Full spectrum flow cytometry in the clinical laboratory

Contemporary full spectrum or "spectral" flow cytometry is a recently developed technology that allows for high-dimensional flow cytometric analyses of cells and particles in suspension. This single-cell technology has gained popularity in research settings because it can conservatively detect 35 or more antigens simultaneously in a single-tube assay format. Recently, spectral flow cytometry has obtained regulatory approval for use as an in vitro diagnostic device in China and Europe, enabling use of this technology in some clinical flow cytometry laboratories. The purpose of this review is to describe the basic principles of conventional and spectral flow cytometry, contrasting these two technologies. To illustrate the analytic power of spectral flow cytometry, we provide an example of spectral flow cytometry data analyses and the use of a machine learning algorithm to harvest the vast amount of information contained within large spectral flow cytometry datasets. Finally, we discuss the advantages of spectral flow cytometry adoption in clinical laboratories and preliminary studies comparing the performance of this technology relative to conventional flow cytometers that are currently used in clinical laboratory environments.

Adhesion molecule immunophenotype of bone marrow multiple myeloma plasma cells impacts the presence of malignant circulating plasma cells in peripheral blood

INTRODUCTION

Multiple myeloma (MM) patients with malignant plasma cells (MMPCs) in their bone marrow (BM) and malignant circulating plasma cells (MMCPCs) in the peripheral blood (PB) are an independent marker of a clinically aggressive disease, and it reflects a poor prognosis defined by a short time to progression and overall survival. We hypothesized that changes in ADM expression on BM MMPCs might contribute to MMCPC presence in the PB of relapsed/refractory multiple myeloma (RRMM) patients.

METHODS

We assessed the difference in expression of adhesion molecules and receptors related to cell-cell interaction: integrins, hyaluronic acid receptors, chemokine receptors and other proteins on healthy donor PCs, RRMM BM and PB MMPCs.

RESULTS

Adhesion immunophenotype showed a significant loss of many adhesion molecules when comparing BM MMPCs of MMCPC- and MMCPC+ MM patients (CD49d, CD49e, CD56, CD138). Further decrease of adhesion molecules was shown in MMCPCs (CD49d, CD49e, CD56, CD138, CD58), suggesting that loss of these molecules may allow cells to leave the BM.

CONCLUSIONS

Loss of adhesion molecule expression enables MMPCs to leave the BM milieu and enter the PB. These changes can be seen in both the PB and BM of MMCPC+ MM patient.

CD200 is a useful diagnostic marker for identifying atypical chronic lymphocytic leukemia by flow cytometry

INTRODUCTION

Immunophenotyping by flow cytometry is routinely employed in distinguishing between chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Inclusion of CD200 has been reported to contribute to more reliable differentiation between CLL and MCL. We investigated the value of CD200 in assessment of atypical CLL cases.

METHODS

CD200 expression on mature B cell neoplasms was studied by eight-color flow cytometry in combination with a conventional panel of flow cytometry markers. The study included 70 control samples, 63 samples with CLL or atypical CLL phenotype, 6 MCL samples, and 40 samples of other mature B cell neoplasms.

RESULTS

All CLL samples were positive for CD200, whereas MCL samples were dim or negative for CD200. Of the CLL samples, 7 were atypical by conventional flow cytometry, with Matutes scores ≤3. These cases were tested for evidence of a t(11;14) translocation, characteristic of MCL, and all were negative, consistent with their classification as atypical CLL. All these atypical CLL samples were strongly positive for CD200.

CONCLUSION

CD200 proved to be a useful marker for differentiation between CLL and MCL by flow cytometry. In particular, CD200 was useful in distinguishing CLL samples with atypical immunophenotypes from MCL.

Paroxysmal nocturnal haemoglobinuria. Experience over a 10 years period

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic, clonal and acquired disorder of the hematopoietic stem cell with a deficiency of all glycophosphatidyl-inositol (GPI) linked proteins. The aim of this retrospective study was to analyse haematological and biochemical data from 152 patients referred to our laboratory for diagnosis of PNH by flow cytometry (FC).

METHODS

Patients and healthy donor (152 and 99 respectively) were studied. Ham, sucrose, lactate dehydrogenase (LDH), Iron, haptoglobin (Hp), blood cell morphology and Kaplow cytochemical stain for leukocyte alkaline phosphatase (LAP) were carried out. GPI-proteins anti-CD55 and CD59 in erythrocytes and the former, plus anti CD16b and CD66b on neutrophils were evaluated by FC.

RESULTS

Anemia and/or leukopenia and/or thrombocytopenia, increased reticulocyte count and LDH were observed in patients with PNH clone. Some of them had dacriocytes, schistocytes. LAP was low. On average, we detected 50% CD59 (-) erythrocytes and 29, 83, 78% CD55/59 (-), CD16b (-), CD66b (-) neutrophils, respectively.

CONCLUSION

Paroxysmal nocturnal hemoglobinuria clone was detected in 20/152 patients. Negative population's percentages were high in patients with classic PNH, Hematimetry, LAP and adequate use of CF contribute to PNH clone detection in the laboratory.

Expression of adhesion molecules on myeloma cells

We investigated the expression of adhesion molecules including LFA-1 alpha (CD11a), Mac-1 (CD11b), LFA-1 beta (CD18), VLA-beta 1 (CD29), H-CAM (CD44), VLA-4 (CD49d), VLA-5 (CD49e), ICAM-1 (CD54), N-CAM (CD56), LFA-3 (CD58), VNR-beta (CD61), and LECAM-1 (CD62L) on fresh myeloma cells and human myeloma cell lines. By two-color flow cytometric analysis with anti-CD38 antibody, we demonstrated that myeloma cells were located in the strongly CD38-positive (CD38++) fractions. Fresh myeloma cells were obtained from 28 patients with multiple myeloma (MM) and 3 patients with plasma cell leukemia (PCL). All myeloma cells expressed VLA-4 on their surface. Most of the myeloma cells also expressed VLA-5, ICAM-1, and LFA-3, H-CAM was strongly expressed in 3 cases of PCL and 2 cases of aggressive myeloma, and moderately expressed in other MMs. N-CAM was expressed in 68% of MMs, but none of the 3 PCLs. LFA-1 was expressed in two cases of aggressive myeloma, but not expressed in other non-aggressive myelomas. Most of the myeloma cells did not express Mac-1, VNR-beta, or LECAM-1. These results suggest that VLA-4, VLA-5, ICAM-1, LFA-3, and H-CAM are involved in cellular interaction and migration in MM, and that the expression of N-CAM and LFA-1 varies with disease activity in MM.