Whole-blood leukoreduction filters are a source for cryopreserved cells for phenotypic and functional investigations on peripheral blood lymphocytes

Differential composition and yield of leukocytes isolated from various blood component leukoreduction filters

In Flanders, an estimated 300,000 leukoreduction filters are discarded as biological waste in the blood establishment each year. These filters are a possible source of fresh donor leukocytes for downstream purposes including research. We investigated leukocyte isolation from two types of filters either used for the preparation of platelet concentrates (PC-LRF) or erythrocyte concentrates (EC-LRF). Outcome parameters were leukocyte yield, differential count, turnaround time and effect of storage conditions. Leukocytes were harvested by reverse flow of a buffer solution. Control was the gold standard density gradient centrifugation of buffy coats. Total leukocyte number isolated from PC-LRF (1049 (± 40) x 106) was almost double that of control (632 (± 66) x 106) but the differential count was comparable. Total leukocyte number isolated from EC-LRF (78 (± 9) x 106) was significantly lower than control, but the sample was specifically enriched in granulocytes (81 ± 4%) compared to control (30 ± 1%). Isolation of leukocytes from either PC- or EC-LRF takes 20 min compared to 240 min for control density gradient centrifugation. Leukocyte viability is optimal when harvested on day 1 post donation (95 ± 0.9%) compared to day 3 (76.4 ± 2.4%). In conclusion, our study demonstrates that leukoreduction filters from specific blood component processing are easy to use and present a valuable source for viable leukocytes of all types.

Evaluation of a New Method of Leukocyte Extractions from the Leukoreduction Filter

This study's purpose was to optimize the leukocyte extraction protocol and evaluate the efficacy of this new protocol. 12BioR blood filters were collected from Tehran Blood Transfusion Center. A twosyringe system and Multi-step rinsing were designed for cell extraction. The final purpose of this optimization was: (1) removed the residual RBCs, (2) reversed the leukocyte trapping process, and (3) remove the microparticles to obtain the high yield of target cells. Finally, Extracted cells were evaluated by Automated Cell count; Samples smear differential cell count, Trypan blue, and Annexin-PI staining. The results showed that on average 11.88 × 108 ± 3.32 leukocytes recovered after indirect washing and that the mean count of granulocytes, lymphocytes, and Monocyte in this sample was 5.24 ± 2.18 × 108, 5.57 ± 1.74 × 108, and 0.56 ± 0.38 × 108 respectively. Also, the mean percent of manual differential cell count after concentration was 42.81%, 41.80%, and 15.82% for granulocytes, lymphocytes, and monocytes respectively. Moreover, viability and apoptosis assay showed > 95% viability in mononuclear cells recovered from LRFs. It is concluded that the use of a double-syringe system and RBC and microparticles removal from leukoreduction filters lead to acceptable viable leukocyte count that can be used in in vitro and in vivo studies.

A high-throughput microfluidic device based on controlled incremental filtration to enable centrifugation-free, low extracorporeal volume leukapheresis

Leukapheresis, the extracorporeal separation of white blood cells (WBCs) from red blood cells (RBCs) and platelets (PLTs), is a life-saving procedure used for treating patients with cancer and other conditions, and as the initial step in the manufacturing of cellular and gene-based therapies. Well-tolerated by adults, leukapheresis poses a significant risk to neonates and low-weight infants because the extracorporeal volume (ECV) of standard centrifugation-based machines represents a particularly large fraction of these patients' total blood volume. Here we describe a novel high-throughput microfluidic device (with a void volume of 0.4 mL) based on controlled incremental filtration (CIF) technology that could replace centrifugation for performing leukapheresis. The CIF device was tested extensively using whole blood from healthy volunteers at multiple hematocrits (5-30%) and flow rates (10-30 mL/min). In the flow-through regime, the CIF device separated WBCs with > 85% efficiency and 10-15% loss of RBCs and PLTs while processing whole blood diluted with saline to 10% hematocrit at a flow rate of 10 mL/min. In the recirculation regime, the CIF device demonstrated a similar level of separation performance, virtually depleting WBCs in the recirculating blood (~ 98% reduction) by the end of a 3.5-hour simulated leukapheresis procedure. Importantly, the device operated without clogging or decline in separation performance, with minimal activation of WBCs and PLTs and no measurable damage to RBCs. Compared to the typical parameters of centrifugation-based leukapheresis, the CIF device had a void volume at least 100-fold smaller, removed WBCs about twice as fast, and lost ~ 2-3-fold fewer PLTs, while operating at a flow rate compatible with the current practice. The hematocrit and flow rate at which the CIF device operated were significantly higher than previously published for other microfluidic cell separation methods. Finally, this study is the first to demonstrate a highly efficient separation of cells from recirculating blood using a microfluidic device. Overall, these findings suggest the feasibility of using high-throughput microfluidic cell separation technology to ultimately enable centrifugation-free, low-ECV leukapheresis. Such a capability would be particularly useful in young children, a vulnerable group of patients who are currently underserved.

Leukocyte reduction filters as an alternative source of peripheral blood leukocytes for research

INTRODUCTION

Peripheral blood leukocytes are a suitable cell model for science research. However, blood samples from healthy volunteers are limited in volume and difficult to obtain due to the complexity of volunteer recruitment.

OBJECTIVE

Therefore, it is urgent to find an alternative source of peripheral blood leukocytes.

METHOD

One of the possibilities is the use of leukocyte reduction filters (LRFs) in blood banks that is used for preparation of leukoreduced blood products. More than 90% of the leukocytes are trapped in the leukofilters allowing the desired blood product to pass through.

RESULTS

It has been reported that the biological function of leukocytes collected from the filters are no different from those isolated from buffy coats, leukapheresis products and whole blood (WB) cells. Moreover, LRFs are waste products that are discarded after leukoreduction.

CONCLUSION

Thus, leukofilters represent an economic source of human cell populations that can be used for a variety of investigative purposes, with no cost. In the present study, we reviewed the different usage of LRFs in the research, clinical and commercial applications.

Thrombopoietin-based CAR-T cells demonstrate in vitro and in vivo cytotoxicity to MPL positive acute myelogenous leukemia and hematopoietic stem cells

While targeting CD19+ hematologic malignancies with CAR T cell therapy using single chain variable fragments (scFv) has been highly successful, novel strategies for applying CAR T cell therapy with other tumor types are necessary. In the current study, CAR T cells were designed using a ligand binding domain instead of an scFv to target stem-like leukemia cells. Thrombopoietin (TPO), the natural ligand to the myeloproliferative leukemia protein (MPL) receptor, was used as the antigen binding domain to engage MPL expressed on hematopoietic stem cells (HSC) and erythropoietic and megakaryocytic acute myeloid leukemias (AML). TPO-CAR T cells were tested in vitro against AML cell lines with varied MPL expression to test specificity. TPO-CAR T cells were specifically activating and cytotoxic against MPL+ leukemia cell lines. Though the TPO-CAR T cells did not extend survival in vivo, it successfully cleared the MPL+ fraction of leukemia cells. As expected, we also show the TPO-CAR is cytotoxic against MPL expressing bone marrow compartment in AML xenograft models. The data collected demonstrate preclinical potential of TPO-CAR T cells for stem-like leukemia through assessment of targeted killing of MPL+ cells and may facilitate subsequent HSC transplant under reduced intensity conditioning regimens.

Lentiviral Gene Therapy for Familial Hemophagocytic Lymphohistiocytosis Type 3, Caused by UNC13D Genetic Defects

Familial hemophagocytic lymphohistiocytosis type 3 (FHL3) is a rare disease caused by mutations to the UNC13D gene and the subsequent absence or decreased activity of the Munc13-4 protein. Munc13-4 is essential for the exocytosis of perforin and granzyme containing granules from cytotoxic cells. Without it, these cells are able to recognize an immunological insult but are unable to execute their cytotoxic functions. The result is a hyperinflammatory state that, if left untreated, is fatal. At present, the only curative treatment is hematopoietic stem cell transplantation (HSCT), but eligibility and response to this treatment are largely dependent on the ability to control inflammation before HSCT. In this study, we describe an optimized lentiviral vector that can restore Munc13-4 expression and degranulation capacity in both transduced FHL3 patient T cells and transduced hematopoietic stem cells from the FHL3 (Jinx) disease model.

Optimizing the recovery of peripheral blood mononuclear cells trapped in leukoreduction filters - A comparison study

Introduction

The isolation of captured peripheral blood mononuclear cells (PBMNCs) from leukoreduction filters (LRFs) can be of great importance in terms of bringing the lost cells back into use.

Objective

The aim of this study was to evaluate various methods based on their potential to recover the peripheral blood cells from LRFs with a focus on mononuclear cells (MNCs).

Method

For cell isolation from LRFs, three distinct methods (back-flushing, direct and vacuum pump) were compared through the calculation of the yield of isolated MNCs. The viability of extracted cells was determined by the flow cytometry technique. Moreover, the recovered MNCs were characterized regarding the presence of blood stem cell purification. The cell culture, microscopic observation, and immunophenotyping were employed to characterize the blood stem cells (hematopoietic, mesenchymal and progenitor endothelial stem cells).

Results

The yield of isolation obtained in the back-flushing, direct and vacuum pump methods were 17.7 ± 1.28, 17.3 ± 0.96 and 21.2 ± 0.90 percent, respectively. Although the highest potential for total blood cell recovery belonged to the vacuum pump method, the lowest cell viability (85.73 ± 4.84%) was observed in this method. However, the isolation process of the back-flushing and direct methods had less effect on cell viability. The characterization of the isolated MNCs displayed that the dominant positive phenotype was for CD34/CD45, indicating hematopoietic stem cells. In addition, the endothelial stem/progenitor cells were significantly detected as CD31/CD133 positive cells.

Conclusion

According to our results and considering the safety and efficiency potential of each of the applied methods, the back-flushing in comparison with the other methods can be considered a suitable procedure for MNC isolation from LRFs.

A Cell-Free Protein Expression System Derived from Human Primary Peripheral Blood Mononuclear Cells

Historically, some of the first cell-free protein expression systems studied in vitro translation in various human blood cells. However, because of limited knowledge of eukaryotic translation and the advancement of cell line development, interest in these systems decreased. Eukaryotic translation is a complex system of factors that contribute to the overall translation of mRNA to produce proteins. The intracellular translateome of a cell can be modified by various factors and disease states, but it is impossible to individually measure all factors involved when there is no comprehensive understanding of eukaryotic translation. The present work outlines the use of a coupled transcription and translation cell-free protein expression system to produce recombinant proteins derived from human donor peripheral blood mononuclear cells (PBMCs) activated with phytohemagglutinin-M (PHA-M). The methods outlined here could result in tools to aid immunology, gene therapy, cell therapy, and synthetic biology research and provide a convenient and holistic method to study and assess the intracellular translation environment of primary immune cells.

Characterization of peripheral blood mononuclear cells isolated using two kinds of leukocyte filters

OBJECTIVE

The objective of this study was to compare the activity and biological function of leukocytes isolated using apheresis platelet leukoreduction system chambers (LRSC), whole blood leukoreduction filters (LRF), and leukocytes in unfiltered peripheral whole blood (WB).

METHODS

Peripheral blood mononuclear cells (PBMCs) and granulocytes were obtained by density gradient centrifugation using recovery filters and WB. Flow cytometry was used to detect the activity, phenotype, and apoptosis ratio of each cell subtype.

RESULTS

The proportion of lymphocytes obtained from PBMCs was similar when using the two different filters as compared to traditional isolation; however, there were significant differences between the monocytes and granulocytes. The phenotypic frequency of lymphocytes was similar, but the apoptosis rate of lymphocytes from the two filters was slightly higher. Additionally, monocytes isolated via the three sources were able to be induced into dendritic cells expressing specific molecules; Granulocytes isolated from the LRF showed a lower purity and a higher level of apoptosis than granulocytes isolated from the WB.

CONCLUSION

Compared with WB, the PBMCs isolated from the filters used in our blood center had no statistical difference in their activity and biological function, but they did differ in the proportion and quantity of monocytes and granulocytes. Our results show that the two filters can be used as an alternative method to collect leukocytes, which solves the problem of an insufficient blood supply for clinical and basic science research. Thus, these filters have significant value beyond their practical use in clinics.

Piloting and implementation of quality assessment and quality control procedures in RBC-Omics: a large multi-center study of red blood cell hemolysis during storage

BACKGROUND

The major aims of the RBC-Omics study were to evaluate the genomic and metabolomic determinants of spontaneous and stress-induced hemolysis during RBC storage. This study was unique in scale and design to allow evaluation of RBC donations from a sufficient number of donors across the spectrum of race, ethnicity, sex, and donation intensity. Study procedures were carefully piloted, optimized, and controlled to enable high-quality data collection.

METHODS

The enrollment goal of 14,000 RBC donors across four centers, with characterization of RBC hemolysis across two testing laboratories, required rigorous piloting and optimization and establishment of a quality assurance (QA) and quality control (QC) program. Optimization of WBC elution from leukoreduction (LR) filters, development and validation of small-volume transfer bags, impact of manufacturing and sample-handling procedures on hemolysis parameters, and testing consistency across laboratories and technicians and over time were part of this quality assurance/quality control program.

RESULTS

LR filter elution procedures were optimized for obtaining DNA for analysis. Significant differences between standard and pediatric storage bags led to use of an alternative LR-RBC transfer bag. The impact of sample preparation and freezing methods on metabolomics analyses was evaluated. Proficiency testing monitored and documented testing consistency across laboratories and technicians.

CONCLUSION

Piloting and optimization, and establishment of a robust quality assurance/quality control program documented process consistency throughout the study and was essential in executing this large-scale multicenter study. This program supports the validity of the RBC-Omics study results and a sample repository that can be used in future studies.

Cellular Cytotoxicity of Next-Generation CD20 Monoclonal Antibodies

CD20 monoclonal antibodies (CD20 mAb) induce cellular cytotoxicity, which is traditionally measured by antibody-dependent cellular cytotoxicity (ADCC) assays. However, data suggest that antibody-dependent cellular phagocytosis (ADCP) is the primary cytotoxic mechanism. We directly compared in vitro ADCP versus ADCC using primary human cells. After establishing the primacy of ADCP, we examined next-generation CD20 mAbs, including clinically relevant drug combinations for their effects on ADCP. ADCP and ADCC induction by rituximab, ofatumumab, obinutuzumab, or ocaratuzumab was measured using treatment-naïve chronic lymphocytic leukemia (CLL) target cells and either human monocyte-derived macrophages (for ADCP) or natural killer (NK) cells (for ADCC). Specific effects on ADCP were evaluated for clinically relevant drug combinations using BTK inhibitors (ibrutinib and acalabrutinib), PI3Kδ inhibitors (idelalisib, ACP-319, and umbralisib), and the BCL2 inhibitor venetoclax. ADCP (∼0.5-3 targets/macrophage) was >10-fold more cytotoxic than ADCC (∼0.04-0.1 targets/NK cell). ADCC did not correlate with ADCP. Next-generation mAbs ocaratuzumab and ofatumumab induced ADCP at 10-fold lower concentrations than rituximab. Ofatumumab, selected for enhanced complement activation, significantly increased ADCP in the presence of complement. CD20 mAb-induced ADCP was not inhibited by venetoclax and was less inhibited by acalabrutinib versus ibrutinib and umbralisib versus idelalisib. Overall, ADCP was a better measure of clinically relevant mAb-induced cellular cytotoxicity, and next-generation mAbs could activate ADCP at significantly lower concentrations, suggesting the need to test a wide range of dose sizes and intervals to establish optimal therapeutic regimens. Complement activation by mAbs can contribute to ADCP, and venetoclax, acalabrutinib, and umbralisib are preferred candidates for multidrug therapeutic regimens. Cancer Immunol Res; 6(10); 1150-60. ©2018 AACR.

Quantity, quality, and functionality of peripheral blood cells derived from residual blood of different apheresis kits

BACKGROUND

Research with primary human white blood cell (WBC) subpopulations requires high quantity, quality, and functionality of peripheral blood mononuclear cells (PBMCs) as a source to further characterize cellular subpopulations such as T and B lymphocytes, monocytes, or natural killer cells. Apart from buffy coats derived from whole blood, residual blood from preparative hemapheresis kits are used as a source for PBMCs, but knowledge on the yield and functionality of cells from different devices is limited.

STUDY DESIGN AND METHODS

We evaluated quantity and quality of PBMCs isolated from apheresis kits of two apheresis devices (AMICUS, Fenwal; and Trima Accel, Terumo BCT), the latter being our standard source for many years. PBMCs derived from Trima or AMICUS were tested for yield and subtype composition by flow cytometry. Functionality was assessed by cytokine induction of CD4⁺ and CD8⁺ T cells and by degranulation. Moreover, cytotoxic activity of natural killer cells was quantified by a real-time killing assay.

RESULTS

Mean numbers of isolated cells were 5.5 ± 2.4 × 10⁸ for AMICUS, and 10.3 ± 6.4 × 10⁸ for Trima Accel, respectively. The proportion of WBC subtypes corresponded to well-known numbers from whole blood, with minor differences between the two apheresis systems. Likewise, minor differences in cytokine induction were found in stimulated CD4⁺ or CD8⁺ T cells. Finally, PBMCs derived from the two systems showed comparable cytotoxic activity.

CONCLUSION

PBMC derived from residual blood of the AMICUS and Trima Accel apheresis devices serve as an economic and easily accessible source for functional PBMCs with comparable quantity and quality to PBMCs derived from whole blood.

Methamphetamine alters T cell cycle entry and progression: role in immune dysfunction

We and others have demonstrated that stimulants such as methamphetamine (METH) exerts immunosuppressive effects on the host’s innate and adaptive immune systems and has profound immunological implications. Evaluation of the mechanisms responsible for T-cell immune dysregulation may lead to ways of regulating immune homeostasis during stimulant use. Here we evaluated the effects of METH on T cell cycle entry and progression following activation. Kinetic analyses of cell cycle progression of T-cell subsets exposed to METH demonstrated protracted G1/S phase transition and differentially regulated genes responsible for cell cycle regulation. This result was supported by in vivo studies where mice exposed to METH had altered G1 cell cycle phase and impaired T-cell proliferation. In addition, T cells subsets exposed to METH had significant decreased expression of cyclin E, CDK2 and transcription factor E2F1 expression. Overall, our results indicate that METH exposure results in altered T cell cycle entry and progression. Our findings suggest that disruption of cell cycle machinery due to METH may limit T-cell proliferation essential for mounting an effective adaptive immune response and thus may strongly contribute to deleterious effect on immune system.

TCR-mediated functions are enhanced in activated peripheral blood T cells isolated from leucocyte reduction systems

Buffy coats are the most common method for the acquisition of activated primary human T cells for research or clinical applications, but recently leukocyte reduction system (LRS) cones have emerged as a viable source for these cells. In this study, we determined if activated human T cells derived from buffy coats or LRS cones had different functionality. No changes in the expression of surface receptors were observed except for a significant increase in CD44 expression on T cells isolated from LRS cones. LRS cone-derived T cells trended towards higher receptor-mediated cytokine production and had significantly increased donor-to-donor variability in IFN-γ production. TCR-induced ERK1/ERK2 and AKT phosphorylation was also increased in T cells isolated from LRS cones. In conclusion, LRS cones are an excellent source of T cells for clinical and research applications, but these cells have subtle functional differences from T cells isolated using standard buffy coats.

Involvement of the TNF-α/TGF-β/IDO axis in IVIg-induced immune tolerance

The immune tolerance induced by IVIg treatment is generally attributed to its capacity to modulate the functions of antigen presenting cells and to induce the expansion of regulatory T cells by mechanisms that are not well-defined. Herein, we investigated the contribution of the TNF-α/TGF-β/IDO axis to IVIg-induced immune tolerance. We show that high dose IVIg is able to markedly increase the expression (>3 fold) of the well-known tolerogenic cytokine TGF-β in monocytes. In addition, the expression of TNF-α, a pleiotropic cytokine that controls TGF-β-induced tolerogenic effects, as well as of its cognate receptors (TNF-R1 and TNF-R2) is also significantly increased following IVIg treatment. Along with TNF-α, the expression of the enzyme and signaling protein IDO, known to mediate TGF-β dependant tolerogenic effect, is similarly increased following IVIg treatment. We thus propose that the complex interplay between plasticity of immune cells and environmental modifications in which the TNF-α/TGF-β/IDO axis may represent a new mechanism contributing to the development of tolerance in IVIg-treated patients.

An innovative biologic recycling process of leukoreduction filters to produce active human antimicrobial peptides

BACKGROUND

Human neutrophil peptides (HNPs) 1 to 3 are the major antimicrobial peptides of the azurophilic granules of neutrophils. They represent an important arm of the innate immune system. Their production by chemical synthesis and recombinant technologies is expensive and limited by technical constraints due to their composition and the presence of three disulfide bonds.

STUDY DESIGN AND METHODS

We have developed an original approach based on the purification of the natural human defensins HNPs 1 to 3 from neutrophils trapped on leukoreduction filters used in blood processing. The purification of HNPs 1 to 3 from these filters is performed in two steps: extraction of HNPs 1 to 3 retained in the filters followed by their immunoprecipitation. Studies were performed to determine the stability of defensins in the filters stored at room temperature. The activity of HNPs 1 to 3 obtained by our rapid protocol was validated by determining minimal inhibitory concentrations (MICs) against six reference bacterial strains and 12 clinical isolates.

RESULTS

The human defensins HNPs 1 to 3 extracted from leukoreduction filters displayed high antimicrobial activity against tested strains, with MIC values between 0.12 and 1 μg/mL. Kinetics assays showed the appearance of activity 15 minutes after peptide addition. Moreover, we found that the HNPs 1 to 3 purified from leukoreduction filters that had been stored for 45 days at room temperature remained active.

CONCLUSION

Leukoreduction filters provide a rich and safe source of active human defensins HNPs 1 to 3. Moreover, the stability of the peptides in filters stored at room temperature allows envisaging a large-scale development of the process.

Modulation of CD40-activated B lymphocytes by N-acetylcysteine involves decreased phosphorylation of STAT3

B lymphocyte activation, maturation and reshaping require the interaction of its receptor CD40 with its ligand CD154, which is expressed on activated T lymphocytes. Metabolism in activated B lymphocytes is also characterized with several REDOX changes including fluctuation of Reactive Oxygen Species (ROS). Herein, we first confirm that stimulation of human peripheral blood B lymphocyte with CD154 increases intracellular ROS level. Then, by treatments with two well-known antioxidants, N-acetylcysteine (NAC) and Trolox, we further investigate the influence of REDOX fluctuation in CD40-activated B lymphocyte homeostasis in long term culture (13 days). Treatments with NAC increase viability, decrease proliferation and Ig secretion and enhance homoaggregation of B lymphocytes while Trolox only induces a marginal increase of their Ig secretion. The NAC-induced homoaggregation phenotype is paralleled with increased expressions of CD54, CD11a, CD27 and CD38. Mechanistically, a 24h exposure of B lymphocytes with NAC is sufficient to show strong inhibition of STAT3 phosphorylation. Besides, the treatment of B lymphocytes with the STAT3 inhibitor VI increases viability and decreases proliferation and secretion as in NAC-treated cells thus showing a role for STAT3 in these NAC-induced phenotypes. This study done in a human-based model provides new findings on how REDOX fluctuations may modulate CD40-activated B lymphocytes during immune response and provide additional hints on NAC its immunomodulatory functions.

Obtaining of CD34+ cells from healthy blood donors: development of a rapid and efficient procedure using leukoreduction filters

BACKGROUND

Human CD34+ cells are mandatory to study many aspects of human hematopoiesis. Their low frequency in blood or marrow and ethical reasons limit their obtainment in large quantities. Leukoreduction filters (LRFs) are discarded after preparation of red blood cells. The CD34+ cell concentration in healthy donor blood is low (1×10(3) -4×10(3) /mL), but their number trapped in one LRF after filtration of 400 to 450mL of blood is high (0.4×10(6) -1.6×10(6) ).

STUDY DESIGN AND METHODS

To develop a procedure allowing obtainment of purified CD34+ cells from LRFs with a good yield, white blood cell (WBC) recoveries after a 500-mL continuous or after sequential elution (50- or 20-mL fractions) were compared. Different WBC and mononuclear cell (MNC) centrifugation methods were tested to minimize their PLT contamination before the CD34+ cell immunomagnetic selection. Cell functionality was finally analyzed under various culture conditions.

RESULTS

The 20-mL back-flushing of LRFs allowed the most efficient WBC recovery. The next steps (110×g centrifugation, MNC separation on Ficoll, and washes) resulted in a cell suspension in which the lymphocyte recovery was approximately 76±10% and the PLT contamination below 1.6%. After immunomagnetic selection, 4×10(5) to 6×10(5) cells containing approximately 85% of functional CD34+ cells were obtained.

CONCLUSION

This procedure allows the easy, rapid (<5hr), and efficient preparation of large quantities of CD34+ cells having functional activities similar to those of CD34+ cells from other sources. Therefore, easily available and virally safe, LRFs represent an important and regular WBC source to work with human CD34+ cells, but also with other WBC types.

Immunomodulation of human B cells following treatment with intravenous immunoglobulins involves increased phosphorylation of extracellular signal-regulated kinases 1 and 2

In the treatment of autoimmune diseases, intravenous Igs (IVIg) are assumed to modulate immune cells through the binding of surface receptors. IVIg act upon definite human B cell populations to modulate Ig repertoire, and such modulation might proceed through intracellular signaling. However, the heterogeneity of human B cell populations complicates investigations of the intracellular pathways involved in IVIg-induced B cell modulation. The aim of this study was to establish a model allowing the screening of IVIg signal transduction in human B cell lines and to attempt transposing observations made in cell lines to normal human B lymphocytes. Nine human B cell lines were treated with IVIg with the goal of selecting the most suitable model for human B lymphocytes. The IgG(+) DB cell line, whose response was similar to that of human B lymphocytes, showed reduced IVIg modulation following addition of PD98059, an inhibitor of extracellular signal-regulated protein kinase 1/2 (ERK1/2). The IVIg-induced ERK1/2 phosphorylation was indeed proportional to the dosage of monomeric IVIg used when tested on DB cells as well as Pfeiffer cells, another IgG(+) cell line. In addition, two other intermediates, Grb2-associated binder 1 (Gab1) and Akt, showed increased phosphorylation in IVIg-treated DB cells. IVIg induction of ERK1/2 phosphorylation was finally observed in peripheral human B lymphocytes, specifically within the IgG(+) B cell population. In conclusion, IVIg immunomodulation of human B cells can thus be linked to intracellular transduction pathways involving the phosphorylation of ERK1/2, which in combination with Gab1 and Akt, may be related to B cell antigen receptor signaling.

Characterization of mononuclear cells remaining in the leukoreduction system chambers of apheresis instruments after routine platelet collection: a new source of viable human blood cells

BACKGROUND

The yield of white blood cells (WBCs) extracted from whole-blood leukoreduction filters can be affected by the storage conditions and delay before filtration. Platelets (PLTs) collected with apheresis instruments (Trima Accel, Gambro BCT) are leukoreduced during the procedure on a fluidized particle bed in a leukoreduction chamber (LRS chamber). In this report, the residual cell content of these LRS chambers was characterized to determine whether it would be a valuable source of viable human blood cells.

STUDY DESIGN AND METHODS

The content of LRS chambers was eluted by gravity, and peripheral blood mononuclear cells (PBMNCs) were purified on a Ficoll-Paque gradient. Analyses were performed before and after freezing. Proportions of CD3+, CD14+, CD16+, CD19+, CD34+, and CD45+ cells were determined by flow cytometry. The frequency of T cells expressing CD4, CD8, and CD27 and of B cells expressing immunoglobulin G (IgG), IgM, and CD27 was also determined.

RESULTS

LRS chambers held approximately 10(9) CD45+ cells representing the normal proportions of CD3+, CD14+, CD16+, and CD19+ cell populations of PBMNCs. A small fraction of these CD45+ cells were CD34+CD38+ cells (0.3 +/- 0.2%). The viability of these cells, measured before and after freezing, was more than 95 percent.

CONCLUSION

The residual cell content of Trima Accel LRS chambers recovered after PLT collection is a good source of viable monocytes and lymphocytes. These PBMNCs, containing CD3+, CD14+, CD16+, CD19+, and CD34+ cells can be frozen to prepare cell banks, which opens new avenues for utilization in several physiologic studies or even in cellular therapy applications.

Flow cytometric measurement of calpain activity in living cells

BACKGROUND

Calpains are intracellular, calcium-sensitive, neutral cysteine proteases that play crucial roles in many physiological and pathological processes. Calpain regulation is complex and activity is poorly correlated with calpain protein levels. Therefore a full understanding of calpain function requires robust methods for measuring activity.

METHODS

We describe and characterize a flow cytometric method for measuring calpain activity in live cells. This method uses the BOC-LM-CMAC reagent that readily diffuses into cells where it reacts with free thiols to enhance retention.

RESULTS

We show that the reagent is cleaved specifically by calpains and follows saturation kinetics. We use the assay to measure calpain activation following PDGF stimulation of rat fibroblasts. We also show that the calpain inhibitor PD150606 inhibits calpain with a K(i) of 12.5 muM and show that Mek inhibitors PD89059 and U0126 also suppress calpain activity. We also show that the assay can measure calpain activity in subpopulations of cells present in unfractionated cord blood or in HL60 human myelomonocytic leukemia cells.

CONCLUSION

Taken together, these experiments demonstrate that this assay is a reliable and useful method for measuring calpain activity in multiple cell types.