[Allergic Broncho-Pulmonary Aspergillosis (ABPA) in cystic fibrosis: Mechanisms, diagnosis and therapeutic options]. / Aspergillose bronchopulmonaire allergique (ABPA) et mucoviscidose : mécanismes, diagnostic et alternatives thérapeutiques.

INTRODUCTION: Fungal aspergillosis colonization and allergic bronchopulmonary aspergillosis (ABPA) can have a strong impact on the prognosis in cystic fibrosis (CF). We conducted round table discussions involving French experts from pediatric and adult centers caring for patients with CF, microbiologists, radiologists and pharmacists. The aim was to explore the current state of knowledge on: the pathophysiological mechanisms of Aspergillus and other micromycetes infections in CF (such as Scedosporium sp.), and on the clinico-biological diagnosis of ABPA. In perspective, the experts explored the role of imaging in the diagnosis of APBA, specifically CT and MRI; as well as the role of bronchoscopy in the management. We also reviewed the therapeutic management, including different corticosteroid regimens, antifungals and anti-IgE antibodies. CONCLUSION: The diagnosis of ABPA in CF should be based on more standardized biological assays and imaging to optimize treatment and follow-up.

Population pharmacokinetics of ceftazidime in critically ill children: impact of cystic fibrosis.

BACKGROUND: Pharmacokinetics data on ceftazidime are sparse for the paediatric population, particularly for children with cystic fibrosis (CF) or severe infections. OBJECTIVES: To characterize the population pharmacokinetics of ceftazidime in critically ill children, identify covariates that affect drug disposition and evaluate the current dosing regimens. METHODS: The study was registered with Clinicaltrials.gov (NCT01344512). Children receiving ceftazidime were selected in 13 French hospitals. Plasma concentrations were determined by UPLC-MS/MS. Population pharmacokinetic analyses were performed using NONMEN software. RESULTS: One hundred and eight patients, aged 28 days to 12 years, with CF (n = 32), haematology and/or oncology disorders (n = 47) or severe infection (n = 29) were included. Ceftazidime was administered by continuous or intermittent infusions; 271 samples were available for analysis. A two-compartment model with first-order elimination and allometric scaling was developed and covariate analysis showed that ceftazidime pharmacokinetics were also significantly affected by CLCR and CF. Ceftazidime clearance was 82% higher in CF than in non-CF patients. Monte Carlo simulations showed that the percentage of target attainment (PTA) for the target of T>MIC = 65% was (i) lower in CF than in non-CF children with intermittent infusions and (ii) higher with continuous than intermittent infusion in all children. CONCLUSIONS: The population pharmacokinetics model for ceftazidime in children was influenced by body weight, CLCR and CF. A higher PTA was obtained with continuous versus intermittent infusions. Further studies should explore the benefits of continuous versus intermittent infusion of ceftazidime, including current versus increased doses in CF children.

Development of a large volume injection method using a programmed temperature vaporization injector - gas chromatography hyphenated to ICP-MS for the simultaneous determination of mercury, tin and lead species at ultra-trace levels in natural waters.

The current EU legislation lays down Environmental Quality Standards (EQS) for 45 priority substances in surface waters; among them levels for (organo)metallic species of Hg, Sn and Pb are set between ng L-1 (for Hg and Sn) and µg L-1 (for Pb). To date, only a few analytical methods can reach these very restrictive limits and there is thus a need for comprehensive methods able to analyze these species down to these levels in natural waters. The aim of this work was to develop an online automated pre-concentration method using large volume injections with a Programmed Temperature Vaporization (PTV) injector fitted with a sorbent packed liner coupled to GC-ICP-MS to further improve the detection limits associated to this well-established method. The influence of several parameters such as the PTV transfer temperature and time, carrier gas flow rate and amount of packing material was investigated. Finally, the maximum volume injected through single or multiple injection modes was optimized to obtain the best compromise between chromatographic resolution and sensitivity. After optimization, very satisfactory results in terms of absolute and methodological detection limits were achieved, down to the pg L-1 level for all species studied. The potential of the method was exemplified by determining the concentrations of organometallic compounds in unpolluted river waters samples from the Adour river basin (SW France) and results were compared with conventional (splitless) GC-ICP-MS. The strength of this analytical method lies in the low detection limits reached for the simultaneous analysis of a wide group of organometallic compounds, and the potential to transfer this method to other gas chromatographic applications with inherent lower sensitivity.

Rapid mobilization of cytotoxic lymphocytes induced by dasatinib therapy.

Tyrosine kinase inhibitors (TKIs) have potent effects on malignant cells, and they also target kinases in normal cells, which may have therapeutic implications. Using a collection of 55 leukemia patients treated with TKI therapy (chronic myeloid leukemia, n=47; acute lymphoblastic leukemia, n=8), we found that dasatinib, a second-generation broad-spectrum TKI, induced a rapid, dose-dependent and substantial mobilization of non-leukemic lymphocytes and monocytes in blood peaking 1-2 h after an oral intake and the blood counts closely mirrored drug plasma concentration. A preferential mobilization was observed for natural killer (NK), NK T, B and γδ+ T cells. Mobilization was coupled with a more effective transmigration of leukocytes through an endothelial cell layer and improved cytotoxicity of NK cells. Platelet numbers decreased markedly after the drug intake in a proportion of patients. Similar effects on blood cell dynamics and function were not observed with any other TKI (imatinib, nilotinib and bosutinib). Thus, dasatinib induces a unique, rapid mobilization and activation of cytotoxic, extravasation-competent lymphocytes, which may not only enhance antileukemia immune responses but can also be causally related to the side-effect profile of the drug (pleural effusions, thrombocytopenia).

Treatment of advanced gastrointestinal stromal tumors in patients over 75 years old: clinical and pharmacological implications.

Data about the patterns of care and the specific outcome of elderly patients with advanced gastrointestinal stromal tumors (GISTs) are almost nonexistent. Between 2001 and 2009, 44 patients ≥75 years old with advanced GISTs started first-line imatinib (400 mg/day) in seven participating institutions. Clinical data were collected by reviewing medical records and were entered in a comprehensive database. During the same period, 160 patients with advanced GIST (136 patients <75 years old, 24 patients ≥75 years old) had access to an imatinib blood level testing program. Imatinib plasma concentration (patient dose 400 mg/day) tests were centralized in a single laboratory. Median age was 78 years old (range 75-86). Thirty-six patients (82 %) experienced at least one adverse event (Table 2). Drug-related adverse events were mainly of grades 1 and 2 and were medically manageable. Permanent dose reduction (200-300 mg/day) was required for 20 patients (45.5 %) and was significantly more frequent for patients with performance status (PS) ≥2: 33.5 versus 8.5 %, p = 0.04. Eight patients (18 %) required imatinib interruption for intolerance. Median PFS was 34.4 months (95 % CI 11.5-57.4) (Fig. 1). Median overall survival (OS) was 50.3 months (95 % CI 37-63.5). Performance status <2 was the sole pre-therapeutic factor associated with improved OS. No correlation was found between comorbidities and tolerance or outcome. Imatinib trough plasma concentrations increase with age, although this correlation did not reach statistical significance. First-line imatinib is a feasible and effective treatment in patients with advanced GISTs ≥75 years. Aging seems to have only a moderate impact on imatinib pharmacokinetics. Overall survival is similar to that of younger patients. Comorbidities did not result in increased incidence of toxicity. Careful follow-up regarding tolerance issues should be considered in elderly patients with poor PS.

Early lesions induced in rat colon epithelium by N-methyl-N'-nitro-N-nitrosoguanidine.

The development of ACF (aberrant crypt foci), adenoma and cancer following intrarectal administration of the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) has been described. However, microscopic lesions not previously reported were observed as soon as two weeks following carcinogen treatment. These lesions protrude slightly over the epithelial lining of the colon, with a micropolyp-like appearance. Oriented sections show that the centre of these lesions present pseudo-"cystic" appearance, with disorganized crypts made of normal cells. The chorion of the lesion is invaded by numerous inflammatory cells and some ACF may be present nearby. The epithelium lining the cysts and the distorted crypts shows expression of gastric mucin M1/MUC5AC, an early marker of colonic carcinogenesis which is not present in normal colon. This mucin is retained within the "cysts" together with some inflammatory cells. The micropolyps observed contain in a minute form some histological elements described in ulcerative colitis or short-term radiotherapy (distortion of crypts, crypt abscesses, increase of chorion cellularity, infiltration by immune cells). In addition, the presence of bifid crypts nearby suggests mucosal regeneration. Our hypothesis is that these modifications are steps in a normal healing pathway that may in some cases degenerate into precancerous lesions and cancer.

STAT3 transcription factor is constitutively activated and is oncogenic in nasal-type NK/T-cell lymphoma.

Nasal-type natural killer (NK) cell lymphoma is an infrequent aggressive malignant disease with very poor prognosis. We aimed to explore the possible role of the transcription factor STAT3 in the pathophysiology of this malignancy, as it was involved in oncogenesis and chemoresistance. For this, we established and characterized a continuous interleukin 2-dependent NK cell line (MEC04) from a patient with a fatal nasal-type NK-cell lymphoma. Cells harbored poor cytotoxic activity against K562 cells, and spontaneously secreted interferon-gamma, interleukin-10 and vascular-endothelium growth factor in vitro. STAT3 was phosphorylated in Y705 dimerization residue in MEC04 cells and restricted to the nucleus. Y705 STAT3 phosphorylation involved JAK2, as exposure of cells to AG490 inhibitor inhibited Y705 STAT3 phosphorylation. By using recombinant transducible TAT-STAT3-beta (beta isoform), TAT-STAT3Y705F (a STAT3 protein mutated on Y705 residue, which prevents STAT3 dimerization) and peptides inhibiting specifically STAT3 dimerization, we inhibited STAT3 phosphorylation and cell growth, with cell death induction. Finally, STAT3 was phosphorylated in Y705 residue in the nuclei of lymphoma cells in eight/nine patients with nasal-type NK/T-cell lymphoma and in YT, another NK cell line. Our results suggest that STAT3 protein has a major role in the oncogenic process of nasal-type NK-cell lymphomas, and may represent a promising therapeutical target.

Selected Stro-1-enriched bone marrow stromal cells display a major suppressive effect on lymphocyte proliferation.

Mesenchymal stem cells (MSCs) have an immunosuppressive effect and can inhibit the proliferation of alloreactive T cells in vitro and in vivo. Cotransplantation of MSCs and hematopoietic stem cells (HSCs) from HLA-identical siblings has been shown to reduce the incidence of acute graft-vs.-host disease. MSCs are heterogeneous and data on the inhibitory effects of different MSC subsets are lacking. The antigen Stro1 is a marker for a pure primitive MSC subset. We investigated whether Stro-1-enriched induce a more significant suppressive effect on lymphocytes in a mixed lymphocyte reaction (MLR), and whether this action is related to a specific gene expression profile in Stro-1-enriched compared to other MSCs. We demonstrated that the Stro-1-enriched population elicits a significantly more profound dose-dependent inhibition of lymphocyte proliferation in a MLR than MSCs. One thousand expanded Stro-1-enriched induced an inhibitory effect comparable to that of 10 times as many MSCs. Inhibition by Stro-1-enriched was more significant in contact-dependent cultures than in noncontact-dependant cultures at higher ratio. The Stro-1-enriched inhibitory effect in both culture types was linked to increased gene expression for soluble inhibitory factors such as interleukin-8 (IL-8), leukemia inhibitory factor (LIF), indoleamine oxidase (IDO), human leukocyte antigen-G (HLA-G), and vascular cell adhesion molecule (VCAM1). However, tumor growth factor-beta1 (TGF-beta) and IL-10 were only up-regulated in contact-dependant cultures. These results may support using a purified Stro-1-enriched population to augment the suppressive effect in allogeneic transplantation.

Toxicity of nonylphenol on the cnidarian Hydra attenuata and environmental risk assessment.

Alkylphenols and their derivatives, alkylphenol polyethoxylates (APEs), are synthetic chemicals of concern owing to their endocrine properties. Nonylphenol (NP) is a critical APE metabolite because of its recalcitrance to biodegradation, toxicity, and ability to bio-accumulate in aquatic organisms. Studies of NP effects in vertebrates demonstrated estrogenic disrupting properties in fish, birds, reptiles, and mammal cells in which NP displaces the natural estrogen from its receptor. Less is known on its toxicity toward invertebrates. Effects on reproduction have been reported, but toxicity on development has been poorly documented thus far. We investigated NP toxicity on survival and regeneration of the freshwater coelenterate Hydra attenuata. Hydra is known for its regenerative capacity and its sensitivity to chemical pollution. It has been used for over 20 years to screen for teratogenicity of chemicals (Johnson et al. (1982) Teratog Carcinog Mutagen 2:263-276). Our results showed that hydra appeared as one of the most sensitive species to acute and chronic toxicity of NP compared to several freshwater invertebrates. Regeneration was disrupted at NP concentrations lower than those affecting survival. Toxicity thresholds of NP for aquatic vertebrates and invertebrates are also reported and discussed in the context of environmental risk assessment and of water quality objectives recommended for surface waters in industrialized countries. NP levels have decreased during the last decade because of a voluntary agreement of surfactant producers and users. At present, concentrations of NP found in surface waters are far below 1 microg/L in Europe, but can reach several microg/L when wastewater treatment plant inefficiency occurs.

Ex vivo expansion of CD34-positive peripheral blood progenitor cells from patients with non-Hodgkin's lymphoma: no evidence of concomitant expansion of contaminating bcl2/JH-positive lymphoma cells.

The aim of the present study was to evaluate the capacity to expand of hematopoietic stem cell (HSC) samples from eight patients with NHL, and to follow in parallel the fate of tumor cells in four of eight samples still containing bcl2/JH+ tumor cells after CD34+ or CD19-/20-/34+ cell selection. The presence of bcl2/JH+ cells was also investigated after expansion in four of eight samples, two of which were bcl2/JH at harvesting and two which were initially bcl2/JH+ but became bcl2/JH (below the level of PCR detection) after cell selection, to assess a possible reappearance of occult tumor cells after expansion culture. We used culture conditions that we previously had established to allow high level expansion of normal precursors, progenitors and LTC-ICs. In this study, particular attention was given to the role of Flt3-ligand, known to favor the growth of B cells. The expansion conditions were: 1.5 x 10(3) cells/ml in serum-free medium containing stem cell factor (SCF), interleukin-3 (IL-3), IL-6, granulocyte-stimulating factor (G-CSF), erythropoietin (Epo) +/- Flt3-ligand (Flt3-L) for 10 days. After culture, total cells, CFU-GMs, BFU-Es and LTC-ICs were expanded to a mean of 833-, 6.6-, 4.6-, and 1.8-fold, respectively with the cocktail of cytokines not including Flt3-L. When Flt3-L was added, the mean expansion values were 1095-, 31-, 15- and three-fold, respectively. Residual bcl2/JH+ cells present in four of eight samples before expansion were not detected after expansion. Similarly, no tumor cells reappeared after expansion of the two samples which had become negative after selection, as well as in the two samples which were bcl2/JH- at harvesting. These results suggest first that ex vivo expansion of hematopoietic stem cells in patients with non-Hodgkin's lymphoma is feasible without incurring the parallel risk of amplifying tumor cells; second, that Flt3-L did not stimulate the growth of tumor cells while it clearly favored the growth of normal progenitors.

Cell culture bags allow a large extent of ex vivo expansion of LTC-IC and functional mature cells which can subsequently be frozen: interest for a large-scale clinical applications.

The aim of this study was to evaluate the ex vivo expansion of normal CD34+ cells in gas-permeable polypropylene bags suitable for clinical use. Cells were cultured for 14 days in serum-free medium supplemented with SCF, IL3, IL6, FLT3-1, G-CSF + MGDF or Epo. The bags supported the expansion of hematopoietic cells in a similar manner to small scale well or flask systems, allowing mean expansions of up to 2193-fold for total nucleated cells, 140-fold for CFU-GM and 66-fold for LTC-IC. Increasing the initial cell concentration from 5 x 10(3) to 1 x 10(5)CD34+ cells/ml induced the production of granulocytic cells with terminal differentiation while simultaneously decreasing the overall extent of expansion of the white blood cells produced. We tested the phagocytic activity and oxidative metabolism of the white blood cells produced. The percentage of phagocytic cells was 39+/-0.5% in expanded cultures derived from fractions initiated at 5 x 10(3), 10(4) or 10(5) cells/ml and 45+/-6% in cultured cells obtained from starting fractions containing 5 x 10(4) cells/ml, as compared to 58+/-4% in normal controls. A study of the potential for oxygen-dependent microbe killing showed that the expanded cells produced H2O2, although in lesser quantities than control cells. We subsequently investigated the possibility of freezing expanded cells. Total cell recovery after thawing was 45+/-4%, while recoveries of progenitors and stem cells ranged from 65 to 90%, without any influence of the initial cell concentration. This new approach could be of major interest for clinical practice, as it would allow evaluation of the quality of a graft prior to its infusion and employs experimental conditions which meet the criteria for potential clinical use.

Quantitative and qualitative alterations of long-term culture-initiating cells in patients with acute leukaemia in complete remission.

Bone marrow (BM) samples from 24 patients with acute leukaemia (AML 17, ALL seven) in first complete remission were compared to samples from 10 normal donors with regard to their content in long-term culture-initiating cells (LTC-IC) as assessed by a limiting dilution assay and the clonogeneic capacity of these cells, in order to determine whether remission marrow cells displayed any specific defect at the primitive stem cell level. The frequency of LTC-IC in the whole patient group was 1 in 3487 +/- 3125 mononuclear cells (MNC) as compared to 1 in 794 +/- 492 MNC in normal controls (P = 0.0009), with no difference between AML and ALL. Moreover, the clonogeneic capacities were 2.66 +/- 0.7 (range 1.8-1.6) and 4.0 +/- 1.6 (range 2.2-7.9) CFC per LTC-IC in patients and controls respectively (P = 0.0015). These quantitative and qualitative defects were aggravated by treatment with mafosfamide at a dose of 50 microg/10(7) MNC/ml, where the mean recovery of LTC-IC after in vitro purging was 42%. In nine patients autografted with purged marrow following high-dose radiochemotherapy, no correlation could be detected between the dose of LTC-IC (mean 6742 +/- 7877/kg) and the kinetics of recovery of haemopoiesis. We concluded that, in acute leukaemia patients in complete remission, the presumably normal residual stem cell pool was not only quantitatively diminished but also qualitatively altered in its capacity to give rise to clonogeneic progenitor cells.

Comparison of CD34+ bone marrow cells purified by immunomagnetic and immunoadsorption cell separation techniques.

We tested two positive selection techniques for separation of CD34+ cells from bone marrow and analyzed the yields of CD34+ cells, BFU-E, CFU-GM, CFU-MK and LTC-IC after selection and expansion. An immunoadsorption procedure (CellPro) and an immunomagnetic (Baxter) CD34+ cell separation method were employed to purify the same bone marrow samples from seven normal subjects. Mean yields of CFU-GM and CFU-MK and absolute numbers of LTC-ICs were not different in the two purified cell populations. In contrast, the mean recovery of BFU-E was significantly lower for the immunoadsorption (21 +/- 14%) than for the immunomagnetic technique (44 +/- 27%). After separation, CD34+ cells were evaluated in 10-day liquid cultures for their expansion capacity in terms of total cells and progenitors. The expansion capacity of progenitors such as CFU-GM, CFU-MK and especially BFU-E selected by immunoadsorption was higher than the capacity of progenitors obtained by immunomagnetism, although final total and progenitor cell numbers are similar. Our results suggest that the populations separated by the two techniques differ mainly in the expansion capacity of progenitors and in the recovery of BFU-E after the selection procedure. These differences between two methods, which already are widely employed in research and in clinical transplantation, should be taken into account when considering the aims of the experiments.

Amifostine improves the antileukemic therapeutic index of mafosfamide: implications for bone marrow purging.

One of the principal challenges of cancer chemotherapy is the relative inability of most anticancer drugs to distinguish between normal and neoplastic tissues. Consequently, a broad range of toxicities are experienced by patients, especially myelosuppression. Amifostine, a phosphorylated aminothiol, increases the selectivity of specific anticancer drugs for neoplastic cells by protecting normal tissues. One potential application of this protector is during bone marrow purging to selectively remove contaminating cancer cells. This study took normal or leukemic marrow from human subjects and evaluated the ability of amifostine to selectively protect normal bone marrow progenitor cells versus leukemic progenitor cells from the cytotoxic effect of mafosfamide. The dose response of mafosfamide amifostine on leukemia colony-forming units or normal marrow progenitor cells was determined and the LD95 was calculated. Amifostine pretreatment resulted in a statistically significant protection of granulocyte-macrophage colony-forming units and erythroid blast-forming units from the toxicity of mafosfamide (P = .031). Thus, amifostine protection of normal marrow progenitor cells allows a higher LD95 concentration of mafosfamide to be used in ex vivo purging. In contrast, amifostine pretreatment increased the cytotoxicity of mafosfamide on the fresh human leukemia progenitor cells (P = .006). The dual effect of amifostine protection of normal marrow progenitor cells coupled with amifostine-induced sensitization of the leukemia cells increases the possible cell-kill of leukemic stem cells. With amifostine pretreatment, at the LD95 concentrations of mafosfamide for marrow progenitor cells, there was an estimated 6 log increase in cell-kill of the leukemia cells. This selective cell-kill offers the potential for lowering the incidence of leukemic relapse, while preserving more normal stem cells for autologous transplantation.

Characterization of late and early hematopoietic progenitor/stem cell sensitivity to mafosfamide.

The preservation of the hematopoietic value of the graft is essential in the context of bone marrow purging for autologous transplantation. In the present study we have investigated mafosfamide toxicity to transplantable hematopoietic stem cells using combinations of recombinant growth factors (GF) in semi-solid assays and by measurement of Long-Term Culture Initiating Cells (LTC-IC). Our data show that various subtypes of progenitor/stem cells were inhibited in a dose-dependent manner by mafosfamide. A hierarchy appeared clearly regarding sensitivity to the drug in the following order of increasing resistance: PCM CFU-GM (grown in presence of placenta-conditioned medium), 4R CFU-GM (grown in presence of GM-CSF + IL-3 + G-CSF + EPO), 5R CFU-GM (grown in presence GM-CSF + IL-3 + G-CSF + EPO + SCF) and LTC-IC with respective lethal dose 95 (LD95) levels of 40 micrograms, 55 micrograms, 90 micrograms and 140 micrograms/10(7) MNC (P = 0.05 to P = 0.018). Even the primitive stem cells treated with very high doses of mafosfamide (2 to 4 times the usually recommended dose) responded to a combination of SCF + GM-CSF + G-CSF + IL-3 in liquid marrow culture, suggesting that they were functionally spared by the treatment. We also observed a higher sensitivity of 5R CFU-GM and LTC-IC from patients with hematological malignancies, compared with normal donors, when marrow was treated with the dose chosen for clinical purging.(ABSTRACT TRUNCATED AT 250 WORDS)

[Towards a standardization of the culture of hematopoietic progenitor cells CFU-GM applied to the transplantation of hematopoietic stem cells in France]. / Vers une standardisation de la culture des progéniteurs hématopoïétiques CFU-GM appliquée à la greffe de cellules souches hématopoïétiques en France.

The CFU-GM (granulo-macrophagic colony forming unit) content of 130 bone marrow samples and 105 cytapheresis blood samples was evaluated by two culture techniques, one in agar with human placenta conditioned medium as stimulating factor, the second in methyl cellulose with a cocktail of recombinant G-CSF, GM-CSF, IL-3 and erythropoietin as stimulating factors. The aim of the study was to evaluate in methyl cellulose the CFU-GM threshold doses necessary to ensure hemopoietic reconstitution in autologous transplantation that we previously determined in the agar technique. Thirty-one out of the 130 BM samples were also tested after incubation with mafosfamide, and 33 after freezing and thawing. Results showed that the numbers of CFU-GM in the 2 techniques were significantly correlated (p < 0.0001). The strongest correlation was found with the formula "log CFU-GM methyl = a log CFU-GM agar + b" with a slight variation in the values of a and b among the 4 settings, i.e. unmanipulated BM, mafosfamide-treated BM, frozen-thawed BM and unmanipulated blood samples. According to the formulas, the threshold doses of CFU-GM for BM and blood, previously determined in the agar technique (respectively 10(4)/kg and 5 x 10(4)/kg) were calculated for CFU-GM grown in methyl and corresponded respectively to 2.3 x 10(4)/kg and 2.1 x 10(5)/kg.

[Positive selection of hematopoietic CD 34 stem cells for autograft]. / Sélection positive de cellules souches hématopoïétiques CD 34 pour autogreffe.

The CD 34 antigen is a glycoprotein found on the surface of hematopoietic stem cells and early committed progenitors. The CE 34 stem cells from 14 samples of bone marrow, cord blood or leucapheresis were isolated using a positive selection procedure involving an anti CD 34 biotinylated monoclonal antibody and an avidin immunoabsorption device. Results showed that in 60 percent of samples, the positively-selected fractions contained more than 70 percent CD 34 cells. Concentration in CFU-GM and BFU-E progenitors increased 15 and 26 fold respectively in the CE 34 enriched samples. Long-term culture of two samples demonstrated that nearly all of the most immature progenitors were recovered in the procedure. These preliminary results showed that the positive selection technique of CD 34 hematopoietic stem cells is now available for use in autologous or allogeneic hematopoietic stem cell transplantation.