Detection of Mature T-Cell Leukemias by Flow Cytometry Using Anti–T-Cell Receptor VβAntibodies

Morphology and multiparameter flow cytometry combined for integrated lymphoma diagnosis on small volume samples: possibilities and limitations

The diagnosis of lymphoma relies mainly on clinical examination and laboratory explorations. Among the latter, morphological and immunohistochemical analysis of a tissue biopsy are the cornerstones for proper identification and classification of the disease. In lymphoma with blood and/or bone marrow involvement, multiparameter flow cytometry is useful. This technique can also be applied to fresh cells released from a biopsy sample. For full comprehension of lymphomas, surgical biopsies are best and indeed recommended by the hematopathological community. Currently, however, there is a global trend towards less invasive procedures, resulting in smaller samples such as core needle biopsies or fine needle aspirations which can make the diagnosis quite challenging. In this review, the possibilities and limitations to make an accurate lymphoma diagnosis on such small volume material are presented. After recalling the major steps of lymphoma diagnosis, the respective value of histology, cytology, and flow cytometry is discussed, including handling of small specimens. The benefits of an integrated approach are then evoked, followed by discussion about which attitude to adopt in different contexts. Perhaps contrary to the prevailing view among many pathologists, a full diagnosis on small volume material, combined with relevant ancillary techniques, is often possible and indeed supported by recent literature. A glimpse at future evolutions, notably the merit of artificial intelligence tools, is finally provided. All in all, this document aims at providing pathologists with an overview of diagnostic possibilities in lymphoma patients when confronted with small volume material such as core needle biopsies or fine needle aspirations.

How I Diagnose Mature T-Cell Proliferations by Flow Cytometry

OBJECTIVES

Mature T-cell neoplasms are a challenging area of diagnostic hematopathology. Flow cytometry has emerged as a useful technique for T-cell assessment.

METHODS

We discuss the application of flow cytometry to the evaluation of mature T-cell proliferations, to include illustrative cases, theoretical framework, detailed review of normal and reactive T-cell subsets, and examination of diagnostic pitfalls.

RESULTS

Immunophenotypic aberrancy can be construed as a direct expression of the neoplastic phenotype, in contrast to clonal expansion, which is seen in reactive and neoplastic T-cell proliferations. Major and minor T-cell subsets show characteristic patterns of antigen expression. Reactive states can manifest expansions of normal minor subsets and also show alterations of antigen expression on certain populations. However, some patterns of antigen expression are either never or very rarely encountered in reactive T cells. Flow cytometric tools are now available to directly assess clonality in specific T-cell populations. Technical and biological pitfalls may complicate the interpretation of T-cell flow cytometry.

CONCLUSIONS

Flow cytometry is a very useful tool in the diagnostic armamentarium for the assessment of mature T-cell proliferations, but it must be interpreted based on a thorough knowledge of the T-cell immune response, as well as an awareness of clinical context.

Anti-TRBC1 Antibody-Based Flow Cytometric Detection of T-Cell Clonality: Standardization of Sample Preparation and Diagnostic Implementation

A single antibody (anti-TRBC1; JOVI-1 antibody clone) against one of the two mutually exclusive T-cell receptor β-chain constant domains was identified as a potentially useful flow-cytometry (FCM) marker to assess Tαβ-cell clonality. We optimized the TRBC1-FCM approach for detecting clonal Tαβ-cells and validated the method in 211 normal, reactive and pathological samples. TRBC1 labeling significantly improved in the presence of CD3. Purified TRBC1⁺ and TRBC1^- monoclonal and polyclonal Tαβ-cells rearranged TRBJ1 in 44/47 (94%) and TRBJ1+TRBJ2 in 48 of 48 (100%) populations, respectively, which confirmed the high specificity of this assay. Additionally, TRBC1⁺/TRBC1^- ratios within different Tαβ-cell subsets are provided as reference for polyclonal cells, among which a bimodal pattern of TRBC1-expression profile was found for all TCRVβ families, whereas highly-variable TRBC1⁺/TRBC1^- ratios were observed in more mature vs. naïve Tαβ-cell subsets (vs. total T-cells). In 112/117 (96%) samples containing clonal Tαβ-cells in which the approach was validated, monotypic expression of TRBC1 was confirmed. Dilutional experiments showed a level of detection for detecting clonal Tαβ-cells of ≤10^-4 in seven out of eight pathological samples. These results support implementation of the optimized TRBC1-FCM approach as a fast, specific and accurate method for assessing T-cell clonality in diagnostic-FCM panels, and for minimal (residual) disease detection in mature Tαβ⁺ leukemia/lymphoma patients.

Utility of a Simple and Robust Flow Cytometry Assay for Rapid Clonality Testing in Mature Peripheral T-Cell Lymphomas

OBJECTIVES

Flow cytometry immunophenotyping is limited by poor resolution of T-cell clones. A newly described antibody was recently used to distinguish normal peripheral blood T cells from malignant T-cell clones. Here, we evaluate this antibody as a new diagnostic tool for detecting T-cell clonality in mature peripheral T-cell lymphomas.

METHODS

Immunostaining for the T-cell receptor β chain constant region 1 (TRBC1) along with routine T-cell markers was performed on 51 peripheral blood and two bone marrow samples submitted to the flow cytometry laboratory for suspected T-cell malignancy.

RESULTS

TRBC immunophenotyping identified malignant T-cell clones with 97% sensitivity and 91% specificity. Findings correlated with molecular T-cell clonality testing. In cases with equivocal molecular results, TRBC1 immunophenotyping provided additional diagnostic information.

CONCLUSIONS

TRBC1 flow cytometric immunophenotyping is a robust and inexpensive method for identifying T-cell clonality that could easily be incorporated into routine flow cytometric practice.

Diagnosis of chronic lymphoproliferative disorders by flow cytometry using four-color combinations for immunophenotyping: A proposal of the brazilian group of flow cytometry (GBCFLUX)

BACKGROUND

Multiparametric flow cytometry (MFC) is a powerful tool for the diagnosis of hematological malignancies and has been useful for the classification of chronic lymphoproliferative disorders (CLPD) according to the WHO criteria. Following the purposes of the Brazilian Group of Flow Cytometry (GBCFLUX), the aim of this report was to standardize the minimum requirements to achieve an accurate diagnosis in CLPDs, considering the different economic possibilities of the laboratories in our country. Most laboratories in Brazil work with 4-fluorescence flow cytometers, which is why the GBCFLUX CLPD Committee has proposed 4-color monoclonal antibody (MoAb) panels.

METHODS/RESULTS

Panels for screening and diagnosis in B, T and NK lymphoproliferative disorders were developed based on the normal differentiation pathways of these cells and the most frequent phenotypic aberrations. Important markers for prognosis and for minimal residual disease (MRD) evaluation were also included. The MoAb panels presented here were designed based on the diagnostic expertise of the participating laboratories and an extensive literature review.

CONCLUSION

The 4-color panels presented to aid in the diagnosis of lymphoproliferative neoplasms by GBCFLUX aim to provide clinical laboratories with a systematic, step-wise, cost-effective, and reproducible approach to obtain an accurate immunophenotypic diagnosis of the most frequent of these disorders. © 2016 International Clinical Cytometry Society.

Clinical Experience With Modified, Single-Tube T-Cell Receptor Vβ Flow Cytometry Analysis for T-Cell Clonality

OBJECTIVES

Analysis of T-cell clonality using the IO Test Beta Mark (Beckman Coulter, Fullerton, CA) flow cytometry assay is cumbersome owing to the required eight-part analyses that limit its clinical utility. Here, we describe a simple modification that may improve its clinical utility.

METHODS

By simply combining all T-cell receptor (TCR) Vβ antibodies into one reagent tube, we show that T-cell repertoire analysis can be efficiently performed with an increased potential to closely link the aberrant immunophenotype of a neoplastic T-cell clone to its apparent clonal TCR Vβ restriction. We review our clinical experience and include flow cytometry sorting studies in conjunction with TRG gene rearrangement analysis to demonstrate the feasibility of this approach.

RESULTS

We show in representative cases that this modified approach permits evaluation of TCR Vβ clonality in T-cell neoplasms without a priori knowledge of the TCR Vβ isoform restriction and that this approach is suitable for samples containing a minor population of neoplastic T cells, hypocellular samples such as skin biopsy specimens and body fluids, and fine-needle aspirations. We estimate a false-positive rate for identifying a clonal population for this approach to be less than 6.2%.

CONCLUSIONS

Our modified approach of TCR Vβ analysis could improve routine clinical evaluation for abnormal T-cell populations by flow cytometry.

Clonality assessment of cutaneous B-cell lymphoid proliferations: a comparison of flow cytometry immunophenotyping, molecular studies, and immunohistochemistry/in situ hybridization and review of the literature

Cutaneous lymphoid infiltrates are diagnostically challenging. Although ancillary techniques to assess clonality can help distinguish between reactive lymphoid hyperplasia and lymphoma, one of the most widely used techniques in hematopathology, flow cytometry immunophenotyping (FCI), has not been routinely applied to skin specimens. We performed FCI on 73 skin specimens from 67 patients clinically suspected of having a cutaneous B-cell lymphoma (CBCL) and compared the results with those obtained from immunoglobulin heavy chain (IGH) gene molecular studies (58 cases, primarily by polymerase chain reaction) and either immunohistochemistry (IHC) or in situ hybridization to evaluate for light chain restriction (22 and 2 cases, respectively). Sufficient quantity of CD45 (leukocyte common antigen)-positive cells and staining quality were achieved in 88% of cases by FCI, and clonality was detected in 68% of CBCLs versus molecular studies showing sufficient DNA quality in 74% and only 39% clonality detection, and interpretable/contributory IHC results in 84% of cases with 55% clonality detection. Clonality was documented more frequently in secondary rather than primary CBCLs by all 3 techniques. Therefore, FCI is feasible and appears to be more reliable than molecular studies or IHC/in situ hybridization for detecting clonality in CBCLs and can provide additional prognostically and therapeutically relevant information. The exception is cases with plasmacytic differentiation such as marginal zone lymphoma for which IHC might be a superior tool. We have also shown that a large subset of primary cutaneous follicle center lymphomas express CD10 and/or BCL2 by FCI. Recent advances in FCI beg the question of applicability to cutaneous T-cell and NK-cell lymphomas.

Broad T-cell receptor repertoire in T-lymphocytes derived from human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) have enormous potential for the treatment of inherited and acquired disorders. Recently, antigen-specific T lymphocytes derived from hiPSCs have been reported. However, T lymphocyte populations with broad T cell receptor (TCR) diversity have not been generated. We report that hiPSCs derived from skin biopsy are capable of producing T lymphocyte populations with a broad TCR repertoire. In vitro T cell differentiation follows a similar developmental program as observed in vivo, indicated by sequential expression of CD7, intracellular CD3 and surface CD3. The γδ TCR locus is rearranged first and is followed by rearrangement of the αβ locus. Both γδ and αβ T cells display a diverse TCR repertoire. Upon activation, the cells express CD25, CD69, cytokines (TNF-α, IFN-γ, IL-2) and cytolytic proteins (Perforin and Granzyme-B). These results suggest that most, if not all, mechanisms required to generate functional T cells with a broad TCR repertoire are intact in our in vitro differentiation protocol. These data provide a foundation for production of patient-specific T cells for the treatment of acquired or inherited immune disorders and for cancer immunotherapy.

Cytopathology in the diagnosis of lymphoma

FNA is a simple, safe, and an inexpensive sampling technique that plays an important role in the evaluation of lymphadenopathy. The key to enhancing the accuracy of FNA diagnosis of lymphoma is the multi parameter approach in which the cytomorphologic features are evaluated in correlation with the results of ancillary studies and clinical context. A full understanding of the current lymphoma classification, clinical features associated with each lymphoma subtype and the impact of the diagnosis on patient management is essential in FNA diagnosis of lymphoma. It is also important to recognize the limitations of FNA in the primary diagnosis of some subtypes of lymphoma, and tissue biopsy should be recommended for a definitive diagnosis and subclassification in such cases.

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.

Flow cytometry for non-Hodgkin and classical Hodgkin lymphoma

Multiparametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes a general approach for the identification of abnormal lymphoid populations by flow cytometry, including B, T, and Hodgkin lymphoma cells suitable for the clinical and research environment. Knowledge of the common patterns of antigen expression of normal lymphoid cells is critical to permit identification of abnormal populations at disease presentation and for minimal residual disease assessment. We highlight an overview of procedures for processing and immunophenotyping non-Hodgkin B- and T-cell lymphomas and also describe our strategy for the sensitive and specific diagnosis of classical Hodgkin lymphoma.

Extracorporeal photopheresis as a curative treatment strategy in non epidermotropic T-cell lymphoma and large granular lymphocyte leukemia

BACKGROUND

To evaluate the efficacy of extracorporeal photopheresis (ECP) in noncutaneous T-cell lymphoma and large granular lymphocytes leukemia (LGL).

PATIENTS AND METHODS

We have treated 12 refractory/relapsed patients. Six peripheral T-cell lymphoma (PTCL), one T-lymphoblastic lymphoma and five LGL with blood involvement received six biweekly leukapheresis as induction phase, followed by one course a week for 4 weeks as consolidation and one course of maintenance per month for responders until progression/relapse or disappearance of the peripheral clone.

RESULTS

Six patients responded to phototherapy. Two PTCL and two LGL achieved a complete response (CR) and two other PTCL a partial response. The median duration of CR was 117 months (45-150 months) for these four patients. The peripheral clone followed by flow cytometry decreased in all six responders. Two patients with a complete disappearance of the peripheral clone have not relapsed.

CONCLUSIONS

As for cutaneous T-cell lymphoma, ECP therefore to be efficient for PTCL and LGL. Early decrease and disappearance of the peripheral clone were the indicators of clinical response and nonrelapse, respectively.

Flow cytometry increases the sensitivity of detection of leukemia and lymphoma cells in bronchoalveolar lavage specimens

BACKGROUND

Recent studies have definitively determined that flow cytometry (FC) is significantly more sensitive than cytomorphology (CM) in detection of hematolymphoid neoplasms (HLNs). However, its utility in paucicellular bronchoalveolar lavage (BAL) specimens has not been established.

METHODS

FC was performed on BAL specimens submitted from 44 patients with a prior diagnosis of HLN. Panels chosen were based upon cellularity of specimen and patient history. FC results were compared with concurrent CM evaluations.

RESULTS

All 44 BALs were deemed satisfactory for FC and yielded informative results that assisted in diagnosis. Diagnoses included 22/44 B-cell neoplasms, 16/44 T-cell neoplasms, four/44 myeloid neoplasms, and two/44 plasma cell neoplasms. Overall concordance was demonstrated between FC and CM in 77% (34/44) of cases. In nine/44 cases (20%), one technique (FC or CM) clearly detected malignant cells when the other did not. FC was more sensitive than CM in detecting a HLN in eight/nine discordant cases. In only one case (one/44, 2%) were malignant HLN cells suspected by CM, but not identified by FC (one/44, 2%).

CONCLUSION

We demonstrate, in the largest series published to date, that FC can be performed on BAL specimens. FC is indicated in evaluation of BAL for HLN and improves sensitivity of detection of HLN over CM alone. An integrated FC and CM approach is superior to either technique alone in diagnostic evaluation of BAL.

Accurate detection of the tumor clone in peripheral T-cell lymphoma biopsies by flow cytometric analysis of TCR-Vβ repertoire

Multiparametric flow cytometry has proven to be a powerful method for detection and immunophenotypic characterization of clonal subsets, particularly in lymphoproliferative disorders of the B-cell lineage. Although in theory promising, this approach has not been comparably fulfilled in mature T-cell malignancies. Specifically, the T-cell receptor-Vβ repertoire analysis in blood can provide strong evidence of clonality, particularly when a single expanded Vß family is detected. The purpose of this study was to determine the relevance of this approach when applied to biopsies, at the site of tumor involvement. To this end, 30 peripheral T-cell lymphoma and 94 control biopsies were prospectively studied. Vβ expansions were commonly detected within CD4+ or CD8+ T cells (97% of peripheral T-cell lymphoma and 54% of non-peripheral T-cell lymphoma cases); thus, not differentiating malignant from reactive processes. Interestingly, we demonstrated that using a standardized evaluation, the detection of a high Vβ expansion was closely associated with diagnosis of peripheral T-cell lymphoma, with remarkable specificity (98%) and sensitivity (90%). This approach also identified eight cases of peripheral T-cell lymphoma that were not detectable by other forms of immunophenotyping. Moreover, focusing Vβ expression analysis to T-cell subsets with aberrant immunophenotypes, we demonstrated that the T-cell clone might be heterogeneous with regard to surface CD7 or CD10 expression (4/11 cases), providing indication on 'phenotypic plasticity'. Finally, among the wide variety of Vβ families, the occurrence of a Vβ17 expansion in five cases was striking. To our knowledge, this is the first report demonstrating the power of T-cell receptor-Vβ repertoire analysis by flow cytometry in biopsies as a basis for peripheral T-cell lymphoma diagnosis and precise T-cell clone identification and characterization.

A new approach to simultaneously quantify both TCR α- and β-chain diversity after adoptive immunotherapy

PURPOSE

T-cell receptor (TCR) variable Vα and Vβ gene diversity is a surrogate biomarker for the therapeutic potential of adoptive immunotherapy and cellular immunity. Therefore, creating a straightforward, rapid, sensitive, and reliable method to view the global changes of both TCRVα and Vβ transcripts in heterogeneous populations of T cells is appealing.

EXPERIMENTAL DESIGN

We designed a "direct TCR expression assay" (DTEA) using a panel of customized bar-coded probes that simultaneously detects and quantifies 45 Vα and 46 Vβ transcripts in a nonenzymatic digital multiplexed assay from a small number of cells (10(4) cells) or as little as 100 ng of total RNA.

RESULTS

We evaluated DTEA on total RNA samples of tumor-infiltrating lymphocytes and peripheral blood obtained from patients with melanoma after adoptive T-cell therapy. DTEA detected a similar spectrum of the dominant patterns of TCRVβ gene usage as sequencing cloned TCRVβ CDR3 regions. However, DTEA was rapid, achieved a level of sensitivity to identify rare T-cell populations, and simultaneously tracked the full array of Vα and Vβ transcripts.

CONCLUSIONS

DTEA can rapidly and sensitively track changes in TCRVα and Vβ gene usages in T-cell pools following immune interventions, such as adoptive T-cell transfer, and may also be used to assess impact of vaccination or reconstitution of T-cell compartment after hematopoietic stem cell transplantation.

Flow cytometric immunophenotypic assessment of T-cell clonality by vβ repertoire analysis in fine-needle aspirates and cerebrospinal fluid

Flow cytometric T-cell receptor V(β) repertoire analysis (TCR-V(β)-R) is a sensitive method to detect T-cell clonality; however, its implementation in low-cellularity specimens has not been established. We developed a strategy to use TCR-V(β)-R in cerebrospinal fluid (CSF) and fine-needle aspirate (FNA) specimens. Initially, full TCR-V(β)-R was evaluated in diagnostic/screening specimens from 8 patients with T-cell neoplasia to determine tumor-specific TCR-V(β) protein expression. Subsequently, an abbreviated, patient-specific TCR-V(β)-R evaluation was performed in 17 paucicellular specimens from the patients (8 CSF, 9 FNA) for staging and monitoring of minimal residual disease (MRD). A single cocktail containing 3 anti-V(β) antibodies (1 tumor-specific and 2 negative controls) in combination with other antibodies chosen to help gate on atypical T cells is highly sensitive and specific for detecting low-level neoplastic T-cell involvement in paucicellular specimens. This TCR-V(β)-R strategy is valuable in staging and evaluating MRD in patients with T-cell non-Hodgkin lymphoma.

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.

Flow cytometric immunophenotypic assessment of T-cell clonality by Vβ repertoire analysis: detection of T-cell clonality at diagnosis and monitoring of minimal residual disease following therapy

Flow cytometric T-cell receptor (TCR)-V(β) repertoire analysis (TCR-V(β)-R) is a sensitive method for detection of T-cell clonality; however, no uniform approach exists to define clonality in neoplastic T cells. TCR-V(β)-R was evaluated in patients with a diagnosis of T-cell neoplasia in initial diagnostic specimens from 41 patients and for minimal residual disease (MRD) monitoring in 61 sequential samples from 14 patients with mature T-cell neoplasia. Gating strategies and criteria for detection of T-cell clonality were determined. In all 41 initial specimens, T-cell clonality was demonstrated via TCR-V(β)-R. The frequency of V(β) usage was consistent with random neoplastic transformation of TCR-V(β) subsets. MRD was successfully detected in follow-up samples from all 14 patients evaluated, Furthermore, MRD after therapy was quantitated in 48 peripheral blood specimens. TCR-V(β)-R analysis is a sensitive method for detection of T-cell clonality and is useful for diagnosis and MRD detection in multiple specimen types.

A practical approach to the flow cytometric detection and diagnosis of T-cell lymphoproliferative disorders

The flow cytometric analysis of T-cell malignancies is difficult due to the heterogeneity of T-cells and the lack of convenient methods to detect T-cell clonality. Neoplastic T-cells are most often detected by their altered level of surface antigen expression, and detection requires an extensive knowledge of the phenotype of normal T-lymphocytes. This review focuses on the methods to distinguish malignant T-cells from their normal counterparts and the phenotypic features of the T-cell lymphoproliferative disorders.

T/NK large granular lymphocyte leukemia and coexisting monoclonal B-cell lymphocytosis-like proliferations. An unrecognized and frequent association

T-cell large granular lymphocyte leukemia (T-LGLL) is a T-cell lymphoproliferative disorder that has recently been associated with B-cell dyscrasias on a spectrum ranging from dysgammaglobulinemia to lymphoma. To investigate the relationship between clonal B-cell and LGLL lymphoproliferations, we systematically studied lymphocytes in 57 patients with T-LGLL or NK lymphocytosis using flow cytometric methods sensitive to low-level B-cell populations. We identified 16 patients (28%) with abnormal B-cell populations; 9 (16%) of the patients had no known history of a B-cell lymphoproliferative disorder. We characterized these abnormal B-cell populations as monoclonal B-cell lymphocytosis and report a high frequency of monoclonal B-cell lymphocytosis in T/NK LGLL. Our findings suggest that certain pathologic factors may operate in patients with T/NK LGLL to drive low-level clonal B-cell proliferations.

Efficient characterization of the TCR repertoire in lymph nodes by flow cytometry

Analysis of the T-cell receptor (TCR) repertoire by flow cytometry proved to be relevant for investigating T-cell diversity and detecting reactive cells in blood samples. We used this approach to characterize non-malignant T-lymphocytes in lymph nodes and give insights into their origin. The TCR repertoire of CD4+ and CD8+ T-cells from 81 lymph nodes was analyzed with a four-color flow cytometer using a wide panel of 25 anti-Vbeta monoclonal antibodies. Flow cytometry proved to be a useful and informative technique. We demonstrated a diversified TCR-Vbeta repertoire, and only low level expansions, in 53% of the samples. They involved nearly all Vbeta families, were more frequent in the CD8+ subset of older patients, but were not related to pathology. No evidence could be demonstrated in favor of stimulation by common antigens. Interestingly, the TCR-Vbeta repertoire proved to be very similar in lymph nodes and blood samples. Our results argue that in the cases studied, lymph node enlargement is mainly due to an increased homing of circulating T-cells. They also provide reference values for expression of 25 TCR-Vbeta in lymph nodes, which could serve as a basis for further applications in diagnosis of T-cell lymphoproliferative disorders.

The leukemias of mature lymphocytes

The leukemias of mature B cells and T cells are a limited set of diseases in which blood and bone marrow are the primary sites of involvement. Although they may superficially resemble one another, they have distinct clinical and pathologic features and must be distinguished from one another. In this article, the major clinical, morphologic, phenotypic, and molecular genetic features of the mature B- and T-cell leukemias are reviewed, and differential diagnostic considerations are discussed.

T-cell large granular lymphocyte leukemia associated with myelodysplastic syndrome: a clinicopathologic study of nine cases

We describe 9 patients with T-cell large granular lymphocyte leukemia (T-LGL) who also had a myelodysplastic syndrome (MDS). There were 6 men and 3 women with a median age of 60 years (range, 25-74 years). All patients had anemia at initial examination, 7 had neutropenia, and 5 had thrombocytopenia. The median absolute lymphocyte count was 1,300/microL (1.3 x 10(9)/L; range, 700-3,600/microL [0.7-3.6 x 10(9)/L]). Immunophenotypic analysis showed a CD8+ T-cell population, and molecular analysis showed monoclonal T-cell receptor gene rearrangement in every case. The MDS was classified as refractory cytopenia with multilineage dysplasia (RCMD, n = 5), refractory anemia (n = 2), RCMD with ringed sideroblasts (n = 1), and chronic myelomonocytic leukemia (n = 1). We compared the data for these patients with T-LGL/MDS with a group that had only T-LGL. The median hemoglobin level and absolute lymphocyte count were lower in patients with T-LGL/MDS (P < .05). The frequency of coexistent T-LGL and MDS at our institution suggests an etiologic relationship rather than simple coincidence.

Pathobiology of mature T-cell lymphomas

Mature T- and natural killer (NK)-cell neoplasms are relatively rare forms of leukemia/lymphoma. The diagnosis of these entities is often difficult, necessitating extensive immunophenotypic, molecular, and genetic testing. Despite the accumulating information on the pathobiology of these neoplasms, in many cases the prognosis remains poor. This article presents an updated view of the morphologic, immunophenotypic, genetic, and molecular characteristics of the mature T- and NK-cell neoplasms. For a better understanding of this complex topic, the development of normal T and NK cells is briefly discussed. The presentation of the characteristic features of the neoplasms in the 2008 World Health Organization classification of hematopoietic neoplasms includes advances in the understanding of the pathobiology of each diagnostic category.

Malleable immunoglobulin genes and hematopathology - the good, the bad, and the ugly: a paper from the 2007 William Beaumont hospital symposium on molecular pathology

Immunoglobulin gene rearrangement analysis is one of the more commonly performed assays available on the hematopathology menu of clinical molecular pathology laboratories. The analysis of these rearrangements provides useful information on a number of different levels in the evaluation of lymphoproliferations. An appreciation of the various mechanisms involved in the numerous physiological pathways affecting the immunoglobulin genes, and hence antibody molecules, is central to an understanding of B-cell development vis-à-vis the generation of immunological diversity. Knowledge about the intricate complexities of these mechanisms is also germane to an evaluation of testing methodologies. With this information, it is easier to develop an understanding of how contemporary molecular testing of immunoglobulin gene rearrangements has evolved, from historically quite heterogeneous, fairly flawed, and rather ugly approaches to current more-standardized protocols. In addition, recognition of how such genetic changes with good intentions can turn bad has fostered increasing insights into the pathogenesis of B-cell lymphomas and leukemias. Despite the significant improvements in the design of immunoglobulin gene rearrangement assays, numerous pitfalls and caveats remain. Accordingly, it is crucial to consider such testing a tool, and although most useful, it is one of many tools that may be required to build cogent diagnoses.

T-cell large granular leukemia and related proliferations

Session 9 of the 2005 Society for Hematopathology/European Association for Haematopathology Workshop focused on large granular lymphocyte (LGL) leukemias and related disorders. T-cell LGL (T-LGL) leukemias, discussed herein, account for 2% to 3% of cases of small lymphocytic leukemia. T-LGL diseases cover a heterogeneous spectrum of disorders that include reactive conditions, typically associated with autoimmune disease, to outright leukemia. These disorders are found in older people, with an average age at initial examination of approximately 60 years and a median survival of more than 10 years in T-LGL leukemia. Systemic symptoms and neutropenia are common at initial examination. Lymphocytosis, composed of small mature lymphocytes with increased cytoplasm, is common. The spleen and bone marrow are involved in T-LGL leukemia, although morphologic findings may be subtle. The immunophenotype is typically that of CD3+/CD8+ cytotoxic T cells. Some cases may be due to chronic immune stimulation, with subsequent clonal escape and proliferation of a neoplastic population of lymphocytes.

Flow cytometric analysis of lymphomas: current status and usefulness

CONTEXT

Immunophenotyping has become a routine practice in the diagnosis and classification of most cases of non-Hodgkin lymphoma, and flow cytometry is often the method of choice in many laboratories. The role that flow cytometry plays, however, extends beyond just diagnosis and classification.

OBJECTIVE

To review and evaluate the current roles of flow cytometry in non-Hodgkin lymphoma, to compare it with immunohistochemistry, and to discuss its potential future applications in the molecular diagnostic era.

DATA SOURCES

The information contained herein is derived from peer-reviewed articles on the subject published in the English-language medical literature during the years 1980 to 2005 that were identified using PubMed (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi, 1980-2005) search, various books and other sources on flow cytometry, and the author's personal experience of more than 10 years with flow cytometric analysis of lymphomas and leukemia using Becton-Dickinson (San Jose, Calif) and Beckman-Coulter (Miami, Fla) flow cytometers.

STUDY SELECTION

Studies were selected based on adequate material and methods, statistically significant results, and adequate clinical follow-up.

DATA EXTRACTION

The data from various sources were compared when the methods used were the same or similar and appropriate controls were included. Most of the studies employed 2-color, 3-color, or 4-color flow cytometers with antibodies from Becton-Dickinson, Beckman-Coulter, or DakoCytomation (Carpinteria, Calif). Results were evaluated from studies utilizing the same or similar techniques and flow cytometers. Only objective data analyses from relevant and useful publications were included for reporting and discussion.

DATA SYNTHESIS

Flow cytometry serves a variety of roles in the field of lymphoma/leukemia including rapid diagnosis, proper classification, staging, minimal residual disease detection, central nervous system lymphoma detection, evaluation of prognostic markers, detection of target molecules for therapies, ploidy analysis of lymphoma cell DNA, and evaluation of multidrug-resistance markers. It offers many advantages in comparison to immunohistochemistry for the same roles and provides uses that are either not possible or not preferable by immunohistochemistry such as multiparameter evaluation of single cells and detection of clonality in T cells.

CONCLUSIONS

By virtue of its ability to evaluate not only surface but also cytoplasmic and nuclear antigens, flow cytometry continues to enjoy widespread use in various capacities in lymphoma evaluation and treatment. Additional roles for flow cytometry are likely to be invented in the future and should provide distinctive uses in the molecular era.

Characterization of the T-cell receptor Vbeta repertoire in the human immune response against Leishmania parasites

In order to explore a possible presence of hyperreactive T-cell clones in human cutaneous leishmaniasis (CL), we have investigated, by flow cytometry, the expression of Vbeta chains of T-cell receptors (TCRs) in the following types of cells: (i) peripheral blood mononuclear cells (PBMCs) from CL patients, which were then compared to those from normal volunteers; (ii) unstimulated and soluble Leishmania antigen-stimulated draining lymph node cells from CL patients; (iii) PBMCs from volunteers before versus after Leishmania immunization; and (iv) PBMCs from healthy volunteers that were primed in vitro with live Leishmania parasites. Our results show a modulation in the TCR Vbeta repertoire during CL and after antigen stimulation of patients' cells. Vaccination, however, leads to a broad expansion of different Vbeta TCRs. We also observed an association between TCR Vbeta12 expression, T-cell activation, and gamma interferon production upon in vitro priming with Leishmania. Collectively, these results both indicate that infection with live parasites or exposure to parasite antigen can modulate the TCR Vbeta repertoire and suggest that TCR Vbeta12 may be implicated in the response to Leishmania.

Identification of the tumor cells in peripheral T-cell lymphomas by combined polymerase chain reaction-based T-cell receptor beta spectrotyping and immunohistological detection with T-cell receptor beta chain variable region segment-specific antibodies

Most nodal peripheral T-cell lymphomas (PTCL) originate from alphabeta-T cells, and they often contain reactive T cells that may hamper immunophenotyping. To specifically identify the neoplastic population in immunohistochemically stained slides, we assessed the heterogeneity of the T-cell receptor beta chain variable region (TCRVbeta). This region contains 65 gene segments, of which only one is expressed after rearrangement. To investigate PTCL, we developed a polymerase chain reaction assay to define the clonally rearranged TCRVbeta segment. Detecting the corresponding epitope with segment-specific antibodies enabled identification of tumor cells among the T cells. The TCRVbeta segment of the tumor cells was defined in 13 of 13 PTCL not otherwise specified and 11 of 13 angioimmunoblastic T-cell lymphomas. Antibodies corresponding to the respective TCRVbeta segment of the tumor were available for seven cases from each group. After applying these antibodies in combination with antibodies against CD3, CD5, CD4, CD8, and cytotoxic molecules, double stains were evaluated by confocal laser scanning microscopy. In 9 of 14 cases, less than 50% of T cells expressed the clonally rearranged TCRVbeta segment. Phenotypes defined in double stains differed from those obtained by conventional immunohistochemistry in 11 of 14 cases. The combination of TCRVbeta polymerase chain reaction and immunohistochemistry may facilitate more reliable detection and characterization of tumor cells in PTCL.

Evidence for Restricted Vβ Usage in the Leukemic Phase of Cutaneous T Cell Lymphoma

Antibodies directed against the beta chain of the T cell receptor (anti-Vbeta antibodies) are useful to identify the Vbeta repertoire of T cells in various diseases and to quantify numbers of Vbeta-bearing T cells. The goals of this study were to identify Vbeta+ cases of leukemic phase cutaneous T cell lymphoma (CTCL) and to compare the percentage of positive calls with other measures of blood tumor burden, i.e., lymphocyte subsets with a CD4+CD7- and CD4+CD26- phenotype and Sezary cell counts. Thirty-three of 49 (67%) cases of leukemic CTCL reacted with an anti-Vbeta antibody. When combined with reports from the literature, the frequency of Vbeta5 (probably Vbeta5.1) usage was relatively high when compared with Vbeta2 that is also frequently expressed by normal CD4+ T cells. The percentage of Vbeta+ cells correlated to the percentage of CD4+CD7- and CD4+CD26- cells for cases in which the neoplastic cells were deficient in expression of CD7 and CD26, respectively, but not the Sezary cell count. We hypothesize that the increased Vbeta5.1 usage in CTCL may be the result of depletion of Vbeta2 and other Vbeta-bearing T cells by staphylococcal superantigens prior to neoplastic transformation, resulting in a relative increase in the frequency of Vbeta5.1 usage in CTCL.

Molecular TCR diagnostics can be used to identify shared clonotypes after allogeneic hematopoietic stem cell transplantation

OBJECTIVE

In allogeneic hematopoietic stem cell (HSCT) transplantation, recovery of the T cell receptor (TCR) repertoire depends upon the composition of the graft and is modulated by peri-transplant immunosuppression, viral infections, and graft-vs-host disease (GVHD). We hypothesized that after allogeneic HSCT, molecular analysis of the TCR repertoire can be used to identify and quantitate immunodominant T cell clones that may play a role in GVHD or other clinical events.

METHODS

We utilized a rational strategy for the analysis of the expanded CTL clones. First, we studied the VB spectrum in a cohort of patients who had received either matched sibling or unrelated donor grafts. The CDR3 sequences of immunodominant clones were identified and clonotypic PCR and sequencing was applied to determine the level of clonotype sharing.

RESULTS

Significant expansions of VB families were observed following transplantations; 61% were oligo/monoclonal. Immunodeficiency was reflected by depletion of multiple VB families from both the CD8 and CD4 repertoires. The level of sharing varied between clonotypes, suggesting that some antigens have a more "public" spectrum while others are restricted to specific patients. Immunodominant CDR3 sequences common to allogeneic HSCT, healthy controls, and other conditions were identified.

CONCLUSION

The clonotypes of expanded CTL clones may reflect responses to alloantigens (e.g., in correlation with clinical GVHD) or pathogens. In the future, molecular T cell diagnostics may become a powerful clinical tool in transplantation to monitor disease and to direct treatment.

Applications of Flow Cytometry and Immunohistochemistry to Diagnostic Hematopathology

Objective.—Diagnostic hematopathology depends on the applications of flow cytometric immunophenotyping and immunohistochemical immunophenotyping combined with the cytomorphology and histologic features of each case. Select cases may require additional ancillary cytogenetic and molecular studies for diagnosis. The purpose of this review is to focus on the applications of flow cytometric and immunohistochemical immunophenotyping of paraffin-embedded tissue to diagnostic hematopathology. Advantages and disadvantages of these techniques are examined.

Data Sources.—The literature is extensively reviewed (PubMed 1985–2003) with an emphasis on the most recent applications and those that are most useful clinically, both diagnostically and prognostically.

Study Selection.—Studies were selected based on statistically significant results in large studies with reported adequate clinical follow-up.

Data Extraction.—The methodology was reviewed in the selected studies to ensure reliable comparison of reported data.

Data Synthesis.—Flow cytometric immunophenotyping offers the sensitive detection of antigens for which antibodies may not be available for paraffin immunohistochemical immunophenotyping. However, paraffin immunohistochemical immunophenotyping offers preservation of architecture and evaluation of expression of some proteins, which may not be available by flow cytometric immunophenotyping. These techniques should be used as complimentary tools in diagnostic hematopathology.

Conclusions.—There are extensive applications of flow cytometric and immunohistochemical immunophenotyping to diagnostic hematopathology. As cytogenetic and molecular findings evolve in diagnostic hematopathology, there may be additional applications of flow cytometric and immunohistochemical immunophenotyping to this field of pathology.

Advances in the diagnosis and classification of chronic lymphoproliferative disorders

In this review, we have highlighted recent advances in chronic lymphoproliferative disorders that commonly involve the peripheral blood. As we have seen, our concepts of certain diseases are changing. Molecular genetic and immunophenotypic studies are allowing more precise characterization of CLL and defining important biologic markers that predict clinical behavior. Prolymphocytic leukemia is now more narrowly defined and its relationship to nucleolated variants of MCL is now apparent. With new reagents and techniques applied to problems such as identification of Sezary cells and T-cell monoclonality determination, our ability to diagnose, monitor, and provide prognostic information is improving. Insight into the biology of these diseases also may provide new therapeutic targets in the future.