Enumeration of peripheral lymphocyte subsets using 6 vs. 4 color staining: A clinical evaluation of a new flowcytometer

Flow cytometric evaluation of peripheral blood for suspected Sézary syndrome or mycosis fungoides: International guidelines for assay characteristics

A peripheral blood flow cytometric assay for Sézary syndrome (SS) or circulating mycosis fungoides (MF) cells must be able to reliably identify, characterize, and enumerate T-cells with an immunophenotype that differs from non-neoplastic T-cells. Although it is also important to distinguish SS and MF from other subtypes of T-cell neoplasm, this usually requires information in addition to the immunophenotype, such as clinical and morphologic features. This article outlines the approach recommended by an international group with experience and expertise in this area. The following key points are discussed: (a) At a minimum, a flow cytometric assay for SS and MF should include the following six antibodies: CD3, CD4, CD7, CD8, CD26, and CD45. (b) An analysis template must reliably detect abnormal T-cells, even when they lack staining for CD3 or CD45, or demonstrate a phenotype that is not characteristic of normal T-cells. (c) Gating strategies to identify abnormal T-cells should be based on the identification of subsets with distinctly homogenous immunophenotypic properties that are different from those expected for normal T-cells. (d) The blood concentration of abnormal cells, based on any immunophenotypic abnormalities indicative of MF or SS, should be calculated by either direct enumeration or a dual-platform method, and reported.

New tools in cytometry

Cytometry aims to analyze cells, of any type, using dedicated instruments. The quantitative aspect makes flow cytometry (FCM) a good complementary tool for morphology. Most of the identification tools are based on immunostaining of cell structure details and more and more tools are available in terms of specificities and labels. FCM is under exponential development thanks to technical, immunological and data analysis progresses. Actual generations are now routinely using 6 to 10 simultaneous immuno-labeling on 20 to 100,000 cells, at high speed and short sample preparation and can easily detect rare events at frequency below 10^-4 cells. Data interpretation is complex and requires expertise. Mathematical tools are available to support analysis and classification of cells based. Cells from tissues can also be analyzed by FCM after mechanical and or enzymatic separation, but in situ cells can also be analyzed with the help of cytometry. Very new instruments bring spectral analysis, image in flow and mass spectrometry. Medical applications are very broad, notably in hemopathies, immunology, solid tumors, but also microbiology, toxicology, drug discovery, food and environmental industry. But, the limit of FCM is its dependence on operator from sample preparation, instrument settings up to data analysis and a strong effort is now under progress for standardization and constitution of international data bank for references and education.

Lymphocyte subpopulations in premature infants: an observational study

BACKGROUND AND OBJECTIVES

The infant's immune system evolves over the first months and years of life. Strong correlation exists between lymphocyte count, lymphocyte subpopulations and gestational age at birth. Associations with antenatal and postnatal steroid treatment, infection and chronic lung disease have also been described. Few published studies report the effect of increasing postnatal age (PNA) and comorbidities on lymphocyte subpopulations in premature infants beyond the first 4 months of life. This study aimed to describe changes in lymphocyte subpopulations in preterm infants up to 13 months PNA.

METHODS

Premature infants (23-34 weeks completed gestation) from five centres had lymphocyte subpopulations measured at 2, 5 or 7, 12 and 13 months PNA alongside their vaccine responses in a vaccination trial.

RESULTS

393 blood samples from 151 babies were analysed. There was an increase in absolute numbers of total lymphocytes (median cell count 6.21×10⁹/L at 13 months compared with 4.9×10⁹/L at 2 months PNA) and CD3⁺, CD4⁺, CD8⁺, natural killer and B cells with increasing age. At 2 months PNA, there was a positive correlation between gestation and CD3⁺ and CD4⁺ counts (r=0.32 and 0.46, respectively) and proportions (r=0.22 and 0.41, respectively), and CD4⁺:CD8⁺ ratios (r=0.57), but a negative correlation with CD8⁺ proportions (r=-0.32).

CONCLUSIONS

This longitudinal study describes the distribution of lymphocyte subpopulations in premature infants and provides reference ranges for the major lymphocyte subsets to help guide clinicians when assessing premature infants for immunodeficiency in the first year of life.

TRIAL REGISTRATION NUMBER

EudraCT 2007-007535-23.

Thirty-five years of CD4 T-cell counting in HIV infection: From flow cytometry in the lab to point-of-care testing in the field

CD4 T-cell counting was introduced in clinical laboratories shortly after the discovery of the human immune deficiency virus (HIV) in the early eighties. In western clinical laboratories, improvements in the CD4 T-cell counting methods were mainly driven by progress in the field of flow cytometry and immunology. In contrast, the development of dedicated CD4 T-cell counting technologies were needs driven. When antiretroviral treatment (ART) was made available on a large scale by international Acquired Immune Deficiency Syndrome (AIDS) relief programs to HIV+ patients living in low income countries in 2003, there was a distinct need for simplified and affordable CD4 T-cell counting technologies. The first decade of 2000, several compact flow cytometers appeared on the market, mainly to the benefit of low income countries with limited resources. More recently, however, portable point-of-care (POC) CD4 T-cell counting devices have been developed especially to improve access to affordable monitoring of HIV+ patients in low income countries. The accuracy of these POC instruments is not yet very well documented as many are still under development and clinical validation but preliminary evidence is encouraging. The new HIV treatment guidelines released by the World Health Organization in 2016 give CD4 T-cell counting a less central role in the management of HIV infection. It is, therefore, to be expected that CD4 T-cell counting will be phased out as a tool to assess eligibility of HIV+ patients for ART in the future. However, CD4 T-cell counting will remain a valuable tool for directing treatment against opportunistic infections. © 2016 International Clinical Cytometry Society.

CD56(dim)CD16(high) and CD56(bright)CD16(-) cell percentages associated with maximum knee extensor strength and incidence of death in elderly

Physical fitness is an indicator of systemic well-being in humans. Little is known about the role of physical fitness for maintaining systemic health in the elderly. Here, we study elderly subjects to determine the relationships between physical fitness and CD56 and CD16 surface NK cell markers on peripheral blood lymphocytes, as well as to analyze the relationship between the surface markers and incidence of death. We selected 253 independent elderly subjects (122 female; 131 male) who were 79–80 years old. Subjects having a higher proportion of CD56^dimCD16^high within CD56⁺CD16⁺ cells, or ration of CD56^dimCD16^high and CD56^dimCD16⁻ cells had a significant positive correlation with maximum bilateral knee extensor strength/weight (kg) (r = 0.425; P < 0.0001 or r = 0.323; P < 0.0001). In contrast, an increased proportion of CD56^brightCD16⁻ cells within lymphocyte significantly negatively correlated with the maximum bilateral knee extensor strength/weight (kg) (r = −0.290; P = 0.0004); and these subjects had a significantly lower mortality during the 5 years following measurement of death. Therefore, we found that a synergistic effect of the right and left leg muscle strength was associated with proportion of matured NK and NKT cells and induced a low proportion of CD56^brightCD16⁻ cells within lymphocyte. Moreover, the low proportion of CD56^brightCD16⁻ cells was associated with incidence of death. In conclusion, measurements of physical fitness, the proportion of CD56^dimCD16^high within CD56⁺CD16⁺ cells, the ratio of CD56^dimCD56^high and CD56^dimCD16⁻ cells, and the proportion of CD56^brightC16⁻ cells in lymphocytes are important indicators to check elderly health.

Lymphocyte subset recovery and outcome after autologous hematopoietic stem cell transplantation for plasma cell myeloma

Rapid immune reconstitution--particularly of natural killer cells (NK cells)--after allogeneic hematopoietic stem cell transplantation (HSCT) is associated with protection from relapse. Whether such an association also exists after autologous stem cell transplantation is less clear. We retrospectively assessed lymphocyte subsets after autologous HSCT in 114 patients and correlated lymphocyte recovery with outcome. CD8 T cell and NK cell counts recovered rapidly to pretransplantation levels, whereas B cell and CD4 T cell recovery were delayed. Compared with patients with low NK cells (<100/uL), high NK cell count at 1 month after HSCT was associated with significantly prolonged progression-free survival: for NK cells 100 to 200/uL hazard ratio [HR], .33 (95% confidence interval [CI]; .16 to .80; P = .004); for NK cells > 200/μL HR, .27 (95% CI, .13 to .58; P = .001). No significant protective effects were associated with rapid recovery of any other lymphocyte subset. None influenced overall survival (OS) or time to next treatment. Early NK cell recovery is associated with better progression-free survival after autologous HSCT. The failure to detect an effect on OS might be due to the salvage strategies available to these patients.

Single-color multitarget flow cytometry using monoclonal antibodies labeled with different intensities of the same fluorochrome

Background

We developed a single-color multitarget flow cytometry (SM-FC) assay, a single-tube assay with graded mean fluorescence intensities (MFIs). We evaluated the repeatability of SM-FC, and its correlation with multicolor flow cytometry (MFC), to assess its application as a routine FC assay.

Methods

We selected CD19, CD3, CD4, and CD8 as antigen targets to analyze a lymphocyte subset. MFIs were graded by adjusting monoclonal antibody (mAb) volumes to detect several cell populations. Dimly labeled mAb was prepared by decreasing mAb volume and the optimum diluted volume was determined by serial dilution. SM-FC repeatability was analyzed 10 times in 2 normal controls. The correlation between SM-FC and MFC was evaluated in 20 normal and 23 patient samples.

Results

CV values (0.8-5.0% and 1.3-4.1% in samples 1 and 2, respectively) acquired by SM-FC with CD3-fluorescein α-isothyocyanate (FITC)_dim+CD4-FITC_bright and with CD19-FITC_dim+CD3-FITC_bright showed good repeatability, comparable to that acquired by MFC (1.6-3.7% and 1.0-4.8% in samples 1 and 2, respectively). Excellent correlation was observed between the 2 methods in the 20 normal samples (B cells, T cells, non-T_helper cells, and T_helper cells; r²=0.87, 0.97, 0.97, and 0.98, respectively; P<0.05). There were also linear relationships between SM-FC with CD19-FITC_dim+CD3-FITC_bright and CD8-PE_dim+CD4-PE_bright, and MFC, in the 23 patient samples (B cells, T cells, T_cytotoxic cells, and T_helper cells; r²≥0.98, 0.99, 0.99, and 0.99, respectively; P<0.05).

Conclusions

The multicolor, single-tube SM-FC technique is a potential alternative tool for identifying a lymphocyte subset.

Variability of CD3 membrane expression and T cell activation capacity

BACKGROUND

AlphabetaT cells have a wide distribution of CD3 membrane density. The aim of this article was to evaluate the significance of the CD3 differential expression on T cell subsets. Analysis was performed on healthy donors and renal transplant patients by flow cytometry. The results obtained are: (1) CD3 expression was widely distributed (CV = 38.3 +/- 3.1 to 43 +/- 2.3%). (2) The CD4, CD8, CD45 and forward scatter were similarly distributed. (3) The diversity of CD3 expression was directly related to the clonotypes: gamma9, non gamma9 from gammadeltaT cells and Vbeta clonotype from alphabetaT cells (e.g., Vbeta3FITC 7,980 +/- 1,628 Vbeta8PE: Vbeta20-FITC 11,768 +/- 1,510). (4) Using a computer simulation, we could confirm differential kinetics of T cell activation according to the initial parameters. Finally, in vitro activation was significantly higher on Vbeta8 and Vbeta9 (high CD3) compared with Vbeta2 and Vbeta3 (low CD3, P = 0.040-0.0003). In conclusion, T cells have highly heterogeneous CD3 expression, possibly predetermined and with clear functional significance.

Lymphocyte subset recovery and outcome after T-cell replete allogeneic hematopoietic SCT

Rapid recovery of lymphocytes after T-cell depleted hematopoietic SCT (HSCT) protects from relapse of myeloid malignancies. Whether lymphocyte reconstitution has a similar role after non-manipulated transplantation is controversial. We assessed numbers of CD4 and CD8 T-cells, natural killer (NK) cells and B-cells, before and 1, 3, 6, 12 and 24 months after T-cell replete transplantation in 345 patients. Lymphocyte subset counts up to 6 months post transplant had no effect on relapse. Elevated number of NK cells 12 months post transplant protected from relapse. As a novel finding, early recovery of NK cells was associated with significant protection from TRM already at the 3 and 6 months time points (P=0.03, P=0.02). In Cox multivariable models, patients with NK cells above 150/μL were significantly protected from TRM (hazard ratio (HR) 0.45, 95% confidence interval (95% CI) 0.21-0.95, P=0.03), an effect comparable in magnitude with that of carrying >200 CD4 T-cells/μL (HR 0.37, 95% CI 0.19-0.74, P=0.005). CD8 T-cell and B-cell recovery did not affect the rates of relapse or TRM. Early reconstitution of NK cells and CD4 T-cells in patients undergoing T-cell replete HSCT independently protected from TRM. Only a weak protection from disease relapse was noted for patients with high numbers of NK cells, and this occurred only late after transplantation.

Toward quantitative fluorescence measurements with multicolor flow cytometry

A procedure is presented for calibrating the output of a multicolor flow cytometer in units of antibodies bound per cell (ABC). The procedure involves two steps. First, each of the fluorescence channels of the flow cytometer is calibrated using Ultra Rainbow beads with assigned values of equivalent number of reference fluorophores (ERF). The objective of this step is to establish a linear relation between the fluorescence signal in a given fluorescence channel of multicolor flow cytometers and the value of ERF. The second step involves a biological standard such as a lymphocyte with a known number of antibody binding sites (e.g., CD4 binding sites). The biological standard is incubated with antibodies labeled with one type of fluorophores for a particular fluorescence channel and serves to translate the ERF scale to an ABC scale. A significant part of the two-step calibration procedure involves the assignment of ERF values to the different populations of Ultra Rainbow beads. The assignment of ERF values quantifies the relative amount of embedded fluorophore mixture in each bead population. It is crucial to insure that the fluorescence signal in a given range of fluorescence emission wavelengths is related linearly to the assigned values of ERF. The biological standard has to poses a known number of binding sites for a given antibody. In addition, this antibody has to be amenable to labeling with different types of fluorophores associated with various fluorescence channels. The present work suggests that all of the requirements for a successful calibration of a multicolor flow cytometer in terms of ABC values can be fulfilled. The calibration procedure is based on firm scientific foundations so that it is easy to envision future improvements in accuracy and ease of implementation.

Evaluation of a multicolor, single-tube technique to enumerate lymphocyte subpopulations

To evaluate the fully automated FACSCanto software, we compared lymphocyte subpopulation counts obtained using three-color FACSCalibur-CELLQuest and six-color FACSCanto-FACSCanto software techniques. High correlations were observed between data obtained with these techniques. Our study indicated that FACSCanto clinical software is accurate and sensitive in single-platform lymphocyte immunophenotyping.

Perinatal stress influences lymphocyte subset counts in neonates. The generation R study

In the general population, it is unknown whether stress-related perinatal factors influence lymphocyte subset counts in neonates. The aim of this study was to assess the associations of perinatal factors related to stress and hypoxia (mode of delivery, Apgar scores, and umbilical cord blood pH) with absolute lymphocyte subset counts (T, B, NK, helper T, cytotoxic T, naïve, memory T) in cord blood of 571 neonates. This study was embedded in a population-based prospective cohort study from fetal life onwards. All models were adjusted for gestational age, birth weight, gender, maternal fever, and each of the other perinatal stress-relating factors. Our results showed that increasing stress-related mode of delivery was positively associated with NK and memory T-lymphocyte subset counts (all p < 0.01). Effects of Apgar scores on lymphocyte subsets were explained by umbilical cord blood pH. Lower umbilical cord blood pH was associated with higher B, NK, and memory T-lymphocyte counts (all p < 0.05). Effects of mode of delivery and umbilical cord blood pH on other lymphocyte subsets were not observed. We conclude that, in the general population, lymphocyte subset counts in neonates increase with increasing stress- and hypoxia-related perinatal factors.

Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis

BACKGROUND

Normal values of lymphocyte subpopulations for healthy children and adults have been published in defined age groups exclusively, which results in difficult data interpretation for patients close to the limit of contiguous age group ranges. In addition, normal values for a number of lymphocyte subpopulations have not been established to date.

OBJECTIVE

The aim of this study was to develop a model which provides continuous age-dependent reference values. This model was applied for lymphocyte subpopulations such as naïve and memory T cells as well as their activation profile with diagnostic relevance in children and adults.

STUDY DESIGN

A total of 100 blood samples, obtained from 80 healthy children and 20 adults were analysed by means of four colour-flow cytometry. Continuous age-dependent reference values were computed based on the residual values in an exponential regression model.

RESULTS

We calculated a continuous age-related regression model for both, absolute cell counts and percentages of CD3(+)CD4(+) T helper (T(H)) cells, CD3(+)CD8(+) cytotoxic T cells, CD56(+)CD3(-) natural killer (NK) cells, CD56(+)CD3(+) T cells, CD3(+)CD4(+)CD45RA(+) naïve T(H) cells, CD3(+)CD4(+)CD45RO(+) memory T(H) cells, CD3(+)CD8(+)CD45RA(+)CD28(+) naïve cytotoxic T cells, CD3(+)CD8(+)CD45RO(+) memory cytotoxic T cells, CD3(+)CD8(+)CD69(+) early activated cytotoxic T cells and CD3(+)CD8(+)HLA-DR(+) late activated cytotoxic T cells, respectively, to obtain reference values.

CONCLUSION

Based on an exponential regression model, the obtained reference values reflect the continuous maturation of lymphocyte subsets during childhood.

Influence of 4- and 6-color flow cytometers and acquisition/analysis softwares on the determination of lymphocyte subsets in HIV infection

BACKGROUND AND OBJECTIVES

Lymphocyte immunophenotyping provides valuable information for the diagnosis and monitoring of patients with cellular immunodeficiencies, such as HIV/AIDS. In this study, we have assessed the influence of 4-color and 6-color flow cytometers, and respective analytical softwares on the enumeration of lymphocytes in HIV infected individuals.

METHODS

The expression of various cell surface markers on lymphocytes was measured from the EDTA blood of 66 HIV infected patients on the FACSCalibur (4-color) and FACSCanto (6-color) flow cytometers. Percentage of lymphocytes expressing a particular cell surface marker was analyzed on FACSCalibur using the Cell Quest Pro software (v 5.2), while the analysis on FACSCanto was done using FACSCanto (v 1.0.3) and FACSDiva (v 4.1) softwares respectively.

RESULTS

The data shows significantly higher mean CD3 T-cell counts on FACSCalibur, Cell Quest Pro (1,864 +/- 1,044 cells/microl) as compared to FACSCanto (1,840 +/- 1,040 cells/microl) (P < 0.05). The CD4 T-cell counts were also higher on FACSCalibur, Cell Quest Pro (885 +/- 770 cells/microl), and FACSDiva (892 +/- 773 cells/microl) versus FACSCanto (867 +/- 767 cells/microl) (P < 0.05). FACSCalibur, Cell Quest Pro, and FACSDiva showed similar values except for CD8 T-lymphocytes where FACSDiva had significantly lower values (P < 0.05). The B-cell counts were unaffected when either of the instruments or softwares were used, while the natural killer (NK) cells (CD16 + 56 positive cells) showed similar trend like CD3 and CD4 counts with significant differences in the mean cell counts between FACSCalibur, Cell Quest Pro (240 +/- 165 cells/microl), and FACSDiva (238 +/- 163 cells/microl) versus FACSCanto with higher NK cell counts (260 +/- 176 cells/microl).

CONCLUSIONS

The enumeration of lymphocyte subsets was comparable between FACSCalibur, Cell Quest Pro, and FACSDiva, based analysis and it was significantly different than FACSCanto software based analysis. Our observations suggest that FACSDiva software should be preferred over the FACSCanto software for immunophenotyping on FACSCanto flow cytometer and the laboratories should report the instrument and software used for the specimen analysis while reporting immunophenotyping results.