Flow Cytometric Method For Detection Research Articles

Establishment of an in vitro flow cytometric detection method for lipid-accumulated cells

Eukaryotic cells can store and converse excess lipid to the cytosolic lipid droplets. Adipogenesis of preadipocytes has been often used to study the molecular basis and the effect of obesity drugs on fat cell conversion. Many methods were developed for the detection of the cytosolic lipid droplets as Nile red, BODIPY 493/503 (4, 4-difluoro-1, 3, 5, 7, 8-pentamethyl-4-bora-3a, 4adiaza-s-indacene), BODIPY 665/676, 1,6-diphenylhexatriene (DPH), DAPI, Hoechst, Sudan III, and Oil-red O. The differences in the spectral properties of these lipophilic dyes and their advantages of each are discussed. In this study, an in vitro flow cytometric detection method was established for the detection of lipid-accumulated cells. Commonly, the longer the period of adipogenic induction, the greater the quantity of lipid in fat cell can accumulate. Thus, to determine whether increasing the fat stored within a cell would result in the greater granularity. 3T3-L1 cells in culture were hormonally induced for adipogenesis. Then, these cells were dissociated and analyzed in a flow cytometer at 0, 5, and 10 days post-induction. After adipogenic induction, the cells had become increasingly heterogeneous in their cellular granularity. The cells containing greater granular structure were markedly increased, and this increase in granularity positively correlated with the time of the post-adipogenic induction. On the other analysis, the 0 and 10 days post adipogenic induction of 3T3-L1 cells were gated for 4 regions. The R1 region contains cells with a level of granularity similar to that seen in the control cells (non-adipogenic induction), whereas R2 to R4 regions contain cells with increasing granularity. According to all data, we have successfully established an in vitro flow cytometric detection method for the detection of lipid-accumulated cells. We wish this method will be applied on the research of obesity drugs and the design of therapeutic strategies for obesity in the future.

O-GlcNAcylation in early stages of chronic lymphocytic leukemia: Protocol development for flow cytometry.

Recent studies proved that metabolic changes in malignant disorders have an impact on protein glycosylation, however, only a few attempts have been made so far to use O-GlcNAc analysis as a prognostic tool. Glucose metabolism is reported to be altered in hematological malignancies thus, we hypothesized that monitoring intracellular O-GlcNAc levels in Rai stage 0-I (Binet A) CLL patients could give deeper insights regarding subtle metabolic changes of progression which are not completely detected by the routine follow-up procedures. In this proof of concept study we established a flow cytometric detection method for the assessment of O-GlcNAcylation as a possible prognostic marker in CLL malignancy which was supported by fluorescence microscopy. Healthy volunteers and CLL patients were recruited for this study. Lymphocytes were isolated, fixed and permeabilised by various methods to find the optimal experimental condition for O-GlcNAc detection by flow cytometry. O-GlcNAc levels were measured and compared to lymphocyte count and various blood parameters including plasma glucose level. The protocol we developed includes red blood cell lysis, formalin fixation, 0.1% Tween 20 permeabilisation and employs standardized cell number per sample and unstained controls. We have found significant correlation between O-GlcNAc levels and WBC (R2= 0.8535, p< 0.0029) and lymphocyte count (R2= 0.9225, p< 0.0006) in CLL patients. Interestingly, there was no such correlation in healthy individuals (R2= 0.05664 for O-GlcNAc vs WBC and R2= 0.04379 for O-GlcNAc vs lymphocytes). Analyzing O-GlcNAc changes in malignant disorders, specifically in malignant hematologic diseases such as CLL, could be a useful tool to monitor the progression of the disease.

Immunodynamics of Paroxysmal Nocturnal Hemoglobinuria

In the context of immune-mediated attack in aplastic anemia (AA), PIGA mutations produce a clonally-restricted escape phenotype in an attempt to restore hematopoiesis. Along with PIGA lesions, HLA class I/II mutations may represent an alternative way to render cytotoxic T cell recognition less effective. Microdeletions of 6p21, uniparental disomy [UPD] of 6p and mutations of HLA genes have been previously identified in AA patients. One could stipulate that paroxysmal nocturnal hemoglobinuria (PNH) may be an alternative mode of clonal evolution as opposed to HLA mutation acquisition or instead be a redundant pathway of immune escape co-existing with such lesions. Here, we took advantage of a large cohort (n=92) of patients with hemolytic PNH (granulocytes clone size >20% and LDH>x2.5 ULN) to elucidate the immunodynamics of PIGA/HLA clone(s) (Fig1A).We first used a deep targeted sequencing panel covering HLA classical loci and applied an in-house newly developed pipeline on 62 patients with PNH. Overall, 35% of cases had HLA alterations, which were found at a similar rate in patients studied at onset (33%) and during the course of the disease (32%). These alterations were classified as allelic losses in 15% of cases while majority of mutations were missense (57%) followed by 5‘ or 3‘ UTR (20%), nonsense (15%) and frameshifts (8%) with a median variant allelic frequency (VAF) of 5% (range, 2-95). Of note, the canonical exon 1 HLA B14:02 mutation (c.19C>T, p.R7X) 1,2was found in 2 patients who both had de novo PNH with a granulocyte clone size of 60% at disease onset (Fig1B).To clarify whether the PNH phenotype conveys an absolute resistance from immune attack, one should determine whether in these patients HLA mutations arise indeed within non-PNH cells. Consequently, we also performed HLA sequencing on 9 patients whose samples (n=18) were previously sorted by flow cytometry to enrich for CD59+ and CD59- fractions. HLA mutations were identified in both CD59+ and CD59- fractions at similar rates (44% each) and VAF (5% vs 3%, p=0.3) while no “canonical” exon 1 mutation was found.When looking at associations with disease-specific characteristics, we did not identify any significant differences in terms of burden of HLA events and disease ontogeny (primary vs secondary to AA cases) as well as baseline demographics characteristics (gender, age at presentation), dominant erythrocytes type (II vs III), and thrombotic events. No correlations with specific types of PIGA mutations nor their burden were found in HLA-mutated vs non-mutated groups as also confirmed by the absence of relationship with PNH granulocyte clone size (62% vs 72%, p=0.5). Of note, in HLA mutants the VAFs of HLA lesions were significantly lower than those of PIGA (5% vs 18%, p<0.001) underlying their possible less powerful role in driving immune escape within the context of AA overshooting reactions. To validate these results, we have designed a highly quantitative flow cytometric method for detection of HLA expression (A, B, C for class I; DQ, DR, DP for class II) on CD59+ vs CD59- fractions of CD34+ and CD15+ cells obtained from PNH patients. Preliminary results in 7 patients showed a general downregulation of HLA expression within PNH clones (delta HLA MFI of CD59+ vs CD59- fractions), consistent with our ability to detect HLA mutations also in PNH cells (Fig1C). This preferential down-modulation on PNH cells suggests a possible selection mechanism operating agonistically and in a non-mutually exclusive fashion with the PNH-intrinsic privilege. Moreover, these findings may also represent a byproduct of antigen processing machinery impairment due to proteasomal accumulation of proteins, which would have been GPI-linked and exported to the membrane.In sum, our study indicates that PNH phenotype conveyed by PIGA mutations operates independently from HLA mutations as means of immune escape. In addition, based on these results we stipulate that HLA down-modulation via various mechanisms is operative in the context of the PNH phenotype and the immune privilege of PIGA clones is not absolutely protective. Patients with PNH may have elements of immune suppression. In fact, their responses in the context of reduced-intensity transplant do eliminate hosts PNH clones following transplantation. 3 [Display omitted] DisclosuresPatel: Alexion: Consultancy, Other: educational talks, Speakers Bureau; Apellis: Consultancy, Other: educational talks, Speakers Bureau. Maciejewski: Bristol Myers Squibb/Celgene: Consultancy; Novartis: Consultancy; Alexion: Consultancy; Regeneron: Consultancy.

A detailed flow cytometric method for detection of low-level in vivo red blood cell–bound IgG, IgA, and IgM

Abstract Flow cytometric methods are commonly used to analyze white blood cell surface antigen expression. We developed a flow cytometric method to detect red blood cell (RBC)-bound immunoglobulin (Ig)G, IgA, and IgM. RBCs were washed; incubated with fluorescein isothiocyanate (FITC)-conjugated anti-IgG, -IgA, or -IgM; washed; and analyzed on the flow cytometer. The method was optimized by determining the dilution of FITC-conjugated anti-IgG, -IgA, and -IgM providing the greatest amount of fluorescence when tested with Ig-coated RBCs and the least amount of fluorescence when tested with naive RBCs. Tannic acid was used to prepare Ig-coated RBCs. Cross-reactivity of FITC-conjugated anti-IgG, -IgA, and -IgM with Ig-coated RBCs was evaluated, and a reference range was established. Use of this method may assist in clinical evaluation of patients who present with hemolysis and a negative direct antiglobulin test. Immunohematology 2016;32:161–169.

Level 2 validation of a flow cytometric method for detection of Escherichia coli O157:H7 in raw spinach

The Bacteriological Analytical Manual (BAM) method currently used by the United States Food and Drug Administration (FDA) to detect Escherichia coli O157:H7 in spinach was systematically compared to a new flow cytometry based method. This Food and Drug Administration (FDA) level 2 external laboratory validation study was designed to determine the latter method's sensitivity and speed for analysis of this pathogen in raw spinach. Detection of target cell inoculations with a low cell count is critical, since enterohemorrhagic strains of E. coli require an infective dose of as few as 10 cells (Schmid-Hempel and Frank, 2007). Although, according to the FDA, the infectious dose is unknown (Food and Drug Administration, 1993). Therefore, the inoculation level into the spinach, a total of 2.0±2.6 viable E. coli O157 cells, was specified to yield between 25% and 75% detection by the new method, out of 20 samples (10 positives and 10 negatives). This criterion was met in that the new method detected 60% of the nominally positive samples; the corresponding sensitivity of the reference method was 50%. For both methods the most likely explanation for false negatives was that no viable cells were actually introduced into the sample. In this validation study, the flow cytometry method was equal to the BAM in sensitivity and far superior in speed.

A flow cytometric method for the detection of alkaline phosphatase expression on the membrane of neutrophils

Objective To establish a flow cytometric method for the detection of alkaline phosphatase (ALP) expression on the membrane of neutrophils (mNAP). Methods EDTA- K2 anticoagulant venous bloods were collected.Expression of mNAP in peripheral blood was measured by flow cytometry using a phycoerythrin (PE)-labeled anti-ALP monoclonal antibody.BD QuantiBRITE PE was used to generate a calibration curve for PE fluorescence and ratios of PE to anti-ALP antibody and detect the bound ALP antibodies per cell (antibodies bound per cell,AB/c).Preanalytical handling including anticoagulants (EDTA- K2,citrate,and heparin),storage temperature,storage time,and plasma ALP were optimized and measured the precision.The expression levels of mNAP from 481 healthy controls were measured to establish a clinical reference range.The mNAP levels of 84 patients with severe infection and local infection,39 patients with virus infection were determined by this method. Results For preanalytical handling,application of PBS washing can effectively eliminate the interference of plasma ALP.The mNAP levels were not influenced by different anticoagulants and storage conditions (stored for 12 h either at room temperature or 4 ℃).This method had preferable reproducibility (CV in batch were 2.01%-3.33%,average 2.67%; CV between batch were 5.80%-6.00%,average 5.90%).The median (quartiles) of mNAP in health controls were 1 758 (1 378-2 310) AB / c for men and 1 897 (1 369-3 249) AB / c for women.There was no significant difference between genders (U=27 140，P=0.243 8).The clinical reference ranges (2.5 percentile to 97.5 percentile) of mALP was 920.5-3 493.0AB / c.The expression levels of mNAP of patients with bacterial infections (13 532,9 756-16 869 AB / c ) were significantly higher than those of patients with virus infection( 1 143,536-2 012 AB / c) and healthy controls (1879,1399-2497 AB / c)( H=221.5,P<0.01). Conclusion BD QuantiBRITE PE kit can be used to standardize flow cytometer settings and quantitatively detect molecules per cell.The flow cytometric method for detection of mNAP has important clinical application for differentiating bacterial and virus infection.（Chin J Lab Med,2014,37:623-627） Key words: Neutrophils; Cell membrane; Alkaline phosphatase; Flow cytometry; Infection

An eight-colour flow cytometric method for the detection of reference values of lymphocyte subsets in selected healthy donors

Determination of immunoregulatory cells in peripheral blood is important in the management of disease or in the therapeutic approaches that involve alterations in lymphocyte subpopulations. The aims of the present study were (1) to develop a standard multiparametric flow cytometric method for phenotypic detection and enumeration of lymphocyte subsets so as to reduce the variability in both sample preparation methodology and flow cytometric operations; (2) to furnish reference values of lymphocytes by using a selected healthy population; and (3) to examine the influence of age and sex on the distribution of lymphocytes expressing surface markers. Eighty healthy donors were analysed, and ten-parameter, eight-colour analytical procedure was performed. We furnished a panel to detect and to enumerate lymphocyte subpopulations by a multiparametric flow cytometric method to set the reference values to a selected healthy population. These values showed statistically but not clinically significant differences in T lymphocyte subsets and natural killer cells. Furthermore, significant age-related correlations in T lymphocyte and natural killer cells were observed. Lastly, males and females in relation to age showed a significant different trend in T and B lymphocyte subsets. We confirmed that this study provides a rapid and accurate method for the detection and quantification of lymphocyte subsets that could be utilized in the clinical settings. The definition of reference values in the healthy selected population could be helpful also to better define the disease status and to evaluate the treatment efficacy during clinical trials.

Hereditary Hemolytic Anemia in Korea From 1997 to 2011: A Study by the Korean Hereditary Hemolytic Anemia Working Party of the Korean Society of Hematology

AbstractAbstract 5157 Background:With the development of diagnostic technique, an accurate diagnosis of hereditary hemolytic anemia (HHA)- red blood cell (RBC) membranopathy, hemoglobinopathy, RBC enzymopahty – have been made. Therefore, we surveyed the prevalence and characteristics of patients diagnosed as HHA during recent five years in Korea. Methods:Through the use of questionnaires, information on the clinical and laboratory findings of HHA diagnosed from 2007 to 2011 in Korea was collected. The globin gene analysis (direct sequencing) and RBC enzyme analysis was performed at the representative laboratories. A total of 203 cases were collected in this study by the Korean Hereditary Hemolytic Anemia Working Party of the Korean Society of Hematology. Results:Patients number of RBC membranopathy, hemoglobinopathy, and RBC enzymopahty was 125, 47, and 31, respectively. Percentage of patients with dominant family history was 57% in patients with hereditary spherocytosis (n=116) and dominant symptoms were anemia, jaundice, splenomegaly and gallstones. Osmotic fragility test and flow cytometric method for detection of RBC membrane defect were performed about 60% of patients. RBC membrane protein analysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis was performed on 59 patients. Of the 47 cases of hemoglobinopathies, 36 cases (77%) were β-thalassemia minor, 10 cases (21%) were α-thalassemia minor and one case (2%) was unstable Hb, Hb M-Saskatoon (beta 64 His-→Tyr). Median age at diagnosis was 7 years (range: 6 months–58 years). Eleven of 47 cases (23%) had family history of HHA. As all thalassemia patients were thalassemia minor, they presented with mild jaundice or pallor. Of the 31 patients were diagnosed as RBC membranopathy, pyruvate kinase deficiency was 3 cases and glucose-6 phosphate dehydrogenase deficiency was 2, and other various forms were reported. Conclusions:We could confirm that accurate diagnosis has been made in more patients using elegant diagnostic technique. However, more defined diagnostic approaches were needed in this rare disease and further systematic supporting systems for patients and their families were warranted in public health aspect. Disclosures:No relevant conflicts of interest to declare.

Many genetically defined ABO subgroups exhibit characteristic flow cytometric patterns

A flow cytometric method for detection of low levels of A/B antigen had been developed previously in our laboratory. The aim of this study was to investigate if this approach could be utilized to characterize different ABO subgroups and constitute a useful tool in a reference laboratory. Blood samples causing ABO discrepancies (n = 94) by routine serology were further analyzed by ABO genotyping and flow cytometry. To verify the specificity of the monoclonal anti-A and -B reagents and to establish normal flow cytometric patterns, samples from 80 blood donors with common phenotypes were also assessed. Distinguishable flow cytometric patterns were detected for several subgroups but were more apparent for A(weak) (n = 80) samples than B(weak) (n = 14). Two subgroups, A(finn) (n = 11) and A(3) (n = 10) displayed diagnostic features and were used to establish reproduciblity over time and between donors. In general, the consistency within subgroups was remarkable. The allelic enhancement phenomenon was clearly visualized among A(x) samples (n = 10) where different alleles in trans resulted in high, low, or no A antigen expression. Nonsubgroup samples including O/A and O/B chimeras or A(h) and B(h) para-Bombay phenotypes displayed clearly distinguishable histograms. Samples from pregnant women (n = 10) displayed acquired A antigen loss, apparently accentuated during the third trimester. Genetically defined ABO subgroups and other anomalous phenotypes displayed flow cytometric profiles that may contribute valuable information to the investigation of ABO discrepancies. We conclude that the presented assay may complement traditional serology and genetic analysis in the reference laboratory setting.

A flow cytometric method for detection and enumeration of low‐level, residual red blood cells in platelets and mononuclear cell products

Conventional automated cell counters cannot accurately count residual red blood cells (rRBCs) that are often present in various blood products. A two-color flow cytometric method (FC) was validated for detecting and enumerating rRBCs in platelets (PLTs) and mononuclear cell (MNC) products. PLT and MNC products for PLTs (CD61-fluorescein isothiocyanate) and rRBC (anti-glycophorin A-phycoerythrin) were double stained, and data were acquired with a flow cytometer. Assay linearity, accuracy, and precision were assessed with a standard-dilution series of rRBCs. This assay was used to determine the rRBCs of apheresis PLTs collected with Trima Accel (Gambro BCT) and MNC products collected with the COBE Spectra (Gambro BCT). The linear range of this assay in PLT and MNC products is 10 to 2000 RBCs per microL (R2=0.994). FC had a mean intraassay coefficient of variation of 11.8 percent at 34 RBCs per microL. A standard clinical hematology analyzer overestimated rRBCs in MNC products by 1.59x10(5)+/-0.7x10(5) RBCs per microL. Apheresis PLTs had a median of 17.4 RBCs per microL, with 99.0 percent containing fewer than 90.0 RBCs per microL. This method for determining rRBCs in blood products is accurate and repeatable with a lower limit of detection adequate to assess currently available blood products. FC should be considered for determining rRBCs in MNC products.

Lack of circulating megakaryoblasts in newborn peripheral blood: development and validation of a sensitive flow cytometric detection method.

It is currently thought that approximately 1% of children with Down syndrome will develop a "premalignant" syndrome known as transient myeloproliferative disorder (TMD). Prospective, population-based studies of the incidence of TMD in Down syndrome infants is lacking. Although most cases of TMD resolve by 1 year of age, data suggest that 10% to 20% of Down syndrome patients with TMD develop AML-M7 (megakaryoblastic leukemia). To identify the true incidence of TMD in the Down syndrome population, a sensitive, rapid, and cost-effective method of quantifying circulating megakaryoblasts in large numbers of patients was needed. In this pilot study, the authors tested the hypothesis that there are fewer than 1% megakaryoblasts of nucleated cells circulating in the blood of normosomic infants. Four-antigen flow cytometry was used to establish the percentage of megakaryoblasts present in each of 100 cord blood samples collected blindly from "normosomic" live births. There was a mean percentage of 0.017% megakaryoblasts in 100 cord blood samples from normosomic infants. Flow cytometry proved to be a sensitive, rapid, and reproducible method for the quantification of megakaryoblasts. Less than 1% of circulating nucleated cells in the blood of newborn infants are megakaryoblasts, providing a comparison population for the authors' larger proposed incidence study.

Isolation of Circulating Cancer Cells From Whole Blood By Immunomagnetic Cell Enrichment and Unenriched Immunocytochemistry In Vitro

Isolation of Circulating Cancer Cells From Whole Blood By Immunomagnetic Cell Enrichment and Unenriched Immunocytochemistry In Vitro

Flow cytometric methods for detection and quantification of apoptosis.

The accumulation of cells characteristic of neoplastic disease results from the combination of unrestrained cell growth and diminished cell death. One form of programmed cell death, apoptosis (a Greek neologism meaning “dropping off” that conjures images of leaves falling from a tree in autumn), is an important mechanism of normal cellular population control (1). Cells that are physiologically unwanted (e.g., auto-reactive lymphocytes) and cells that have suffered irreversible DNA-damaging injury (e.g., from ultraviolet light or irradiation) may be eliminated via apoptosis. Cytoreductive antineoplastic therapy operates in part by triggering apoptosis of susceptible cells (2,3).

New diagnostic tool for differentiation of idiopathic hypereosinophilic syndrome (HES) and secondary eosinophilic states.

The hypereosinophilic syndrome (HES) is a very rare disease, characterized by persistent eosinophilia with tissue involvement and organ dysfunction which often precedes a subsequent T cell lymphoma. Interleukin-5 secreted by a T lymphocyte subpopulation has been described in previous reports as the most important factor responsible for the prolonged lifespan of the eosinophils. The goal of the present study was to describe a fast, simple diagnostic method for the differentiation of HES and secondary eosinophilic states. Beside the surface marker analysis of peripheral blood mononuclear cells (PBMC) we measured surface bound IgE molecules on lymphocytes and eosinophil cells, intracellular cytokines (IL-5, INFgamma) in CD4+ lymphocytes and eosinophil major basic protein (MBP) in eosinophils using flow cytometric detection method. The appearance of an IL-5 producing cell population with a decreased number of INFgamma positive lymphocytes was characteristic for the blood samples of HES patients. Predominance of Th2 cells with the appearance of a CD8+/CD3 /CD56+ cell population was restricted for the HES cases and could not be detected in secondary eosinophilic individuals. Our flow cytometric cytokine detection method (with parallel cell surface marker analysis) does not require cell separation or long term cell culture steps previously described for the detection of IL-5 producing cells. Therefore it seems to be a more appropriate approach for the differential diagnosis of primary and secondary eosinophilic states.

Assessment of In Vitro-Generated Platelet Microparticles Using a Modified Flow Cytometric Strategy

Quantification of platelet microparticles (PMPs) may be a useful marker for the detection of in vivo platelet activation. Optimisation of flow cytometric methods for detection and quantification of PMPs has not been systemically evaluated. This study reports the optimisation of flow cytometric procedures for the detection of PMPs, the determination of limits of size detection using microbeads, and the characterisation of PMP generation by in vitro activation of platelets using collagen and adenosine 5′ diphosphate (ADP). Fluorescent and plain microbeads proved useful for defining the limits of the flow cytometer in detecting PMPs. A systematic calibration of the forward scatter (FS) threshold parameter (size) of the flow cytometer using microbeads allowed for the detection of very small particles (down to 0.1 μm diameter). PMPs generated in vitro using ADP and collagen were reliably detected by flow cytometry using monoclonal antibodies (MAb) directed towards platelet surface membrane glycoproteins (Gp). The PMP events were detected in the FS low (i.e., small size events) and fluorescence (FL) high (i.e., platelet Gp MAb-labelled events) region. PMPs of different size profiles were observed for each of the agonists. Flow cytometry can be used as a tool in the assessment of PMPs. As detection of particles of this type is at the limit of resolution of flow cytometers, careful attention is required with the choice of platelet-specific MAb, isotype control, and optimisation of procedure setup and performance.

Evaluation of performance of white blood cell reduction filters: An original flow cytometric method for detection and quantification of cell-derived membrane fragments

Contamination of blood products by white blood cells leads to a risk of transmission of infectious agents, particularly abnormal prion protein, the probable causative agent of new-variant Creutzfeldt-Jakob disease. Blood product filtration could reduce this risk, but the filtration systems might generate potentially infectious membrane fragments. We developed an original flow cytometric method that allows the detection and quantification of membrane fragments in filtered products and the evaluation of the quantity of destroyed cells.This method has four technical requirements: cytofluorometric acquisition of forward scatter parameters on a log scale, use of a fluorescent aliphatic reporter molecule (PKH26-GL) to identify membrane fragments, quantification with fluorescent beads, and the drawing up of a standard curve on the basis of cells destroyed by freezing/thawing to generate cell debris (i.e., quantity of membrane fragments measured versus quantity of destroyed cells).This original method can be used to test new filtration devices and it allows optimization of the filtration process or comparison of different filtration systems. We tested the method with three commercial white cell removal filters. We demonstrated that it is possible to evaluate the filter quality, particularly the likelihood of fragment removal during the filtration process.

A simple and rapid flow cytometric method for detection of porcine cell surface markers

The objective of this study was to develop a rapid and reliable method for flow cytometric analysis of porcine whole blood cells. Fifty-microliters of heparin- or EDTA-treated whole blood was added to wells of a round-bottom 96-well microtitration plate. Each well contained 10 μl of an appropriate dilution of four different antibodies (40 μl total; two primary monoclonal antibodies and two fluorescent-labeled secondary antibodies). For convenience, the antibody mixture could be added to plates 1–2 days prior to assay and stored at 4°C. Once whole blood was added to wells, plates were mixed gently, placed in a sealed bag and incubated in the dark at room temperature for 20 min. Contents of wells were then transferred to polystyrene tubes containing 2 ml of 1.5% formalin in distilled water and mixed gently. Cells were fixed for a minimum of 30 min and then stored in the dark at 4°C until analysis by flow cytometry. Analysis of cell samples may be done up to 3 days after fixation. Results indicate that the percentages of Class I, Class II, CD3, CD8, CD4, CD45, monocyte, gamma-delta T-cell populations, and total number of granulocytes identified using this method were comparable to standard values or to values obtained following separation of white blood cells from red blood cells. The percentage of labeled B-cells was lower than standard values. Total assay time from receipt of blood to acquisition of data by flow cytometry required less than 2 h. This modified assay was shown to be simple, reliable, and useful for screening large numbers of porcine samples in a minimal period of time.

Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry.

The laboratory determination of the level of fetal cells in maternal circulation remains an important support in the obstetrical management of women with suspected uterine trauma and in the proper dose administration of anti-D for prevention of Rh hemolytic disease of the newborn. Limitations in the sensitivity and precision of the widely used manual Kleihauer-Betke test have prompted an increased utilization of flow cytometric methods for fetal cell detection in maternal blood samples. Murine monoclonal antibodies directed against fetal hemoglobin (HbF) were developed, conjugated to fluorescein isothiocyanate, and used in a multiparametric flow cytometric assay developed for the quantitation of fetal red cells. A rapid intracellular staining method using brief glutaraldehyde fixation and Triton X-100 permeabilization prior to monoclonal antibody incubation was developed, along with optimization of the flow cytometric analysis protocol for the analysis of 50,000 cells. The performance of the assay was assessed for linearity and precision and correlated with the Kleihauer-Betke acid elution method. The anti-HbF flow cytometric method showed good correlation with the Kleihauer-Betke method (r2 = 0.86) and superior precision with a CV < 15 percent for blood samples with > 0.1 percent fetal cells. Analysis of 150 blood samples from nonpregnant adults, including individuals with elevated HbF due to hemoglobinopathies and hereditary persistence of HbF, gave a mean value of 0.02 percent fetal cells, and all results were less than 0.1 percent. The anti-HbF flow cytometric method for detection of fetal cells offers a simple, reliable, and more precise alternative to the Kleihauer-Betke manual technique for the assessment of fetomaternal hemorrhage. The method has additional potential applications for the study of HbF levels or frequency of adult red cells with low levels of HbF (F cells) in individuals with hemoglobinopathies.

Antibiotic susceptibility testing forChlamydia trachomatis using flow cytometry

The aim of this study was to compare the effectiveness of two methods of antibiotic susceptibility testing performed on Chlamydia trachomatis-infected cells: a flow cytometric detection method and the standard method, which consists of a microscopic reading of minimal inhibitory concentration (MIC). The L2 reference strain and 13 clinical strains isolated from six patients presenting recurrent infections were tested. McCoy cells infected with an inoculum of 10(5) inclusion forming units (IFU)/ml were incubated with serial dilutions of doxycycline, ofloxacin, and erythromycin. Mean fluorescence intensity (MFI) of cells was determined by flow cytometry after staining of chlamydial inclusions with an anti-Chlamydia fluorescent monoclonal antibody. The end-point values determined by flow cytometry and microscopic reading were equivalent but presented the same imprecision. Calculation of the inhibitory concentration 50 (IC50) by flow cytometry, defined as the antibiotic concentration required to reduce the drug-free control MFI by 50%, allowed a more objective and precise evaluation of antibiotic activity than MIC. Moreover, IC50 values were reproducible, independent of the antibiotic dilution series tested, and could be used to compare the in vitro efficiency of various drugs on C. trachomatis. No resistant strain was found among the 13 clinical isolates of C. trachomatis tested.

Antibiotic susceptibility testing for Chlamydia trachomatis using flow cytometry

The aim of this study was to compare the effectiveness of two methods of antibiotic susceptibility testing performed on Chlamydia trachomatis-infected cells: a flow cytometric detection method and the standard method, which consists of a microscopic reading of minimal inhibitory concentration (MIC). The L2 reference strain and 13 clinical strains isolated from six patients presenting recurrent infections were tested. McCoy cells infected with an inoculum of 105 inclusion forming units (IFU)/ml were incubated with serial dilutions of doxycycline, ofloxacin, and erythromycin. Mean fluorescence intensity (MFI) of cells was determined by flow cytometry after staining of chlamydial inclusions with an anti-Chlamydia fluorescent monoclonal antibody. The end-point values determined by flow cytometry and microscopic reading were equivalent but presented the same imprecision. Calculation of the inhibitory concentration 50 (IC50) by flow cytometry, defined as the antibiotic concentration required to reduce the drug-free control MFI by 50%, allowed a more objective and precise evaluation of antibiotic activity than MIC. Moreover, IC50 values were reproducible, independent of the antibiotic dilution series tested, and could be used to compare the in vitro efficiency of various drugs on C. trachomatis. No resistant strain was found among the 13 clinical isolates of C. trachomatis tested. Cytometry 31:37–44, 1998. © 1998 Wiley-Liss, Inc.