Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony stimulating factor

CD34+ stem cell counting using labeled immobilized anti-CD34 antibody onto magnetic nanoparticles and EasyCounter BC image cytometer

The ability of immobilized conjugate anti-CD34⁺ monoclonal antibody-dR110 and free conjugate anti-CD45⁺ monoclonal antibody-ATTO620 to precisely enumerate CD34⁺ stem cells and CD45⁺ cells in apheresis samples were evaluated. The conjugates anti-CD34⁺ antibody-dR110 and anti-CD45⁺- antibody-ATTO620 were prepared. Functionalized magnetic nanoparticles (MNPs) were synthesized. The anti-CD34⁺ antibody-dR110 conjugate was immobilized on the modified MNPs using a carbodiimide method. The stem cell count in thawed apheresis samples was determined using the free and the immobilized conjugate anti-CD34⁺ antibody-dR110 on MNPs and an image cell counter EasyCounter BC. A higher stem cell count and more accurate results were obtained with the immobilized conjugate, because a separation and concentration of the stem cells bound to antibody-dR110 on MNPs by external magnet were performed. Coefficients of variation of CD34⁺ cell count in apheresis samples, determined by EasyCounter BC, were ranged from 5.5 to 6.9% and those of CD45⁺ cell count from 3.8 to 4.7%. The viability of CD34⁺ cells was high from 98.5 to 99.6%. It was found that correlation coefficient between the flow cytometer and automatic cell counter, using free anti-CD34⁺ antibody-dR110 was 0.94, and when using immobilized anti-CD34⁺antibody-dR110 on MNPs, the correlation coefficient was 0.97.

Th2 polarization in target organs is involved in the alleviation of pathological damage mediated by transplanting granulocyte colony-stimulating factor-primed donor T cells

Acute graft-versus-host disease (aGVHD) is caused by allo-activated donor T cells infiltrating target organs. As a regulator of immune function, granulocyte colony-stimulating factor (G-CSF) has been demonstrated to relieve the aGVHD reaction. However, the role of G-CSF-primed donor T cells in specific target organs is still unknown. In this study, we employed a classical MHC-mismatched transplantation mouse model (C57BL/6 into BALB/c) and found that recipient mice transplanted with G-CSF-primed T cells exhibited prolonged survival compared with that of the PBS-treated group. This protective function against GVHD mediated by G-CSF-primed donor T cells was further confirmed by decreased clinical and pathological scores in this aGVHD mouse model, especially in the lung and gut. Moreover, we found that T cells polarized towards Th2 cells and regulatory T cells were increased in specific target organs. In addition, G-CSF treatment inhibited inducible co-stimulator (ICOS) expression and increased the expression of tolerance-related genes in recipient mice. Our study provides new insight into the immune regulatory effects of G-CSF on T cell-mediated aGVHD, especially for its precise regulation in GVHD target organs.

Enumeration of CD34-positive Stem Cells Using the ADAMII Image-based Fluorescence Cell Counter

Background

It is very important to accurately enumerate CD34-positive (CD34+) cells for successful hematopoietic stem cell transplantation (HSCT). We evaluated the ability of the newly developed image based-immunofluorescence cell counter ADAMII (NanoEntek, Seoul, Korea) to enumerate CD34+ cells, which was improved through simultaneous CD45 analysis.

Methods

We enumerated CD34+ cells with ADAMII using 19 peripheral blood (PB) and 91 leukapheresis samples from HSCT donors. Analytical performance, including precision and linearity, was analyzed, and sample stability during storage was evaluated. Viable CD34+ cell count (vCD34) and viable CD45+ cell count (vCD45) and the percentage of viable CD34+ cells among viable CD45+ cells (CD34/CD45) as measured by ADAMII were compared with the corresponding values from two flow cytometry assays, using regression analysis.

Results

ADAMII demonstrated acceptable precision, as CV values of vCD34 from six samples with different counts were all <10% (range: 3.49–9.51%). CV values of the vCD45 and CD34/45 ranged from 4.03% to 9.67% and from 2.48% to 10.07%, respectively. The linearity of vCD34 showed an excellent R² value (0.99) when analyzed using the intended count and flow cytometry data. The ADAMII and two flow cytometry-based assays generated very similar data for the PB and leukapheresis samples.

Conclusions

ADAMII demonstrated excellent performance for use as a routine clinical assay in terms of CD34+ cell enumeration from PB and leukapheresis samples. Moreover, it could be used as a point-of-care-test for determining mobilization time and predicting an adequate apheresis stem cell product.

Impact of T cells on hematopoietic stem and progenitor cell function: Good guys or bad guys?

When hematopoietic stem and progenitor cells (HSPC) are harvested for transplantation, either from the bone marrow or from mobilized blood, the graft contains a significant number of T cells. It is these T cells that are the major drivers of graft-vs-host disease (GvHD). The risk for GvHD can simply be reduced by the removal of these T cells from the graft. However, this is not always desirable, as this procedure also decreases the engraftment of the transplanted HSPCs and, if applicable, a graft-vs-tumor effect. This poses an important conundrum in the field: T cells act as a double-edged sword upon allogeneic HSPC transplantation, as they support engraftment of HSPCs and provide anti-tumor activity, but can also cause GvHD. It has recently been suggested that T cells also enhance the engraftment of autologous HSPCs, thus supporting the notion that T cells and HSPCs have an important functional interaction that is highly beneficial, in particular during transplantation. The underlying reason on why and how T cells contribute to HSPC engraftment is still poorly understood. Therefore, we evaluate in this review the studies that have examined the role of T cells during HSPC transplantation and the possible mechanisms involved in their supporting function. Understanding the underlying cellular and molecular mechanisms can provide new insight into improving HSPC engraftment and thus lower the number of HSPCs required during transplantation. Moreover, it could provide new avenues to limit the development of severe GvHD, thus making HSPC transplantations more efficient and ultimately safer.

Long-term Tolerance Toward Haploidentical Vascularized Composite Allograft Transplantation in a Canine Model Using Bone Marrow or Mobilized Stem Cells

BACKGROUND

The development of safe and reliable protocols for the transplantation of the face and hands may be accomplished with animal modeling of transplantation of vascularized composite allografts (VCA). Previously, we demonstrated that tolerance to a VCA could be achieved after canine recipients were simultaneously given marrow from a dog leukocyte antigen-identical donor. In the present study, we extend those findings across a dog leukocyte antigen mismatched barrier.

METHODS

Eight recipient dogs received total body irradiation (4.5 cGy), hematopoietic cell transplantation (HCT), either marrow (n = 4) or granulocyte-colony stimulating factor mobilized peripheral blood stem cells (n = 4), and a VCA transplant from the HCT donor. Post grafting immunosuppression consisted of mycophenolate mofetil (28 days) and cyclosporine (35 days).

RESULTS

In 4 dogs receiving bone marrow, 1 accepted both its marrow transplant and demonstrated long-term tolerance to the donor VCA (>52 weeks). Three dogs rejected both their marrow transplants and VCA at 5 to 7 weeks posttransplant. Dogs receiving mobilized stem cells all accepted their stem cell transplant and became tolerant to the VCA. However, 3 dogs developed graft-versus-host disease, whereas 1 dog rejected its stem cell graft by week 15 but exhibited long-term tolerance toward its VCA (>90 weeks).

CONCLUSIONS

The data suggest that simultaneous transplantation of mobilized stem cells and a VCA is feasible and leads to tolerance toward the VCA in a haploidentical setting. However, there is a higher rate of donor stem cell engraftment compared with marrow HCT and an increase in the incidence of graft-versus-host disease.

Ex vivo expansion of hematopoietic stem and progenitor cells: Recent advances

Hematopoietic stem cells (HSCs) have become the most extensively studied stem cells and HSC-based cellular therapy is promising for hematopoietic cancers and hereditary blood disorders. Successful treatment of patients with HSC cells depends on sufficient number of highly purified HSCs and progenitor cells. However, stem cells are a very rare population no matter where they come from. Thus, ex vivo amplification of these HSCs is essential. The heavy demands from more and more patients for HSCs also require industrial-scale expansion of HSCs with lower production cost and higher efficiency. Two main ways to reach that goal: (1) to find clinically applicable, simple and efficient methods (or reagents) to enrich HSCs; (2) to find new developmental regulators and chemical compounds in order to replace the currently used cytokine cocktails for HSCs amplification. In this Editorial review, we would like to introduce the current status of ex vivo expansion of HSCs, particularly focusing on enrichment and culture supplements.

Multicenter prospective nonrandomized controlled clinical trial to prove neurotherapeutic effects of granulocyte colony-stimulating factor for acute spinal cord injury: analyses of follow-up cases after at least 1 year

STUDY DESIGN

An open-labeled multicenter prospective nonrandomized controlled clinical trial.

OBJECTIVE

To confirm the feasibility of using granulocyte colony-stimulating factor (G-CSF) for treatment of acute spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

We previously reported that G-CSF promotes functional recovery after compression-induced SCI in mice. On the basis of these findings, we conducted a multicenter prospective controlled clinical trial to assess the feasibility of G-CSF therapy for patients with acute SCI.

METHODS

The trial ran from August 2009 to March 2011, and included 41 patients with SCI treated within 48 hours of onset. Informed consent was obtained from all patients. After providing consent, patients were divided into 2 groups. In the G-CSF group (17 patients), G-CSF (10 μg/kg/d) was intravenously administered for 5 consecutive days, and in the control group (24 patients), patients were similarly treated except for the G-CSF administration. We evaluated motor and sensory functions using the American Spinal Cord Injury Association score and American Spinal Cord Injury Association impairment scale at 1 week, 3 months, 6 months, and 1 year after onset.

RESULTS

Only 2 patients did not experience American Spinal Cord Injury Association impairment scale improvement in the G-CSF group. In contrast, 15 patients in the control group did not experience American Spinal Cord Injury Association impairment scale improvement. In the analysis of increased American Spinal Cord Injury Association motor score, a significant increase in G-CSF group was detected from 1 week after the administration compared with the control group. After that, some spontaneous increase of motor score was detected in control group, but the significant increase in G-CSF group was maintained until 1 year of follow-up.

CONCLUSION

Despite the limitation that patient selection was not randomized, the present results suggest the possibility that G-CSF administration has beneficial effects on neurological recovery in patients with acute SCI.

LEVEL OF EVIDENCE

3.

G-CSF in Healthy Allogeneic Stem Cell Donors

Mobilization of peripheral blood stem cells (PBSC) in healthy volunteers with granulocyte colony-stimulating factor (G-CSF) is currently carried out at many institutions worldwide. This report presents the experience of the Dresden center regarding donor evaluation and mobilization schedule. Data regarding efficacy, short- and long-term safety of G-CSF treatment gained from 8290 PBSC collections in healthy donors are outlined. These results are discussed against the background of the available evidence from the literature. Although established as a standard procedure, G-CSF application to allogeneic donors will always be a very delicate procedure and requires the utmost commitment of all staff involved to ensure maximum donor safety.

Neuroprotective therapy using granulocyte colony-stimulating factor for acute spinal cord injury: a phase I/IIa clinical trial

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that is clinically used to treat neutropenia. G-CSF also has non-hematopoietic functions and could potentially be used to treat neuronal injury. To confirm the safety and feasibility of G-CSF administration for acute spinal cord injury (SCI), we have initiated a phase I/IIa clinical trial of neuroprotective therapy using G-CSF.

METHODS

The trial included a total of 16 SCI patients within 48 h of onset. In the first step, G-CSF (5 μg/kg/day) was intravenously administered for 5 consecutive days to 5 patients. In the second step, G-CSF (10 μg/kg/day) was similarly administered to 11 patients. We evaluated motor and sensory functions of patients using the American Spinal Cord Injury Association (ASIA) score and ASIA impairment scale (AIS) grade.

RESULTS

In all 16 patients, neurological improvement was obtained after G-CSF administration. AIS grade increased by one step in 9 of 16 patients. A significant increase in ASIA motor scores was detected 1 day after injection (P < 0.01), and both light touch and pin prick scores improved 2 days after injection (P < 0.05) in the 10 μg group. No severe adverse effects were observed after G-CSF injection.

CONCLUSION

These results indicate that intravenous administration of G-CSF (10 μg/kg/day) for 5 days is essentially safe, and suggest that some neurological recovery may occur in most patients. We suggest that G-CSF administration could be therapeutic for patients with acute SCI.

Allogeneic transplantation: peripheral blood vs. bone marrow

PURPOSE OF REVIEW

Peripheral blood stem cells (PBSCs) have been widely adopted as a source of stem cells for allogeneic transplantation, although controversy remains regarding their role compared to the use of bone marrow.

RECENT FINDINGS

Ten-year follow-up has been reported from several large randomized trials and a recently completed trial using unrelated donor stem cells has been reported. In addition, two meta-analyses have been reported from the findings of a number of randomized studies. Several studies indicate that PBSCs confer survival advantages over bone marrow with matched sibling donors for most disease categories except where the risks of disease recurrence within the first year are low, but with the extra risk of more chronic graft-versus-host disease (GVHD). Using PBSCs from unrelated donors does not appear to be more beneficial than bone marrow, but with early follow-up. New strategies for rapid mobilization of PBSCs from normal donors using plerixafor have been reported. Early studies suggest that filgrastim-stimulated bone marrow may confer some of the advantages of PBSCs without the risks of chronic GVHD.

SUMMARY

PBSCs are a preferred source of stem cells for many types of allogeneic transplant, in which matched related donors are available. Whether the same benefits accrue from unrelated donors will require further follow-up.

Cannabinoid receptor 2 and its agonists mediate hematopoiesis and hematopoietic stem and progenitor cell mobilization

Endocannabinoids are arachidonic acid derivatives and part of a novel bioactive lipid signaling system, along with their G-coupled cannabinoid receptors (CB₁ and CB₂) and the enzymes involved in their biosynthesis and degradation. However, their roles in hematopoiesis and hematopoietic stem and progenitor cell (HSPC) functions are not well characterized. Here, we show that bone marrow stromal cells express endocannabinoids (anandamide and 2-arachidonylglycerol), whereas CB₂ receptors are expressed in human and murine HSPCs. On ligand stimulation with CB₂ agonists, CB₂ receptors induced chemotaxis, migration, and enhanced colony formation of bone marrow cells, which were mediated via ERK, PI3-kinase, and Gαi-Rac1 pathways. In vivo, the CB₂ agonist AM1241 induced mobilization of murine HSPCs with short- and long-term repopulating abilities. In addition, granulocyte colony-stimulating factor -induced mobilization of HSPCs was significantly decreased by specific CB₂ antagonists and was impaired in Cnr2(-/-) cannabinoid type 2 receptor knockout mice. Taken together, these results demonstrate that the endocannabinoid system is involved in hematopoiesis and that CB₂/CB₂ agonist axis mediates repopulation of hematopoiesis and mobilization of HSPCs. Thus, CB₂ agonists may be therapeutically applied in clinical conditions, such as bone marrow transplantation.

Treatment of acute leukemia with unmanipulated HLA-mismatched/haploidentical blood and bone marrow transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains one of the best therapeutic options to cure acute leukemia (AL). However, many patients have no human leukocyte antigen (HLA)-matched donor. Recently, we developed a new method for HLA-mismatched/haploidentical transplantation without in vitro T cell depletion (TCD). This method combined granulocyte-colony stimulating factor (G-CSF)-primed bone marrow and peripheral blood with intensive immunosuppression. We analyzed the outcome of 250 consecutive patients with AL who underwent HLA-mismatched/haploidentical transplantation with 1-3 mismatched loci of HLA-A, B, and DR from family donors via our new transplant protocol. Two hundred forty-nine patients achieved sustained, full donor chimerism. The incidence of grade 2-4 acute graft-versus-host disease (aGVHD) was 45.8%, and that of grades 3 and 4 was 13.4%, which was not associated with the extent of HLA disparity. The cumulative incidence of total chronic GVHD (cGVHD) was 53.9% and that of extensive cGVHD was 22.6% in 217 evaluable patients. One hundred forty-one of the 250 patients survived free of disease recurrence at a median of 1092 days (range: 442-2437 days) of follow-up. Seventeen patients received DLI as a treatment for relapse after transplantation and 7 patients achieved leukemia-free survival (LFS). The 3-year probability of LFS for acute myelogenous leukemia (AML) was 70.7% and 55.9%, and for acute lymphoblastic leukemia (ALL) it was 59.7% and 24.8% in standard-risk and high-risk groups, respectively. Lower LFS were associated with diagnosis of acute leukemia in the high-risk group (P= .001, relative risk [RR], 95% confidence interval [CI]: 2.94[1.535-5.631]) and the occurrence of aGVHD of grades 3 and 4 (P= .004). HLA-mismatched/haploidentical HSCT was feasible with unmanipulated blood and bone marrow harvest.

Maintaining hyporesponsiveness and polarization potential of T cells after in vitro mixture of G-CSF mobilized peripheral blood grafts and G-CSF primed bone marrow grafts in different proportions

BACKGROUND AND OBJECTIVES

Granulocyte colony-stimulating factor (G-CSF) primed bone marrow grafts (G-BM) plus G-CSF mobilized peripheral blood grafts (G-PB) were used successfully in haploidentical transplantation and the incidence of graft-versus-host disease (GVHD) was not higher compared with that in patients with HLA-matched donors. The immunological characteristics of T cells in G-BM and G-PB mixed in vitro in different proportions were investigated.

DESIGN AND METHODS

Lymphocyte proliferation ability, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) secreted by T cells were determined using a monotetrazolium (MTT) assay and sandwich enzyme-linked immunosorbent assay (ELISA), respectively. T cell subgroups, dendritic cells (DC) subsets, and monocytes were analyzed using flow cytometry in steady-state bone marrow (SS-BM), G-PB, and G-BM and calculated in mixture grafts.

RESULTS

The quantities of IFN-gamma and IL-4 secreted by lymphocytes per microliter in the three mixture grafts were 2- to 4-fold lower than in G-PB and 1- to 3-fold higher than in SS-BM and G-BM, while the IL-4/IFN-gamma ratio was higher than SS-BM and G-PB and lower than G-BM, although no significant difference was confirmed. Lymphocyte proliferation ability in the three mixture grafts was comparable to G-BM and significantly lower than SS-BM and G-PB. Lymphocytes, monocytes, T cell subsets, and DC subsets were 2- to 8-fold lower than in G-PB and 2- to 22-fold higher than in SS-BM and G-BM. The DC1/DC2 ratio was significantly higher in SS-BM than G-PB, G-BM, and the three mixture grafts (P<0.05).

INTERPRETATION AND CONCLUSIONS

Our results suggest that T cell hyporesponsiveness and polarization of T cell from Th1 to Th2 could be maintained after in vitro mixture of G-PB and G-BM in different proportions.

Successful induction of clinically competent dendritic cells from granulocyte colony-stimulating factor-mobilized monocytes for cancer vaccine therapy

Recent studies have suggested that dendritic cell (DC)-based immunotherapy is one promising approach for the treatment of cancer. We previously studied the clinical toxicity, feasibility, and efficacy of cancer vaccine therapy with peptide-pulsed DCs. In that study, we used granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood monocytes as a cell source of DCs. However, previous investigations have suggested that G-CSF-mobilized peripheral blood monocytes produce reduced levels of proinflammatory cytokines such as interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha. These T helper (Th)-1-type cytokines are thought to promote antitumor immune response. In this study, we assessed the functional abilities of DCs generated from G-CSF-mobilized monocytes obtained from 13 patients with CEA-positive advanced solid cancers. Peripheral blood mononuclear cells were obtained from leukapheresis products collected before and after systemic administration of G-CSF (subcutaneous administration of high-dose [5-10 microg/kg] human recombinant G-CSF for five consecutive days). In vitro cytokine production profiles after stimulation with lipopolysaccharide (LPS) were compared between monocytes with and without G-CSF mobilization. DCs generated from monocytes were also examined with respect to cytokine production and the capacity to induce peptide-specific T cell responses. Administration of G-CSF was found to efficiently mobilize peripheral blood monocytes. Although G-CSF-mobilized monocytes (G/Mo) less effectively produced Th-1-type cytokines than control monocytes (C/Mo), DCs generated from G/Mo restored the same level of IL-12 production as that seen in DCs generated from C/Mo. T cell induction assay using recall antigen peptide and phenotypic analyses also demonstrated that DCs generated from G/Mo retained characteristics identical to those generated from C/Mo. Our results suggest that G-CSF mobilization can be used to collect monocytes as a cell source for the generation of DCs for cancer immunotherapy. DCs generated in this fashion were pulsed with HLA-A24-restricted CEA epitope peptide and administered to patients safely; immunological responses were induced in some patients.

Granulocyte Colony-Stimulating Factor Mediates Cardioprotection Against Ischemia/Reperfusion Injury via Phosphatidylinositol-3-Kinase/Akt Pathway in Canine Hearts

PURPOSE

Recent studies suggest that G-CSF prevents cardiac remodeling following myocardial infarction (MI) likely through regeneration of the myocardium and coronary vessels. However, it remains unclear whether G-CSF administered at the onset of reperfusion prevents ischemia/reperfusion injury in the acute phase. We investigated acute effects of G-CSF on myocardial infarct size and the incidence of lethal arrhythmia and evaluated the involvement of the phosphatidylinositol-3 kinase (PI3K) in the in vivo canine models.

METHODS

In open-chest dogs, left anterior descending coronary artery (LAD) was occluded for 90 minutes followed by 6 hours of reperfusion. We intravenously administered G-CSF (0.33 micro/kg/min) for 30 minutes from the onset of reperfusion. Wortmannin, a PI3K inhibitor, was selectively administered into the LAD after the onset of reperfusion.

RESULTS

G-CSF significantly (p<0.05) reduced myocardial infarct size (38.7+/-4.3% to 15.7+/-5.3%) and the incidence of ventricular fibrillation during reperfusion periods (50% to 0%) compared with the control. G-CSF enhanced Akt phospholylation in ischemic canine myocardium. Wortmannin blunted both the infarct size-limiting and anti-arrhythmic effects of G-CSF. G-CSF did not change myeloperoxidase activity, a marker of neutrophil accumulation, in the infarcted myocardium.

CONCLUSION

An intravenous administration of G-CSF at the onset of reperfusion attenuates ischemia/reperfusion injury through PI3K/Akt pathway in the in vivo model. G-CSF administration can be a promising candidate for the adjunctive therapy for patients with acute myocardial infarction.

Proteomic signature of myeloproliferation and neutrophilia: analysis of serum and plasma from healthy subjects given granulocyte colony-stimulating factor

OBJECTIVE

Proteomic analysis could improve our understanding of the mechanisms and consequences of myeloproliferation. Healthy subjects treated with granulocyte colony-stimulating factor (G-CSF) were used as a model of myeloproliferation.

METHODS

Levels of 80 soluble factors were measured by enzyme-linked immunosorbent assay before and after 5 days of G-CSF. Both serum and plasma levels were measured to generate a comprehensive profile and determine whether serum or plasma best portrays biological and physiological changes.

RESULTS

Comparison of samples collected prior to G-CSF demonstrated that 44 factors differed between serum and plasma. Concentrations of several growth factors and chemokines were greater in serum than in plasma, while the opposite was true for several interleukins. Following G-CSF serum levels of 14 factors and plasma levels of 15 factors changed. Eleven increased in both serum and plasma, including cell adhesion molecules (vascular cell adhesion molecule-1, E-selectin, and L-selectin), matrix metalloproteases (MMP-1, -8, and -13), cytokine receptors (tumor necrosis factor receptor 1 and 2, and interleukin-2 receptor), the acute phase reactant, serum amyloid A, and a growth factor, hepatocyte growth factor.

CONCLUSION

Some protein levels differ markedly in serum and plasma. Myeloproliferation is associated with changes in the levels of several proteases, adhesion molecules, and cytokines.

Preservation from left ventricular remodeling by front-integrated revascularization and stem cell liberation in evolving acute myocardial infarction by use of granulocyte-colony-stimulating factor (FIRSTLINE-AMI)

BACKGROUND

Considering experimental evidence that stem cells enhance myocardial regeneration and granulocyte colony-stimulating factor (G-CSF) mediates mobilization of CD34+ mononuclear blood stem cells (MNCCD34+), we tested the impact of G-CSF integrated into primary percutaneous coronary intervention (PCI) management of acute myocardial infarction in man.

METHODS AND RESULTS

Fifty consecutive patients with ST-segment elevation myocardial infarction were subjected to primary PCI stenting with abciximab and followed up for 6 months; 89+/-35 minutes after successful PCI, 25 patients were randomly assigned in this pilot study (PROBE design) to receive subcutaneous G-CSF at 10 microg/kg body weight for 6 days in addition to standard care, including aspirin, clopidogrel, an ACE inhibitor, beta-blocking agents, and statins. By use of CellQuest software on peripheral blood samples incubated with CD45 and CD34, mobilized MNCCD34+ were quantified on a daily basis. With homogeneous demographics and clinical and infarct-related characteristics, G-CSF stimulation led to mobilization of MNCCD34+ to between 3.17+/-2.93 MNCCD34+/microL at baseline and 64.55+/-37.11 MNCCD34+/microL on day 6 (P<0.001 versus control); there was no indication of leukocytoclastic effects, significant pain, impaired rheology, inflammatory reactions, or accelerated restenosis at 6 months. Within 35 days, G-CSF and MNCCD34+ liberation led to enhanced resting wall thickening in the infarct zone of between 0.29+/-0.22 and 0.99+/-0.32 mm versus 0.49+/-0.29 mm in control subjects (P<0.001); under inotropic challenge with dobutamine (10 microg.kg(-1).min(-1)), wall motion score index showed improvement from 1.66+/-0.23 to 1.41+/-0.21 (P<0.004 versus control) and to 1.35+/-0.24 after 4 months (P<0.001 versus control), respectively, coupled with sustained recovery of wall thickening to 1.24+/-0.31 mm (P<0.001 versus control) at 4 months. Accordingly, resting wall motion score index improved with G-CSF to 1.41+/-0.25 (P<0.001 versus control), left ventricular end-diastolic diameter to 55+/-5 mm (P<0.002 versus control), and ejection fraction to 54+/-8% (P<0.001 versus control) after 4 months. Morphological and functional improvement with G-CSF was corroborated by enhanced metabolic activity and 18F-deoxyglucose uptake in the infarct zone (P<0.001 versus control).

CONCLUSIONS

G-CSF and mobilization of MNC(CD34+) after reperfusion of infarcted myocardium may offer a pragmatic strategy for preservation of myocardium and prevention of remodeling without evidence of aggravated restenosis.

Granulocyte colony-stimulating factor modulates alpha-galactosylceramide-responsive human Valpha24+Vbeta11+NKT cells

Despite more than a 10-fold increase in T cell numbers in G-CSF-mobilized peripheral blood stem cell (PBSC) grafts, incidence and severity of acute graft-vs-host disease (GVHD) are comparable to bone marrow transplantation. As CD1d-restricted, Valpha24+Vbeta11+ NKT cells have pivotal immune regulatory functions and may influence GVHD, we aimed to determine whether G-CSF has any effects on human NKT cells. In this study, we examined the frequency and absolute numbers of peripheral blood NKT cells in healthy stem cell donors (n = 8) before and following G-CSF (filgrastim) treatment. Effects of in vivo and in vitro G-CSF on NKT cell cytokine expression profiles and on responsiveness of NKT cell subpopulations to specific stimulation by alpha-galactosylceramide (alpha-GalCer) were assessed. Contrary to the effects on conventional T cells, the absolute number of peripheral blood NKT cells was unaffected by G-CSF administration. Furthermore, responsiveness of NKT cells to alpha-GalCer stimulation was significantly decreased (p < 0.05) following exposure to G-CSF in vivo. This hyporesponsiveness was predominantly due to a direct effect on NKT cells, with a lesser contribution from G-CSF-mediated changes in APC. G-CSF administration resulted in polarization of NKT cells toward a Th2, IL-4-secreting phenotype following alpha-GalCer stimulation and preferential expansion of the CD4+ NKT cell subset. We conclude that G-CSF has previously unrecognized differential effects in vivo on NKT cells and conventional MHC-restricted T cells, and effects on NKT cells may contribute to the lower than expected incidence of GVHD following allogeneic peripheral blood stem cell transplantation.

The whys and hows of hematopoietic progenitor and stem cell mobilization

Intentional mobilization of hematopoietic/stem cells into the circulation has improved the efficiency of their collection. Transplantation of mobilized blood stem cells to patients with marrow aplasia results in a faster pace of hematopoietic recovery than transplantation of marrow-derived stem cells. Autologous and allogeneic hematopoietic stem cell transplantation are increasingly performed with blood-derived cells. Donors of both autologous and allogeneic blood stem cells do not always respond well to therapies designed to produce mobilization. Autologous donors may respond poorly as a result of myelotoxic damage inflicted by prior antitumor therapy, but this explanation is not valid for allogeneic donors. The mechanism(s) involved in the process of mobilization are incompletely understood. Until these mechanisms are elucidated, methods to improve mobilization vigor on a rational basis will not be obvious. In the meanwhile, clinical observations may provide some hints regarding the whys and hows of mobilization and permit incremental improvements in this process.

Granulocyte colony-stimulating factor directly affects human monocytes and modulates cytokine secretion

OBJECTIVE

Recent reports have indicated that monocytes express receptors for the granulocyte colony-stimulating factor (G-CSF). The direct effects of G-CSF on cytokine secretion in monocytes were examined.

MATERIALS AND METHODS

A monocytic cell line NOMO-1 that secretes multiple cytokines upon stimulation with lipopolysaccharide (LPS) was used. Normal human monocytes were purified by negative selection using magnetic beads. Cells pretreated with or without G-CSF were stimulated with LPS, and the subsequent concentrations of cytokines and chemokines in supernatants were determined by sandwich enzyme-linked immunosorbent assay.

RESULTS

NOMO-1 cells were found to express receptors for G-CSF. Although G-CSF stimulation did not induce cytokine secretion, pretreatment with G-CSF significantly attenuated LPS-stimulated secretion of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin (IL)-12 in NOMO-1 cells. Simultaneously, however, G-CSF pretreatment apparently enhanced LPS-induced secretion of IL-10 and monocyte chemoattractant protein-1, whereas secretions of IL-1beta, IL-6, and IL-8 were unaffected. When normal human monocytes from healthy volunteers were similarly examined, marked individual variations in LPS-induced secretion of cytokines were observed. Although some exceptions exist, a similar tendency as to the effects of G-CSF treatment on cytokine secretions as that in NOMO-1 cells was observed in human monocytes.

CONCLUSIONS

Our data suggest that G-CSF directly affects monocytes and modulates their cytokine secretion. NOMO-1 cells can provide an alternate model for in vitro culture of monocytes to investigate the effects of G-CSF on cytokine secretion by these cells.

CD41+ and CD42+ hematopoietic progenitor cells may predict platelet engraftment after allogeneic peripheral blood stem cell transplantation

The objective of this study was to quantify subpopulations of CD34+ cells such as CD41+ and CD42+ cells that might represent megakaryocyte (MK) precursors in peripheral blood stem cell (PBSC) collections of normal, recombinant human granulocyte-colony stimulating factor (rhG-CSF) primed donors and to determine whether there is a statistical association between the dose infused megakaryocytic precursors and the time course of the platelet recovery following an allogeneic PBSC transplantation. Twenty-six patients with various hematologic malignancies transplanted from their HLA identical siblings between July 1997 and December 1999 were used. All patients except one with severe aplastic anemia who had cyclophosphamide (CY) alone received busulfan-CY as preparative regimen and cyclosporine-methotrexate for GVHD prophylaxis. Normal healthy donors were given rhG-CSF 10 microg/kg/day subcutaneously twice daily and PBSCs were collected on days 5 and 6. The median number of infused CD34+, CD41+ and CD42+ cells were 6.61 x 10(6)/kg (range 1.47-21.41), 54.85 x 10(4)/kg (5.38-204.19), and 49.86 x 10(4)/kg (6.82-430.10), respectively. Median days of ANC 0.5 x 10(9)/L and platelet 20 x 10(9)/L were 11.5 (range 9-15) and 13 (8-33), respectively. In this study, the number of CD41+ and CD42+ cells infused much better correlated than the number of CD34+ cells infused with the time to platelet recovery of 20 x 10(9)/L in 26 patients receiving an allogeneic match sibling PBSC transplantation (r = -0.727 and P < 0.001 for CD41+ cells, r = -0.806 and P < 0.001 for CD42+ cells, r = -0.336 and P > 0.05 for CD34+ cells). There was an inverse correlation between the number of infused CD41+ and CD42+ cells and duration of platelet engraftment. Therefore, as the number of CD41+ and CD42+ cells increased, duration of platelet engraftment (time to reach platelet count of > or = 20 x 10(9)/L) shortened significantly. Based on this data we may conclude that flow cytometric measurement of CD41+ and CD42+ progenitor cells may provide an accurate indication of platelet reconstitutive capacity of the allogeneic PBSC transplant.

Decreased immune functions of blood cells following mobilization with granulocyte colony-stimulating factor: association with donor characteristics

In this study, mononuclear cells (MNCs) from granulocyte colony-stimulating factor (G-CSF)-mobilized blood stem cell (BSC) harvests from 104 healthy donors were analyzed for their immunological functions and compared with MNCs from 28 steady-state nonmobilized donors. The relationships between donor characteristics (age, gender, weight, and HLA type) and immune functions of the harvests were also analyzed. There was a significant (P <.01) decrease in natural killer and lymphokine-activated killer (LAK) cell-mediated cytotoxicity for G-CSF-mobilized effector cells compared with nonmobilized cells. Similarly, there was a significant (P <.005) decrease in both T-cell and B-cell mitogen response in G-CSF-mobilized cells compared with nonmobilized cells. There was dose-dependent inhibition of LAK cell-mediated cytotoxicity, but this effect was not seen with other immune function assays. Changes in immune function did not appear to be determined by frequency of cellular phenotypes or expression of effector function genes seen in a reverse-transcription polymerase chain reaction. There was a significant relationship between expression of certain HLA alleles (A1, A3, A24, B44, B62, DR15, DR17; all P <.01) and increased immune function, such as cytotoxicity and/or mitogen response. A decrease in immune function with the HLA-DR13 expression was also observed (P <.01). Since the G-CSF increases the number of MNCs, the increase in effector cells might compensate for decreased immune functions of these cells in vivo when transplanted into patients. These results suggest a decreased immune function in G-CSF-mobilized BSC harvests and warrant further studies to correlate these data with clinical outcome.

Allogeneic peripheral blood stem cell transplantation

Granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSC) are now widely used instead of bone marrow for autologous transplantation due to earlier hematopoietic recovery after transplant. The low toxicity of G-CSF has prompted phase I and II studies to evaluate PBSC for allogeneic transplantation; these studies have demonstrated that engraftment of neutrophils, red blood cells and platelets is faster with peripheral blood cells compared to marrow. In randomized studies comparing mobilized PBSC and marrow for allogeneic transplantation, most trials have confirmed significantly earlier engraftment with PBSC and similar risks of acute graft-vs.-host disease (GVHD). In some trials, an increase of 10-15% in grade II-IV GVHD has been noted with PBSC. All studies showed a trend towards more chronic GVHD with PBSC. Some randomized studies have shown improved survival and disease-free survival with the use of PBSC due to lowered transplant-related mortality and fewer relapses in recipients of PBSC as a result of improved immune reconstitution and a graft-vs.-leukemia (GVL) effect. This survival benefit is most apparent in patients with more advanced hematologic malignancies, but further studies are needed to define the relative benefits of PBSC for patients with less advanced disease. The GVL effect of PBSC is currently being exploited with the use of non-ablative allografts.

Hepatic graft-versus-host disease presenting as an acute hepatitis after allogeneic peripheral blood stem cell transplantation

Hepatic graft-versus-host disease (GVHD) generally presents as cholestatic jaundice, and increased serum alkaline phosphatase (ALP) is followed by hyperbilirubinemia and clinical jaundice. Currently accepted standards for evaluating the clinical severity of GVHD are based not on serum aminotransferase levels but on the serum bilirubin level. We describe a 17-year-old Japanese female who had increased aminotransferases without cholestasis on day 23 after allogeneic peripheral blood stem cell transplantation (allo-PBSCT). Liver biopsy revealed lymphocytic infiltration of the portal tracts and pericentral necrosis of the lobuli. The limiting plates were not clearly defined due to cellular infiltrates. There was periductal lymphocytic infiltration and vacuolization of the biliary epithelial cells with exocytosis, compatible with GVHD of cholangiohepatitic type. These findings indicate that acute hepatic GVHD may present as acute hepatitis and this should be included in the differential diagnosis for patients with increased aminotransferases after allogeneic stem cell transplantation.

OKT-3-based reconditioning regimen for early graft failure in HLA-non-identical stem cell transplants

Primary non-engraftment or early rejection after transplantation of haematopoietic stem cells represent life-threatening complications of allogeneic stem cell transplantation. Management of early graft failure has been problematic, as the risk of fatal infectious complications increases with the time of pancytopenia and as a second transplant preceded by a conventional myeloablative conditioning regimen has been associated with high rates of cumulative organ toxicity. For paediatric patients with early graft failure following the transplantation of highly purified major histocompatibility complex (MHC)-disparate haematopoietic stem cells, we have evaluated an immunosuppressive OKT-3/methylprednisolone-based reconditioning regimen with low toxicity in preparation for a secondary transplant of purified haematopoietic stem cells from the same donor. This report presents the results from a 4-year pilot study including six patients with early graft failure. The results demonstrate that this antibody-based regimen can be used effectively to prepare patients for secondary transplantation. Successful engraftment after a second transplant procedure was achieved in five of these six high-risk patients. The median interval between first and second transplant was 27 d (range 22-51 d), and the median time for engraftment was 10 d (range 9-13 d). Chimaerism analysis of microsatellite regions by polymerase chain reaction (PCR) demonstrated complete donor chimaerism in four of these patients within the first month after secondary transplant and revealed mixed chimaerism in one patient who converted to complete chimaerism after T-cell add-back.

Mobilization and transplantation of peripheral blood stem cells

Two hundred nineteen patients underwent peripheral blood stem cell (PBSC) transplantation from 1990 to 1997. Stem cells were mobilized with cyclophosphamide (CY), or with CY plus Taxol or etoposide, followed by cytokines, and collected when leukocyte counts > or = 1,000/microl, or when CD34+ counts > or = 20/microl. On average, four to five collections were needed to obtain sufficient PBSC for engraftment. When CD34+ counts were used, the average number of collections decreased from 5.4 to 4.2. A discrepancy was noted in the extraction ratios and number of collections that depended on the optical density (I/O) setting of the leukapheresis machine. Patients collected at a setting of 100 had higher extraction ratios and required fewer collections (mean = 2.7) than those collected at 150 (mean = 4.4). This result was unexpected, because the entire mononuclear cell layer is collected at the higher I/O setting. Further analysis revealed that a larger volume of red cells was collected at 150 than at 100. These procedures used a small-volume collection chamber, so the chamber was apparently overloaded by RBC at the higher setting. More rapid recovery of neutrophil counts and platelet counts was seen in PBSC transplants than in autologous marrow transplants; moreover, PBSC transplant patients required fewer RBC and platelet transfusions. Sixteen out of 21 normal donors for allogeneic PBSC transplants gave adequate collections (> 2.5 x 10(6) CD34+ cells/kg), but three donors failed to yield > or = 1.5 x 10(6) CD34 cells/kg. This suggests an inherent difference among certain normal donors that may make PBSC mobilization difficult.

Mobilization of blood stem cells

Deliberately increasing the number of hematopoietic stem and progenitor cells in the circulation allows faster and more efficient collection of sufficient cells for transplantation in both the allogeneic and autologous settings. These mobilized stem cells, when transplanted, provide quicker hematopoietic recovery for the patient than do nonmobilized blood stem cells or steady-state marrow-derived stem cells. Currently used clinical procedures to produce stem cell mobilization include administration of G-CSF or GM-CSF, either as single agents or in combination with myelosuppressive chemotherapy. Some autologous blood stem cell donors exhibit indifference to currently applied mobilization therapies. This failure to mobilize has been associated with prior stem cell toxic therapy, e.g., radiation therapy and chemotherapy, but the association is incomplete. The observation that occasional normal donors have failed to respond to mobilization therapy indicates that factors other than stem cell damage could also be involved. Recently, a murine model has provided evidence that a circulating factor inhibits mobilization in some settings. Preliminary investigations have suggested that a circulating factor may inhibit mobilization of human hematopoietic progenitor cells in some instances. Studies to identify this factor(s) are underway. The mechanisms of blood stem cell mobilization are still poorly understood and there continues to be the potential to improve this process.

Allogeneic peripheral blood stem cell transplantation for standard risk leukemia: experience of Ibni Sina Hospital

Fifty-three patients with standard risk leukemia who underwent allogeneic peripheral blood stem cell transplantation (alloPBSCT) from their HLA-identical siblings were analyzed for engraftment, incidence and severity of GVHD, and relapse rate. Standard risk leukemia was defined as AML in first complete remission or CML in first chronic phase within the first year after diagnosis. The median age was 34.5 years (range 13-47). Stem cells were mobilized by using 10 microg/kg G-CSF subcutaneously for 5 days. A median of 5. 7 (2.1-21.4) x 106/kg CD34+ cells was collected over a median of 2 (range 1-5) apheresis procedures. Cyclosporin A (CsA) plus short-course MTX were used for GVHD prophylaxis. Recovery to granulocytes >0.5 x 109/l and platelets >20 x 109/l occurred at a median of day +13 (range 8-32) and +13 (range 8-51), respectively. Day +100 transplant-related mortality was 13.2% (7/53). Acute GVHD occurred in 20 of 49 (41%) evaluable patients and only six (12.3%) of them had severe disease (grade III-IV). Chronic GVHD occurred in 30 of 42 (71.4%) evaluable patients. Relapse rate at 2 years was 7. 5%. The median overall and leukemia-free survivals were 22 (4-44) and 20 (3-44) months, respectively. Estimated 4 year leukemia-free and overall survival rates were 60% and 62%, respectively. In conclusion, alloPBSCT in standard risk leukemia seems to be associated with a low relapse rate and no increased risk of acute GVHD, but there is a trend for higher incidence of cGVHD. Bone Marrow Transplantation (2000) 25, 1229-1232.

Granulocyte-colony stimulating factor mobilizes T helper 2-inducing dendritic cells

Peripheral blood stem cells (PBSC) obtained from granulocyte-colony stimulating factor (G-CSF)-mobilized donors are increasingly used for allogeneic transplantation. Despite a 10-fold higher dose of transplanted T cells, acute graft-versus-host disease (GVHD) does not develop in higher proportion in recipients of PBSC than in recipients of marrow. T cells from G-CSF-treated experimental animals preferentially produce IL-4 and IL-10, cytokines characteristic of Th2 responses, which are associated with diminished GVHD-inducing ability. We hypothesized that G-CSF-mobilized PBSC contain antigen-presenting cells, which prime T-lymphocytes to produce Th2 cytokines. Two distinct lineages of dendritic cells (DC) have been described in humans, DC1 and DC2, according to their ability to induce naive T-cell differentiation to Th1 and Th2 effector cells, respectively. We have used multicolor microfluorometry to enumerate DC1 and DC2 in the peripheral blood of normal donors. G-CSF treatment with 10 to 16 μg/kg per day for 5 days increased peripheral blood DC2 counts from a median of 4.9 × 106/L to 24.8 × 106/L (P = .0009), whereas DC1 counts did not change. Purified DC1, from either untreated or G-CSF treated donors, induced the proliferation of allogeneic naive T cells, but fresh DC2 were poor stimulators. Tumor necrosis factor- (TNF-)-activated DC1 induced allogeneic naive T cells to produce IFN-γ, which is typical of Th1 responses, whereas TNF--activated DC2 induced allogeneic naive T cells to produce IL-4 and IL-10, which are typical of Th2 responses. PBSC transplants contained higher doses of DC2 than marrow transplants (median, 2.4 × 106/kg versus 0.5 × 106/kg) (P = .006), whereas the dose of DC1 was comparable. Thus, it is conceivable that transplantation of G-CSF-stimulated PBSC does not result in overwhelming acute GVHD because the graft contains predominantly Th2-inducing DC. Adoptive transfer of purified DC2 may be exploited to induce immune deviation after transplantation of hematopoietic stem cells or organ allografts.

Granulocyte-colony stimulating factor mobilizes T helper 2-inducing dendritic cells

Peripheral blood stem cells (PBSC) obtained from granulocyte-colony stimulating factor (G-CSF)-mobilized donors are increasingly used for allogeneic transplantation. Despite a 10-fold higher dose of transplanted T cells, acute graft-versus-host disease (GVHD) does not develop in higher proportion in recipients of PBSC than in recipients of marrow. T cells from G-CSF-treated experimental animals preferentially produce IL-4 and IL-10, cytokines characteristic of Th2 responses, which are associated with diminished GVHD-inducing ability. We hypothesized that G-CSF-mobilized PBSC contain antigen-presenting cells, which prime T-lymphocytes to produce Th2 cytokines. Two distinct lineages of dendritic cells (DC) have been described in humans, DC1 and DC2, according to their ability to induce naive T-cell differentiation to Th1 and Th2 effector cells, respectively. We have used multicolor microfluorometry to enumerate DC1 and DC2 in the peripheral blood of normal donors. G-CSF treatment with 10 to 16 μg/kg per day for 5 days increased peripheral blood DC2 counts from a median of 4.9 × 106/L to 24.8 × 106/L (P = .0009), whereas DC1 counts did not change. Purified DC1, from either untreated or G-CSF treated donors, induced the proliferation of allogeneic naive T cells, but fresh DC2 were poor stimulators. Tumor necrosis factor- (TNF-)-activated DC1 induced allogeneic naive T cells to produce IFN-γ, which is typical of Th1 responses, whereas TNF--activated DC2 induced allogeneic naive T cells to produce IL-4 and IL-10, which are typical of Th2 responses. PBSC transplants contained higher doses of DC2 than marrow transplants (median, 2.4 × 106/kg versus 0.5 × 106/kg) (P = .006), whereas the dose of DC1 was comparable. Thus, it is conceivable that transplantation of G-CSF-stimulated PBSC does not result in overwhelming acute GVHD because the graft contains predominantly Th2-inducing DC. Adoptive transfer of purified DC2 may be exploited to induce immune deviation after transplantation of hematopoietic stem cells or organ allografts.

Pharmacologic doses of granulocyte colony-stimulating factor affect cytokine production by lymphocytes in vitro and in vivo

Peripheral blood stem cell (PBSC) transplantation is successful in improving engraftment without increasing acute graft-versus-host disease (GVHD), despite much larger numbers of T cells in unmanipulated PBSCs than in bone marrow grafts. In mouse models and retrospective human studies, granulocyte colony-stimulating factor (G-CSF) therapy has been associated with less acute GVHD. We studied the effect of G-CSF on interferon (IFN)-γ and IL-4 expression in CD4+lymphocytes. CD4+ cells co-cultivated with G-CSF and stimulated with PHA or CD3 monoclonal antibodies showed significant decreases in IFN-γ and increases in IL-4 expression (n = 13;P &lt; .01). G-CSF appeared to have a direct effect on CD4+ cells independent of monocytes present in the culture because purified CD4+ cells exposed to G-CSF, washed, and cocultivated with untreated monocytes demonstrated similar changes in IFN-γ and IL-4 expression, whereas untreated CD4+ cells cocultured with G-CSF–stimulated monocytes behaved as controls. We then studied peripheral blood mononuclear cells (PBMCs) from G-CSF–mobilized PBSC donors. When their PBMCs were cultured with PHA or CD3 monoclonal antibody, the percent of IFN-γ–expressing cells decreased by a mean of 55% and 42%, respectively, whereas the percent of IL-4–containing cells increased by a mean of 39% and 58%, respectively, following G-CSF stimulation. Increased apoptosis of IFN-γ–producing CD4+ cells was not responsible for the shift in TH1/TH2 subsets. G-CSF-R mRNA was present in both CD4+ and CD8+ cells. These results suggest that G-CSF decreases IFN-γ and increases IL-4 production in vitro and in vivo and likely modulates a balance between TH1 and TH2 cells, an effect that may be important in PBSC transplantation.

Pharmacologic doses of granulocyte colony-stimulating factor affect cytokine production by lymphocytes in vitro and in vivo

Peripheral blood stem cell (PBSC) transplantation is successful in improving engraftment without increasing acute graft-versus-host disease (GVHD), despite much larger numbers of T cells in unmanipulated PBSCs than in bone marrow grafts. In mouse models and retrospective human studies, granulocyte colony-stimulating factor (G-CSF) therapy has been associated with less acute GVHD. We studied the effect of G-CSF on interferon (IFN)-γ and IL-4 expression in CD4+lymphocytes. CD4+ cells co-cultivated with G-CSF and stimulated with PHA or CD3 monoclonal antibodies showed significant decreases in IFN-γ and increases in IL-4 expression (n = 13;P < .01). G-CSF appeared to have a direct effect on CD4+ cells independent of monocytes present in the culture because purified CD4+ cells exposed to G-CSF, washed, and cocultivated with untreated monocytes demonstrated similar changes in IFN-γ and IL-4 expression, whereas untreated CD4+ cells cocultured with G-CSF–stimulated monocytes behaved as controls. We then studied peripheral blood mononuclear cells (PBMCs) from G-CSF–mobilized PBSC donors. When their PBMCs were cultured with PHA or CD3 monoclonal antibody, the percent of IFN-γ–expressing cells decreased by a mean of 55% and 42%, respectively, whereas the percent of IL-4–containing cells increased by a mean of 39% and 58%, respectively, following G-CSF stimulation. Increased apoptosis of IFN-γ–producing CD4+ cells was not responsible for the shift in TH1/TH2 subsets. G-CSF-R mRNA was present in both CD4+ and CD8+ cells. These results suggest that G-CSF decreases IFN-γ and increases IL-4 production in vitro and in vivo and likely modulates a balance between TH1 and TH2 cells, an effect that may be important in PBSC transplantation.