGLL-associated PRCA.

T-cell large granular lymphocyte leukemia in solid organ transplant recipients: case series and review of the literature

T-cell large granular lymphocyte (T-LGL) leukemia is a rare clonal proliferation of cytotoxic lymphocytes rarely described in solid organ transplant (SOT). We reviewed records from 656 kidney transplant recipients in follow-up at our Center from January 1998 to July 2017. In addition, we researched, through PubMed, further reports of T-LGL leukemia in SOT from March 1981 to December 2017. We identified six cases of T-LGL leukemia in our cohort of patients and 10 in the literature. This lymphoproliferative disorder was detected in one combined liver-kidney, one liver and 14-kidney transplant recipients. Median age at presentation was 46.5 years (IQR 39.2-56.9). The disease developed after a median age of 10 years (IQR 4.9-12) from transplantation. Anemia was the most common presentation (62.5%) followed by lymphocytosis (43.7%) and thrombocytopenia (31.2%). Splenomegaly was reported in 43.7% of the patients. Eight patients (50%) who experienced severe symptoms were treated with non-specific immunosuppressive agents. Six of them (75%) had a good outcome, whereas two (25%) remained red blood cell transfusion dependent. No cases progressed to aggressive T-LGL leukemia or died of cancer at the end of follow-up. These results suggest that T-LGL leukemia is a rare but potentially disruptive hematological disorder in the post-transplant period.

Skewing of the T-cell receptor repertoire in patients receiving rituximab after allogeneic hematopoietic cell transplantation: what lies beneath?

Rituximab is known to affect T cell immune responses. We and others have reported expansions of T large granular lymphocytes (T-LGLs) in lymphoma patients after Rituximab. We report here the immunogenetic profiling of the T cell receptor (TR) gene repertoire in 14 patients who received Rituximab post allo-HCT and explore clinicobiological correlations. All experienced antigenic triggers, CMV, EBV re-activation and chronic GvHD and had been treated with Rituximab. Skewing of TRBV genes was observed: 3 TRBV genes accounted for half of the repertoire. Oligoclonal pattern with expanded clonotypes was common. Patients with oligoclonality exhibited frequently cGvHD. Longitudinal samples in one revealed distinct clonotypes, suggesting clonal drift. T-LGL leukemia of donor origin with mixed chimerism eventually developed. In conclusion, we report development of oligoclonal T-LGLs after Rituximab post allo-HCT, alluding to antigen selection. Persistence of this phenomenon likely reflects strong antigenic stimulation by viruses and/or cGVHD aggravated by Rituximab.

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.

Clonal T-cell Large Granular Lymphocytic Disorders Manifesting in Patients with HIV-1 Infection: Case Series and Review of the Literature

We report five patients with human immunodeficiency virus-1/acquired immunodeficiency syndrome (HIV-1/AIDS) who developed T-cell large granular lymphocytic proliferation (T-LGLP) or leukemia (T-LGLL). None of the patients fulfilled criteria for diagnosis of diffuse infiltrative lymphocyte syndrome (DILS) or HIV-associated CD8+ lymphocytosis syndrome at the time of diagnosis of LGL. The immunophenotype of malignant T-cells was identical in three patients with co-expression of CD3, CD8, CD57, and T-cell receptor (TCR) alpha/beta. Three out of five patients were also diagnosed with clonal disorders of B-cell origin including diffuse large B-cell lymphoma, Burkitt’s lymphoma, and monoclonal gammopathy of undetermined significance (MGUS). Two patients developed cytopenias due to T-LGLL prompting initiation of therapy. Our study suggests that chronic viral infection with HIV can contribute to the evolution of T-LGLP. Clinical and laboratory characteristics of T-LGLP associated with HIV-1/AIDS resemble those of immunocompetent patients.

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.

T-Cell Large Granular Lymphocytic Leukemia and Coexisting B-Cell Lymphomas: A Study From the Bone Marrow Pathology Group

OBJECTIVE

T-cell large granular lymphocytic (T-LGL) leukemia is associated with B-cell lymphomas (BCLs), especially small BCLs. We aimed to explore and expand upon its association with BCLs.

METHODS

We retrospectively studied clinicopathologic features of T-LGL leukemia patients with coexisting BCL from January 2001 to December 2016.

RESULTS

Among 432 patients with T-LGL leukemia, 22 (5.1%) had an associated B-cell non-Hodgkin lymphoma. Thirteen (59%) patients had large and nine (41%) had small BCL. T-LGL leukemia occurred synchronously with BCL in five, preceded BCL in three, and followed BCL in 14 patients. Anemia was the most common cytopenia (68%). Only one patient had a history of rheumatoid arthritis.

CONCLUSION

To our knowledge, this is the first multicenter study looking at the spectrum and incidence of BCLs in patients with T-LGL leukemia and highlights its association with large BCLs (3% of T-LGL leukemias).

Livedoid eruption in a patient affected by T-γδ large granular lymphocyte leukaemia

Livedo is an ischaemic dermopathy characterised by a reddish-blue to violaceous mottling of the skin with a net-like reticular appearance. Livedo has been described in association with several medical conditions including lymphoproliferative disorders. Here, we describe the case of a 60-year-old woman who was presented with asymptomatic and persistent livedoid eruption on her trunk, lower and upper extremities as manifestation of an indolent form of T-γδ large granular lymphocyte leukaemia. To the best of our knowledge, this is the first report describing the association between livedo reticularis and T-γδ large granular lymphocyte leukaemia. It is plausible that a pathogenetic role of the neoplastic process is based on a cytotoxic antiendothelial activity.

Neutropenia in the Elderly: A Rheumatology Perspective

The majority of rheumatic diseases are chronic and require long-term use of disease-modifying agents to confer the best chance of controlling the disease. A significant proportion of these drugs have a risk, albeit small, of potentially serious side effects, such as neutropenia; therefore, there has been an understandable concern over the use of potentially toxic rheumatic drugs in the elderly. Factors that may contribute to this concern include age, pre-existing co-morbidities, polypharmacy, difficulty in monitoring side effects, and patient perception. The risk of using such medication needs to be balanced with their benefits in controlling chronic disease. This review discusses how rheumatic disease and anti-rheumatic medication are associated with neutropenia in an older age group. Of the rheumatic diseases, we give special focus to rheumatoid arthritis and the use of methotrexate, as well as touching on management considerations in neutropenia.

STAT3 mutation impacts biological and clinical features of T-LGL leukemia

STAT3 mutations have been described in 30-40% of T-large granular lymphocyte (T-LGL) leukemia patients, leading to STAT3 pathway activation. Considering the heterogeneity of the disease and the several immunophenotypes that LGL clone may express, the aim of this work was to evaluate whether STAT3 mutations might be associated with a distinctive LGL immunophenotype and/or might be indicative for specific clinical features. Our series of cases included a pilot cohort of 101 T-LGL leukemia patients (68 CD8+/CD4- and 33 CD4+/CD8±) from Padua Hematology Unit (Italy) and a validation cohort of additional 20 patients from Rennes Hematology Unit (France). Our results indicate that i) CD8+ T-LGL leukemia patients with CD16+/CD56- immunophenotype identify a subset of patients characterized by the presence of STAT3 mutations and neutropenia, ii) CD4+/CD8± T-LGL leukemia are devoid of STAT3 mutations but characterized by STAT5b mutations, and iii) a correlation exists between STAT3 activation and presence of Fas ligand, this molecule resulting highly expressed in CD8+/CD16+/CD56- patients. Experiments with stimulation and inhibition of STAT3 phosphorylation confirmed this relationship. In conclusion, our data show that T-LGL leukemia with specific molecular and phenotypic patterns is associated with discrete clinical features contributing to get insights into molecular bases accounting for the development of Fas ligand-mediated neutropenia.

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.