Julia Almeida

EuroFlow antibody panels for standardized n-dimensional flow cytometric immunophenotyping of normal, reactive and malignant leukocytes

Most consensus leukemia & lymphoma antibody panels consist of lists of markers based on expert opinions, but they have not been validated. Here we present the validated EuroFlow 8-color antibody panels for immunophenotyping of hematological malignancies. The single-tube screening panels and multi-tube classification panels fit into the EuroFlow diagnostic algorithm with entries defined by clinical and laboratory parameters. The panels were constructed in 2–7 sequential design–evaluation–redesign rounds, using novel Infinicyt software tools for multivariate data analysis. Two groups of markers are combined in each 8-color tube: (i) backbone markers to identify distinct cell populations in a sample, and (ii) markers for characterization of specific cell populations. In multi-tube panels, the backbone markers were optimally placed at the same fluorochrome position in every tube, to provide identical multidimensional localization of the target cell population(s). The characterization markers were positioned according to the diagnostic utility of the combined markers. Each proposed antibody combination was tested against reference databases of normal and malignant cells from healthy subjects and WHO-based disease entities, respectively. The EuroFlow studies resulted in validated and flexible 8-color antibody panels for multidimensional identification and characterization of normal and aberrant cells, optimally suited for immunophenotypic screening and classification of hematological malignancies.

EuroFlow standardization of flow cytometer instrument settings and immunophenotyping protocols

The EU-supported EuroFlow Consortium aimed at innovation and standardization of immunophenotyping for diagnosis and classification of hematological malignancies by introducing 8-color flow cytometry with fully standardized laboratory procedures and antibody panels in order to achieve maximally comparable results among different laboratories. This required the selection of optimal combinations of compatible fluorochromes and the design and evaluation of adequate standard operating procedures (SOPs) for instrument setup, fluorescence compensation and sample preparation. Additionally, we developed software tools for the evaluation of individual antibody reagents and antibody panels. Each section describes what has been evaluated experimentally versus adopted based on existing data and experience. Multicentric evaluation demonstrated high levels of reproducibility based on strict implementation of the EuroFlow SOPs and antibody panels. Overall, the 6 years of extensive collaborative experiments and the analysis of hundreds of cell samples of patients and healthy controls in the EuroFlow centers have provided for the first time laboratory protocols and software tools for fully standardized 8-color flow cytometric immunophenotyping of normal and malignant leukocytes in bone marrow and blood; this has yielded highly comparable data sets, which can be integrated in a single database.

Prognosis in adult indolent systemic mastocytosis: A long-term study of the Spanish Network on Mastocytosis in a series of 145 patients

BACKGROUND Indolent systemic mastocytosis is a group of rare diseases for which reliable predictors of progression and outcome are still lacking. OBJECTIVE Here we investigate the prognostic impact of the clinical, biological, phenotypic, histopathological, and molecular disease characteristics in adults with indolent systemic mastocytosis, who were followed using conservative therapy. METHODS A total of 145 consecutive patients were prospectively followed between January 1983 and July 2008; in addition, from 1967 to 1983, 20 patients were retrospectively studied. RESULTS Multivariate analysis showed that serum beta2-microglobulin (P = .003) together with the presence of mast/stem cell growth factor receptor gene (KIT) mutation in mast cells plus myeloid and lymphoid hematopoietic lineages (P = .02) was the best combination of independent parameters for predicting disease progression (cumulative probability of disease progression of 1.7% +/- 1.2% at 5-10 years and of 8.4% +/- 5.0% at 20-25 years). Regarding overall survival, the best predictive model included age >60 years (P = .005) and development of an associated clonal hematological non-mast cell disorder (P = .03) with a cumulative probability of death of 2.2% +/- 1.3% at 5 years and of 11% +/- 5.9% at 25 years. CONCLUSIONS Indolent systemic mastocytosis in adults has a low disease progression rate, and the great majority of patients have a normal life expectancy, with the presence of KIT mutation in all hematopoietic lineages and increased serum beta2-microglobulin the most powerful independent parameters for predicting transformation into a more aggressive form of the disease.

Human peripheral blood B-Cell compartments: A crossroad in B-cell traffic

A relatively high number of different subsets of B‐cells are generated through the differentiation of early B‐cell precursors into mature B‐lymphocytes in the bone marrow (BM) and antigen‐triggered maturation of germinal center B‐cells into memory B‐lymphocytes and plasmablasts in lymphoid tissues. These B‐cell subpopulations, which are produced in the BM and lymphoid tissues, recirculate through peripheral blood (PB), into different tissues including mucosa and the BM, where long‐living plasma cells produce antibodies. These circulating PB B‐cells can be classified according to their maturation stage into i) immature/transitional, ii) naïve, and iii) memory B‐lymphocytes, and iv) plasmablasts/plasma cells. Additionally, unique subsets of memory B‐lymphocytes and plasmablasts/plasma cells can be identified based on their differential expression of unique Ig‐heavy chain isotypes (e.g.: IgM, IgD, IgG, IgA). In the present paper, we review recent data reported in the literature about the distribution, immunophenotypic and functional characteristics of these cell subpopulations, as well as their distribution in PB according to age and seasonal changes. Additional information is also provided in this regard based on the study of a population‐based cohort of 600 healthy adults aged from 20 to 80 years, recruited in the Salamanca area in western Spain. Detailed knowledge of the distribution and traffic of B‐cell subsets through PB mirrors the immune status of an individual subject and it may also contribute to a better understanding of B‐cell disorders related to B‐cell biology and homeostasis, such as monoclonal B‐cell lymphocytosis (MBL).

Utility of Flow Cytometry Immunophenotyping in Multiple Myeloma and Other Clonal Plasma Cell-Related Disorders

In recent years, multiparameter flow cytometry (MFC) immunophenotyping has become mandatory in the clinical management of hematological malignancies, both for diagnostic and monitoring purposes. Multiple myeloma (MM) and other clonal plasma cell‐related (PC) disorders should be no exception to this paradigm, but incorporation of immunophenotypic studies in the management of patients with PC disorders is still far from being routinely established in many diagnostic flow cytometry laboratories. For clonal PC disorders, MFC is of clear and established clinical relevance in: (1) the differential diagnosis between MM and other PC‐related disorders; (2) the identification of high‐risk MGUS and smoldering MM; (3) minimal residual disease investigation after therapy; additionally it may also be useful for (4) the definition of prognosis‐associated antigenic profiles; and (5) the identification of new therapeutic targets. In this article, we review the clinical value of MFC in the study of PC disorders, with specific emphasis in those areas where consensus exists on the need to incorporate MFC into routine evaluation of MM and other clonal PC‐related disorders.

Immunophenotypic analysis of mast cells in mastocytosis: When and how to do it. Proposals of the Spanish Network on Mastocytosis (REMA)

Mastocytosis is a term used for a heterogeneous group of disorders characterized by an abnormal proliferation and accumulation of mast cells (MCs) in one or multiple tissues including skin, bone marrow, liver, spleen, and lymph nodes, among others.

Incidence of phenotypic aberrations in a series of 467 patients with B chronic lymphoproliferative disorders: basis for the design of specific four-color stainings to be used for minimal residual disease investigation

Multiparameter immunophenotypic analysis of neoplastic cells has proven to be of great help for the investigation of minimal residual disease in acute leukemias; however, its utility has not been systematically explored in B cell chronic lymphoproliferative disorders. The aim of the present study was to investigate the incidence of phenotypic aberrations in a series of 467 consecutive leukemic B cell chronic lymphoproliferative disorders through the comparison of the phenotypic characteristics of tumor vs normal peripheral blood (n = 10) and bone marrow (n = 10) B cells, in order to explore the applicability of this strategy for minimal residual disease monitoring. An additional goal of our study was to evaluate the sensitivity of multiparameter flow cytometry for the detection of minimal residual disease in leukemic B cell chronic lymphoproliferative disorders through dilutional experiments (n = 19). From the patients analyzed 382 corresponded to B cell chronic lymphocytic leukemia/small lymphocytic lymphoma (353 typical and 29 atypical); five to prolymphocytic leukemia; 13 to hairy cell leukemias; 12 to lymphoplasmacytic lymphomas; 14 to splenic marginal zone lymphomas; 22 were follicular lymphomas; and 19 mantle cell lymphomas. The following triple stainings were systematically applied to both normal and leukemic samples: FMC7/CD5/CD19, CD22/CD23/CD19, CD103/CD25/CD19, CD10/CD11c/CD19 and sIg/sIgλ/CD19. Overall, 98% of the leukemic B cell chronic lymphoproliferative disorders cases displayed aberrant phenotypes at diagnosis with no significant differences being found between cases analyzed in peripheral blood vs bone marrow samples. The most common types of aberrant criteria detected included asynchronous antigen expression (92%) and antigen over-expression (54%); abnormally light scatter characteristics were found in 17% of the cases. Most of the cases studied (90%) displayed four or more phenotypic aberrations. Once patients were divided according to the different diagnostic subgroups, the overall incidence of aberrant phenotypes ranged from 79 to 80% among atypical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia to 97% of follicular lymphoma and 100% of typical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia, lymphoplasmacytic lymphomas, splenic marginal zone lymphomas and mantle cell lymphomas. Based on the aberrant phenotypes detected unique four-color stainings could be built for the specific identification of aberrant phenotypes. These include CD22/CD23/CD19/CD5 and sIgκ/sIgλ/CD19/CD5 for lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia, CD103/CD25 or CD22/CD19/CD11c for hairy cell leukemia, FMC7/CD22/CD19/CD103 and sIgκ/sIgλ/CD22/CD19 for splenic marginal zone lymphomas, CD22/CD23/CD19/CD10 for follicular lymphomas and CD10/CD22/CD19/CD5 for mantle cell lymphomas. Serial dilutional experiments showed that the sensitivity level of immunophenotyping ranges between 10−4 and 10−5. In summary, the present study shows that immunophenotypic analysis allows the identification of aberrant phenotypes in 98% of leukemic B cell chronic lymphoproliferative disorders and these phenotypes can be used for minimal residual disease monitoring with a sensitivity limit of 10−4–10−5.

High‐sensitive immunophenotyping and DNA ploidy studies for the investigation of minimal residual disease in multiple myeloma

Sensitive techniques for monitoring minimal residual disease (MRD) in multiple myeloma (MM) are needed to evaluate the effectiveness of new intensive treatment strategies. The aim of the present study was to explore the applicability and sensitivity of flow cytometry immunophenotyping and DNA ploidy studies for the investigation of residual myelomatous plasma cells (PC) in MM patients. Bone marrow (BM) samples from 61 untreated MM patients were immunophenotypically analysed with a panel of 21 monoclonal antibodies, using a high‐sensitive method based on a two‐step acquisition procedure through a SSC/CD38+++‐CD138+‘live‐gate’. Overall, in 87% of MM cases, PC displayed an aberrant phenotype at diagnosis. The most important aberrant criteria were: antigen over‐expression of CD56 (62%), CD28 (16%) and CD33 (6%) and asynchronous expression of CD117 (28%), sIg (21%) and CD20 (10%). DNA aneuploidy was found in 62% of cases. The simultaneous use of these two techniques allowed the detection of aberrant/aneuploid PC in 95% of the cases. Based on dilutional experiments, the detection limit of both techniques ranged from 10−4 to 10−5. In 29 stem cells harvests and 19 BM samples obtained 3 months after autologous transplantation, we have investigated the presence of residual myelomatous PC; they were detected in 44% of the stem cell collections and in 61% of the BM samples obtained after transplant. The percentage of pathological PC did not significantly change during the days of harvest. In summary, the present study shows that the combined use of immunophenotyping and DNA ploidy studies is a suitable approach for MRD investigation in MM patients based on their applicability (95% of cases) and sensitivity (up to 10−5).

Expression of the c-kit (CD117) Molecule in Normal and Malignant Hematopoiesis

The c-kit proto-oncogen (CD 117) has been shown to be present in several cell types including normal and neoplastic hemopoietic cells. Among normal BM cells, CD117 expression has been found in about half of the CD34+ precursors including progenitors committed to the erythroid, granulo-monocytic, and megakaryocytic cell lineages. In addition, strong CD117 expression is detected in bone marrow mast cells as well as in a small subset of NK cells displaying strong reactivity for CD56, and in a relatively important proportion of CD3 /CD4 /CD8 prothymocytes. These results suggest that CD117 expression can be detected in both myeloid and lymphoid lineages although for the lymphoid lineage it would be restricted to a small NK-cell subset and early T-cell precursors. In acute leukemias CD117 expression was initially associated with AML. Nevertheless, at present it is well established that CD 117 expression may also be found in a relatively important proportion of T-ALL while it is usually absent in B-lineage ALL. Moreover, recent studies have shown that in about one-third of multiple myeloma cases and patients with monoclonal gammopathy of undetermined significance plasma cells display reactivity for CD1117. The prognostic influence of CD117 expression has not yet been clearly established. The analysis of this marker may also be of value for the investigation of minimal residual disease (MRD). It has been suggested that CD117 in combination with other antigens may be of great help for the identification of leukemia-associated phenotypes that could be used to monitor MRD in both acute myeloid leukemias and multiple myeloma patients achieving morphological complete remission.

Immunophenotypic Analysis of the TCR-Vβ Repertoire in 98 Persistent Expansions of CD3+/TCR-αβ+ Large Granular Lymphocytes : Utility in Assessing Clonality and Insights into the Pathogenesis of the Disease

At present, a major challenge in the initial diagnosis of leukemia of large granular lymphocytes (LGLs) is to establish the clonal nature of the expanded population. In the present study we have analyzed by flow cytometry immunophenotyping the TCR-Vβ repertoire of 98 consecutive cases of persistent expansions of CD4 + or CD8 +bright CD3 + /TCR-αβ + LGLs and compared the results with those obtained in molecular studies of TCR-β gene rearrangements. Fifty-eight cases were considered to be monoclonal in molecular studies whereas in the remaining 40 cases there was no evidence for monoclonality (11 cases were considered oligoclonal and 29 polyclonal). The TCR-Vβ repertoire was biased to the preferential use of one or more TCR-Vβ families in 96% of cases, a total of 124 TCR-Vβ expansions being diagnosed: one TCR-Vβ expansion in 71 cases and two or more TCR-Vβ expansions in 23 cases. The highest TCR-Vβ expansion observed in each case was higher among monoclonal (74 ± 19%) as compared to nonmonoclonal cases (24 ± 14%) ( P = 0.001), as did the fraction of LGLs that exhibited a TCR-Vβ-restricted pattern (86 ± 16% and 42 ± 23%, respectively; P = 0.0001); by contrast, the proportion of cases displaying more than one TCR-Vβ expansion was higher in the latter group: 7% versus 48%, respectively ( P = 0.001). Results obtained in oligoclonal cases were intermediate between those obtained in polyclonal and monoclonal cases and similar results were observed for CD4 + as for CD8 +bright T-cell expansions. TCR-Vβ familiesexpressed in CD8 +bright T-cell-LGL proliferations showed a pattern of distribution that mimics the frequency at which the individual TCR-Vβ families are represented in normal peripheral blood T cells. Assuming that a given proliferation of LGLs is monoclonal whenever there is an expansion of a given TCR-Vβ family of at least 40% of the total CD4 + or CD8 +bright T-cell compartment, we were able to predict clonality with a sensitivity of 93% and a specificity of 80%. By increasing the cut-off value to 60%, sensitivity and specificity were of 81% and 100%. In summary, our results suggest that flow cytometry immunophenotypic analysis of the TCR-Vβ repertoire is a powerful screening tool for the assessment of T-cell clonality in persistent expansions of TCR-αβ + LGLs.