Outcome of T- Large Granular Lymphocyte Leukemia from a Tertiary Care Centre in North India

Retrospective Review of Patients with Large Granular Lymphocyte (LGL) Leukemia in a Single Institution over a Period of 11 Years

Literature Review of All Cases of Aggressive T-Cell Large Granular Lymphocytic Leukemia Cases and Report of an Additional Case

Large granular lymphocyte leukaemia (LGLL) is a rare lymphoproliferative disease with three recognised subgroups including T-cell large granular lymphocytic leukaemia (T-LGLL), chronic natural killer (NK) cell lymphocytosis, and NK cell leukaemia.1 Approximately 85% of LGLLs is T-LGLL, which is caused by persistence of increased large granular cells in the peripheral blood, bone marrow, spleen and liver resulting in cytopenia, autoimmune diseases and so on. T-LGLL is characterised by expansion of cytotoxic T cells expressing αβ T-cell receptor (TCR), CD2, surface CD3, CD8, CD57 as well as cytotoxic molecules. Signal transducer and activator of transcription 3 (STAT3) mutations have been identified in approximately one-third of T-LGLL cases.2 The 2016 World Health Organization (WHO) classification highlights the discovery of signal transducer and activator of STAT3 and STAT5b mutations.3 Treatment should not be initiated until the presence of treatment indications.4 Although cases of T-LGLL are usually CD8+ and express αβTCR, there are variants with atypical immunophenotypes including CD4+ TCRαβ+, CD8+ TCRγδ+ and CD4−CD8− TCRγδ+.5-9 Yabe et al.7 reported 14 TCRγδ+ T-LGLL patients with lower neutrophil and platelet counts and a higher frequency of the CD4−CD8− immunophenotype, compared to TCRαβ+ T-LGLL cases. And CD56, uncommonly detected on the cell surface of CD8+ T-LGLL cells, was uniformly expressed by the CD4+ T-LGLL cells.6 Additionally, patients with TCRγδ+ T-LGLL were more likely to develop rheumatoid arthritis (RA).7 Furthermore, there are differences between Asian patients with T-LGLL and Western patients with T-LGLL.10 Interestingly, there was a significantly higher incidence of pure red cell aplasia (PRCA) and a much lower incidence of RA in Asian patients with T-LGLL.11 Atypical immunophenotypes of T-LGLL are therefore worthy of further exploration. We retrospectively analysed immunophenotypes and clinicopathological features of 96 T-LGLL cases from 2009 to 2017 based on the 2008 WHO classification.12 Immunophenotyping, TCR Vβ repertoire of the T lymphocytes and genomic DNA testing were performed according to the previously reported method.13 A total of 96 patients with T-LGLL (49 males and 47 females) were identified, with a median age of 59 years. Table 1 shows the baseline characteristics. In all, 26 patients had PRCA and four had RA. The median large granular lymphocytes count was 2.94 × 109/l. Neutropenia, thrombocytopenia and anaemia were found in 51.0%, 16.7% and 55.2% respectively. Seven patients had STAT3 mutations, and none had STAT5b mutations. Chromosomal abnormalities occurred in 12 patients but without specific changes (data not shown). In all, 79 cases with typical immunophenotypes were CD8+CD4– TCRαβ+. In 17 cases with atypical immunophenotypes, eight cases were CD4+CD8– TCRαβ+ and nine cases were TCRγδ+. In TCRγδ+ cases, seven were both CD4 and CD8 negative, while the other two cases were CD4 negative and CD8 positive. The incidence of PRCA was significantly higher in patients with typical immunophenotypes than that with atypical immunophenotypes (p = 0.005). There were no important clinically differences between the two groups in other parameters. We then compared clinical features between TCRγδ+ T-LGLL and those with TCRαβ+ T-LGLL (Table S2). The incidence of PRCA (p = 0.108) and STAT3 mutation (p = 0.100) appeared lower in patients with TCRγδ+ T-LGLL, although there was no statistical significance. We also explored the distinction between CD4+ TCRαβ+ and CD4− TCRαβ+ cases and found no significant differences (Table S3). Overall survival (OS) of different immunophenotypic subgroups was similar in our study (Figure 1A, T-LGLL with typical immunophenotypes vs. T-LGLL with atypical immunophenotypes, p = 0.148; Figure 1B, TCRαβ+ T-LGLL vs. TCRγδ+ T-LGLL, p = 0.565; Figure 1C, CD4− TCRαβ+ T-LGLL vs. CD4+ TCRαβ+ T-LGLL, p = 0.160). The median OS in each group was not reached. There was also no significant difference in overall response rate (ORR) between immunophenotypic subgroups (T-LGLL with typical immunophenotypes vs. T-LGLL with atypical immunophenotypes, 70.2% vs. 88.9%, p = 0.425; TCRαβ+ T-LGLL vs. TCRγδ+ T-LGLL, 70.0% vs. 83.3%, p = 0.664; CD4− TCRαβ+ T-LGLL vs. CD4+ TCRαβ+ T-LGLL, 68.4% vs. 100%, p = 0.547). As shown in Figure 1D, individuals with an indication for T-LGLL treatment, 30 receiving first-line methotrexate (MTX) showed a comparable OS to those with first-line cyclosporine A (CsA; n = 17, p = 0.152) and a better OS than those with other regimens (n = 19, p = 0.008). The ORR to the first-line MTX and CsA was 90.0% and 76.5% respectively. There was no statistical difference between the two drug groups (p = 0.235). Patients with other regimens had an ORR of 42.1%, significantly lower than those who received MTX (p = 0.001) and CsA (p = 0.049). The frequency of TCRγδ+ LGLL (nine of 96 cases) in our cohort was similar to that in another study.8 It is important to differentiate TCRγδ+ T-LGLL from aggressive clinical process such as hepatosplenic T-cell lymphoma. However, only two patients with TCRγδ+ T-LGLL had mild splenomegaly and only one patient with TCRγδ+ T-LGLL presented with thrombocytopenia. Furthermore, none of the patients with TCRγδ+ T-LGLL had PRCA, indicating TCRαβ+ and TCRγδ+ T-LGLL may have different clinical manifestations. Patients with TCRγδ+ LGLL were reported to be more likely to have RA and thrombocytopenia, compared to TCR αβ+ LGLL cases.7, 8 Meanwhile, none of the patients with TCRγδ+ LGLL had RA and only one patient with TCRγδ+ LGLL had thrombocytopenia. The CD4+ phenotype has been reported in a minority of T-LGLL cases.5, 6 CD4+ T-LGLL needs to be differentiated from other CD4+ mature T-cell leukaemias. Consistent with previous studies,5, 6 cytopenia was infrequent in patients with CD4+ T-LGLL in our cohort. Additionally, autoimmune phenomena including RA and PRCA and additional malignancies were not observed in these eight patients. Gene expression analysis revealed that TCRγδ+ T-LGLL cells had abnormal apoptosis and proliferation.14 Interestingly, TCRγδ+ T-LGLL cases showed a restricted usage of Vγ and Vδ families with a similar pattern as normal TCRγδ+ T cells, indicating antigen stimulation might be involved in the pathogenesis of TCRγδ+ T-LGLL.8 Regarding CD4+ T-LGLL, STAT5B mutations were identified in about half of the cases, which may be responsible for the pathogenesis of CD4+ T-LGLL.15 Over one-third of the CD4+ T-LGLL cases expressed monoclonal TCR-Vbeta13.1.5, 9 Interestingly, the sequencing of TCR segments in these TCR-Vbeta13.1-restricted T cells indicated that the expansion of the CD4+ positive T cells may be driven by a common antigen. Additional efforts are needed to better understand the pathogenesis of rare, atypical immunophenotypes T-LGLL cases. Pearson chi-squared test and Fisher’s exact test were used as appropriate. The OS was defined as time from the diagnosis until death or last follow-up. The Kaplan–Meier method was used for plotting survival curves and the log-rank test was used for comparison. GraphPad Prism 6 (GraphPad Software, San Diego, CA, USA), as well as the Statistical Package for the Social Sciences (SPSS, version 19.0) (IBM Corp., Armonk, NY, USA ), were used for data analysis. A p < 0.05 was defined as statistically significant. We thank all members for their efforts and enthusiasm. The authors declare that they have no conflict of interest. This study was partly supported by the National Natural Science Foundation of China (81720108002, 82100211), Jiangsu Provincial Special Program of Medical Science (BE2017751), CSCO Research Foundation(Y-Roche2019/2–0090), Translational Research Grant of NCRCH (Grant no. 2020ZKZB01) and Science and Technology Development Fund Project of Pukou branch of Jiangsu People’s Hospital (no. KJ2021-4). Jing-jing Guo and Lei Cao analysed and interpreted the patients’ data regarding the T-LGLL disease. Hua-yuan Zhu, Yi Miao, Xin-yi Du, Li Wang and Wei Xu participated in the treatment of these patients and collection of clinical information. Jian-yong Li and Lei Fan designed and guided the research. Ethics approval and consent to participate. Appropriate T-LGLL consents were obtained from all donors prior to specimen collection in accordance with the Declaration of Helsinki and approved by the ethics committees of the First Affiliated Hospital of Nanjing Medical University. All co-authors have seen the manuscript and approved to submit to your journal for publication. The authors uploaded the supplementary tables for details. Appendix S1. Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

T-cell large granular lymphocytic (T-LGL) leukemia is a rare lymphoproliferative disease which usually affects elderly people. The clinical course of T-LGL leukemia is generally indolent, with lymphocytosis and splenomegaly in 20-50% patients, hepatomegaly in 5-20% of patients, and less commonly, lymphadenopathy. T-LGL leukemia is associated with immunological abnormalities: rheumatoid factor with or without rheumatoid arthritis (RA), Coombs positive hemolytic anemia, idiopathic thrombocytopenic purpura (ITP), pure red cell aplasia (PRCA), positive anti-nuclear antibodies (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), hypogammaglobulinemia, and polyclonal hypergammaglobulinemia. Aim To compare clinical and laboratory features of T-LGL leukemia patients and their responses to different chemotherapy regimens. Six patients (3 males and 3 females) with T-LGL leukemia were analyzed. The diagnosis was based on accepted morphologic criteria, immunophenotype, and polymerase chain reaction (PCR) detection of T-cell receptor (TCR) gene rearrangements. All patients exhibited lymphocytosis, mainly with unusual morphologies, splenomegaly, and elevated serum lactate dehydrogenase (LDH). Three patients were treated with a Fludarabine-Cyclophosphamide (FC) combination as initial therapy while three patients received CHOP. Two patients received more than one treatment regimen. One patient died due to T-LGL leukemia in first year after diagnosis, one patient died 4 years after diagnosis, two patients interrupted their treatment, and two patients are still alive. Further prospective studies are needed for establishing a gold standard therapy for T-LGL leukemia.

A Population-Based Study of Large Granular Lymphocyte Leukemia: Analysis of 978 Patients Using the SEER and NCDB Databases

The activation of signal transducer and activator of transcription (STAT) family genes, especially STAT5 and STAT3, has been established in multiple solid tumors and hematological malignancies. Recently we discovered somatic activating STAT3 mutations in 40% of T-cell large granular lymphocytic (LGL) leukemia and 30% of NK-cell LGL leukemia patients (Koskela, Eldfors et al. NEJM, 2012, 17;366(20):1905-13 and Jerez et al. Blood, 2012, 120(15):3048-57). Interestingly, our current findings indicate that also activating STAT5b mutations can be found in LGL leukemia patients (Rajala et al. Blood Apr 17, 2013). LGL leukemia is incurable disease, characterized by chronic expansion of cytotoxic T or NK cells, and it often manifests with other hematological and autoimmune disorders such as rheumatoid arthritis. Autoimmune mediated cytopenias such as neutropenia are common and can be life-threatening due to increased infection-susceptibility. Leukemic T-LGLs have a phenotype of terminally differentiated effector-memory cells and, accordingly, the role of viral antigens or autoantigens as potential drivers of the clonal expansion has been speculated. However, in leukemic LGL cells the normal activation-induced cell death (AICD) is impaired, and several cell-survival signaling pathways such as JAK-STAT, MAPK/ERK/Ras, PI3K-AKT, and NfκB are activated. Common immunosuppressive agents such as prednisone and methotrexate are current first-line treatments, and no targeted therapies exist. By means of whole exome sequencing we identified a STAT5b mutation Y665F in two STAT3 mutation-negative LGL leukemia patients, and in the following screening of a large patient cohort (n>200) another STAT5b mutation N642H in two additional patients. Both these mutations are located in the src-like homologue 2 (SH2) domain of STAT5b. No mutations were found in STAT5a, which shares over 90% of similarity with STAT5b in cDNA level. SH2 domain plays a crucial role in STAT5b activation and facilitates the dimerization of phosphorylated STAT5b monomers and their subsequent translocation to the nucleus where they activate the transcription of downstream target genes by binding to consensus DNA motifs. STAT5 is important in normal lymphocyte development, and in a mice model STAT5a/b double-deficiencyleads to perinatal death and severely impaired development of lymphoid tissue. In humans, homozygous germline STAT5b mutations are linked with disturbed T and NK cell homeostasis in addition to postnatal growth failure due to growth hormone-insensitivity. STAT5 is constitutively activated in many human malignancies such as in breast and prostate cancer, glioblastoma, acute myeloid leukemia (AML), myeloproliferative disorders and chronic myeloid leukemia (CML). In these conditions STAT5 activation is hypothesized to be a secondary event caused either by overly active upstream pathway or defective dephosphorylation and inactivation of STAT5 (Figure ​(Figure1).1). For example in CML, the STAT5 activation is induced by oncogenic BCR-ABL1 fusion protein, and the silencing of STAT5 in BCR-ABL1 expressing cells triggers apoptosis. Figure 1 Different mechanisms of STAT5 activation in cancer Our results in LGL leukemia patients demonstrate a novel mechanism of STAT5 activation in cancer: somatic point mutations (Figure ​(Figure1).1). Based on the three-dimensional model of STAT5, we speculate that the mutations located in the SH2 domain stabilize the dimer structure, thus inclining the balance of STAT5 activation-deactivation toward the constitutively active dimer form. In concordance with this theory, our results showed that the STAT5b mutations Y665F and N642H increased the phosphorylation and transcriptional activity of STAT5. Furthermore, in an earlier in vitro study in which the mutation STAT5b N642H was discovered by random mutagenesis, it caused cytokine-independent growth of mouse Ba-F3 cells and hyperphosphorylation of STAT5 after IL-3 stimulation. Similarly in LGL leukemia, we discovered increased phosphorylation of STAT5b, but it was only observed in the patients with the STAT5b mutations. This differs from STAT3 phosphorylation, which is universally seen in leukemic LGLs. However, there are intriguing connections between STAT3 and STAT5 downstream pathways. Recent publication presenting ChIP-seq data from T-cells showed that 90% of STAT5 binding sites are co-occupied with STAT3. This is in accordance with our results demonstrating that LGL leukemia patients with STAT3 and STAT5b mutations share similar gene expression patterns. Although LGL leukemia is not always life-threatening, a majority of patients need treatment due to cytopenias or autoimmune manifestations. Importantly, the two patients who had somatic STAT5b N642H mutations suffered from a rare, rapidly-progressing chemorefractory form of LGL leukemia. They were the only ones with the aggressive type of the disease in the patient cohort screened (n>200). Thus, it is likely that this mutation is a driver mutation in this type of aggressive LGL leukemia and it is tempting to speculate that targeted STAT5 inhibition may have clear therapeutic potential. Currently, specific STAT5 inhibitors are not in clinical use, but they are under development. One non-specific STAT5b inhibitor, pimozide, has been shown to induce apoptosis through BCR-ABL1-independent STAT5 inhibition in CML cells and also in FLT3-mutated AML model. Other promising therapeutic agents include small-molecule inhibitors, which bind directly to the STAT5 SH2 domain and prevent phosphorylation and dimerization required for STAT5 activation. In a previous study, which tested a series of chromone-derived acylhydrazone compounds, STAT5 inhibition was demonstrated in Daudi-cells, and in another study similar effects were seen with SH2 domain-binding salicylic acid-containing inhibitors. Our discovery of STAT5b and STAT3 mutations suggests novel therapeutic targets for LGL leukemia. Recently similar STAT3 mutations have been discovered in a proportion of CD30+ T-cell lymphoma patients and in inflammatory hepatocellular adenomas, but so far STAT5b mutations have only been found in LGL leukemia patients. However, as STAT5 activation is an important secondary event in many cancers, the targeted STAT5 inhibition may have a clear therapeutic potential in the future.

An 85-year-old African American woman was referred to the hematology-oncology clinic for evaluation of lymphocytosis in August 2000. Her past medical history was significant for rheumatoid arthritis that had caused chronic pain for years. Lymphocytosis (lymphocyte count, 5312/μL) had been present for 4 months. She had noted fatigue since then without other symptoms. At that time, physical examination showed no evidence of lymphadenopathy. Radiographs and a computed tomography scan of the abdomen and pelvis did not show retroperitoneal or mediastinal lymphadenopathy or splenomegaly. Mild normocytic normochromic anemia was noted (hematocrit, 36%; hemoglobin concentration, 11.3 g/dL). There was no evidence of neutropenia (neutrophil count, 2407/μL). A presumptive diagnosis of chronic lymphocytic leukemia was made clinically. In May 2001, another complete blood count showed a white blood cell count of 7800/μL with 71% lymphocytes (absolute number, 5538/μL).In November 2001, test results indicated that the lymphocytosis had progressed; the lymphocyte count was 13 350/μL (89% white blood cells), and mild neutropenia was present (neutrophil count, 1500/μL). A review of the peripheral blood smear revealed that the majority of lymphocytes had atypical morphology with large atypical nuclei and abundant cytoplasm containing fine azurophilic granules (Figure 1). A flow cytometry study showed that 92% of the lymphocytes expressed CD2, CD3, and CD5, and most (85%) expressed CD4. The majority of these cells also expressed CD56 and CD57 but not CD7, CD16, or CD26. The representative histograms are shown in Figures 2 through 4.What is your diagnosis?In the current World Health Organization classification for lymphoid tumors, T-cell large granular lymphocyte leukemia (T-LGL) is defined as a heterogeneous disorder characterized by a persistent (>6-month) elevation of the number of peripheral blood large granular lymphocytes, usually to a value between 2000 and 20 000/μL (reference range, 223 ± 99/μL), without a clearly identified cause.1 The number of large granular lymphocytes required for diagnosis remains controversial; however, a value of greater than 5000/μL is considered to be diagnostic, and a value of greater than 2000/μL is considered to be consistent with the diagnosis.2 Clinically, the disease occurs in adults with a median age of 55 years and has an equal male-to-female distribution. Neutropenia with or without anemia is a frequent disease feature. Recurrent infections due to neutropenia are the main reason for medical attention. Some patients present with moderate splenomegaly, yet lymphadenopathy is very rare. About 40% of cases are asymptomatic at presentation. Of particular interest, as seen in our patient, is the co-occurrence of rheumatoid arthritis in patients with T-LGL (with rheumatoid arthritis usually occurring first).3Morphologically, the circulating neoplastic lymphocytes are characterized by abundant cytoplasm with fine or coarse azurophilic granules. The granules in the lymphocytes often exhibit a characteristic ultrastructural appearance described as parallel tubular arrays.4 In addition, they contain a number of proteins that play a role in cytolysis, such as perforin and granzyme B. T-LGL may involve bone marrow, spleen, and liver. Bone marrow involvement is typically interstitial and rarely shows a nodular pattern. Usually, the extent of involvement is less than 50% of the marrow cellularity. Characteristic findings in splenic involvement include infiltration of the lymphocytic red pulp cords and frequent reactive germinal follicles. Touch imprints of splenic tissue are important for showing the presence of large granular lymphocyte morphology. Plasmacytosis of the splenic red pulp is frequently observed.5 Liver involvement is characterized by a lymphocytic infiltration of hepatic sinusoids with portal area involvement in extensive disease.The neoplastic lymphocytes in T-LGL have a mature T-cell immunophenotype. In the most common variant, 80% of cases, the cells express CD3 and CD8 but do not express CD4.6 Other rare variants include (1) CD3+, CD4+, and CD8−, (2) CD3+, CD4+, and CD8+, and (3) CD3+, CD4−, and CD8−. The cells are usually TIA-1 positive, whereas they variably express CD56 and CD57. In the common type of T-LGL, the cells often express CD57.On the genetic level, by definition, T-LGL is clonal, which is documented by T-cell receptor (TCR) gene rearrangement studies.7 Most cases have TCRβ chain gene rearrangement, whereas the minority show a TCRγ chain gene rearrangement. The gene rearrangement study is particularly useful in patients with a large granular lymphocyte count of 2000/μL or less, since demonstration of an expansion of a restricted clonal large granular lymphocyte subset has been suggested to be evidence for the diagnosis.2 There is no unique karyotypic abnormality in T-LGL, but chromosomal translocations have been described in a minority of cases.8In the current case, the morphology and the immunophenotypic pattern of circulating neoplastic lymphocytes were consistent with those of T-LGL (one of the rare variants: CD3+ and CD4+ but CD8−). Deletion of CD7 and CD26 in these lymphocytes further supports their neoplastic nature. The clinical picture of a progressive increase in the number of large granular lymphocytes, from 5312 to 13 350/μL over 15 months, with development of neutropenia confirms the diagnosis of T-LGL. The main differential diagnoses for our case included aggressive natural killer (NK)-large granular lymphocyte leukemia (NK-LGL) and reactive large granular lymphocyte lymphocytosis. NK-LGL has morphologic features very similar to those of T-LGL but is surface CD3− and usually CD16+. Clinically, NK-LGL usually has an acute clinical course, with a rapid increase in large granular lymphocyte counts over a few weeks. Anemia, thrombocytopenia, and massive hepatosplenomegaly are more common and pronounced in NK-LGL than in T-LGL. Patients with reactive large granular lymphocyte lymphocytosis have increased numbers of large granular lymphocytes with the immunophenotype of NK cells (surface CD3−). This disease has a chronic and indolent clinical course in contrast to NK-LGL.X-linked gene analysis has supported a polyclonal NK-cell proliferation in patients with T-LGL.9 The vast majority of cases that were thought to be reactive large granular lymphocyte lymphocytosis of T-cell origin in the old literature are indeed T-LGL since almost all cases, even those with large granular lymphocyte counts of 2000/μL, or less, show clonal TCR gene rearrangement by molecular methods.210T-LGL typically has an indolent course. Morbidity is associated with the neutropenia, but mortality is uncommon. Usually, no treatment is required; however, patients who require treatment may benefit from cyclosporin A and methotrexate. Infrequently, splenectomy is performed in patients with splenomegaly, but this does not reduce the cytopenia.

Somatic PTPRT and ANGPT2 Mutations in Large Granulocyte Leukemia

Recurrent Missense Mutations in the STAT3 Gene in LGL Leukemia Provide Insights to Pathogenetic Mechanisms and Suggest Potential Diagnostic and Therapeutic Applications

Ruxolitinib for refractory large granular lymphocyte leukemia.

T-cell large granular lymphocytic (T-LGL) leukemia is a rare lymphoproliferative disorder, characterized by peripheral blood and bone marrow infiltration with large granular lymphocytes (LGL), splenomegaly, cytopenias, and a frequent association with autoimmune diseases. Recurrent bacterial infections due to neutropenia are the main reason why patients come to medical attention. Despite not being a curable disease, T-LGL leukemia usually has an indolent course, with deaths mainly resulting from severe infections. Treatment is often not required, however, when needed, aims to relieve symptoms, and reduce infections and transfusion needs.We describe a case of an 86-year-old female patient with febrile neutropenia, diagnosed with T-LGL leukemia after the resolution of infection and exclusion of other causes of neutropenia. A “watch and wait” approach was established after a multidisciplinary discussion.This case shows a frequent presentation of a rare disease, as well as the approach from diagnosis to treatment, reminding clinicians that T-LGL leukemia should be considered in the differential diagnosis of adults with febrile neutropenia.

Large Granular Lymphocytic Leukemia with Coexisting Malignancies

Epidemiological Insights into Large Granular Lymphocyte Leukemia: A Nationwide SEER Database Study

T-cell large granular lymphocyte (T-LGL) leukemia is a clonal proliferation of cytotoxic T cells, characterized by peripheral blood and marrow lymphocytic infiltration with LGL. Common clinical manifestations are splenomegaly, cytopenias (neutropenia) , anemia, and thrombocytopenia. This condition is often associated with autoimmune disorders and other lymphoproliferative disorders. T-LGL leukemia has been rarely reported in children. We report a child with T-LGL leukemia who presented with neutropenia and went on to develop juvenile systemic lupus erythematosus

Synergistic Role of Leukemic and Non-Leukemic Immune Repertoires in CD8+ T-Cell Large Granular Lymphocytic Leukemia As Identified By Single-Cell Transcriptomics