Analysis of progenitor cell involvement in B-CLL by simultaneous immunophenotypic and genotypic analysis at the single cell level

B-cell chronic lymphocytic leukaemia (B-CLL) results from the clonal expansion of mature B lymphocytes. The detection of leukaemia-associated genetic markers in CD34-positive progenitor cells in a subset of B-CLL patients suggests that malignant transformation in B-CLL occurs in an immature progenitor cell compartment. To further quantify the percentage of B-CLL patients with genetically aberrant progenitor cells we have investigated CD34+ bone marrow cells in 11 B-CLL patients at the single cell level by simultaneous genetic and immunophenotypic analysis (FICTION). In five patients with trisomy 12, CD34+ haemopoietic progenitor cells were detectable on bone marrow smears. In one patient with trisomy 12, CD34+ progenitor cells were isolated by FACS sorting. In all six patients trisomy 12 was not found in the CD34+ cells. Progenitor cells were also analysed in three patients with Rb-deletion and in two patients with deletion of p53. In all patients the genetic marker was not detected in the CD34+ cells. In conclusion, we did not find genetically aberrant progenitor cells in this group of B-CLL patients. These results suggest that the subset of B-CLL patients with genetically aberrant CD34+ cells may be very small. This is of significance for our understanding of B-CLL biology and for future strategies using autologous stem cell transplantation.     

Circulating mononuclear cells from pure red cell aplasia of chronic lymphocytic leukemia suppress in vitro erythropoiesis

In vitro studies were performed in a patient with B-cell chronic lymphocytic leukemia who developed pure red cell aplasia (CLL-PRCA). The patient's irradiated circulating mononuclear blood cells and supernatant markedly inhibited normal marrow erythroid (but not granulocyte-monocyte) progenitor colony proliferation. In contrast, irradiated peripheral blood mononuclear cells and supernatant obtained from a B-CLL patient (Rai stage III) and from a hematologically normal donor, did not affect hematopoietic progenitor colony growth. These findings suggest that the anemia of CLL-PRCA evolves different mechanisms of those causing anemia in CLL, and is mediated through cellular and secretory mechanisms.     

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.     

Molecularly cloned and expressed murine T-cell gene product is biologically similar to interleukin-3

Clonal lines of mouse inducer ly1+ly2- inducer T-lymphocytes that depend for growth upon interleukin-2 have been demonstrated to produce a factor that stimulates colony formation by bone marrow granulocyte-macrophage (GM-CFUc) progenitor cells and replication of factor-dependent mast cell/basophil and multipotential hematopoietic cell lines in vitro. The molecularly cloned and expressed gene product for this growth factor demonstrates the following activities in vitro: using fresh bone marrow or purified subpopulations of nonadherent cells from murine continuous bone marrow cultures as target cells: stimulation of colony formation by GM-CFUc, mast cell progenitor cells, multipotential granulocyte/erythroid/megakaryocyte/macrophage progenitor cells (CFU-GEMM) colonies, erythroid progenitor cells forming macroscopic bursts (BFUe), and megakaryocyte progenitor cells (CFU-mega). The gene product also supports growth of previously reported mast cell growth-factor-dependent cell lines and several classes of interleukin-3 (IL-3)-dependent hematopoietic progenitor cell lines that are multipotential (neutrophil/basophil/eosinophil or neutrophil/basophil/erythroid); or committed to granulocyte-macrophage, or mast cell/basophil differentiation. The gene product does not detectably support replication of IL-2-dependent murine T-cell lines. The biologic activity of the gene product was inhibited greater than or equal to 90% by rabbit antisera prepared against purified interleukin-3. The data indicate that this T-cell derived lymphokine gene product is biologically very similar to interleukin-3.     

Transforming growth factor beta directly regulates primitive murine hematopoietic cell proliferation

We previously reported that transforming growth factor beta (TGF-beta) selectively inhibits colony-stimulating factor-driven hematopoietic progenitor cell growth. We report here that TGF-beta 1 can act directly on hematopoietic progenitors to inhibit the growth of the most primitive progenitors measurable in vitro. Highly enriched populations of hematopoietic progenitor cells were obtained by isolating lineage negative (Lin-), Thy-1-positive (Thy-1+) fresh bone marrow cells, or by isolating cells from interleukin-3 (IL-3) supplemented bone marrow cultures expressing Thy-1 antigen with the fluorescent activated cell sorter. TGF-beta 1 inhibited IL-3-induced Thy-1 expression on Thy-1-negative (Thy-1-) bone marrow cells in a dose-dependent manner with an ED50 of 5 to 10 pmol/L. In addition, TGF-beta 1 inhibited the formation of multipotent and mixed colonies by isolated Thy-1+ cells, while single lineage granulocyte and macrophage colonies were not affected. The growth of Thy-1+ Lin- cells incubated as single cells in Terasaki plates in medium supplemented with IL-3 were inhibited by TGF-beta, demonstrating a direct inhibitory effect. Hematopoietic stem cells, which have a high proliferative potential (HPP) when responding to combinations of growth factors in vitro, have been detected in the bone marrow of normal mice and mice surviving a single injection of 5-fluorouracil. TGF-beta 1 inhibited the growth of all subpopulations of HPP colony forming cells (CFC) in a dose-dependent manner with an ED50 of 5 to 10 pmol/L. Thus, TGF-beta directly inhibits the growth of the most immature hematopoietic cells measurable in vitro.     

Lymphokine-activated killer cells selectively kill tumor cells in bone marrow without compromising bone marrow stem cell function in vitro

Although it has been demonstrated that lymphokine-activated killer (LAK) cells kill tumor cells in a selective way without being toxic to a variety of normal cells, contradictory results exist about the possible toxicity of natural killer (NK) and LAK cells for hematopoietic progenitor cells. Therefore, the cytolytic activity and growth inhibitory effects of LAK cells on normal bone marrow progenitor cells and the ability of LAK cells to eliminate neoplastic hematopoietic cells from populations of bone marrow cells in vitro was studied. The results of these experiments show the following: (1) LAK cells have little cytolytic activity against normal bone marrow cells; (2) normal bone marrow cells fail to cold target compete for the killing of the hematopoietic tumor cell lines K562 and HL60 or freshly frozen acute myelocytic leukemia (AML) blast cells by LAK cells; (3) LAK cells inhibit the growth of K562 and HL60 to more than 90% in clonogenic assays; (4) LAK cells have no inhibitory effect on hematopoietic progenitor growth in CFU-GM (colony-forming unit- granulocytes, macrophages), CFU-E (colony-forming unit-erythrocytes), BFU-E (burst-forming units-erythrocytes), or CFU-GEMM (colony-forming unit-granulocytes, erythrocytes, macrophages, megakaryocytes) assays. These results indicate that LAK cells have low toxicity for normal bone marrow and that LAK activity against tumor cells is not adversely affected by the presence of normal bone marrow cells. The differences in cytolysis and growth inhibition of neoplastic hematopoietic cells and hematopoietic progenitor cells by LAK cells in vitro could create a therapeutic index that might allow the use of LAK cells for cleansing of the autologous bone marrow graft and for adjuvant therapy in combination with autologous bone marrow transplantation without compromising the reconstitution of the bone marrow in the host.     

In vitro and in vivo effects of recombinant interferon gamma on the growth of hematopoietic progenitor cells from patients with myelodysplastic syndrome

Recombinant interferon gamma (rIFN-gamma) has been shown to have antiproliferative effects on normal and leukemic hematopoietic cells, to induce cell differentiation and to modulate hematopoietic growth factor production. We have studied the effects of rIFN-gamma on the growth of hematopoietic progenitors from 3 patients with myelodysplastic syndrome who were treated with rIFN-gamma (0.01 mg/m2 given subcutaneously three times a week) as part of an Italian pilot study. When bone marrow cells were cultured in semisolid medium in the continuous presence of rIFN-gamma (10-10(4) U/ml), inhibition of colony formation was the most common response. However, an enhancement of hematopoietic progenitor growth was observed in one patient at the lowest concentration tested (10 U/ml). Preincubation of bone marrow mononuclear cells with low concentrations of rIFN-gamma in suspension culture for 5 days induced or enhanced in vitro colony formation in two cases; again, higher concentrations resulted in inhibition of hematopoietic progenitor growth. Two patients showed a slight improvement of in vitro progenitor growth after one month of treatment with rIFN-gamma. Although preliminary, these data indicate that rIFN-gamma may have both stimulatory and inhibitory effects on myelodysplastic hematopoiesis, depending on both the effective concentrations and the interactions with accessory cells.     

Mechanisms of mobilization of hematopoietic progenitors with granulocyte colony-stimulating factor

Hematopoietic progenitor cells can be mobilized from the bone marrow to the blood by a wide variety of stimuli, including hematopoietic growth factors, chemotherapy, and chemokines. Increasingly, mobilized peripheral blood hematopoietic progenitor cells instead of bone marrow hematopoietic progenitor cells have been used to reconstitute hematopoiesis after myeloablative therapy because of their reduced engraftment times and relative ease of collection. A striking feature of hematopoietic progenitor cell mobilization is the ability of hematopoietic growth factors with distinct cellular targets and biologic activities to mobilize a similar spectrum of pluripotent and lineage-committed hematopoietic progenitor cells into the blood. Recent studies have identified some of the key adhesive interactions that regulate hematopoietic progenitor cell trafficking in the bone marrow. In addition, pathways linking mobilizing agents to hematopoietic progenitor cell mobilization have begun to be elucidated. This review summarizes these advances, emphasizing the mechanisms regulating granulocyte colony-stimulating factor-induced mobilization.     

Lack of evidence for infection of or effect on growth of hematopoietic progenitor cells after in vivo or in vitro exposure to human immunodeficiency virus

The pathogenesis of the hematologic abnormalities commonly observed in patients with acquired immunodeficiency syndrome (AIDS) is incompletely understood. We report here that in vitro growth of myeloid (CFU-GM) and erythroid (BFU-E) progenitor cells from six patients with AIDS was not significantly different from that of normal human immunodeficiency virus (HIV) seronegative donors: 25.3 +/- 5 CFU-GM per 5 x 10(4) low density marrow cells and 33.5 +/- 5 BFU-E were observed in AIDS patients versus 32.7 +/- 5 CFU-GM and 42.1 +/- 5 BFU-E in controls. Furthermore, no HIV-DNA in individual colonies (CFU-GM and BFU-E) could be detected using the polymerase chain reaction (PCR) technique, although HIV-1 DNA was detected in peripheral blood mononuclear cells from the same patients. Similarly, normal bone marrow cells exposed in vitro to different isolates of HIV or recombinant purified HIV-1 envelope glycoprotein (gp) 120 did not exhibit any difference in growth of CFU-GM or BFU-E as compared with mock exposed bone marrow cells. HIV-1 DNA could not be detected by the PCR technique in individual colonies derived from HIV exposed marrow. This study suggests that committed myeloid and erythroid progenitors from AIDS patients are responsive to hematopoietic growth factors in vitro and do not appear to contain HIV-1 DNA. Also, HIV or its envelope gp did not alter the growth of hematopoietic progenitor cells in vitro. No evidence of HIV infection of progenitor cells could be demonstrated. Impaired hematopoiesis in patients with AIDS may not be related to direct effects of HIV on committed progenitor cells.     

Study of possible correlations between in vitro growth of bone marrow stromal and hematopoietic precursor cells early after allogeneic bone marrow transplantation.

Growth characteristics of stromal cells, assessed as adherent cells in long-term bone marrow cultures, and of hematopoietic progenitor cells, prior to and shortly after allogeneic bone marrow transplantation (BMT), were investigated, more specifically with regard to their possible correlations. The main constituent cells of the bone marrow stroma, that is, endothelial cells, reticular cells/fibroblasts, and monocytes/macrophages, showed an as yet inexplicable increased growth in samples taken from recipients prior to BMT, as compared with the growth in samples from their healthy donors and those taken after BMT. In the third week after BMT the in vitro outgrowth of hematopoietic precursors was severely depressed, but cell numbers in the adherent layer were normal. No relationship between in vitro growth of hematopoietic precursor cells and stromal cells was observed at that time. Probably the precursor cells growing in vitro are committed progenitor cells, relatively independent of stromal influences. In the eight week after grafting, endothelial cell outgrowth in vitro was highly correlated with granulocyte-macrophage colony-forming unit (CFU-GM) colony formation and to a lesser extent with mixed-lineage colony-forming unit (CFU-Mix) colony formation. This may indicate the reappearance of cytokine-mediated influences or the reappearance of a direct interaction, for example, by cell-cell contact between stromal cells and hematopoietic progenitor cells at that time.     

B cells in chronic lymphocytic leukaemia comparative analysis of blood and bone marrow

Summary A study was performed on cell suspension from peripheral blood and bone marrow aspirates and on cryostat sections from bone marrow biopsies in order to investigate the membrane phenotype of neoplastic B cells in chronic lymphocytic leukaemia (B-CLL). The immunological analyses, performed on 43 patients, included rosetting ability with sheep and mouse erythrocytes, evaluation of surface immunoglobulins and reactivity with anti-HLA-DR, UCHT 1 (OKT-3 like) and RFA-1 (OKT-1 like) monoclonal antibodies.The results demonstrate that neoplastic B lymphocytes in B-CLL display an identical phenotype in peripheral blood and bone marrow. Possible interpretations on the origin of proliferating cells in B-CLL are discussed.     

Steel factor (c-kit ligand) promotes the survival of hematopoietic stem/progenitor cells in the absence of cell division

It is known that the majority of primitive hematopoietic progenitors are in a noncycling quiescent state. In addition, normal hematopoietic progenitors and progenitor cell lines show an absolute dependence on growth factors for their survival in vitro, yet the effect of growth factors on progenitor cell survival has not been separated from effects on both proliferation and differentiation. Using an in vitro assay system, we examined whether growth factors could promote the survival of stem cells in culture in the absence of cell division. These studies show that steel factor (SLF) and, to a lesser extent, interleukin-3 (IL- 3) directly promoted the survival of elutriated bone marrow progenitor cells (countercurrent centrifugal elutriation [CCE]-27) that are enriched for primitive hematopoietic progenitors that respond to the combination of SLF plus IL-3. Furthermore, SLF promoted the survival of short-term reconstituting cells (STRC), and long-term reconstituting cells (LTRC) with trilineage reconstitution potential in vivo. In comparison, granulocyte colony-stimulating factor (G-CSF), IL-6, leukemia inhibitory factor, IL-11, IL-1, granulocyte macrophage CSF (GM- CSF), and macrophage CSF (M-CSF) had no effect on the survival of these cells. In the presence of mitotic inhibitors (nocodazole or aphidicolin), SLF promoted the survival of CCE-27 progenitor cells that respond to the combination of SLF plus IL-3 in vitro and STRCs and LTRCs that are detected in vivo. Taken together, these data show that SLF can directly promote the survival of hematopoietic progenitor cells in the absence of cell division.     

Hematopoietic progenitors in cyclic neutropenia: effect of granulocyte colony-stimulating factor in vivo.

The number and growth factor requirements of committed progenitor cells (colony-forming units-granulocyte/macrophage and burst-forming units-erythroid) in three patients with cyclic neutropenia (two congenital, one acquired) were studied before and during therapy with recombinant human granulocyte colony-stimulating factor (G-CSF; 3 to 10 micrograms/kg/d). When the patients with congenital disease were treated with G-CSF, the cycling of blood cells persisted, but the cycle length was shortened from 21 days to 14 days, and the amplitude of variations in blood counts increased. There was a parallel shortening of the cycle and increase of the amplitude of variations (from two- to three-fold to 10- to 100-fold) in the number of both types of circulating progenitor cells in these two patients. In the patient with acquired cyclic neutropenia, cycling of both blood cells and progenitors could not be seen. In cultures deprived of fetal bovine serum, erythroid and myeloid bone marrow progenitor cells from untreated patients and from normals differed in growth factor responsiveness. As examples, maximal growth of granulocyte/macrophage (GM) colonies was induced by granulocyte/macrophage (GM)-CSF plus G-CSF in the patients, whereas a combination of GM-CSF, G-CSF and interleukin-3 (IL-3) was required in the normals, and erythropoietin alone induced fourfold more erythroid bursts from cyclic neutropenic patients than from normal donors (46% versus 11% of the maximal colony number, respectively). The growth factor responsiveness of marrow progenitor cells slightly changed during the treatment toward the values observed with normal progenitors. These results indicate that treatment with G-CSF not only ameliorated the neutropenia, but also increased the amplitude and the frequency of oscillation of circulating progenitor cell numbers. These data are consistent with the hypothesis that G-CSF therapy affects the proliferation of the hematopoietic stem cell.     

Murine embryonic yolk sac cells promote in vitro proliferation of bone marrow high proliferative potential colony-forming cells

To examine the influence of the hematopoietic microenvironment on hematopoietic cell proliferation and differentiation during the yolk sac phase of hematopoiesis, we have recently established cell lines from embryonic yolk sac visceral endoderm (YSE) and mesoderm (YSM). In the present experiments, we compared in vitro growth of adult murine bone marrow high proliferative potential colony-forming cells (HPP-CFC) in coculture with YSE- and YSM-derived or adult bone marrow stromal cell lines. Whereas both yolk sac-derived and adult stromal cell lines supported the proliferation of HPP-CFC during coculture, YSE- and YSM- derived cells stimulated a significant increase in total HPP-CFC compared with adult bone marrow stromal cell lines. Conditioned media from both YSE- and YSM-derived cell lines also stimulated the growth of HPP-CFC in vitro, but only in combination with exogenous recombinant hematopoietic growth factors. Although multiple hematopoietic growth factor mRNAs were detected in the yolk sac-derived cells by polymerase chain reaction, only macrophage colony-stimulating factor (M-CSF) activity was detected in conditioned media using an enzyme-linked immunosorbent assay. A neutralizing polyclonal antibody against M-CSF did not diminish the YSE- or YSM-derived cell line conditioned media promotion of HPP-CFC colony formation. These results suggest that murine yolk sac-derived cell lines produce a novel soluble factor(s) that recruits primitive bone marrow hematopoietic cells to grow in vitro in response to a combination of hematopoietic growth factors.     

Prolonged impairment of hematopoiesis after high-dose therapy followed by autologous bone marrow transplantation

Hematopoietic reconstitution has been studied in 180 patients after autologous bone marrow transplantation based on peripheral blood cell (PBC) recovery time and marrow progenitor counts sequentially tested for up to 4 years. Several factors that could influence hematopoietic reconstitution have been analyzed including sex, age, diagnosis, disease status, conditioning regimen, graft progenitor content, graft in vitro purging, and postgrafting administration of growth factors. Before transplantation, marrow progenitor values were normal only for colony-forming unit granulocyte macrophage (CFU-GM) in contrast to colony-forming unit-erythroid (CFU-E), burst-forming unit-erythroid (BFU-E), and colony-forming unit-megakaryocyte (CFU-Meg). After transplantation, as described with allogenic grafts, these values remained low for several years, although PBC counts were nearly normalized within a few weeks. Pregraft values were reached after 2 years for CFU-GM and BFU-E, and after 4 years for CFU-E, while CFU-Meg failed to reach pregraft values after this time. Normal levels were reached after 4 years only by CFU-GM. On univariate and multivariate analysis, the following factors appeared to delay both PBC and marrow progenitor reconstitution: underlying disease (particularly acute myeloid leukemias), graft characteristics such as low stem cell content and in vitro purging, conditioning regimens with total body irradiation or busulfan, and lack of postgraft administration of growth factors. In conclusion, high-dose therapy followed by bone marrow transplantation induces a deep and prolonged impairment of hematopoiesis irrespective of any alloimmune reaction or postgraft immunosuppressive therapy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thymic humoral factor-gamma 2, an immunoregulatory peptide, enhances human hematopoietic progenitor cell growth.

Thymus humoral factor-gamma 2 (THF gamma 2), an octapeptide important for T-lymphocyte regulation, was assessed for its effect on the in vitro growth of human hematopoietic progenitor cells. This was achieved using a recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF)-stimulated myeloid cell colony formation (granulocyte-macrophage colony-forming cells, GM-CFC) assay as well as a recombinant erythropoietin (rEpo)-stimulated erythroid burst formation (erythroid burst-forming units, BFU-E) assay. Cells were obtained from bone marrow (BM) and peripheral blood (PB) of normal healthy donors and from patients with suppressed bone marrows. The latter group included aplastic anemia, leukemia, and lymphoma patients and patients with solid tumors who responded to intensive chemotherapy with significant pancytopenia. THF gamma 2 significantly enhanced normal BM and PB GM-CFC and PB BFU-E by 2- to 2.5-fold. This effect was totally dependent on the presence of the respective growth factors, that is, rGM-CSF or rEpo, and was specifically reversed by an anti-THF gamma 2 antiserum. Furthermore, although THF gamma 2-induced enhancement of GM-CFC colony formation was not affected by lymphocyte or monocyte depletion, the augmenting effect of the peptide on BFU-E was completely abrogated in the absence of lymphocytes. THF gamma 2-induced augmented growth of progenitor cells derived from severely suppressed marrows was minimal. However, cells from moderately neutropenic patients with leukemia in remission or with lymphoma under chemotherapy responded to the peptide similarly to cells from normal donors. These results suggest a stimulatory role for THF gamma 2 on human myeloid and erythroid hematopoietic progenitor cells. They also suggest the lymphocyte dependence of BFU-E enhancement and lymphocyte independence of GM-CFC stimulation by THF gamma 2. In the former case the thymus-derived peptide may act through the induction of certain erythroid-enhancing lymphokines.     

Identification and characterization of osteoclast progenitors by clonal analysis of hematopoietic cells.

We have identified a distinct population of colony-forming cells that give rise to mononuclear cells expressing an enzyme marker and other features of the osteoclast in bone marrow cultures stimulated by conditioned medium of a murine tumor cell line. These colony-forming cells were defined as osteoclast colony-forming units (CFU-O). The tumor cell-derived activity was recently isolated and was named osteoclast colony-stimulating factor (O-CSF). To understand the development of osteoclast progenitors and to clarify the relationship of osteoclast progenitors to other hematopoietic progenitors, we examined CFU-O in hematopoietic tissues obtained from normal adult mice, mouse fetuses, and mice with 5-fluorouracil (5FU) treatment. CFU-O were present in the adult mouse bone marrow, adherent cell-depleted marrow, in the spleen, and in the day 14 fetal liver, with an incidence similar to other hematopoietic progenitors. The culture period required for the development of CFU-O-derived colonies in vitro and the manner in which CFU-O responded to 5FU suggested that CFU-O belonged to a relatively primitive progenitor population; they are clearly more immature than macrophage progenitors that respond to macrophage-CSF, but more mature than multilineage progenitors that respond to stem cell factor. Our studies have defined and characterized an osteoclast progenitor and distinguished it from other hematopoietic progenitors for the first time.     

The role of interleukin-1 in hematopoiesis.

The polypeptide interleukin 1 (IL-1) is the primary mediator of the acute-phase response and is responsible for many changes that are associated with the onset of infection. It induces fever and has profound endocrinologic metabolic and hematologic effects. Two structurally related forms of IL-1 have been described, termed IL-1 alpha and IL-1 beta. Both forms of IL-1 bind to a common receptor that is present on a variety of target cells. Recently, IL-1 has been recognized as a molecule that is important in the regulation of hematopoiesis. IL-1 induces the production of several different hematopoietic growth factors including granulocyte-macrophage, granulocyte and macrophage colony-stimulating factors and interleukin 6 by a variety of accessory cells. In addition, IL-1 acts synergistically with colony-stimulating factors in the proliferation of primitive hematopoietic progenitor cells. In vivo, the administration of IL-1 accelerates hematopoietic reconstitution after chemotherapy or radiation induced myelosuppression. In untreated animals, IL-1 may induce a shift of hematopoietic progenitor cells into the peripheral blood, and these cells may be used to repopulate the bone marrow of lethally irradiated recipients. These studies suggest that IL-1 may be used as a therapeutic agent to accelerate bone marrow recovery after myelosuppression.     

Chronic lymphocytic leukemia associated with bone marrow fibrosis: Possible role of interleukin 1α in the pathogenesis

B-cell chronic lymphocytic leukemia (B-CLL) associated with bone marrow fibrosis is described. The conditioned medium of the CLL cells contained a high quantity of interleukin 1α (IL-1α), and showed growth promoting activity for marrow fibroblasts which was partially inhibited by anti IL-1α antibody. In addition, the conditioned medium as well as IL-1α stimulated the growth of marrow fibroblasts from the patient. These results strongly suggested the marrow fibrosis occurred by the secretion of IL-1α from the CLL cells and its growth stimulation of marrow fibroblasts. As far as we know, this is the first case in which B-CLL was associated with marrow fibrosis, and its mechanism was investigated.     

Reduced oxygen tension increases hematopoiesis in long-term culture of human stem and progenitor cells from cord blood and bone marrow.

Growth of hematopoietic stem and progenitor cells found in the mononuclear cell (MNC) fraction of human cord blood and bone marrow was evaluated under atmospheres containing reduced (5%) and normal (20%) oxygen tension. Cord blood MNC were grown in suspension and on preestablished irradiated bone marrow stromal layers, whereas bone marrow MNC were used to initiate one-step long-term bone marrow cultures (LTBMC). Reduced oxygen tension resulted in a substantial increase in both the number and frequency of colony-forming cells observed in all three types of long-term hematopoietic cultures (LTHC) studied. At various time points under low oxygen, progenitor cell numbers were as much as 12-fold, 3-fold, and 4-fold higher for granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst-forming units (BFU-E), and granulocyte erythrocyte macrophage megakaryocyte colony-forming units (CFU-GEMM), respectively. In addition to these numerical increases, progenitor cells were maintained for 1-2 weeks longer under low oxygen conditions. Reduced oxygen tension also increased total cell numbers by as much as fivefold in cord blood suspension cultures, but this effect on total cell numbers was less pronounced in cultures containing a stromal layer. The rate of irradiated stromal layer degeneration, as judged by cell counts and microscopic examination, was reduced under low oxygen. Finally, the beneficial effect of reduced oxygen was comparable to the effect of an irradiated stromal layer for maintaining cord blood progenitor cells in LTHC. These results indicate that low oxygen, which better approximates the in vivo environment, enhances the growth and maintenance of both stromal and progenitor cells for a longer period of time in vitro.