Issue Highlights—July 2013

Authors


Correspondence to: R. Clive Landis, Edmund Cohen Laboratory for Vascular Research, Chronic Disease Research Centre, University of the West Indies, Barbados. E-mail: clive.landis@cavehill.uwi.edu

CD38 IN REVIEW

This issue leads with a wide-ranging review by Fabio Malavasi's group on the history, genetics, basic science, and disease associations of CD38 and its homolog CD157. CD38 will be familiar to flow cytometrists to identify plasma cells and as a prognostic marker for chronic lymphocytic leukemia (CLL; [1-3]). It has also found utility in a developing world setting as part of a relatively cost-effective minimal residual disease panel applicable to 90% of acute lymphoblastic leukemias [4]. High levels of CD38 expressed on CD8 T lymphocytes also act as a surrogate marker for disease progression in HIV infection [5]. This review discusses CD38 and CD157 in a rich biological and clinical context to enhance our understanding of these multifunctional molecules endowed with enzymatic properties in the regulation of immune activation and integration of signals within the prevailing microenvironment. This review is likely to prove popular with readers both from within and without the flow cytometry field.

ADVANCES IN CEREBROSPINAL FLUID CYTOMETRY

Analysis of cerebrospinal fluid (CSF) presents some challenges to flow cytometrists, from limited sample volume, paucicellularity, and continued loss of cell counts post collection. Nevertheless, flow cytometry is becoming the technique of choice to define the immunopathology in neuroinflammatory diseases and neoplastic meningitis [6-9]. In this issue, Gratama and colleagues have compared the distribution of effector memory (CD45RA-CD27/28+) and late memory (CD45RA+) T lymphocytes between cerebrospinal and peripheral blood compartments, in cytomegalovirus (CMV) infected and noninfected individuals. Flow cytometry is anticipated to gain in popularity as a technique to analyze CSF following recent improvements to cell recovery through stabilization protocols [10, 11].

THERAPEUTIC TARGETING OF BIOMARKERS

There is great interest in extending CD markers from diagnostic targets to therapeutic targets in the treatment of hematological malignancies [12]. In this issue, Wenli Zheng and colleagues present an exploratory article examining the expression and stability of biomarkers on plasma cell myelomas that could potentially serve as therapeutic targets in future. CD49d is identified as a highly expressed and stable marker, for which therapeutic antibodies already exist [13].

PAROXYSMAL NOCTURNAL HEMOGLOBINURIA IN THE MAINSTREAM

Interest in flow cytometric testing for paroxysmal nocturnal hemoglobinuria (PNH) has mushroomed since publication of the International Clinical Cytometry Society Guidelines in 2010 [14]. Flow cytometry is now accepted as the definitive test for PNH, which is characterized by loss of glycosylphosphatidylinositol (GPI)-linked proteins such as CD59, CD71, or CD235. Further practical refinements in how to automate the analysis and how to compose the “perfect cocktail” of antibody clones were proposed in 2012 by groups led by Bagwell, Sutherland, and Paterakis [15-17]. Now Andrea Illingworth and colleagues have field-tested the Practical Guidelines proposed by Sutherland in a real-life setting comprising five hematology centers in Central Europe. This revealed good intra and interlaboratory performance for the Practical Guidelines in both precision and reproducibility, regardless of PNH clone size.

Bcl-2 AS A BIOMARKER FOR CLL PHENOTYPING

Readers of Cytometry B will be familiar with the use of intracellular staining for zeta-chain-associated protein kinase (ZAP) 70 as a biomarker for poor prognosis in B cell CLL [18-21]. This issue sees a fascinating extension of this paradigm to the proto-oncogene Bcl-2, whose expression is controlled via microRNA encoded in the chromosomal region 13q14 commonly deleted in CLL. Marti and colleagues describe an intracellular Bcl-2 gating strategy that uses T cell expression as an internal control to generate a so-called c-index of Bcl-2 expression. A high c-index is strongly statistically associated with 13q14 deletion and can distinguish homozygous, heterozygous, and diploid CLL clonal cells. As with ZAP70, further work is warranted to ensure that the c-index is not affected by any gating artifacts [22].

NOTHING BEATS A FIELD-TEST

There has been some debate regarding the superiority of single versus dual platform technologies to enumerate CD4 T lymphocytes in monitoring the immune status of patients with HIV. Multicentre studies in developed- versus developing- world settings have sometimes yielded contrasting results [23-25]. In this issue, the UK NEQAS organization analyzed results from 824 laboratories worldwide participating in their external quality assurance scheme, comparing the relative error and confidence limits for CD4 absolute counts between single versus dual platform technologies. This revealed significantly improved performance by single platform technologies to reduce variability in the clinically relevant range >350 CD4 counts/ml.

NEW FRONTIERS IN PERSONALIZED CYTOMICS

An exciting proof of principle article by the group of Emile Mohler (Kurtzman et al.) has pushed back the frontiers of personalized cytomics with an evaluation of vascular heath profiles in patients with long-term type 2 diabetes (at high risk of cardiovascular events). Previous studies published in this and other journals have explored the use of flow cytometry to detect circulating progenitor cells and prothrombotic microparticles that may influence vascular health [26-28]. In this issue, the Mohler group adopted a systems biology approach to integrate these cytomic measures without a priori criteria to identify unique patterns in diabetic versus control populations and to create personalized vascular health signatures for individuals.

ADVANCES IN MYELODYSPLASIA DIAGNOSTICS

New cytometric approaches to myelodysplastic syndrome (MDS) diagnosis have been a hot topic in the journal recently [29-32]. Here Feng Xu and colleagues constructed a progressive cytometric scoring system comprised of CD34 expression and CD19/CD117 expression on CD34 blasts as a technique to discriminate MDS from nonclonal cytopenias. What makes this article unusual is that it also contained a prospective validation cohort and this showed convincing association between a high-flow cytometric progress score with disease progression and death.

  • R. Clive Landis*

  • University of the West Indies, Barbados

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