C Arbona, F Prosper, I Benet, F Mena, C Solano and J Garcia-Conde. Summary:

Transcription

1 Bone Marrow Transplantation, (1998) 22, Stockton Press All rights reserved /98 $ Comparison between once a day vs twice a day G-CSF for mobilization of peripheral blood progenitor cells (PBPC) in normal donors for allogeneic PBPC transplantation C Arbona, F Prosper, I Benet, F Mena, C Solano and J Garcia-Conde Hematology and Oncology Department, Hospital Clinico Universitario, University of Valencia, Spain Summary: Despite the wide use of G-CSF for mobilization of PBPC the best dose and schedule of G-CSF has not been definitively established. In this study we have compared three different schedules of G-CSF for mobilization of PBPC in normal donors including a single daily dose of 10 g/kg/day for 5 days (21 donors) and doses of 6 (21 donors) or 8 g/kg/12 h (6 donors) for 5 days. We demonstrate that G-CSF at doses of 6 and 8 g/kg/12 h mobilizes significantly more CD34 cells/ml of blood ( and , respectively) than 10 g/kg/day ( ). Mobilization with 6 or 8 g/kg/12 h of G-CSF was also associated with collection of significantly more CD34 cells in comparison with 10 g/kg/24 h ( and vs CD34 cells/kg of donor/blood volume). PBPC collection was associated with a significant decrease in platelet count which was not significantly different between the three groups. Ten days after the last PBPC collection platelet counts were within normal limits while there was a decrease in WBC and ANC. We conclude that G-CSF administered every 12 h at doses of 6 g/kg provides better CD34 cell yield than 10 g/kg once a day in normal donors which may translate into a decrease in the number of aphereses required to obtain enough numbers of CD34 cells for allogeneic PBPC transplant. Keywords: mobilization; G-CSF; PBPC; allogeneic stem cell transplant; normal donors The demonstration of the presence of hematopoietic stem cells and progenitor cells in human peripheral blood has led to the use of PBPC for transplantation. 1 3 However, the frequency of progenitors in the peripheral blood under steady-state conditions is extremely low, making it very costly and cumbersome to obtain enough PBPC for transplantation. 4 The finding that the use of chemotherapy with or without the addition of growth factors such as granulocyte colony-stimulating factor (G-CSF), granulocyte macro- Correspondence: Dr J Garcia-Conde, Hematology and Oncology Department, Hospital Clinico Universitario, Av Blasco Ibanez 17, Valencia, Spain Received 9 January 1998; accepted 24 February 1998 phage (GM)-CSF, interleukin 3 (IL3) or stem cell factor (SCF) is able to increase the number of hematopoietic progenitors in the PB has led to an increase in the number of hematopoietic stem cell transplants performed using PBPC instead of steady-state bone marrow (BM). 5 8 Recent studies comparing transplantation using BM progenitors or mobilized PBPC have demonstrated that autologous PBPC transplantation is associated with faster neutrophil and platelet engraftment, decreased length of hospitalization and decreased use of antibiotics which translates into reducing the costs of transplantation. 4,9 11 More recently, a number of studies have demonstrated that PBPC can also be used for allogeneic transplantation Despite the fact that mobilized PBPC contain 10 times more T cells than steadystate BM the incidence of acute GVHD in allogeneic PBPC transplantation is similar to allogeneic BM transplantation. 12,15 However, preliminary evidence suggests that the incidence and severity of chronic GVHD may be increased after allogeneic PBPC transplant. 16 Among the different growth factors, G-CSF has been most extensively used for mobilization of PBPC due to its efficacy in cancer patients and normal donors and the low incidence of side-effects. 17 G-CSF-induced toxicity is usually mild and includes fever, bone pain, headaches, fatigue and occasionally nausea and/or vomiting. 18 The use of other growth factors such as GM-CSF, IL3 or SCF despite being good mobilizers has been more restricted due to their increased toxicity which is particularly relevant in normal donors. 19 Long-term side-effects are currently unknown for any clinically approved growth factor. Beside mobilization of colony-forming cells (CFC) and CD34 + cells, we and others have recently demonstrated that G-CSF mobilizes long-term culture-initiating cells (LTC-IC) as well as phenotypically immature progenitors G-CSF-mobilized PBPC have a decreased NK cytotoxicity and proliferative capacity which is associated with a decrease in the number of mature as well as progenitor NK cells. 23 T cell populations are also altered in G-CSF-mobilized PBPC. 24 These abnormalities may partially explain the low incidence of acute GVHD in allogeneic PBPC despite the high number of T cells. The optimal dose and schedule of G-CSF treatment for mobilization of PBPC in normal donors has not been definitively established. Doses of G-CSF have ranged between 2 and 24 g/kg/day for up to 10 days with apheresis being performed on days Some studies have also used divided doses every 12 h although the benefit of

2 40 Mobilization of PBPC with twice a day G-CSF this approach is unclear. 25 The EBMT has recently recommended that normal donors undergoing mobilization for allogeneic PBPC transplant should receive doses of 10 g/kg/day for 5 days starting PBPC collections one day after the fourth dose of G-CSF. 14 In this study we have compared three different schedules of G-CSF for mobilization of PBPC in normal donors including a single daily dose of 10 g/kg/day for 5 days and doses of 6 or 8 g/kg/12 h for 5 days. We have determined the number of CD34 + cells and CFU-GM mobilized, the number of aphereses needed to obtain the target dose as well as the adverse effects in each group showing that G-CSF administered in divided doses (6 g/kg/12 h) provides a significantly better mobilization than 10 g/kg/day. Subjects and methods Normal donors A total of 48 consecutive normal PBPC donors were included in the study. Protocols for collection of PBPC were approved by the Ethics Committee and written informed consent was obtained from every donor before the procedure. PBPC collections were used for either HLA identical or haploidentical allogeneic PBPC transplant. Mobilization and apheresis Normal donors received filgrastim according to three different schedules in a consecutive way: group 1: 10 g/kg/day (21 donors); group 2: 8 g/kg/12 h (six donors); group 3: 6 g/kg/12 h (21 donors). The first dose of G-CSF was given on day 1, considering day 0 as the day before starting mobilization. PBPC collection was started 18 h after the fourth dose of G-CSF in group 1 and 2 h after the eighth dose in groups 2 and 3. In the first 16 patients, the target CD34 + cell dose was /kg of recipient body weight. However, in the following 32 patients the target cell dose was increased to /kg. Because we initiated a program of allogeneic transplantation with CD34 + selected PBPC we needed to obtain higher CD34 + cell numbers to account for the loss of CD34 + cells that is associated with CD34 column selection. Administration of G-CSF was continued until the target dose of CD34 + cells had been obtained. Aphereses were performed using a blood cell separator (Fenwal CS-3000 plus; Baxter Healthcare, Deerfield, IL, USA) using ACD-A as anticoagulant. The flow rates were ml/min and a total of 9 15 l of blood were processed over 4 h. Blood counts Blood count and differential from PB and apheresis product were performed with an automated cell counter (H-3 Technicon). Flow cytometry An aliquot of PB or apheresis product containing cells was incubated with 10 l of antibody to CD34 (anti- HPCA-2; Becton Dickinson, San Jose, CA, USA) coupled to fluorescein isothiocyanate (FITC) for 20 min at 4 C. After lysis of red cells with ammonium chloride, the cells were washed with phosphate-buffered saline solution (PBS) and then resuspended in 1 ml PBS. IgG1 coupled to FITC was used as negative control. For analysis, cells were acquired in list-mode using a flow cytometer (FACScan, Becton Dickinson) and software (LYSIS II; Becton Dickinson). Before acquisition, propidium iodide was added to exclude dead cells. Total nucleated cells were gated by forward and side scatter. A side scatter vs fluorescence two dot plot (SSC vs FL2) was established to exclude dead cells. The percentage of CD34 + cells was determined from a SSC vs FL1 (FITC) dot plot obtained by gating viable nucleated cells. The percentage of CD34 + cells was determined by setting the gate above the background level for the isotype FITC control. Since the WBC count was known, the number of CD34 + cells per ml of blood was calculated by multiplying the percentage of CD34 + cells by the WBC count. Hematopoietic cell culture A total of nucleated cells were plated in methylcellulose containing Iscove s modified Dulbecco s medium (IMDM) (GIBCO Laboratories, Grand Island, NY, USA), supplemented with 20% fetal calf serum (FCS) (Hyclone, Logan, UT, USA) and 100 ng/ml of G-CSF (Amgen, Thousand Oaks, CA, USA). Cultures were incubated in a humidified atmosphere at 37 C and 5% CO 2. The cultures were assessed at days 14 to 18 for the presence of CFU- GM as previously described. 20 Statistics Statistical analysis was performed using SPSS software. Variables are expressed as mean s.d. unless otherwise stated. Differences between groups were determined by the Mann Whitney U test and Kruskal Wallis test for multiple groups. Correlations were calculated using Pearson s correlation coefficient. Distribution between categorial variables was examined by 2 test. Results Donor characteristics The 48 donors ranged in age from 12 to 69 years (Table 1). Mean age for the whole group was 40 years. There were no differences between the three groups for age or sex distribution. Adverse effects Administration of G-CSF and leukapheresis were completed in every donor without G-CSF dose reduction. Aphereses were performed through peripheral venous access (antecubital veins) in 37 donors. However, in five donors (10%) placement of a percutaneous central venous catheter (Quinton) was required. Adverse effects include mild to

3 Mobilization of PBPC with twice a day G-CSF Table 1 Donor characteristics according to type of mobilization Group 1 (10 g/kg/day) Group 2 (8 g/kg/12 h) Group 3 (6 g/kg/12 h) 41 No. of donors Age (range) 40 (12 65) 42 (20 69) 40 (18 68) Sex Male Female No. of donors according to target dose CD CD No of apheresis according to target dose CD (1 4) CD (1 4) 2 2 (1 3) WBC (10 9 /l) Baseline 6.82 ± ± ± 2.17 Pre-apheresis ± ± ± 11.5 CD34 + cells in PB (%) Pre-apheresis (day +5) 0.18 ± ± ± 0.04 CD34 + cells in PB (10 6 /l) Baseline 4.56 ± ± ± 1.7 Pre-apheresis (day +5) ± ± 6.9* 83.3 ± 6.7* Age is expressed as median (range). Number of aphereses according to target dose is expressed as median (range). CD34 + cells in PB is expressed as mean s.e.m. *P 0.01 between CD34 + cells/ml of PB in donors receiving 6 or 8 g/kg/12 h and 10 g/kg/day. moderate bone pain in 33 (69%) donors (15 of 21 in group 1, four of six in group 2 and 15 of 21 in group 3). Nine donors (20%) experienced headaches related to G-CSF administration (three of 21 in group 1, one of six in group 5 and nine of 21 in group 3). Three donors (6%) experienced insomnia (one donor in each group). Other adverse effects included, body aches, fatigue or nausea. Adverse effects were independent of the type of mobilization and disappeared upon discontinuation of G-CSF. Effect of the different schedules of G-CSF on the WBC, platelet count, CD34 + cells and CFU-GM All three schedules of G-CSF significantly increased the total number of WBC after 5 days of treatment. WBC count in donors receiving 10 g/kg/day increased from /l to /l while in donors receiving 6 or 8 g/kg/12 h the total WBC count went from baseline values of /l and /l to /l and /l respectively. The WBC count was significantly higher for donors receiving twice a day G-CSF in comparison with donors receiving G-CSF once a day (Figure 1) (P 0.01). There were no statistically significant differences in WBC between donors receiving 6 g/kg/12 h or 8 g/kg/12 h. The platelet count remained unchanged during the administration of G-CSF. However, we observed a statistically significant decrease in the platelet count following initiation of leukapheresis for every group of patients (Figure 2) (P 0.01). Interestingly, when we measured the number of platelets immediately after each collection and immediately before the next collection, there were no differences in the total platelet count suggesting that the decrease in platelet count was not only due to the apheresis procedure but also to decreased platelet production (Figure WBC 109/l * * µ µ µ 10 g/kg/24 h 8 g/kg/12 h 6 g/kg/12 h Baseline Day 5 Day 6 Day 7 Day 8 Figure 1 Effect of G-CSF treatment on the total number of WBC according to the schedule of G-CSF. Results represent mean s.e.m. (standard error of the mean) for all the donors in each group. *P 0.01 between donors mobilized with 10 g/kg/day and 6 or 8 g/kg/12 h. 2). Although there were no complications related to thrombocytopenia, in 11 cases the platelet count decreased below /l with a minimum of /l. Ten days after the last apheresis, the platelet count was similar to baseline values for each donor (Figure 2). There was no statistically significant difference in platelet count between donors receiving G-CSF at doses of 10 g/kg/day, 6 g/kg/12 h or 8 g/kg/12 h. As has been previously reported, treatment of normal donors with G-CSF induced an increase in the percentage and total number of CD34 + cells per ml of PB. 6,18,20 The percentage of CD34 + cells after 4 days of treatment with G-CSF in donors treated with 10 g/kg/day, 6 g/kg/12 hor8 g/kg/12 h were %, % and %. respectively (P 0.4). However, when we analyzed the total number of CD34 + cells mobilized per

4 Mobilization of PBPC with twice a day G-CSF µ g/kg/24 h 8 µ g/kg/12 h 6 µ g/kg/12 h 6000 µ µ µ 10 g/kg/24 h 8 g/kg/12 h 6 g/kg/12 h Platelet 109/l CFU-GM 104/l * * Baseline Day 5 pre Day 5 post Day 6 pre Day 6 post Day 7 pre Day 7 post Day 17 Figure 2 Effect of G-CSF treatment on the total platelet count according to the schedule of G-CSF and the initiation of apheresis. An aliquot of PB was obtained 30 min before starting PBPC collection and 1 h after PBPC collection. Results represent mean s.e.m. for all the donors in each group. ml of blood we found statistically significant differences between donors mobilized with 6 g/kg/12 h or 8 g/kg/12 h and donors receiving 10 g/kg/day (Table 1) (Figure 3) (P 0.01). The highest value of CD34 + cells was detected after 5 days of treatment with G-CSF and declined following initiation of leukapheresis (Figure 3). There was a 16-fold increase in the number of CD34 + cells per ml of blood in donors receiving 10 g/kg/day, a 20- fold increase for those receiving 6 g/kg/12 h and a 27- fold increase in donors treated with 8 g/kg/12 h. Similarly, when we determined the number of CFU-GM per ml of blood after 4 days of G-CSF we found that donors treated with 6 and 8 g/kg/12 h mobilized significantly more CFU-GM than donors treated with 10 g/kg/day (P 0.01) (Figure 4). Analysis of apheresis Although the median number of aphereses required to obtain the target CD34 + cell dose was two for every group of patients, in the group of donors mobilized with 10 g/kg/day three out of six donors required up to four CD34+ cells 106/l * 10 µ g/kg/24 h 8 µ g/kg/12 h 6 µ g/kg/12 h Baseline Day 5 Day 6 Day 7 Figure 3 Effect of G-CSF treatment on the number of CD34 + cells in mobilized PB according to the schedule of G-CSF. Results represent mean s.e.m. for all the donors in each group. *P 0.01 between donors mobilized with 10 g/kg/day and 6 or 8 g/kg/12 h. 0 Day 5 Day 6 Figure 4 Effect of G-CSF treatment on the number of CFU-GM according to the schedule of G-CSF. Results represent mean s.d. for all the donors in each group. *P 0.01 between donors mobilized with 10 g/kg/day and 6 or 8 g/kg/12 h. aphereses to obtain CD34 + cells/kg while only one donor out of 26 receiving twice a day doses required more than two collections to obtain CD34 + cells/kg. According to the recipient weight, we processed two to three times the donor blood volume in each apheresis. Because the total yield of CD34 + cells depends not only on the number of aphereses but also on the volume processed we determine the yield of CD34 + cells per blood volume processed. The CD34 + yield was significantly higher in donors receiving twice a day G-CSF (P 0.05) (Table 2). Correlations between donor characteristics and CD34 + yield The number of CD34 + cells in steady-state PB was significantly correlated with age (r = 0.49; P 0.05) and with the number of CD34 + cells in mobilized PB (r = 0.42; P 0.05). However, unlike reports from other groups 26 we did not find any correlation between age and efficacy of CD34 mobilization. As has been previously reported, 18 there was a significant correlation between the number of CD34 + cells in the PB pre-apheresis and the number of CD34 + cells in the apheresis product (r = 0.87; P 0.05). Similarly, the number of CD34 + cells was significantly associated with the number of CFU-GM (r = 0.4; P 0.05). Analysis of blood counts 10 days after discontinuation of G-CSF treatment Finally, we analyzed the effect of G-CSF on PB counts 10 days after the last apheresis procedure. We observed a decrease in the number of WBC, ANC and lymphocytes 10 days after the last dose of G-CSF in comparison with baseline values (Table 3). However, WBC, ANC and lymphocyte counts were within the normal limits for our laboratory. Furthermore, no symptoms associated with decreased counts were reported by any of the donors. There were no differences in the number of WBC, lymphocytes or platelets between donors receiving G-CSF daily or every 12 h (data not shown). Hemoglobin levels were unchanged throughout the study up to 10 days after mobilization.

5 Table 2 CD34 yield according to G-CSF schedule and plasma volume processed Mobilization of PBPC with twice a day G-CSF 43 G-CSF No. of donors CD /kg of CD /kg of donor per CD /kg of donor per recipient apheresis blood volume 10 g/kg/day ± ± ± g/kg/12 h ± ± 4.11* 2.46 ± 1.22* 6 g/kg/12 h ± ± 3.1* 2.24 ± 1.2 CD /kg of donor per apheresis and CD /kg of donor per blood volume were calculated in the first apheresis. *P 0.01 comparison between patients receiving 10 g/kg/day and 6 or 8 g/kg/12 h. Values represent mean s.d. Table 3 Hematological values 10 days after the last apheresis WBC 10 9 /l ANC 10 9 /l Lymphocyte 10 9 /l Hemoglobin g/dl Platelets 10 9 /l Baseline 7.3 ± ± ± ± ± days after last apheresis 5.27 ± ± ± ± ± 34 % difference with baseline P NS Values represent mean s.d. Comparison between baseline values and values 10 days after the last apheresis. Discussion Despite the extensive use of G-CSF for mobilization of PBPC 7,25 27 the optimal schedule and dose of growth factor has not been established. Our results suggest that administration of G-CSF in normal donors at doses of 6 g/kg/12 h mobilizes significantly more progenitors than 10 g/kg/day in a single dose which translates into better PBPC collections. Although previous studies have demonstrated that G- CSF mobilization is dose-dependent 28 it has also been suggested that there are no differences in mobilization of PBPC between normal donors receiving G-CSF at doses between 10 and 16 g/kg/day. This indicates that the differences observed in our study may be related to the schedule of administration. We did not find differences in mobilization between donors mobilized with 6 g/kg/12 h or 8 g/kg/12 h, also suggesting that G-CSF schedule is responsible for improved mobilization. However, the group of patients receiving 8 g/kg/12h is very small to draw any definite conclusions. Another possible explanation for improved mobilization and collection of PBPC in donors receiving G-CSF every 12 h could be the different timing between the last dose of G-CSF and the apheresis procedure. Cells from donors receiving once a day G-CSF were collected 18 h after the dose of G-CSF while donors receiving twice a day G-CSF underwent PBPC collection 2 hours after G- CSF. Studies previously published 29 indicate that a higher yield of PBPC is obtained when collections are performed h after the administration of G-CSF suggesting that the interval between G-CSF and the PBPC collection is unlikely to be the cause for the differences observed. Furthermore, even in the case that the interval between the dose of G-CSF and the time of PBPC collection contributed to improved mobilization it would not invalidate our conclusion that mobilization with 6 g/kg/12 h G-CSF is significantly better than 10 g/kg/day. G-CSF-induced mobilization is characterized by a significant increase in the number of progenitors in the PB starting between 48 and 72 h after initiation of G-CSF treatment and reaching a maximum level between days 4 and 6 of treatment. 18 We did not observe any significant differences in mobilization kinetics in either group of donors between them or with regard to previous reports. 18,25,26 Similarly, the increase in WBC, CD34 + cells or CFU-GM after 5 days of G-CSF in donors receiving 10 g/kg/day was not significantly different from previous studies. 18,25,26,30 Mobilization and collection of PBPC using G- CSF has been associated with a significant decrease in the platelet count. 18,30 However, it is unclear whether thrombocytopenia is solely due to the apheresis procedure or if there is a component of platelet production inhibition. In our study there was a statistically significant decrease in the platelet numbers during the days of PBPC collection as can be seen in Figure 3. This suggests a main role for the apheresis procedure in the thrombocytopenia observed after PBPC collection. Interestingly, when we performed platelet counts after each PBPC collection and immediately before the next collection we could not detect any increase in platelet count suggesting that G-CSF mobilization contributed to some extent to the decreased platelet count by inhibiting thrombopoiesis. Furthermore, the platelet count recovered to steady-state levels within 10 days of G-CSF discontinuation. Most of the clinical studies report the number of CD34 + cells obtained on the basis of recipient body weight. 12,15,17 Because the total number of CD34 + cells obtained also depends on the actual weight of the donor, the number of aphereses and the blood volume processed, we evaluated the total number of CD34 + cells/kg of donor in the first apheresis and also the number of CD34 + cells/kg of donor in the first apheresis per volume processed. As we have shown in Table 2 there was a significant increase in PBPC yield in donors mobilized with twice a day G-CSF. The

6 44 Mobilization of PBPC with twice a day G-CSF number of CD34 + cells/kg/blood volume collected in donors receiving 6 g/kg/12 h was 100% higher than in donors mobilized with 10 g/kg/day. However, there was only a 15% difference in the number of CD34 + cells/ml of blood between donors receiving 6 g/kg/12 h or 10 g/kg/day. As the settings for PBPC collection were the same in both groups, these differences argue in favor of a higher efficiency of PBPC collection in donors receiving 6 g/kg/12 h. We hypothesized that higher WBC counts may increase the collection efficiency. Alternatively, twice a day doses of G-CSF may increase the number of progenitors in the BM that are released into the PB due to the mobilizing effect of the apheresis procedure. 31 In any case we do not have a definite explanation for this differences. In accordance with other studies the number of CD34 + cells in steady-state PB was correlated with the number of CD34 + after mobilization. Although statistically significant, the value of this correlation is questionable as the r value is Unlike previous reports we did not find any correlation between age and mobilization 26 which may be explained by the fact that most of our donors were comprised of a similar age group which makes statistical analysis less significant. Finally, side-effects associated with G- CSF were consistent with previous reports 18 and we did not find any differences between patients receiving twice a day or once a day doses. Unlike in others series of normal donors mobilized with G-CSF every donor in our study was able to complete the treatment including the apheresis procedure. 18 In conclusion, our results indicate that administration of G-CSF at doses of 6 g/kg/12 h in normal donors provides better mobilization and PBPC collection than 10 g/kg/day without any increase in morbidity. These results suggest that twice a day doses may be a more appropriate schedule of G-CSF for mobilization of PBPC in normal donors and that similar studies in patients receiving G-CSF for mobilization with or without chemotherapy may be warranted to try to optimize mobilization of PBPC. Acknowledgements This work was supported in part by a Grant (FIS94/0525) from Fondu Investigaciones Sanitarias. References 1 Cavins JW, Scheer SC, Thomas ED, Ferrebee JW. The recovery of lethally irradiated dogs given infusions of autologous leukocytes preserved at 80 C. Blood 1964; 23: Goodman JW, Hodgson GS. Evidence for stem cells in the peripheral blood of mice. Blood 1962; 19: Storb R, Graham TC, Epstein RB et al. Demonstration of hematopoietic stem cells in the peripheral blood of baboons by cross circulation. Blood 1977; 50: Kessinger A, Armitage JO, Landmark JD et al. Reconstitution of hematopoietic function with autologous cryopreserved circulating stem cells. Exp Hematol 1986; 14: Duhrsen U, Villeval JL, Boyd J et al. Effects of recombinant human granulocyte colony stimulating factor on hematopoietic progenitor cells in cancer patients. Blood 1988; 72: Socinski MA, Cannistra SA, Elias A et al. Granulocytemacrophage colony-stimulating factor expands the circulating hematopoietic progenitor cell compartment in man. Lancet 1988; 1: Sheridan WP, Begley CG, Juttner C et al. Effect of peripheralblood progenitor cells mobilized by filgrastim (G-CSF) on platelet recovery after high-dose chemotherapy. Lancet 1992; 1: Brugger W, Bross KJ, Frisch J et al. Mobilization of peripheral blood progenitor cells by sequential administration of IL-3 and GM-CSF following chemotherapy with etoposide, ifosfamide, and cisplatin. Blood 1992; 79: Elias AD, Ayash L, Anderson KC et al. Mobilization of peripheral blood progenitor cells by chemotherapy and granulocyte macrophage colony stimulating factor for hematological support after high dose intensification for breast cancer. Blood 1992; 79: Juttner CA, To LB, Haylock DN et al. Circulating autologous stem cells collected in very early remission from acute nonlymphoblastic leukemia produce prompt but incomplete haematopoietic reconstitution after high dose melphalan or supralethal chemoradiotherpay. Br J Haematol 1985; 61: Kessinger A, Armitage JO. The evolving role of autologous peripheral stem cell transplantation following high-dose chemotherapy for malignancies. Blood 1991; 77: Bensinger WI, Weaver CH, Appelbaum FR et al. Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony-stimulating factor. Blood 1995; 85: Korbling M, Przepiorka D, Huh YO et al. Allogeneic blood stem cell transplantation for refractory leukemia and lymphoma: potential advantage of blood over marrow allografts. Blood 1995; 85: Rusell NH. The place of blood stem cells in allogeneic transplantation. Br J Haematol 1996; 93: Schmitz N, Dreger P, Suttorp M et al. Primary transplantation of allogeneic peripheral blood progenitor cells mobilized by filgrastim (Granulocyte colony-stimulating factor). Blood 1995; 85: Brown RA, Adkins D, DiPersio J, Goodnough T. Allogeneic peripheral blood stem cell transplantation (PBSC) is associated with an increased risk of chronic graft versus host disease. Blood 1997; 90: 225a. 17 Bensinger W, Singer J, Appelbaum F et al. Autologous transplantation with peripheral blood mononuclear cells collected after administration of recombinant granulocyte stimulating factor. Blood 1993; 81: Stroncek DF, Clay ME, Petzoldt ML et al. Treatment of normal individuals with granulocyte-colony stimulating factor: donor experiences and the effects on peripheral blood CD34 + cell counts and on the collection of peripheral blood stem cells. Transfusion 1996; 36: To LB, Haylock DN, Simmons PJ, Juttner CA. The biology and clinical uses of blood stem cells. Blood 1997; 89: Prosper F, Stroncek D, Verfaillie CM. Phenotypic and functional characterization of long-term culture initiating cells (LTC-IC) present in peripheral blood progenitor collections of normal donors treated with G-CSF. Blood 1996; 88: Murray L, Chen B, Galy A et al. Enrichment of human stem cell activity in the CD34+Thy+Lin subpopulation from mobilized peripheral blood. Blood 1995; 85: Humeau L, Bardin F, Maroc C et al. Phenotypic, molecular

7 Mobilization of PBPC with twice a day G-CSF and functional characterization of human peripheral blood CD34 + /Thy + cells. Blood 1996; 87: Miller JS, Prosper F, McCullar V. Natural killer (NK) cells are functionally abnormal and NK cell progenitors are diminished in granulocyte colony-stimulating factor-mobilized peripheral blood progenitor cell collection. Blood 1997; 90: Kusnierz-Glaz CR, Still BJ, Amano M et al. Granulocyte colony-stimulating factor induced comobilization of CD4 CD8 T cells and hematopoietic progenitor cells (CD34+) in the blood of normal donors. Blood 1997; 89: Anderlini P, Przepiorka D, Seong D et al. Clinical toxicity and laboratory effects of granulocyte-colony stimulating factor (filgrastim) mobilization and blood stem cell apheresis from normal donors, and analysis of charges for the procedures. Transfusion 1996; 36: Anderlini P, Przepiorka D, Seong C et al. Factors affecting mobilization of CD34+ cells in normal donors treated with filgrastrim. Transfusion 1997; 37: Simmons PJ, Leavesley DI, Levesque JP et al. The mobilization of primitive hematopoietic progenitors into the peripheral blood. Stem Cells 1994; 12 (Suppl. 1): Hoglund M, Smedmyr B, Simonsson B et al. Dose-dependent mobilisation of haematopoietic progenitor cells in healthy volunteers receiving glycosylated rhug-csf. Bone Marrow Transplant 1996; 18: Fujisaki T, Otsuka T, Harada M et al. Granulocyte colonystimulating factor mobilizes primitive hematopoietic stem cells in normal individuals. Bone Marrow Transplant 1995; 16: Stroncek DF, Clay ME, Herr G et al. Blood counts in healthy donors 1 year after the collection of granulocyte-colony-stimulating factor-mobilized progenitor cells and the results of a second mobilization and collection. Transfusion 1997; 37: Grigg AP, Roberts AW, Raunow H et al. Optimizing dose and scheduling of filgrastim (granulocyte colony-stimulating factor) for mobilization and collection of peripheral blood progenitor cells in normal volunteers. Blood 1995; 86: