PubMed Health⌕ Search

Biomedical subjects

A L Petzer

Publications and source records attributed to A L Petzer.

At least 19 recordsLinked to original sources
PubMed2005

Different subsets of primary chronic myeloid leukemia stem cells engraft immunodeficient mice and produce a model of the human disease.

Xenograft models of chronic phase human chronic myeloid leukemia (CML) have been difficult to develop because of the persistence of normal hematopoietic stem cells in most chronic phase CML patients and the lack of methods to selectively isolate the rarer CML stem cells. To circumvent this problem, we first identified nine patients' samples in which the long-term culture-initiating cells were predominantly leukemic and then transplanted cells from these samples into sublethally irradiated NOD/SCID and NOD/SCID-beta2microglobulin-/- mice. This resulted in the consistent and durable (>5 months) repopulation of both host genotypes with similar numbers of BCR-ABL+/Ph+ cells. The regenerated leukemic cells included an initial, transient population derived from CD34+CD38+ cells as well as more sustained populations derived from CD34+CD38- progenitors, indicative of a hierarchy of transplantable leukemic cells. Analysis of the phenotypes produced revealed a reduced output of B-lineage cells, enhanced myelopoiesis with excessive production of erythroid and megakaropoietic cells and the generation of primitive (CD34+) leukemic cells displaying an autocrine IL-3 and G-CSF phenotype, all characteristics of primary CML cells. These findings demonstrate the validity of this xenograft model of chronic phase human CML, which should enable future investigation of disease pathogenesis and new approaches to therapy.

Animals↗
PubMed2004

Suppression of natural killer cells in the presence of CD34+ blood progenitor cells and peripheral blood lymphocytes.

Abstract Mobilization of CD34 + peripheral blood progenitor cells (PBPCs) with granulocyte-colony stimulating factor (G-CSF) may induce functional alterations in peripheral blood lymphocyte (PBL) subsets. We and others have shown that natural killer (NK) cells from PBPC collections are less expandable in vitro than those obtained during steady-state hematopoiesis. We show here that the extent of this proliferation deficit is related to the number of circulating CD34 + cells in vivo at the time of PBPC apheresis. Likewise, addition of autologous CD34 + cells to unseparated PBL reduced the expansion of the NK-cell subset by 22.2% +/- 6.0% (n = 10; P <.005). In contrast, when using purified NK cells, their proliferation remained unimpaired by autologous CD34 + cells. Supernatants from CD34 + cells cultured with autologous PBLs had an inhibitory effect on proliferation of purified NK cells (n = 16; P =.03), indicating that an interaction between CD34 + cells and lymphocytes is essential for the suppressive effect on NK cells. To investigate the role of T cells in this interaction, intracellular cytokines were determined in T cells cultured for 7 days with or without autologous CD34 + cells. When cultured with CD34 + cells, the frequency of IL-2-producing CD4 + and CD8 + T cells was reduced by 19% and 24%, respectively, compared with T cells cultured alone (n = 7; P =.016). Interferon-gamma-producing T cells were slightly reduced ( P = not statistically significant [ns]). Finally, the influence of T cells and NK cells on the recovery of myeloid colony-forming cells (CFU-GMs) from purified CD34 + cells was examined. In the presence of T cells, 16% +/- 6% of the input CFU-GM recovered after 7 days, compared with 5% +/- 4% in the presence of NK cells (n = 5; P = ns). Our findings point to an inhibition of NK-cell proliferation mediated by an interaction of CD34 + cells and T cells occurring during PBPC mobilization with G-CSF.

Antigens, CD34↗
PubMed2001

Candida ciferrii, a new fluconazole-resistant yeast causing systemic mycosis in immunocompromised patients.

Systemic infections related to fluconazole-resistant yeasts are increasingly observed in immunocompromised patients receiving fluconazole as a prophylactic antifungal treatment. Here, we report a case of invasive candidiasis caused by Candida ciferrii in a patient with acute myeloid leukemia and who suffered a relapse after autologous peripheral blood progenitor cell transplantation. Erythematous skin papulae and spotted pulmonary infiltrations were present. A skin biopsy led to the diagnosis of invasive candidiasis, emphasizing the diagnostic usefulness of this procedure. The yeast was identified as Candida ciferrii and in vitro susceptibility testing revealed its resistance to fluconazole. Until now, Candida ciferrii has not been known to cause invasive fungal infections in humans. Thus, we add another fungus to the list of flucanozole-resistant yeasts and suggest that in vitro susceptibility testing of isolated fungi should be performed for the selection of appropriate antimycotic drugs.

Antifungal Agents↗
PubMed2001

Hematopoietic stem cells.

The adequate production of blood cells is maintained by a set of immature hematopoietic stem cells (HSC) located in the bone marrow after birth. HSC are able to reconstitute the hematopoietic system in disease-related bone marrow failure and bone marrow aplasia. Nowadays, HSC cells can be mobilized from the bone marrow into the peripheral blood using hematopoietic cytokines, allowing a convenient harvest of these cells for clinical transplantation. This review outlines the development of the hematopoietic system in the embryo and in adults and the characterization, enumeration, purification and ex vivo expansion of HSC for clinical use. Future directions include the genetic manipulation of HSC and the identification/expansion of bone marrow-derived stem cells capable of generating non-hematopoietic tissues.

Animals↗
PubMed2001

Optimal timing for the collection and in vitro expansion of cytotoxic CD56(+) lymphocytes from patients undergoing autologous peripheral blood stem cell transplantation.

To identify the optimal time for the collection of CD56(+) cytotoxic lymphocytes for adoptive immunotherapy in patients undergoing high-dose chemotherapy (HDCT) and peripheral blood stem cell (PBSC) transplantation, 18 breast cancer patients receiving either three cycles of epirubicin/paclitaxel (CT x 3) followed by HDCT and PBSC transplantation (n = 12) or CTx6 (n = 6) were studied. Blood samples were obtained before each CT/HDCT cycle, from PBSC collections, and repeatedly after autografting for up to 12 months. The number of CD56(+)3(-) and CD56(+)3(+) lymphocytes, their in vitro expandability with interleukin-2, and their cytotoxicity against MCF-7 and Daudi cells were analyzed. Six healthy females served as controls. CD56(+) cell counts in both treatment groups were subnormal but stable during the observation period. The cytotoxicity of the expanded CD56(+) cells was normal and unaffected by the treatment. The in vitro CD56(+) cell expandability (controls, 100 +/- 31-fold, mean +/- SEM) was normal before CT1 and CT2, but reduced in PBSC harvests performed after CT2 and application of G-CSF (21 +/- 6-fold; p < 0.01). After PBSC harvesting, the CD56(+) cell expandability increased to 185 +/- 74-fold and 170 +/- 69-fold (before CT3 and HDCT). This increase was not observed in those patients who did not undergo PBSC mobilization. Two weeks after autografting, the CD56(+) cell expandability was minimal (6 +/- 1-fold), and recovered to 34 +/- 6-fold. Thus, CT, HDCT and autografting do not alter the frequency and inducible cytotoxicity of CD56(+) cells in breast cancer patients. However, the proliferative capacity of CD56(+) cells obtained from PBSC harvests and after autografting is impaired. Therefore, instead of the PBSC graft, maximally expandable CD56(+) cells obtained at least 1 week after PBSC collection should be considered for adoptive immunotherapy after PBSC autografting.

Adult↗
PubMed2000

Evidence from a leukaemia model for maintenance of vascular endothelium by bone-marrow-derived endothelial cells.

BACKGROUND: Vascular endothelial cells lost from the blood-vessel endothelium through necrosis or apoptosis must be replaced. We investigated in a leukaemia model whether bone-marrow-derived endothelial cells contribute to this maintenance angiogenesis. METHODS: We studied six patients with chronic myelogenous leukaemia (CML) carrying the BCR/ABL fusion gene in their bone-marrow-derived cells. We screened endothelial cells generated in vitro from bone-marrow-derived progenitor cells and vascular endothelium in myocardial tissue for the BCR/ABL fusion gene by in-situ hybridisation. For detection of donor-type endothelial cells after transplantation of haemopoietic stem cells, recipient tissue was stained with monoclonal antibodies against donor-type HLA antigens. FINDINGS: We identified the BCR/ABL fusion gene in variable proportions (0-56%) of endothelial cells generated in vitro. Endothelial cells expressing the fusion gene were found in the vascular endothelium of a patient. In a recipient of an allogeneic stem-cell transplant, normal donor-type endothelial cells were detected in the vascular endothelium. INTERPRETATION: These findings suggest that CML is not solely a haematological disease but originates from a bone-marrow-derived haemangioblastic precursor cell that can give rise to both blood cells and endothelial cells. Moreover, normal bone-marrow-derived endothelial cells can contribute to the maintenance of the blood vascular endothelium. The integration of bone-marrow-derived endothelial cells into the vascular endothelium provides a rationale for developing vascular targeting strategies in vasculopathies, inflammatory diseases, and cancer.

Adult↗
PubMed2000

Evaluation of optimal survival of primitive progenitor cells (LTC-IC) from PBPC apheresis products after overnight storage.

Optimal overnight (ON) storage of PBPC aphereses is becoming an increasingly important issue and different options for storing PBPC products exist. The survival of primitive progenitor cells is of major interest, as recent data suggest that these progenitors are not only important for long-term engraftment but also contribute significantly to the early phase of hematopoietic engraftment after myeloablative therapy. We therefore investigated the survival of primitive progenitor cells (ie long-term culture initiating cells, LTC-IC) before (ie within 2 h after finishing the apheresis procedure) and after ON storage lasting 16 to 20 h. In addition, we compared the % of recovery of LTC-IC with that of mature progenitors (ie colony-forming cells, CFC) and with the % viability of the mononuclear cells in the apheresis product. Aliquots of PBPC aphereses products were tested in collection bags at room temperature (RT), in EDTA tubes both at RT or 4 degrees C +/- the addition of autologous plasma (AP; 2.6-fold the apheresis volume) and +/- the possibility of gas exchange. Mean viable cell counts did not show strong differences between the different storage conditions and were poor predictors for the survival of CFC and LTC-IC. At RT (collection bags, EDTA tubes +/- gas exchange) recoveries (% of input) of both, CFC (18%, 18% and 31%) and LTC-IC (10%, 4%, 17%) were low. The addition of AP at RT improved the survival of CFC and LTC-IC to 66% and 38%, respectively. Optimal recoveries for both types of progenitors (CFC: 99%, LTC-IC: 109%) were obtained at 4 degrees C in the presence of AP. In addition, a good correlation between the survival of CFC and LTC-IC was obtained (r = 0.76) suggesting that the analysis of CFC may also allow some conclusions to be drawn on the survival of LTC-IC. Bone Marrow Transplantation (2000) 25, 197-200.

Blood Component Removal↗
PubMed1999

Aspergillus osteoarthritis in acute lymphoblastic leukemia.

We report an unusual case of arthritis of the right wrist due to Aspergillus fumigatus without evidence for a generalized infection, following chemotherapy for acute lymphoblastic leukemia. The diagnosis was made by surgical biopsy. Amphotericin-B (Am-B) was not tolerated by the patient. Liposomal preparations of Am-B penetrate poorly into bone and cartilage. Therefore, oral itraconazole was given; the arthritis improved and chemotherapy was continued without infectious complications. Two weeks after complete hematopoietic recovery, an intracranial hemorrhage from a mycotic aneurysm of a brain vessel occurred, although the patient was still receiving itraconazole. We emphasize the importance of prompt and thorough efforts to identify the causative agent in immunocompromised patients with a joint infection. Itraconazole is effective in Aspergillus osteoarthritis but, due to its poor penetration into the brain, the combination with a liposomal formulation of Am-B is recommended.

Antifungal Agents↗
PubMed1998

Differences between normal and CML stem cells: potential targets for clinical exploitation.

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder in which there is a deregulated amplification of CML progenitors at intermediate stages of their differentiation along the myeloid, erythroid and megakaryocyte pathways. Such cell populations are routinely quantified using standard in vitro colony-forming cell (CFC) assays. The excessive production of leukemic CFC that is seen in most CML patients at diagnosis may be explained at least in part by their increased proliferative activity. An anomalous cycling behavior in vivo has also been found to extend to more primitive CML progenitor populations detectable as long-term culture-initiating cells (LTC-IC). Although the molecular basis of these changes in CML progenitor regulation is not fully understood at the level of the primitive CFC compartment, a selective inability of CML progenitors to be inhibited by certain -C-C-type chemokines has been demonstrated. Failure of the CML stem cell compartment to expand in vivo at the same rate as later progenitor cell types may be explained by their unique additional possession of an intrinsically upregulated probability of differentiation. Such a mechanism would be consistent with the observed loss of LTC-IC activity by CML cells incubated in vitro under conditions that sustain or expand normal LTC-IC populations. Initial clinical studies undertaken at our center established the feasibility of exploiting the differential behavior of primitive normal and CML cells in vitro as a potential purging strategy for reducing the leukemic stem cell content of CML marrow autografts. The results of a larger, second trial now in progress on a group of unselected patients are encouraging. Future studies of nonobese diabetic/severe-combined immunodeficiency mice engrafted with CML cells should provide another useful preclinical model for evaluating treatments that may more effectively eradicate the neoplastic clone in vivo.

Animals↗
PubMed1997

Selective expansion of primitive normal hematopoietic cells in cytokine-supplemented cultures of purified cells from patients with chronic myeloid leukemia.

We have previously reported that primitive normal hematopoietic cells detectable as long-term culture-initiating cells (Ph-LTC-IC) are present at high levels in the blood of some patients with chronic myeloid leukemia (CML). We now show that this population can be expanded several-fold when highly purified CD34+CD38- cells isolated from the blood of such patients are cultured for 10 days in a serum-free medium containing 100 ng/mL of Flt3-ligand and Steel factor and 20 ng/mL of interleukin-3 (IL-3) and IL-6, and granulocyte colony-stimulating factor. In similar cultures initiated with CD34+CD38- cells from CML blood samples in which all of the LTC-IC were leukemic (Ph+), Ph+ LTC-IC activity was rapidly lost both in the presence and absence of admixed CD34+CD38- cells isolated from normal marrow. Conversely, the ability of normal LTC-IC to expand their numbers was shown to be independent of the presence of Ph+LTC-IC and later types of Ph+colony-forming cell (CFC) progenitors. In contrast to the LTC-IC, CFC were consistently amplified in cultures initiated with CML-derived CD34+CD38- cells and the additional CFC present after 10 days were, like the starting population of CFC, almost exclusively Ph+ regardless of the genotype(s) of the LTC-IC in the original CML samples. Amplification of the Ph+CFC population in these cultures showed the same factor dependence as previously demonstrated for the in vitro expansion of CFC from normal marrow CD34+CD38- cells. Ph+LTC-IC disappeared regardless of the cytokines present. Taken together these findings support a model of CML in which the leukemic stem cells are characterized by a decreased probability of self-renewal and an increased probability of differentiation. In addition, they suggest new opportunities for improving the treatment of CML using strategies that require autologous stem cell rescue.

Cell Division↗