Improved flow cytometric method to enumerate residual cells: minimal linear detection limits for platelets, erythrocytes, and leukocytes

Light-Triggered Drug Release from Red Blood Cells Suppresses Arthritic Inflammation

Arthritis is a leading cause of disability in adults, which can be intensely incapacitating. The location and intensity of the pain is both subjective and challenging to manage. Consequently, patient-directed delivery of anti-inflammatories is an essential component of future therapeutic strategies for the management of this disorder. We describe the design and application of a light responsive red blood cell (RBC) conveyed dexamethasone (Dex) construct that enables targeted drug delivery upon illumination of the inflamed site. The red wavelength (650 nm) responsive nature of the phototherapeutic was validated using tissue phantoms mimicking the light absorbing properties of various skin types. Furthermore, photoreleased Dex has the same impact on cellular responses as conventional Dex. Murine RBCs containing the photoactivatable therapeutic display comparable circulation properties as fluorescently labelled RBCs. In addition, a single dose of light-targeted Dex delivery is 5-fold more effective in suppressing inflammation than the parent drug, delivered serially over multiple days. These results are consistent with the notion that the circulatory system be used as an on-command drug depot, providing the means to therapeutically target diseased sites both efficiently and effectively.

Biochemical and cellular markers differentiate recovered, in-line filtered plasma, and plasma obtained by apheresis methods

BACKGROUND AND OBJECTIVES

Assessment of plasma quality often focuses on the common safety tests for minimizing the risk of transmitting blood-borne pathogens. Little attention is paid to the possible quality attributes that ensure a consistent biochemical composition of plasma for fractionation. We therefore investigated the suitability of selected biochemical and haematological attributes that could be used as markers of plasma quality obtained by different separation and pre-treatment procedures.

MATERIAL AND METHODS

We characterized six plasma types, including source plasma, plasma recovered by classic means and in-line filtered plasma, by determining the analytical attributes protein content, coagulation factors and markers of coagulation, contact and complement activation. Residual cell content and cell-specific variables were also measured.

RESULTS

We found relevant differences between the plasma types in complement activation, as indicated by C3a measurements, while thrombin antithrombin complex values and, to a minor extent, activated factor XII concentrations indicated only moderate differences in activation levels of coagulation and contact systems. The most striking differences, however, were detected in residual cell content and concentrations of the platelet-associated proteins, platelet factor 4 and β-thromboglobulin. We showed that leucocyte reduction filters disrupt cells. This includes platelets, thereby releasing the platelet-associated proteins platelet factor 4 and β-thromboglobulin, and leucocytes as demonstrated by the release of elastase from polymorphonuclear leucocytes. Furthermore, the filtration processing of whole blood can lead to activation of the complement system.

CONCLUSION

Our results show that biochemical and cellular surrogate markers are valuable discriminators of plasma types.

Residual red cells in blood components: A multisite study of fully automated enumeration using a hematology analyzer

Background

Manufacture of platelet concentrates (PCs) and plasma may fail to remove all residual red blood cells (rRBCs). Measuring rRBCs for compliance to guidelines has proven challenging, leading to an absence of a consensus methodology. Sysmex hematology analyzers with the Blood Bank mode (BB mode) analysis option offer the potential for automated rRBC counting. We therefore performed a two‐site appraisal of the system.

Study Design and Methods

Performance characteristics were determined using platelet and plasma samples spiked with RBCs. Sample stability (n = 47) and the impact of sample type were also assessed. Components (platelets, n = 1474; plasma, n = 77) prepared using different routine manufacturing methods were tested to assess variation in rRBC concentration.

Results

Linearity studies up to 19 000 RBCs/μL demonstrated good correlation between expected and observed results (R² ≥ 0.9731), and flow cytometric results also correlated well with BB mode (R² = 0.9400). Precision analysis gave a limit of quantitation of 6 to 7 RBCs/μL, and carryover was 0.03%. Ethylenediaminetetraacetic acid and plain tube results were not significantly different (P ≥ 0.10), and samples were stable up to 24 hours. Apheresis PCs produced at two sites had lower rRBC concentrations (medians, 17 and 13 RBCs/μL) than those produced with the buffy coat method either manually (median, 681 RBCs/μL) or with the automated Terumo Automated Centrifuge and Separator Integration process (median, 81 RBCs/μL). All PCs failing visual inspection as having RBCs ≥4000 RBCs/μL were also detected by the BB mode.

Conclusion

The BB mode had acceptable performance characteristics and has the potential for integration into a fully automated process control system for rRBC enumeration in plasma and PCs.

Evaluation of droplet digital PCR for quantification of residual leucocytes in red blood cell concentrates

BACKGROUND AND OBJECTIVES

Enumeration of residual white blood cells in leucoreduced blood components is essential part of quality control. Digital PCR has substantially facilitated quantitative PCR and was thus evaluated for measurements of leucocytes.

MATERIALS AND METHODS

Target for quantification of leucocytes by digital droplet PCR was the blood group gene RHCE. The SPEF1 gene was added as internal control for the entire assay starting with automated DNA extraction. The sensitivity of the method was determined by serial dilutions of standard samples. Quality control samples were analysed within 24 h, 7 days and 6 months after collection. Routine samples from leucodepleted red blood cell concentrates (n = 150) were evaluated in parallel by flow-cytometry (LeucoCount) and by digital PCR.

RESULTS

Digital PCR reliably detected at least 0·4 leucocytes per assay. The mean difference between PCR and flow-cytometric results from 150 units was -0·01 (±1·0). DNA samples were stable for up to at least six months. PCR measurement of leucocytes in samples from plasma and platelet concentrates also provided valid results in a pilot study.

CONCLUSION

Droplet digital PCR to enumerate leucocytes offers an alternative for quality control of leucoreduced blood products. Sensitivity, specificity and reproducibility are comparable to flow-cytometry. The option to collect samples over an extended period of time and the automatization introduce attractive features for routine quality control.

Novel single-platform multiparameter FCM analysis of apoptosis: Significant differences between wash and no-wash procedure

FCM is a generally accepted tool to analyze apoptosis. Unfortunately, the cell preparation of all commercial kits available includes cell washing known to cause cell loss which is most likely to affect apoptotic cells in particular. To address this, we developed a seven-color single-platform no-wash analysis technique and compared the results with those from an analogous procedure including cell washing. A five-color mAb cocktail was employed to address target cells by surface labeling, Yo-PRO-1® and DAPI were used to discriminate apoptotic and necrotic from viable cells. Cells were quantified on the basis of internal-standard fluorescent beads. Jurkat cells ACC 282 treated with camptothecin were employed to establish the staining procedure, which was then applied to blood cells collected by extracorporeal apheresis and treated with UV irradiation. Data evaluation showed that although each method by itself was highly reproducible (R(2) = 0.973), the numbers of apoptotic cells detected with the no-wash procedure were significantly higher than those obtained after cell washing (P = 6.6 E(-5), Wilcoxon Test). In addition, the observed differences increased with higher cell numbers (Bland and Altmann). We conclude that the described test is a feasible and reliable tool for apoptosis measurement and it provides results that are definitely closer to the truth than those obtained from kits that require cell washing.

Depletion of peripheral blood B cells with Rituximab and phenotype characterization of the recovering population in a patient with follicular lymphoma

The monoclonal antibody Rituximab is useful for treatment of patients with B-cell non-Hodgkin's lymphoma. We phenotypically analyzed reconstitution of peripheral B cells in a male patient with follicular lymphoma following their depletion with Rituximab. CD19+ and CD20+ B cell counts in peripheral blood decreased rapidly following Rituximab treatment. Six months after the end of treatment, a few CD19+ B cells were detected in peripheral blood. These cells had a naive B cell phenotype (IgD+, CD27-) and they expressed high levels of CD38 and CD24, which show that the B cell pool was repopulated mainly with immature, naive B cells.

Quantitative measurement of Plasmodium-infected erythrocytes in murine models of malaria by flow cytometry using bidimensional assessment of SYTO-16 fluorescence

Flow cytometry is a powerful tool for measuring parasitemias in murine malaria models used to test new antimalarials. Measurement of the emission of the nonpermeable nucleic acid dye YOYO-1 (at 530 and 585 nm after excitation at 488 nm) allowed the unambiguous detection of low parasitemias (> or =0.01%) but required prolonged fixation and permeabilization of the sample. Thus, we tested whether this issue could be overcome by use of the cell-permeant dye SYTO-16 with this same bidimensional method. Blood samples from CD1 mice infected with Plasmodium yoelii, Plasmodium vinckei, or Plasmodium chabaudi or from NOD(scidbeta2m-/-) engrafted with human erythrocytes and infected with P. falciparum were stained with SYTO-16 in the presence or absence of TER-119 mAb (for engrafted mice) in 96-well plate format and acquired in Trucount tubes. Bidimensional analysis with SYTO-16 was quantitatively equivalent to YOYO-1. Moreover, by combining SYTO-16 with the use of TER-119-PE antimouse erythrocyte mAb and Trucount tubes, the measurement of the concentration of P. falciparum-infected erythrocytes over a range of five orders of magnitude was achieved. Bidimensional analysis using SYTO-16 can be used to accurately measure the concentration of Plasmodium spp.-infected erythrocytes in mice without complex sample preparation.

A murine model of falciparum-malaria by in vivo selection of competent strains in non-myelodepleted mice engrafted with human erythrocytes

To counter the global threat caused by Plasmodium falciparum malaria, new drugs and vaccines are urgently needed. However, there are no practical animal models because P. falciparum infects human erythrocytes almost exclusively. Here we describe a reliable falciparum murine model of malaria by generating strains of P. falciparum in vivo that can infect immunodeficient mice engrafted with human erythrocytes. We infected NOD(scid/beta2m-/-) mice engrafted with human erythrocytes with P. falciparum obtained from in vitro cultures. After apparent clearance, we obtained isolates of P. falciparum able to grow in peripheral blood of engrafted NOD(scid/beta2m-/-) mice. Of the isolates obtained, we expanded in vivo and established the isolate Pf3D7(0087/N9) as a reference strain for model development. Pf3D7(0087/N9) caused productive persistent infections in 100% of engrafted mice infected intravenously. The infection caused a relative anemia due to selective elimination of human erythrocytes by a mechanism dependent on parasite density in peripheral blood. Using this model, we implemented and validated a reproducible assay of antimalarial activity useful for drug discovery. Thus, our results demonstrate that P. falciparum contains clones able to grow reproducibly in mice engrafted with human erythrocytes without the use of myeloablative methods.

Flow cytometric and morphological characterization of platelet-rich plasma gel

BACKGROUND OF PROBLEMS: Platelet-rich plasma (PRP) gel is derived from an autogenous preparation of concentrated platelets and is widely used in implant dentistry as a vector for cell growth factors. However, limited data are available on its structure and composition. The present study was aimed at providing a flow cytometric and ultrastructural characterization of PRP gel.

MATERIALS AND METHODS

Twenty PRP gel samples were obtained from healthy volunteers. These PRP gel specimens were prepared for transmission (TEM) and scanning electron microscopy (SEM) examination of their morphological ultrastructure. Flow cytometry with CD41-PE monoclonal antibody was used to detect platelet cells, as this antibody recognizes human-platelet-specific antigen CD41.

RESULTS

Both SEM and TEM showed that PRP gel contains two components: a fibrillar material with striated band similar to fibrin filaments, and a cellular component that contains human platelet cells. Both techniques indicated that no morphological elements were bound between the cellular component and the fibrillar material. The cells were confirmed as platelet cells by flow cytometric study after incubation with specific monoclonal antibody CD41-PE.

CONCLUSION

PRP gel contains a fibrillar and a cellular (largely human platelet cell) component. This unique structure may be capable of acting as a vehicle for carrying of cells that are essential for soft/hard tissue regeneration.

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

BACKGROUND

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.

STUDY DESIGN AND METHODS

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).

RESULTS

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.

CONCLUSIONS

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.

A simple method for quantifying high density antigens in erythrocyte membrane by flow cytometry

RBC flow cytometric analysis is usually used to quantify antigen content. Calibration systems enable antigen content determination by relating mean fluorescence intensity with the number of bound antibody molecules (equivalent to the number of antigen molecules). For that reason, antibodies must be used at saturating concentration, which may lead to agglutination when working with high density antigens. Then, forward scattering, side scattering and fluorescence will be increased, thus obtaining wrong results. In this work, the simple Langmuir adhesion model was applied. Flow cytometry was used to quantify GPA, a transmembrane protein present at high density on RBC. The fluorescence intensity of samples at different anti-GPA sub-saturating concentrations was measured. Sometimes, agglutinates were present and two peaks of fluorescence were observed, the principal one corresponding to isolated cells and the secondary one corresponding to agglutinated cells. In those cases, the principal peak was taken into account for the analysis. The GPA antigen content obtained for nine analyzed samples ranged from 3 to 13 x 10(5) sites per cell, which is similar to those values found in literature. Therefore, the Langmuir adsorption model enables us to determine the antigen content for the anti-GPA/GPA system on RBC membrane. This model could be used to quantify high density antigens in RBC and in other cells.