Donor leukocyte infusions after unrelated donor hematopoietic stem cell transplantation

Genetically enhanced T lymphocytes and the intensive care unit

Chimeric antigen receptor-modified T cells (CAR-T cells) and donor lymphocyte infusion (DLI) are important protocols in lymphocyte engineering. CAR-T cells have emerged as a new modality for cancer immunotherapy due to their potential efficacy against hematological malignancies. These genetically modified receptors contain an antigen-binding moiety, a hinge region, a transmembrane domain, and an intracellular costimulatory domain resulting in lymphocyte T cell activation subsequent to antigen binding. In present-day medicine, four generations of CAR-T cells are described depending on the intracellular signaling domain number of T cell receptors. DLI represents a form of adoptive therapy used after hematopoietic stem cell transplant for its anti-tumor and anti-infectious properties. This article covers the current status of CAR-T cells and DLI research in the intensive care unit (ICU) patient, including the efficacy, toxicity, side effects and treatment.

Immunothérapie et greffe de cellules souches hématopoïétiques allogéniques

IMMUNOTHERAPY AND ALLOGENEIC STEM CELLS TRANSPLANTATION

Allogeneic stem cell transplantations represent perfect example of immunotherapy. Its positive aspects are due to the graft versus tumor effect. Unfortunately, this therapeutic advantage is usually associated with graft versus host effects. While the mechanism of these two graft reactions remain unclear, this is possible to modulate these immunologic effects. The type of conditioning regimen, the source of donor and the use of donor cells after the transplantation may influence the toxicity and the tumor response, leading to a better optimization of the procedure. This paper is presenting all the parameters which may contribute to improve allogeneic stem cell transplantations.

T-Cell Therapy: Options for Infectious Diseases

The emergence of drug-resistant tuberculosis is challenging tuberculosis control worldwide. In the absence of an effective vaccine to prevent primary infection with Mycobacterium tuberculosis and tuberculosis disease, host-directed therapies may offer therapeutic options, particularly for patients with multidrug-resistant and extensively drug-resistant tuberculosis where prognosis is often limited. CD8⁺ and CD4⁺ T cells mediate antigen-specific adaptive cellular immune responses. Their use in precision immunotherapy in clinical conditions, especially in treating cancer as well as for prevention of life-threatening viral infections in allogeneic transplant recipients, demonstrated safety and clinical efficacy. We review key achievements in T-cell therapy, including the use of recombinant immune recognition molecules (eg, T-cell receptors and CD19 chimeric antigen receptors), and discuss its potential in the clinical management of patients with drug-resistant and refractory tuberculosis failing conventional therapy.

CD8(+) Tregs promote GVHD prevention and overcome the impaired GVL effect mediated by CD4(+) Tregs in mice

Adoptive natural regulatory T cell (nTreg) therapy has improved the outcome for patients suffering from graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (Allo-HCT). However, fear of broad immune suppression and subsequent dampening of beneficial graft-versus-leukemia (GVL) responses remains a challenge. To address this concern, we generated alloreactive induced Tregs (iTregs) from resting CD4(+) or CD8(+) T cells and tested their ability to suppress GVH and maintain GVL responses. We utilized major mismatched and haploidentical murine models of HCT with host-derived lymphoma or leukemia cell lines to evaluate GVH and GVL responses simultaneously. Alloreactive CD4(+) iTregs were effective in preventing GVHD, but abrogated the GVL effect against aggressive leukemia. Alloreactive CD8(+) iTregs moderately attenuated GVHD while sparing the GVL effect. Hence, we reasoned that using a combination of CD4(+) and CD8(+) iTregs could achieve the optimal goal of Allo-HCT. Indeed, the combinational therapy was superior to CD4(+) or CD8(+) iTreg singular therapy in GVHD control; importantly, the combinational therapy maintained GVL responses. Cellular analysis uncovered potent suppression of both CD4(+) and CD8(+) effector T cells by the combinational therapy that resulted in effective prevention of GVHD, which could not be achieved by either singular therapy. Gene expression profiles revealed alloreactive CD8(+) iTregs possess elevated expression of multiple cytolytic molecules compared to CD4(+) iTregs, which likely contributes to GVL preservation. Our study uncovers unique differences between alloreactive CD4(+) and CD8(+) iTregs that can be harnessed to create an optimal iTreg therapy for GVHD prevention with maintained GVL responses.

Cellular immunotherapy with ex vivo expanded cord blood T cells in a humanized mouse model of EBV-associated lymphoproliferative disease

BACKGROUND

Donor lymphocyte infusion is not feasible in recipients of cord blood transplantation.

AIM

We investigated whether infusion of T cells expanded from cord blood is effective in the treatment of model mice of Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD).

MATERIALS & METHODS

Humanized mice with reconstituted human immune system were prepared and LPD was induced by inoculating EBV intravenously. T cells were expanded from the same sample of cord blood as used for generation of humanized mice and infused to EBV-infected humanized mice.

RESULTS

Mice treated with expanded cord blood T cells lived significantly longer than control mice (p = 0.036).

CONCLUSION

Infusion of T cells expanded from cord blood was effective in the treatment of model mice for EBV-associated LPD.

Improving cytomegalovirus-specific T cell reconstitution after haploidentical stem cell transplantation

Cytomegalovirus (CMV) infection and delayed immune reconstitution (IR) remain serious obstacles for successful haploidentical stem cell transplantation (haplo-SCT). CMV-specific IR varied according to whether patients received manipulated/unmanipulated grafts or myeloablative/reduced intensity conditioning. CMV infection commonly occurs following impaired IR of T cell and its subsets. Here, we discuss the factors that influence IR based on currently available evidence. Adoptive transfer of donor T cells to improve CMV-specific IR is discussed. One should choose grafts from CMV-positive donors for transplant into CMV-positive recipients (D+/R+) because this will result in better IR than would grafts from CMV-negative donors (D−/R+). Stem cell source and donor age are other important factors. Posttransplant complications, including graft-versus-host disease and CMV infection, as well as their associated treatments, should also be considered. The effects of varying degrees of HLA disparity and conditioning regimens are more controversial. As many of these factors and strategies are considered in the setting of haplo-SCT, it is anticipated that haplo-SCT will continue to advance, further expanding our understanding of IR and CMV infection.

"Cell biology meets physiology: functional organization of vertebrate plasma membranes"--the immunological synapse

The immunological synapse (IS) is an excellent example of cell-cell communication, where signals are exchanged between two cells, resulting in a well-structured line of defense during adaptive immune response. This process has been the focus of several studies that aimed at understanding its formation and subsequent events and has led to the realization that it relies on a well-orchestrated molecular program that only occurs when specific requirements are met. The development of more precise and controllable T cell activation systems has led to new insights including the role of mechanotransduction in the process of formation of the IS and T cell activation. Continuous advances in our understanding of the IS formation, particularly in the context of T cell activation and differentiation, as well the development of new T cell activation systems are being applied to the establishment and improvement of immune therapeutical approaches.

Investigative and clinical applications of synthetic immune synapses

The immune synapse (IS) has emerged as a compelling model of cell-cell communication. This interface between a T cell and antigen-presenting cell (APC) serves as a key point in coordinating the immune response. A distinguishing feature of this interface is that juxtacrine signaling molecules form complex patterns that are defined at micrometer and submicrometer scales. Moreover, these patterns are highly dynamic. While cellular and molecular approaches have provided insight into the influence of these patterns on cell-cell signaling, replacing the APC with a synthetic, micro/nanoengineered surface promises a new level of sophistication to these studies. Micropatterning of multiple ligands onto a surface, for example, allowed the direct demonstration that T cells can sense and respond to microscale geometry of the IS. Supported lipid bilayers have captured the lateral mobility of natural ligands, allowing insight into this complex property of the cell-cell interface in model systems. Finally, engineered surfaces have allowed the study of forces and mechanosensing in T cell activation, an emerging area of immune cell research. In addition to providing new insight into biophysical principles, investigations into IS function may allow control over ex vivo T cell expansion. Bioreactors based on these concepts may find immediate application in enhancing cellular-based immunotherapy.

Production of cytotoxic, KIR-negative NK cells from CD34+ cord blood cells with the use of Notch signaling

The use of natural killer (NK) cells as cell therapy against acute leukemia is an active area of investigation. The optimal source of cytotoxic NK cells for therapeutic use is presently unknown. With funds from the National Blood Foundation, the author's lab has developed in vitro culture systems that use the Notch receptor ligand Delta4 for the differentiation and expansion of functional NK cells from CD34+ cord blood hematopoietic progenitor cells. These Notch-induced NK (N-NK) cells display a predominantly immature, CD56(bright) surface phenotype, with expression of activating receptors important for leukemia cell recognition and killing, but with an absence of inhibitory receptors that bind major histocompatibility complex (MHC) class I, making them free of restriction by self-MHC. They are capable of directly killing hematopoietic tumor cell lines and primary leukemia cells in vitro. Thus, cytotoxic, HLA-independent N-NK cells may represent a novel cell therapy for hematopoietic malignancy.

Murine rhabdomyosarcoma is immunogenic and responsive to T-cell-based immunotherapy

BACKGROUND

Immunotherapies targeting cellular immunity are currently approved for treatment of melanoma, renal cell carcinoma, and prostate cancer. Studies on the immunogenicity and immune responsiveness of pediatric tumors are limited, therefore, it remains unclear to what extent T-cell-based immunotherapy holds promise for pediatric solid tumors.

PROCEDURE

A new rhabdomyosarcoma cell line (M3-9-M) was derived from an embryonal rhabdomyosarcoma (ERMS) occurring in a C57BL/6 mouse transgenic for hepatocyte growth factor and heterozygous for mutated p53. Primary tumors and metastases derived from M3-9-M were studied for similarities to human ERMS, and for immunogenicity and immune responsiveness.

RESULTS

Primary and metastatic tumors develop after orthotopic injection of M3-9-M into immunocompetent C57BL/6 mice, which mirror human ERMS with regard to histology, gene expression, and metastatic behavior. Whole cell vaccination using irradiated M3-9-M cells or M3-9-M-pulsed dendritic cells (DC)-induced tumor-specific T-cell responses that prevent tumor growth following low-dose tumor injection, and slow tumor growth following higher doses. Administration of anti-CD25 moAbs to deplete CD4(+)CD25(+)FOXP3(+) regulatory T cells prior to tumor vaccination enhanced the potency of the ERMS tumor vaccine. Adoptive immunotherapy with M3-9-M primed T cells plus DC-based vaccination resulted in complete eradication of day 10 M3-9-M derived tumors.

CONCLUSIONS

M3-9-M derived murine ERMS is immunogenic and immunoresponsive; regulatory T cells contribute to immune evasion by murine rhabdomyosarcoma. Adoptive immunotherapy with DC vaccination can eradicate low tumor burdens. Future work will seek to identify the tumor-associated antigens that mediate protective and therapeutic immunity in this model.

Clinical options after failure of allogeneic hematopoietic stem cell transplantation in patients with hematologic malignancies

Disease recurrence is the single most common cause of death after allogeneic or autologous hematopoietic stem cell transplantation (HSCT). Disease status and chemosensitivity at the time of transplantation, as well as the development of graft-versus-host disease (GVHD), are factors known to influence the risk of relapse post-HSCT. Both acute and chronic GVHD have been associated with decreased relapse rates; however, owing to toxicity, overall survival is not consistently improved in these patients. Furthermore, there is a transient period of immunodeficiency after HSCT, which may permit residual malignant cells to proliferate early in the post-transplant course, before the donor immune system can establish a graft-versus-tumor response. Patients who fail an initial HSCT have an extremely poor outcome; therefore, maneuvers to prevent, identify and treat recurrent disease as early as possible in these situations are necessary. Strategies to distinguish graft-versus-tumor from GVHD, to enhance both general and disease-specific immune reconstitution after transplantation, and to increase donor-mediated anti-host immune reactions are being investigated in clinical trials. Single agent nontoxic post-HSCT chemotherapy, cellular therapies and second allogeneic HSCT using reduced intensity regimens are among the modalities under investigation.

Program death-1 signaling and regulatory T cells collaborate to resist the function of adoptively transferred cytotoxic T lymphocytes in advanced acute myeloid leukemia

Tumor-induced immune defects can weaken host immune response and permit tumor cell growth. In a systemic model of murine acute myeloid leukemia (AML), tumor progression resulted in increased regulatory T cells (Treg) and elevation of program death-1 (PD-1) expression on CD8(+) cytotoxic T cells (CTLs) at the tumor site. PD-1 knockout mice were more resistant to AML despite the presence of similar percentage of Tregs compared with wild type. In vitro, intact Treg suppression of CD8(+) T-cell responses was dependent on PD-1 expression by T cells and Tregs and PD-L1 expression by antigen-presenting cells. In vivo, the function of adoptively transferred AML-reactive CTLs was reduced by AML-associated Tregs. Anti-PD-L1 monoclonal antibody treatment increased the proliferation and function of CTLs at tumor sites, reduced AML tumor burden, and resulted in long-term survivors. Treg depletion followed by PD-1/PD-L1 blockade showed superior efficacy for eradication of established AML. These data demonstrated that interaction between PD-1 and PD-L1 can facilitate Treg-induced suppression of T-effector cells and dampen the antitumor immune response. PD-1/PD-L1 blockade coupled with Treg depletion represents an important new approach that can be readily translated into the clinic to improve the therapeutic efficacy of adoptive AML-reactive CTLs in advanced AML disease.

Donor lymphocyte infusion for leukemia relapse after hematopoietic stem cell transplantation

Leukemia relapse is a serious therapeutic challenge following hematopoietic stem cell transplantation (HSCT). In this retrospective study, 23 patients [15 (65.2%) AML, 8 (34.8%) ALL] who received DLI+/-reinduction chemotherapy for post-transplant relapse were reviewed. The overall response rate of DLI was 66.7% for AML and 50% for ALL. A total of 15 patients (65.2%) developed acute graft versus host disease (GVHD). Response rates were higher in patients with GVHD (80% versus 25%; p=0.01; OR: 12.0). The probability of OS was better in patients who respond to DLI (p=0.04). Further strategies are required to improve the anti-tumor properties of alloreactive donor lymphocytes and to obtain durable responses with DLI in patients with relapsed acute leukemia after allogeneic HSCT.

Recent advances in quantitative chimerism analysis

Quantitative chimerism analysis is a diagnostic tool used to monitor engraftment kinetics after allogeneic stem cell transplantation. It reflects the proportion of recipient and donor genotypes and is based on the identification of genetic markers characteristic to a given transplant pair. Currently, PCR amplification of short tandem repeats and single-nucleotide polymorphism-specific quantitative real-time PCR are the most widely used techniques for this purpose. In this review, we will address advances as well as technology-specific imperfections, of both techniques that have emerged over the recent years. We will discuss new principles that may simplify assay design, and improve its robustness and reliability. A better chimerism assay could then guide clinical interventions and may, eventually, improve the outcome of allogeneic stem cell transplantation.

The Notch ligands Jagged2, Delta1, and Delta4 induce differentiation and expansion of functional human NK cells from CD34+ cord blood hematopoietic progenitor cells

Notch receptor signaling is required for T cell development, but its role in natural killer (NK) cell development is poorly understood. We compared the ability of the 5 mammalian Notch ligands (Jagged1, Jagged2, Delta1, Delta3, or Delta4) to induce NK cell development from human hematopoietic progenitor cells (HPCs). CD34(+) HPCs were cultured with OP9 stromal cell lines transduced with 1 of the Notch ligands or with OP9 stromal cells alone, in the presence of IL-7, Flt3L, and IL-15. Differentiation and expansion of CD56(+)CD3(-) cells were greatly accelerated in the presence of Jagged2, Delta-1, or Delta-4, versus culture in the absence of ligand or in the presence of Jagged1 or Delta3. At 4 weeks, cultures containing Jagged2, Delta1, or Delta4 contained 80% to 90% NK cells, with the remaining cells being CD33(+) myelogenous cells. Notch-induced NK (N-NK) cells resembled CD56(bright) NK cells in that they were CD16(-), CD94(-), CD117(+), and killer immunoglobulin-like receptors (KIR(-)). They also expressed NKp30, NKp44, NKp46, 2B4, and DNAM-1, with partial expression of NKG2D. The N-NK cells displayed cytotoxic activity against the K562 and RPMI-8226 cell lines, at levels similar to activated peripheral blood (PB) NK cells, although killing of Daudi cells was not present. N-NK cells were also capable of interferon (IFN)-gamma secretion. Thus, Notch ligands have differential ability to induce and expand immature, but functional, NK cells from CD34(+) HPCs. The use of Notch ligands to generate functional NK cells in vitro may be significant for cellular therapy purposes.

Ex vivo expanded cord blood CD4 T lymphocytes exhibit a distinct expression profile of cytokine-related genes from those of peripheral blood origin

With an increase in the importance of umbilical cord blood (CB) as an alternative source of haematopoietic progenitors for allogenic transplantation, donor lymphocyte infusion (DLI) with donor CB-derived activated CD4(+) T cells in the unrelated CB transplantation setting is expected to be of increased usefulness as a direct approach for improving post-transplant immune function. To clarify the characteristics of activated CD4(+) T cells derived from CB, we investigated their mRNA expression profiles and compared them with those of peripheral blood (PB)-derived activated CD4(+) T cells. Based on the results of a DNA microarray analysis and quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR), a relatively high level of forkhead box protein 3 (Foxp3) gene expression and a relatively low level of interleukin (IL)-17 gene expression were revealed to be significant features of the gene expression profile of CB-derived activated CD4(+) T cells. Flow cytometric analysis further revealed protein expression of Foxp3 in a portion of CB-derived activated CD4(+) T cells. The low level of retinoic acid receptor-related orphan receptor gamma isoform t (RORgamma t) gene expression in CB-derived activated CD4(+) T cells was speculated to be responsible for the low level of IL-17 gene expression. Our data indicate a difference in gene expression between CD4(+) T cells from CB and those from PB. The findings of Foxp3 expression, a characteristic of regulatory T cells, and a low level of IL-17 gene expression suggest that CB-derived CD4(+) T cells may be a more appropriate source for DLI.

Depletion of endogenous tumor-associated regulatory T cells improves the efficacy of adoptive cytotoxic T-cell immunotherapy in murine acute myeloid leukemia

Tumor-induced immune suppression can permit tumor cells to escape host immune resistance. To elucidate host factors contributing to the poor response of adoptively transferred tumor-reactive cytotoxic T lymphocytes (CTLs), we used a systemic model of murine acute myeloid leukemia (AML). AML progression resulted in a progressive regulatory T-cell (Treg) accumulation in disease sites. The adoptive transfer of in vitro-generated, potently lytic anti-AML-reactive CTLs failed to reduce disease burden or extend survival. Compared with non-AML-bearing hosts, transferred CTLs had reduced proliferation in AML sites of metastases. Treg depletion by a brief course of interleukin-2 diphtheria toxin (IL-2DT) transiently reduced AML disease burden but did not permit long-term survival. In contrast, IL-2DT prevented anti-AML CTL hypoproliferation, increased the number of transferred CTLs at AML disease sites, reduced AML tumor burden, and resulted in long-term survivors that sustained an anti-AML memory response. These data demonstrated that Tregs present at AML disease sites suppress adoptively transferred CTL proliferation, limiting their in vivo expansion, and Treg depletion before CTL transfer can result in therapeutic efficacy in settings of substantial pre-existing tumor burden in which antitumor reactive CTL infusion alone has proven ineffective.

Toward effective immunotherapy for the treatment of malignant brain tumors

The immunologic treatment of cancer has long been heralded as a targeted molecular therapeutic with the promise of eradicating tumor cells with minimal damage to surrounding normal tissues. However, a demonstrative example of the efficacy of immunotherapy in modulating cancer progression is still lacking for most human cancers. Recent breakthroughs in our understanding of the mechanisms leading to full T-cell activation, and recognition of the importance of overcoming tumor-induced immunosuppressive mechanisms, have shed new light on how to generate effective anti-tumor immune responses in humans, and sparked a renewed and enthusiastic effort to realize the full potential of cancer immunotherapy. The immunologic treatment of invasive malignant brain tumors has not escaped this re-invigorated endeavor, and promising therapies are currently under active investigation in dozens of clinical trials at several institutions worldwide. This review will focus on some of the most important breakthroughs in our understanding of how to generate potent anti-tumor immune responses, and some of the clear challenges that lie ahead in achieving effective immunotherapy for the majority of patients with malignant brain tumors. A review of immunotherapeutic strategies currently under clinical evaluation, as well as an outline of promising novel approaches on the horizon, is included to provide perspective on the active and stalwart progress toward effective immunotherapy for the treatment of malignant brain tumors.

Clinical and immunologic outcomes following haplocompatible donor lymphocyte infusions

We retrospectively analyzed the characteristics of 16 consecutive pediatric patients who received one or more G-CSF-mobilized donor lymphocyte infusions (DLI) following a T-cell-depleted haplocompatible hematopoietic SCT (HSCT) to enhance immune recovery and/or treat an infection. The median time from HSCT to administration of first DLI was 12 weeks and the median dose of DLI administered was 3 x 10(4)/kg (range, 2.5-6 x 10(4)/kg). The incidence of Grade I-II acute GVHD was 19% (95% confidence interval (CI), 6-44%), and there were no cases of Grade III-IV acute GVHD. Chronic GVHD developed in 13% (95% CI, 2-37%) of patients. In surviving patients who did not undergo a second stem cell infusion, T-cell numbers and function increased to a protective level in a median of 3 months (range, 2-12.5 months) following the first DLI administration. In patients given DLI for treatment of an infection, 75% (95% CI, 46-92%) cleared their infection after a median of 9 weeks (range, 1-27 weeks). In patients with CMV infection, the development of CMV-specific T cells was observed following DLI. The 1-year overall survival following haplocompatible DLI was 71% (95% CI, 59-83%), with a median follow-up of 16 months from the first DLI.

The EBMT activity survey 2007 with focus on allogeneic HSCT for AML and novel cellular therapies

The 2007 report describes the current status of HSCT activity in Europe, highlights the increasing role of allogeneic HSCT in treatment of AML and gives the first quantitative information on novel cellular therapies. In 2007, there were 25 563 first HSCTs, 10 072 allogeneic (39%), 15 491 autologous (61%) and 3606 additional transplants reported from 613 centers in 42 countries. The main indications were leukemias (8061 (32%; 89% allogeneic)); lymphomas (14 627 (57%; 89% autologous)), solid tumors (1488 (6%; 96% autologous)) and nonmalignant disorders (1302 (5%; 91% allogeneic)). Peripheral blood was the main source of stem cells for autologous HSCT (98%) and the predominant source for allogeneic HSCT (71%). Among allogeneic HSCTs, the number of unrelated donor grafts equaled the number of HLA-identical sibling donor grafts for the first time (47% each). AML was the most frequent indication for allogeneic HSCT (32% of all allogeneic HSCTs), with an increase of 247 (8%). Information on novel cellular therapies was collected for the first time; there were 212 mesenchymal SCTs and 212 HSCTs for nonhematopoietic use. The indications for the latter were cardiovascular disorders (97; 46%), neurological disorders (94; 44%) and tissue repair (21; 10%). These data illustrate the expanding role of cellular therapies.

Donor leukocyte infusions for the treatment of relapsed acute leukemia after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (SCT) offers the only hope for cure for many adults with acute leukemia. Unfortunately, many patients relapse and die of their disease even after transplantation. Although in some cases, allogeneic SCT is effective because the intensive conditioning therapy eradicates all malignant cells, it has long been recognized that the adoptive transfer of donor immunity plays a critically important role in the induction and maintenance of remission. Recognition of the graft-versus-leukemia (GVL) effect of allogeneic SCT has prompted attempts at remission re-induction by adoptive immunotherapy with donor lymphocyte infusions (DLIs) in patients with relapsed disease after allogeneic SCT. In some cases, DLI-induced remissions are sustained and patients cured when no other treatment modality was effective. This review discusses the rationale, biology, complications and future applications of DLI in acute leukemia patients after allogeneic SCT.

Short-term liquid storage of CD14+ monocytes, CD11c+, and CD123+ precursor dendritic cells produced by leukocytapheresis

BACKGROUND

This prospective study compared white blood cell (WBC) storage in polyvinylchloride (PVC) bags and in polyolefin (POF) bags. After leukapheresis, CD14+ monocytes, CD11c+, and CD123+ precusor dendritic cells (DCs) were analyzed under platelet (PLT) storage conditions.

STUDY DESIGN AND METHODS

Twenty-five leukapheresis procedures were performed on blood cell separators (AS.TEC204 [PVC; Fresenius HemoCare GmbH] and the COBE Spectra [POF, Gambro BCT]). Blood cell counts, glucose, lactic acid, pO(2), pCO(2), and pH were measured in mononuclear cell (MNC) harvests on Days 0, 1, 3, and 5. WBCs were analyzed by flow cytometry.

RESULTS

The WBC yields of the AS.TEC204 harvests were 25 percent higher (13.4 x 10(9) +/- 2.7 x 10(9) WBCs) compared to the COBE Spectra (9.9 x 10(9) +/- 2.5 x 10(9) WBCs). During 5-day storage, WBC counts (PVC bags) decreased significantly (24%). Storage in POF bags showed more consistent results (WBC loss, 6%). Loss of CD14+ monocytes and CD11c+ precursor DCs did not differ significantly in leukapheresis products. CD123+ precursor DCs stored in PVC bags dropped by more than 90 percent (POF bags, 24%). Lactic acid concentrations exceeded 20 mmol per L after 24 hours in PVC bags and after 72 hours in POF bags. The mean pH value on Day 5 was 6.2 (PVC) and 6.3 (POF). On Day 1, the product glucose concentration decreased by 76 percent after storage in PVC bags and by 16 percent in POF bags.

CONCLUSIONS

Storage of MNCs within 72 hours in the original harvest container assures stable WBC content and is easy to perform. POF bags should be preferred in the case of extended WBC storage. Patient studies should clarify changes in efficiency of hematopoietic reconstitution that might occur over time during MNC storage.