Pathologic clonal cytotoxic T-cell responses: nonrandom nature of the T-cell–receptor restriction in large granular lymphocyte leukemia

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.

Large granular lymphocyte leukemia: An indolent clonal proliferative disease associated with an array of various immunologic disorders

Large granular lymphocyte leukemia (LGLL) is a chronic lymphoproliferative disorder characterized by the proliferation of T or NK cytotoxic cells in the peripheral blood, the spleen and the bone marrow. Neutropenia leading to recurrent infections represents the main manifestation of LGLL. One specificity of LGLL is its frequent association with auto-immune disorders, among them first and foremost rheumatoid arthritis, and other hematologic diseases, including pure red cell aplasia and bone marrow failure. The large spectrum of manifestations and the classical indolent course contribute to the diagnosis difficulties and the frequency of underdiagnosed cases. Of importance, the dysimmune manifestations disappear with the treatment of LGLL as the blood cell counts normalize, giving a strong argument for a pathological link between the two entities. The therapeutic challenge results from the high rate of relapses following the first line of immunosuppressive drugs. New targeted agents, some of which are currently approved in autoimmune diseases, appear to be relevant therapeutic strategies to treat LGLL, by targeting key activated pathways involved in the pathogenesis of the disease, including JAK-STAT signaling.

Gamma Heavy Chain Disease Associated with T-Cell Large Granular Lymphocyte Lymphoproliferative Disorder: Case Report and Literature Review

Heavy chain diseases are rare B-cell neoplasms consisting of the production of a monoclonal immunoglobulin composed of the only heavy chain without corresponding light chains. It is a rare adult disease that may involve several sites with a variable clinical course. It manifests itself on a large spectrum from indolent to rapidly progressive. We present a case of heavy chain disease and concomitant T- cell large granular lymphoproliferative disorder, an association described in only six cases before. 

Bone marrow mesenchymal stem cells regulate the dysfunction of NK cells via the T cell immunoglobulin and ITIM domain in patients with myelodysplastic syndromes

BACKGROUND

Myelodysplastic syndrome (MDS) is a clonal disease of hematopoietic cells, characterized by hematopoietic cell hematopoiesis and a high risk of transformation into acute myeloid leukemia (AML). Although the underlying mechanism is unclear, MDS is often associated with immune system disorders, especially cellular immune abnormalities. We analyzed the number of lymphocyte subsets by flow cytometry assay and explored the alteration of lymphocyte subsets in MDS.

METHODS

Healthy controls, inpatients with primary MDS and patients with AML diagnosed from January 2017 to July 2021 were included. Flow cytometry assays were used to study lymphocyte subsets obtained from the bone marrow of the participants as well as changes in natural killer (NK) cell function. One-way analysis of variance and Student's t-test were used to analyze the data.

RESULTS

We found a reduction in the number and function of NK cells in patients with MDS. By further measuring the activating and inhibitory receptors on the surface of NK cells, we found that the T cell immunoglobulin and ITIM domain (TIGIT) was the highest expressed marker on NK cells. Additionally, the expression of CD155, which is the ligand of TIGIT, was significantly higher than expressions of CD112 and CD113 on bone marrow mesenchymal stem cells (BMSCs).

CONCLUSIONS

The co-culture results of BMSCs and NK cells demonstrated that BMSCs regulate NK cells through the TIGIT/CD155 interaction, indicating that NK cells play a vital role in MDS progression. BMSCs regulate the function of NK cells via TIGIT/CD155. Video Abstract.

T cell clonal expansion and STAT3 mutations: a characteristic feature of acquired chronic T cell-mediated pure red cell aplasia

Acquired chronic pure red cell aplasia (PRCA) develops idiopathically or in association with other medical conditions, including T cell large granular lymphocytic leukemia (T-LGLL) and thymoma. T cell dysregulation is considered a cardinal pathogenesis of PRCA, but genetic-phenotypic associations in T cell abnormalities are largely unclear. We evaluated an extended cohort of 90 patients with acquired PRCA, including 26 with idiopathic, 36 with T-LGLL-associated and 15 with thymoma-associated PRCA, for their T cell immuno-phenotypes, clonalities and STAT3 mutations. TCR repertoire skewing of CD8⁺ T cells was detected in 37.5% of idiopathic, 66.7% of T-LGLL-associated and 25% of thymoma-associated PRCA patients, and restriction to Vβ1 was most prominent (41%). Clonalities of TCRβ or γ chain and STAT3 mutational status were statistically associated (P = 0.0398), and they were detected in all three subtypes. The overall response rate to cyclosporin A was 73.9%, without significant difference by subtypes nor STAT3 mutational status. The T cell dysregulations, such as TCR repertoire skewing with predominant Vβ1 usage, clonality and STAT3 mutations, were frequently found across the subtypes, and the close associations between them suggest that these T cell derangements reflect a common pathophysiological mechanism among these PRCA subtypes.

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.

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.

Neutropenia and Large Granular Lymphocyte Leukemia: From Pathogenesis to Therapeutic Options

Large granular lymphocyte leukemia (LGLL) is a rare lymphoproliferative disorder characterized by the clonal expansion of cytotoxic T-LGL or NK cells. Chronic isolated neutropenia represents the clinical hallmark of the disease, being present in up to 80% of cases. New advances were made in the biological characterization of neutropenia in these patients, in particular STAT3 mutations and a discrete immunophenotype are now recognized as relevant features. Nevertheless, the etiology of LGLL-related neutropenia is not completely elucidated and several mechanisms, including humoral abnormalities, bone marrow infiltration/substitution and cell-mediated cytotoxicity might cooperate to its pathogenesis. As a consequence of the multifactorial nature of LGLL-related neutropenia, a targeted therapeutic approach for neutropenic patients has not been developed yet; moreover, specific guidelines based on prospective trials are still lacking, thus making the treatment of this disorder a complex and challenging task. Immunosuppressive therapy represents the current, although poorly effective, therapeutic strategy. The recent identification of a STAT3-mediated miR-146b down-regulation in neutropenic T-LGLL patients emphasized the pathogenetic role of STAT3 activation in neutropenia development. Accordingly, JAK/STAT3 axis inhibition and miR-146b restoration might represent tempting strategies and should be prospectively evaluated for the treatment of neutropenic LGLL patients.

Acquired Pure Red Cell Aplasia and Acquired Amegakaryocytic Thrombocytopenia Associated With Clonal Expansion of T-Cell Large Granular Lymphocytes in a Patient With Lipopolysaccharide-responsive Beige-like Anchor (LRBA) Protein Deficiency

Acquired pure red cell aplasia and acquired amegakaryocytic thrombocytopenic purpura are rare in children. Similarly, clonal expansion of T-cell large granular lymphocytes is infrequently seen in pediatrics. Lipopolysaccharide-responsive beige-like anchor (LRBA) protein deficiency is a recently described immunodeficiency syndrome that has been associated with inflammatory bowel disease and autoimmune phenomena such as Evans syndrome. Here, we describe a patient with LRBA deficiency who developed acquired pure red cell aplasia and acquired amegakaryocytic thrombocytopenic purpura associated with expansion of clonal T-cell large granular lymphocytes. This has not been described in the literature previously and adds to the knowledge on the spectrum of manifestations of LRBA deficiency.

Retroviral sero-reactivity in LGL leukaemia patients and family members

T-cell large granular lymphocyte (T-LGL) leukaemia is characterized by a clonal proliferation of cytotoxic T cells and is frequently associated with rheumatoid arthritis. Sera from some LGL leukaemia patients react to a portion of the human T-cell leukaemia virus (HTLV-1/2) transmembrane envelope protein, BA21, although HTLV-1/2 infection is rare in LGL leukaemia patients. Here we show that family members, including spouses, of an LGL leukaemia patient had elevated LGL counts, BA21 reactivity and, additionally, recognition of HIV-1 gp41. Thus, both LGL leukaemia patients and clinically normal contacts sharing the same environment have evidence of exposure to a retrovirus.

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.

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.

Constitutional SAMD9L mutations cause familial myelodysplastic syndrome and transient monosomy 7

Familial myelodysplastic syndromes arise from haploinsufficiency of genes involved in hematopoiesis and are primarily associated with early-onset disease. Here we describe a familial syndrome in seven patients from four unrelated pedigrees presenting with myelodysplastic syndrome and loss of chromosome 7/7q. Their median age at diagnosis was 2.1 years (range, 1-42). All patients presented with thrombocytopenia with or without additional cytopenias and a hypocellular marrow without an increase of blasts. Genomic studies identified constitutional mutations (p.H880Q, p.R986H, p.R986C and p.V1512M) in the SAMD9L gene on 7q21, with decreased allele frequency in hematopoiesis. The non-random loss of mutated SAMD9L alleles was attained via monosomy 7, deletion 7q, UPD7q, or acquired truncating SAMD9L variants p.R1188X and p.S1317RfsX21. Incomplete penetrance was noted in 30% (3/10) of mutation carriers. Long-term observation revealed divergent outcomes with either progression to leukemia and/or accumulation of driver mutations (n=2), persistent monosomy 7 (n=4), and transient monosomy 7 followed by spontaneous recovery with SAMD9L-wildtype UPD7q (n=2). Dysmorphic features or neurological symptoms were absent in our patients, pointing to the notion that myelodysplasia with monosomy 7 can be a sole manifestation of SAMD9L disease. Collectively, our results define a new subtype of familial myelodysplastic syndrome and provide an explanation for the phenomenon of transient monosomy 7. Registered at: www.clinicaltrials.gov; #NCT00047268.

STAT3 mutation and its clinical and histopathologic correlation in T-cell large granular lymphocytic leukemia

Although T-cell large granular lymphocytic leukemia (T-LGLL) is a clinically indolent disorder, patients with moderate to severe cytopenia require therapeutic intervention. The recent discovery of STAT3 mutations has shed light on the genetic basis of T-LGLL pathogenesis. However, the association of STAT3 mutational status with patients' clinical, histopathologic, and other laboratory features has not been thoroughly evaluated in T-LGLL. In this study, STAT3 mutations were identified in 18 of 36 patients with T-LGLL (50%), including Y640F (12/18, 66.7%), N647I (3/18, 16.7%), E638Q (1/18, 5.6%), I659L (1/18, 5.6%), and K657R (1/18, 5.6%). Interestingly, pure red cell aplasia was seen exclusively in T-LGLL patients without STAT3 mutations (6/15 in the wild-type STAT3 group versus 0/13 in the mutant STAT3 group; P = .02); these patients also were the only responders to T-LGLL therapy (mainly cyclophosphamide) in wild-type STAT3 group. Patients harboring STAT3 mutations were more prone to rheumatoid arthritis (4/13 versus 0/15 in the wild-type STAT3 group; P = .04), frequently requiring therapy for neutropenia/neutropenia-associated infections, and demonstrated good therapeutic responses to methotrexate. No significant differences were seen in complete blood count, flow cytometric immunophenotypic features, T-cell receptor γ V-J rearrangement repertoire, and bone marrow biopsy morphology among the STAT3-mutation and wild-type groups other than significantly larger tumor burden in patients with STAT3 mutations. The distinct disease association and therapeutic responses observed in patients with mutant and wild-type STAT3 warrant further investigation to elucidate the underlying mechanisms. They also highlight the importance of identifying STAT3 mutational status in patients with T-LGLL, which may aid in clinical therapeutic choice.

Mesenchymal Cell Reprogramming in Experimental MPLW515L Mouse Model of Myelofibrosis

Myelofibrosis is an indicator of poor prognosis in myeloproliferative neoplasms (MPNs), but the precise mechanism(s) contributing to extracellular matrix remodeling and collagen deposition in the bone marrow (BM) niche remains unanswered. In this study, we isolated mesenchymal stromal cells (MSCs) from mice transplanted with wild-type thrombopoietin receptor (MPLWT) and MPLW515L retroviral-transduced bone marrow. Using MSCs derived from MPLW515-transplant recipients, excessive collagen deposition was maintained in the absence of the virus and neoplastic hematopoietic cells suggested that the MSCs were reprogrammed in vivo. TGFβ production by malignant megakaryocytes plays a definitive role promoting myelofibrosis in MPNs. However, TGFβ was equally expressed by MSCs derived from MPLWT and MPLW515L expressing mice and the addition of neutralizing anti-TGFβ antibody only partially reduced collagen secretion in vitro. Interestingly, profibrotic MSCs displayed increased levels of pSmad3 and pSTAT3 suggesting that inflammatory mediators cooperating with the TGFβ-receptor signaling may maintain the aberrant phenotype ex vivo. FGFb is a known suppressor of TGFβ signaling. Reduced collagen deposition by FGFb-treated MSCs derived from MPLW515L mice suggests that the activating pathway is vulnerable to this suppressive mediator. Therefore, our findings have implications for the future investigation of therapies to reverse fibrosis in MPNs.

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.

Thrombocytopenia in cancer patients

Thrombocytopenia is a frequent complication of cancer and its treatment. The causes of thrombocytopenia in cancer patients can be diverse and multifactorial. Systemic chemotherapy is the most frequent cause of thrombocytopenia. The degree and duration thrombocytopenia depends upon whether the chemotherapeutic treatment is myeloablative, as used in stem cell transplants, or non-myeloablative, as typically used in solid non-hematologic malignancies. Additional causes of significant thrombocytopenia include tumor involvement of bone marrow and spleen; microangiopathic disorders such as disseminated intravascular coagulation, thrombotic thrombocytopenic purpura or hemolytic uremia syndrome. Lymphoproliferative malignancies can also be associated with secondary immune thrombocytopenia. Due to the broad differential diagnosis associated with cancer related thrombocytopenia, a careful diagnostic evaluation is indicated. The goal of treatment should be to maintain a safe platelet count to allow effective treatment of the underlying malignancy, prevent bleeding complications and to minimize the use of platelet product transfusion.

Pathology of T-cell lymphomas: diagnosis and biomarker discovery

T-cell lymphomas are a group of predominantly rare hematologic malignancies that tend to recapitulate different stages of T-cell development, in a similar way that B-cell lymphomas do. As opposed to B-cell lymphomas, the understanding of the biology and the classification of T-cell lymphomas are somewhat rudimentary, and numerous entities are still included as 'provisional categories' in the World Health Classification of hematolopoietic malignancies. A relevant and useful classification of these disorders have been difficult to accomplish because of the rarity nature of them, the relative lack of understanding of the molecular pathogenesis, and their morphological and immunophenotypical complexity. Overall, T-cell lymphomas represent only 15 % of all non-Hodgkin lymphomas. This review is focused on addressing the current status of the categories of mature T-cell leukemias and lymphomas (nodal and extranodal) using an approach that incorporates histopathology, immunophenotype, and molecular understanding of the nature of these disorders, using the same philosophy of the most recent revised WHO classification of hematopoietic malignancies.

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.

Advances in diagnosis and treatment of large granular lymphocyte syndrome

PURPOSE OF REVIEW

Large granular lymphocyte (LGL) syndrome comprises a clonal spectrum of T-cell and natural killer (NK)-cell LGL lymphoproliferative disorders associated with neutropenia. This review presents advances in diagnosis and therapy of LGL syndrome.

RECENT FINDINGS

Due to the lack of a single unique genetic or phenotypic feature and clinicopathological overlap between reactive and neoplastic entities, accurate LGL syndrome diagnosis should be based on the combination of morphologic, immunophenotypic, and molecular studies as well as clinical features. For diagnosis and monitoring of LGL proliferations, it is essential to perform flow cytometric blood and/or bone marrow analysis using a panel of monoclonal antibodies to conventional and novel T-cell and NK-cell antigens such as NK-cell receptors and T-cell receptor β-chain variable region families together with TCR gene rearrangement studies. Treatment of symptomatic cytopenias in patients with indolent LGL leukemia is still based on immunosuppressive therapy. Treatment with purine analogs and alemtuzumab may be considered as an alternative option.

SUMMARY

Progress in understanding the pathogenetic mechanisms of these entities, especially resistance of clonal LGLs to apoptosis, due to constitutive activation of survival signaling pathways, has its impact on identification of potential molecular therapeutic targets.

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.

Assessment of clonality in T-cell large granular lymphocytic leukemia: flow cytometric T cell receptor Vβ repertoire and T cell receptor gene rearrangement

The usefulness of flow cytometric variable β-chain repertoire (FC-Vβ) and T-cell receptor gene rearrangement (TCR-GR) analyses for differentiating T-cell large granular lymphocytic leukemia (T-LGLL) from reactive T-large granular lymphocyte (T-LGL) lymphocytosis has been insufficiently studied to date. In this study, we analyzed the diagnostic value of TCR-GR and FC-Vβ analysis in T-LGLL, and compared these results. In our study, FC-Vβ analysis was positive in all cases of T-LGLL, and clonality assessment of FC-Vβ had equal sensitivity and specificity to GeneScanning analysis but was more sensitive than heteroduplex analysis. Suspected T-cell clonality can best be addressed by evaluating two TCR targets (TCRβ and TCRγ), either in parallel or consecutively. Signal transducer and activator of transcription 3 (STAT3) mutation may provide a diagnostic tool for classifying some cases of T-LGL lymphocytosis as true T-LGLL. Our results further demonstrate a significant correlation of STAT3 mutation with pure red cell aplasia, neutropenia, hepatomegaly, β2-microglobulin and anemia.

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.

[Large granular lymphocytic leukemia. A rare disease with personalized treatment options]

INTRODUCTION

Large granular lymphocyte leukemia is rare, mainly chronic disease. The most common complication is neutropenia, but other immune-mediated cytopenia may also occur. There are no unified treatment recommendations and initiation of treatment mainly depends on the severity of the symptoms.

AIM

The aim of the authors was to analyze the main steps of the diagnosis and the necessity and outcome of treatment in their patients diagnosed with large granular lymphocyte leukaemia.

METHOD

The authors retrospectively analyzed the data of 17 large granular lymphocyte leukemia patients.

RESULTS

Of the 17 patients, 7 patients required treatment because of transfusion dependent anemia (4 patients) or neutropenia (3 patients). In 4 patients corticosteroid was given (supplemented with cyclosporine in one patients), while the other patients received anti-CD52 (one patient), low dose methotrexate (one patient) and combined chemotherapy (one patient). Five patients achieved partial response, and two patients died in sepsis.

CONCLUSIONS

In this cohort only a smaller proportion of patients required therapy. Immunosuppression can be successful, but the effect in most cases was temporary. The most serious complication was sepsis, which is associated with a significant risk of mortality in cases with neutropenia.

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.

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.

T-large granular lymphocyte leukemia: current molecular concepts

T-large granular lymphocyte (T-LGL) leukemia is a chronic and often indolent T cell lymphoproliferation characterized by extreme expansion of a semi-autonomous cytotoxic T lymphocyte (CTL) clone. Clinically, T-LGL can be associated with various cytopenias; neutropenia constitutes the most frequent manifestation. LGL clone represents a pathologic counterpart of the cytotoxic effector T cell but an abnormal memory CD8 cell seems to provide the supply of the matured LGL population. Analysis of clonal T cell receptor (TCR) rearrangement and complementarity determining region 3 (CDR3) of the TCR beta-chain is a useful tool to investigate clonal expansions, track the frequency of expanded clones and also clinically useful to monitor the response to therapy. The lessons learned from molecular analysis of clonal repertoire support a clinically-derived conclusion that the LGL clone arises in the context of an initially polyclonal immune response or an autoimmune process. Consequently, specific manifestations of T-LGL may be a result of the recognition spectrum of the transformed clone and the cytokines it produces. Due to the often monoclonal manifestation, T-LGL constitutes a suitable model to investigate polyclonal CTL-mediated processes. Application of new technologies, including TCR repertoire analysis by sequencing, clonotypic quantitative PCR and VB flow cytometry facilitate clinical diagnosis and may allow insights into the regulation of TCR repertoire and consequences resulting from the contraction of clonal diversity.

A case of CD4(+)T-cell large granular lymphocytic leukemia

We report here a case of a 59-yr-old man with CD4⁺ T-cell large granular lymphocytic leukemia (T-LGL). Peripheral blood examination indicated leukocytosis (45×10⁹ cells/L) that consisted of 34% neoplastic lymphoid cells. Other laboratory results indicated no specific abnormalities except for serum antinuclear antibody titer (1:640), glucose (1.39 g/L), and hemoglobin A1c (7.7%) levels. Computed tomography indicated multiple small enlarged lymph nodes (<1 cm in diameter) in both the axillary and inguinal areas, a cutaneous nodule (1.5 cm in diameter) in the left suboccipital area, and mild hepatosplenomegaly. Bone marrow examination revealed hypercellular marrow that consisted of 2.4% neoplastic lymphoid cells. The neoplastic lymphoid cells exhibited a medium size, irregularly shaped nuclei, a moderate amount of cytoplasm, and large granules in the cytoplasm. Immunohistochemical analysis indicated CD3⁺, CD4⁺, T-cell receptor βF1⁺, granzyme B⁺, and TIA1⁺. Flow cytometric analysis of the neoplastic lymphoid cells revealed CD3+, cytoplasmic CD3⁺, CD4⁺, and CD7⁺. Cytogenetic analysis indicated an abnormal karyotype of 46,XY,inv(3)(p21q27),t(12;17)(q24.1;q21),del(13)(q14q22)[2]/46,XY[28]. The patient was diagnosed with CD4⁺ T-LGL and received chemotherapy (10.0 mg methotrexate). This is the second case of CD4⁺ T-LGL that has been reported in Korea.

The different immunoregulatory functions on dendritic cells between mesenchymal stem cells derived from bone marrow of patients with low-risk or high-risk myelodysplastic syndromes

Myelodysplastic syndrome (MDS) is a group of progressive,clonal, neoplastic bone marrow disorders characterized by hematopoietic stem cell dysregulation and abnormalities in the immune system. Mesenchymal stem cells (MSC) appear to modulate the immune system at the very first step of the immune response through the inhibition of dendritic cells (DCs) differentiation and maturation. However, it is still unclear whether the effects of MSC on the development of DCs will be altered with disease state. In addition, it is not clear whether there are differences in the effects between low-risk and high-risk MDS-MSC on DCs development. In this study, our data confirm that MDS-MSC mediate a potent inhibition of DCs differentiation. Additionaly, MDS-MSC greatly alter DCs functions, including endocytosis, IL-12 secretion, their ability to inhibit T cell proliferation. Moreover, our results show that there are major differences in DCs development and function between low-risk and high-risk MDS-MSC. Compared to high-risk MDS-MSC, low-risk MDS-MSC is characterized by a poor ability to inhibit DCs differentiation and maturation; and correspondingly, less dysfunctional DC endocytosis, mildly decreased IL-12 secretion, and a reduction in DC-mediated inhibition of T cell proliferation. Finally, our results demonstrate that MDS-MSC derived TGF-β1 is largely responsible for the inhitory effects. These results elucidate the different immunoregulatory role of MSC in low-risk and high-risk MDS on DCs development, which may be important for understanding the pathogenesis of MDS and the development of novel immune therapies for the treatment of MDS.

The different immunoregulatory functions of mesenchymal stem cells in patients with low-risk or high-risk myelodysplastic syndromes

Myelodysplastic syndrome (MDS) are a group of progressive, clonal, neoplastic bone marrow disorders characterized by hematopoietic stem cell dysregulation and abnormalities in the immune system. Mesenchymal stem cells (MSC) have gained further interests after the demonstration of an immunoregulatory role. Nevertheless, the immunoregulatory function of MDS bone marrow derived MSC (MDS-MSC) remains poorly defined. In addition, it is not clear whether there are differences in the regulatory functions between low-risk and high-risk MDS-MSC. In this study, we obtain and expand MSC from bone marrow of patients with MDS. Our results show that there are significant differences in the immunoregulatory functions between low-risk and high-risk MDS-MSC. Compare to low-risk MDS-MSC, high-risk MDS-MSC is associated with the presence of increased TGF-β1, higher apoptosis, higher immunosuppressive rate and a poor ability of hematopoietic support. In addition, our results find that there are great differences in the CD4+CD25+Foxp3+Tregs inducible rate between high-risk MDS-MSC and low-risk MDS-MSC. Compared to high-risk MDS-MSC, the inducible rate of CD4+CD25+Foxp3+Tregs of low-risk MDS-MSC is lower. At last, we find that MDS-MSC derived TGF-β1 is largely responsible for the increase in CD4+CD25+Foxp3+Tregs based on knockdown studies. These results elucidate the different immunoregulatory role of MSC in low-risk and high-risk MDS, which may be important for understand the pathogenesis of MDS and the development of novel immunomodulatory strategies for the treatment of MDS.

Monoclonal B-cell lymphocytosis (MBL, CD4+/CD8 weak T-cell large granular lymphocytic leukemia (T-LGL leukemia) and monoclonal gammopathy of unknown significance (MGUS): molecular and flow cytometry characterization of three concomitant hematological disorders

The diagnosis of T-cell large granular lymphocytic leukemia in association with other B-cell disorders is uncommon but not unknown. However, the concomitant presence of three hematological diseases is extraordinarily rare. We report an 88-year-old male patient with three simultaneous clonal disorders, that is, CD4+/CD8(weak) T-cell large granular lymphocytic leukemia, monoclonal gammopathy of unknown significance and monoclonal B-cell lymphocytosis. The patient has only minimal complaints and has no anemia, neutropenia or thrombocytopenia. Lymphadenopathy and hepatosplenomegaly were not present. The three disorders were characterized by flow cytometry analysis, and the clonality of the T-cell large granular lymphocytic leukemia was confirmed by polymerase chain reaction. Interestingly, the patient has different B-cell clones, given that plasma cells of monoclonal gammopathy of unknown significance exhibited a kappa light-chain restriction population and, on the other hand, B-lymphocytes of monoclonal B-cell lymphocytosis exhibited a lambda light-chain restriction population. This finding does not support the antigen-driven hypothesis for the development of multi-compartment diseases, but suggests that T-cell large granular lymphocytic expansion might represent a direct antitumor immunological response to both B-cell and plasma-cell aberrant populations, as part of the immune surveillance against malignant neoplasms.

Spliceosomal gene aberrations are rare, coexist with oncogenic mutations, and are unlikely to exert a driver effect in childhood MDS and JMML

Somatic mutations of the spliceosomal machinery occur frequently in adult patients with myelodysplastic syndrome (MDS). We resequenced SF3B1, U2AF35, and SRSF2 in 371 children with MDS or juvenile myelomonocytic leukemia. We found missense mutations in 2 juvenile myelomonocytic leukemia cases and in 1 child with systemic mastocytosis with MDS. In 1 juvenile myelomonocytic leukemia patient, the SRSF2 mutation that initially coexisted with an oncogenic NRAS mutation was absent at relapse, whereas the NRAS mutation persisted and a second, concomitant NRAS mutation later emerged. The patient with systemic mastocytosis and MDS carried both mutated U2AF35 and KIT in a single clone as confirmed by clonal sequencing. In the adult MDS patients sequenced for control purposes, we detected previously reported mutations in 7/30 and a novel SRSF2 deletion (c.284_307del) in 3 of 30 patients. These findings implicate that spliceosome mutations are rare in pediatric MDS and juvenile myelomonocytic leukemia and are unlikely to operate as driver mutations.

Functional characterization of CD4+ T cells in aplastic anemia

The role of CD4+ T cells in the pathogenesis of aplastic anemia (AA) is not well characterized. We investigate CD4+ T-cell subsets in AA. Sixty-three patients with acquired AA were studied. Th1 and Th2 cells were significantly higher in AA patients than in healthy donors (HDs; P = .03 and P = .006). Tregs were significantly lower in patients with severe AA than in HDs (P < .001) and patients with non-severe AA (P = .01). Th17 cells were increased in severe AA (P = .02) but normal in non-severe AA. Activated and resting Tregs were reduced in AA (P = .004; P = .01), whereas cytokine-secreting non-Tregs were increased (P = .003). Tregs from AA patients were unable to suppress normal effector T cells. In contrast, AA effector T cells were suppressible by Tregs from HDs. Th1 clonality in AA, investigated by high-throughput sequencing, was greater than in HDs (P = .03). Our results confirm that Th1 and Th2 cells are expanded and Tregs are functionally abnormal in AA. The clonally restricted expansion of Th1 cells is most likely to be antigen-driven, and induces an inflammatory environment, that exacerbate the functional impairment of Tregs, which are reduced in number.

Cytomegalovirus-specific regulatory and effector T cells share TCR clonality--possible relation to repetitive CMV infections

Cytomegalovirus (CMV) infections have a major impact on morbidity and mortality of transplant patients. Among the complex antiviral T-cell response, CMV-IE-1 antigen-specific CD8+ cells are crucial for preventing CMV disease but do not protect from recurring/lasting CMV reactivation. Recently, we confirmed that adoptive transfer of autologous IE-1/pp65-specific T-cell lines was able to combat severe CMV disease; however, the control of CMV infection was only temporary. We hypothesized that CMV-induced regulatory T cells (iTreg) might be related to recurring/lasting CMV infection. In fact, kidney transplant patients with recurring CMV infections expressed enhanced suppression on CMV response. Analysis of in vitro expanded CD4+ epitope-specific cells revealed that CMV-specific CD4+CD25(high) Treg cells functionally suppress CD25(low) effector T cells (Teff) upon epitope-specific reactivation. Their phenotype is similar to iTreg - CD39(high) /Helios-/IL-2(low) /IFNγ(high) /IL-10±/TGFß-LAP±/FOXP3+ and methylated foxp3 locus. Remarkably, in vitro expanded CD4+CD25(high) iTreg share the same dominant TCR-Vβ-CDR3 clones with functionally distinct CD4+CD25(low) Teff. Moreover, the same clones were present in freshly isolated CD4+CD25(high) and CD4+CD25(low) T cells suggesting their in vivo generation. These findings directly demonstrate that Teff and iTreg can differentiate from one "mother" clone with specificity to the same viral epitope and indicate that peripheral iTreg generation is related to frequent antigen appearance.

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

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

Evolving insights in the pathogenesis and therapy of cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome)

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of malignancies derived from skin-homing T cells. The most common forms of CTCL are Mycosis Fungoides (MF) and Sezary Syndrome (SS). Accurate diagnosis remains a challenge due to the heterogeneity of presentation and the lack of highly characteristic immunophenotypical and genetic markers. Over the past decade molecular studies have improved our understanding of the biology of CTCL. The identification of gene expression differences between normal and malignant T-cells has led to promising new diagnostic and prognostic biomarkers that now need validation to be incorporated into clinical practice. These biomarkers may also provide insight into the mechanism of development of CTCL. Additionally, treatment options have expanded with the approval of new agents, such as histone deacetylase inhibitors. A better understanding of the cell biology, immunology and genetics underlying the development and progression of CTCL will allow the design of more rational treatment strategies for these malignancies. This review summarizes the clinical epidemiology, staging and natural history of MF and SS; discusses the immunopathogenesis of MF and the functional role of the malignant T-cells; and reviews the latest advances in MF and SS treatment.

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

T-cell large granular lymphocyte leukemia (T-LGLL) is characterized by chronic lymphoproliferation of cytotoxic T lymphocytes (CTLs) and is associated with lineage-restricted cytopenias. Introduction of T-cell receptor (TCR) variable β-chain (Vβ) monoclonal antibodies has facilitated identification and enumeration of clonal CTLs by flow cytometry. A highly skewed TCR Vβ repertoire identified by flow cytometry is strongly associated with monoclonal CDR3 regions by quantitative sequencing and positive TCRγ rearrangement assays. Therefore, Vβ expansions can serve as surrogate markers of CTL clonality to assess clonal kinetics in T-LGLL. We analyzed the TCR repertoire in 143 patients, 71 of which were available for serial measurements over 6 to 96 months. Although the majority (38/71, 54%) maintained a consistent monoclonal expansion, many (26/71, 37%) unexpectedly displayed a change in the dominant clone, whereby the original CTL clone contracted and another emerged as demonstrated by Vβ typing. Our results demonstrate that the T-cell repertoire is more dynamic in T-LGLL than recognized previously, illustrating the heterogeneity of disorders under this categorization.

Therapeutic implications of variable expression of CD52 on clonal cytotoxic T cells in CD8+ large granular lymphocyte leukemia

BACKGROUND

T-cell large granular lymphocytic leukemia is a clonal proliferation of cytotoxic T-lymphocytes which often results in severe cytopenia. Current treatment options favor chronic immunosuppression. Alemtuzumab, a humanized monoclonal antibody against glycophosphatidylinositol-anchored CD52, is approved for patients refractory to therapy in other lymphoid malignancies.

DESIGN AND METHODS

We retrospectively examined treatment outcomes in 59 patients with CD8+ T-cell large granular lymphocytic leukemia, 41 of whom required therapy. Eight patients with severe refractory cytopenia despite multiple treatment regimens had been treated with subcutaneous alemtuzumab as salvage therapy. Flow cytometry was used to monitor expression of glycophosphatidylinositol-anchored CD52, CD55, and CD59 as well as to characterize T-cell clonal expansions by T-cell receptor variable beta-chain (Vbeta) repertoire.

RESULTS

Analysis of the effects of alemtuzumab revealed remissions with restoration of platelets in one of one patient, red blood cell transfusion independence in three of five patients and improvement of neutropenia in one of three, resulting in an overall response rate of 50% (4/8 patients). Clonal large granular lymphocytes exhibited decreased CD52 expression post-therapy in patients refractory to treatment. Samples of large granular lymphocytes collected prior to therapy also unexpectedly had a significant proportion of CD52-negative cells while a healthy control population had no such CD52 deficiency (p=0.026).

CONCLUSIONS

While alemtuzumab may be highly effective in large granular lymphocytic leukemia, prospective serial monitoring for the presence of CD52-deficient clonal cytotoxic T-lymphocytes should be a component of clinical trials investigating the efficacy of this drug. CD52 deficiency may explain lack of response to alemtuzumab, and such therapy may confer a survival advantage to glycophosphatidylinositol-negative clonal cytotoxic T-lymphocytes.

T-cell and natural killer-cell large granular lymphocyte leukemia neoplasias

Large granular lymphocyte (LGL) leukemia is a rare disorder of cytotoxic lymphocytes. LGL cells play an integral role in the immune system and are divided into two major lineages of CD3(-)natural killer (NK) cells and CD3(+) T cells that circulate throughout the blood in search of infected cells, in which they will make contact through a receptor ligand and induce cell death. LGL cells are also programmed to undergo apoptosis after contact with an infected target cell; however, they continue to survive in individuals with LGL leukemia. This unchecked proliferation and cytotoxicity of LGLs in patients results in autoimmunity or malignancy. Rheumatoid arthritis is the most common autoimmune condition seen in individuals with LGL leukemia; however, LGL leukemia is associated with a wide spectrum of other autoimmune diseases. Patients may also suffer from other hematological conditions including hemolytic anemia, pure red cell aplasia, and neutropenia, which lead to recurrent bacterial infections. Currently, the only established treatment involves a low dose of an immunosuppressive regimen with methotrexate, in which 40-50% of patients are either resistant or do not respond. In order to establish new therapeutics it is important to understand the current state of LGL leukemia both in the clinic and in basic research.

The spectrum of large granular lymphocyte leukemia and Felty's syndrome

PURPOSE OF REVIEW

Patients with chronic large granular lymphocyte (LGL) leukemia often have rheumatoid arthritis (RA), neutropenia and splenomegaly, thereby resembling the manifestations observed in patients with Felty's syndrome, which is a rare complication of RA characterized by neutropenia and splenomegaly. Both entities have similar clinical and laboratory presentation, as well as a common genetic determinant, HLA-DR4, indicating they may be part of the same disease spectrum. This review paper seeks to discuss the underlying pathogenesis and therapeutic algorithm of RA, neutropenia and splenomegaly in the spectrum of LGL leukemia and Felty's syndrome.

RECENT FINDINGS

We hypothesize that there may be a common pathogenic mechanism between LGL leukemia and typical Felty's syndrome. Phenotypic and functional data have strongly suggested that CD3 LGL leukemia is antigen-activated. Aberrations in the T-cell repertoire with the emergence of oligoclonal/clonal lymphoid populations have been found to play a pivotal role in pathogenesis of RA. The biologic properties of the pivotal T cell involved in RA pathogenesis are remarkably similar to those in leukemic LGL.

SUMMARY

RA-associated T-cell LGL leukemia and articular manifestations of typical Felty's syndrome are not distinguishable. A common pathogenetic link between LGL leukemia and RA is proposed.

Single-cell analysis of T-cell receptor repertoire of HTLV-1 Tax-specific cytotoxic T cells in allogeneic transplant recipients with adult T-cell leukemia/lymphoma

Adult T-cell leukemia (ATL) is a lymphoproliferative malignancy associated with human T-cell lymphotropic virus type 1 (HTLV-1) infection. Recently, it has been shown that allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment for ATL, and that HTLV-1 Tax-specific CD8(+) cytotoxic T cells (CTL) contribute to the graft-versus-ATL effect. In the present study, we, for the first time, analyzed the T-cell receptor (TCR) repertoire of isolated Tax(301-309) (SFHSLHLLF)-specific CTLs in HLA-A*2402(+) ATL patients before and after allo-HSCT by single-cell reverse transcription-PCR. The Tax(301-309)-specific CTLs in bone marrow and peripheral blood showed highly restricted oligoclonal diversity. In addition, a unique conserved amino acid motif of "P-D/P-R" in TCR-beta complementarity-determining region 3 in either BV7- or BV18-expressing CTLs was observed not only in all of the samples from ATL patients, but also in samples from the same patient before and after HSCT. Furthermore, the P-D/P-R motif-bearing CTL clones established from peripheral blood samples after HSCT exhibited strong killing activity against the HTLV-1-infected T cells of the patient. CTL clones were not established in vitro from samples prior to allo-HSCT. In addition, CTL clones with a strong killing activity were enriched in vivo after HSCT in the patient. Hence, Tax(301-309)-specific CTLs in ATL patients might have a preference for TCR construction and induce strong immune responses against the HTLV-1-infected T cells of patients, which contribute to the graft-versus-ATL effects after allo-HSCT. However, further analyses with a larger number of patients and more frequent sampling after allo-HSCT is required to confirm these findings.

MICA polymorphism identified by whole genome array associated with NKG2D-mediated cytotoxicity in T-cell large granular lymphocyte leukemia

BACKGROUND

Large granular lymphocyte leukemia is a semi-autonomous clonal proliferation of cytotoxic T cells accompanied by immune cytopenias and various autoimmune conditions. Due to the rarity of this disease and its association with autoimmune diseases, a theoretical germline or somatic mutation might have significant penetrance, thus enabling detection, even from samples of suboptimal size, through genome-wide association studies.

DESIGN AND METHODS

To investigate a non-mendelian genetic predisposition to large granular lymphocyte leukemia, we used a step-wise method for gene discovery. First, a modified 'random forests' technique was used for candidate gene identification: this was followed by traditional allele-specific polymerase chain reaction, sequencing modalities, and mechanistic assays.

RESULTS

Our analysis found an association with MICA, a non-peptide-presenting, tightly regulated, stress-induced MHC-like molecule and cognate receptor for NKG2D, found abundantly on large granular lymphocyte leukemia cells. Sequencing of germline DNA revealed a higher frequency of MICA*00801/A5.1 in patients with large granular lymphocyte leukemia than in matched controls (64% versus 41%, P<0.001, homozygous 40% versus 15%, P<0.001). Flow cytometry was employed to determine the expression of MICA within hematologic compartments, showing that the signal intensity of MICA was increased in granulocytes from neutropenic patients with large granular lymphocyte leukemia in comparison with that in controls (P=0.033). Furthermore, neutrophil counts were inversely correlated with MICA expression (R(2)=0.50, P=0.035). Finally, large granular lymphocyte leukemia cells were able to selectively kill MICA(+) Ba/F3 lymphocytes transfected with human MICA*019 in a dose-dependent manner compared to naïve cells (P<0.001), an effect mitigated by administration of an anti-NKG2D antibody (P=0.033).

CONCLUSIONS

Our results illustrate that MICA-NKG2D played a role in disease pathogenesis in the majority of patients in our cohort of cases of large granular lymphocyte leukemia and further investigation into this signaling axis may provide potent therapeutic targets.