Growth factor receptor profile of CD34+ cells in AML and B-lineage ALL and in their normal bone marrow counterparts

Leukaemic cells show a low clonogenic activity and a heterogeneous proliferative response to growth factors. We investigated whether this could be due to an altered expression of growth factor receptors on the leukaemic precursors. Receptors for G-CSF, stem cell factor (SCF), IL-3, IL-6 and IL-7 were detected on CD34+ cells in AML and B-lineage ALL with monoclonal antibodies and flow cytometry. The expression was compared with that on myeloid and B-lymphoid CD34+ cells in normal bone marrow. Leukaemic CD34+ cells expressed the same receptors as their normal counterparts. AML and B-lineage ALL could be distinguished by the growth factor receptor profile of their CD34+ cells. SCFR, G-CSFR and IL-6Ralpha were found in AML, IL-7R in B-lineage ALL and IL-3Ralpha in both. IL-3Ralpha was upregulated in AML and B-lineage ALL CD34+ cells, while samples with low or high expression were present for the other receptors. This variable expression could correlate with the heterogeneous response of leukaemic cells to growth factors. Functional studies on isolated CD34+ cells are needed to investigate this further.     

Different expression of adhesion molecules on myeloid and B-lymphoid CD34+ progenitors in normal bone marrow

Abstract: The expression of adhesion molecules was studied on B lymphoid and myeloid CD34⁺ precursors in normal bone marrow. Bone marrow aspirates were labelled in a double fluorescence procedure with the CD34 monoclonal antibody 43A1 and with antibodies directed against maturation and differentiation antigens and adhesion molecules. Three clusters of CD34⁺ cells could be distinguished by their light scatter characteristics in flow cytometry. The population with the lowest forward scatter contained B-lymphoid precursors while the two others showed phenotypic characteristics of, respectively, early and late myeloid precursors. Nearly all CD34⁺ cells in the 3 subpopulations expressed VLA-4, VLA-5, LFA-3 and H-CAM. B-lymphoid progenitors showed a higher density of VLA-4 and VLA-5 than the myeloid progenitors. Myeloid precursors, and particularly the late subset, expressed more HCAM than the B-lymphoid progenitors. The majority of the CD34⁺ cells also expressed LFA-1 and L-selectin. Higher numbers of positive cells were found in the myeloid subset. The early myeloid subset showed the highest positivity for L-selectin. We conclude that B lymphoid and early and late myeloid CD34⁺ precursors in normal bone marrow show a different profile of adhesion molecules. These profiles could reflect a higher tendency of the myeloid CD34⁺ precursors to circulate.     

Circulating CD34+ cells in cord blood and mobilized blood have a different profile of adhesion molecules than bone marrow CD34+ cells

Abstract: The expression of adhesion molecules was studied on CD34+ hematopoietic precursors in cord blood, bone marrow and mobilized blood. The samples were labeled in a double immunofluorescence procedure with a CD34 monoclonal antibody and with antibodies against maturation and differentiation antigens and adhesion molecules. Myeloid precursors formed the majority of the CD34+ cells in all samples. In bone marrow a separate cluster of B-cell precursors with low forward scatter was present. Nearly all CD34+ cells in normal bone marrow expressed VLA-4 and VLA-5, PECAM-1, LFA-3 and HCAM. The majority of the CD34+ cells also had LFA –1 and L-selectin on the surface membrane. A small subset was VLA-2, VLA-3, ICAM-1 or Mac-1 positive. CD34+ cells expressing the vitronectin receptor or the CD11c antigen were rare. Cord blood and mobilized blood CD34+ cells had a lower expression of VLA-2, VLA-3 and VLA-5 and a higher expression of LFA-1, ICAM-1 and L-selectin than bone marrow CD34+ cells. Except for LFA-1, this was not due to the presence of more myeloid precursors in these samples. Low β₁ integrin expression may lead to less adhesion to the extracellular matrix. High expression of L-selectin may facilitate interaction with endothelial cells. Therefore, this phenotype may favour mobilization.     

Adhesion molecules on CD 34+ hematopoietic cells in normal human bone marrow and leukemia

Summary Expression of selected adhesion molecules of the integrin and immunoglobulin family was investigated on CD 34+ leukemic cells in 19 AML and 11 ALL cases to evaluate phenotypic differences in adhesive properties of malignant hematopoietic precursor cells in comparison to normal bone marrow CD 34+ cells. Of the 2-integrin family, CD 11a was expressed on > 50% of CD 34+ cells in normal bone marrow and almost all leukemias, whereas CD 11 b and CD 11 c were not expressed on CD 34+ cells in normal bone marrow, but were found on CD 34+ blasts in some leukemias of a heterogeneous immunophenotype. Of the 1-family, CDw 49d (VLA-4) was strongly expressed on normal CD 34+ bone marrow cells and on the blasts of all 30 CD 34+ leukemic samples, whereas CDw 49 b (VLA-2) was absent on CD 34+ cells in normal bone marrow, but detected on CD 34+ cells in a few leukemias which did not constitute a clinical or phenotypic entity according to the FAB classification or immunocytological analysis. The lymphocyte-homing-associated adhesion molecule CD 44 (HCAM) and CD 58 (LFA-3) were expressed on CD 34+ cells in all investigated cases of normal and leukemic bone marrow. ICAM-1 (CD 54), the inducible receptor ligand for CD 11 a/CD 18, although present on CD 34+ cells in normal bone marrow, was lacking on blast cells of some ALL and AML cases. So far, the variable expression of 2-integrins as well as of VLA-2 and of ICAM-1 could indicate distinct differences in cell-cell or cell-matrix adhesion of leukemic cells in ALL and AML patients.     

Adhesion molecule expression on CD34+ progenitor cells from normal and aplastic anaemia bone marrow

Summary. Aplastic anaemia (AA) is a disease of bone marrow failure. Evidence has been produced for both a stem cell and a stromal cell defect in this disease. The contribution of deficient or defective cell adhesion molecules (CAMs) has not been determined. CAMs have been shown to be important in stem cell-stromal cell interactions and maintenance of haemopoiesis.
In this study the expression of CAMs (LFA-1, LFA-3, ICAM-1, VLA-4, CD44, sLe^x and L-selectin) on CD34+ progenitor cells from 10 normal donors and eight patients with AA was investigated using double immunofluorescence. There was no significant difference in the percentage of CD34⁺ cells that were CAM⁺ between normal and AA bone marrow, suggesting that abnormal CAM expression on AA progenitor cells is not responsible for nor contributes to the pathogenesis of the disease. However, these findings do not exclude abnormal CAM function on progenitor cells, or abnormal expression or function of CAM ligands or counter-receptors on AA stromal cells.     

Increased expression of Fas antigen on bone marrow CD34+ cells of patients with aplastic anaemia

Summary Fas antigen, a receptor molecule that mediates signals for programmed cell death, is involved in T-cell-mediated killing of malignant, virus-infected or allogeneic target cells. Interferon- γ (IFN- γ ) and tumour necrosis factored (TNF- α ), potent inhibitors of haemopoiesis, enhance Fas receptor expression on bone marrow (BM) CD34⁺ cells, and both cytokines render haemopoietic progenitor cells susceptible to Fas-mediated inhibition of colony formation due to the induction of apoptosis. Haemopoietic suppression in aplastic anaemia (AA) has been associated with aberrant IFN- γ , increased TNF- β expression, and elevated numbers of activated cytotoxic T-cells in marrow. We have now examined Fas antigen expression in fresh AA BM samples. In normal individuals few CD34⁺ cells expressed Fas antigen and normal marrow cells had low sensitivity to Fas-mediated inhibition of colony formation. In contrast, in early AA, BM CD34⁺ cells showed markedly increased percentages of Fas receptor-expressing CD34⁺ cells, which correlated with increased sensitivity of AA marrow cells to anti-Fas antibody-mediated inhibition of colony formation. The proportion of Fas antigen-bearing cells was lower in recovered patients'BM. Fas antigen was also detected in the marrow of some patients with myelodysplasia, especially the hypocellular variant. These results are consistent with the hypothesis that AA CD34⁺ cells, probably including haemopoietic progenitor cells, express high levels of Fas receptor due to in vivo exposure to IFN- γ and/or TNF-α and are suitable targets for T-cell-mediated killing. Our results suggest that the Fas receptor/Fas ligand system are involved in the pathophysiology of BM failure.     

A comparative study of CD34+ cells, CD34+ subsets, colony forming cells and cobblestone area forming cells in cord blood and bone marrow allografts

Cord blood (CB) has become an alternative source of hematopoietic progenitor cells (HPCs) for allogeneic transplantation. We have developed a new efficient protocol for CB collection. Using this method an average of 17.7 x 10(8) [range (6.8-29.6) x 10(8), n = 13] total nucleated cells (TNCs) were harvested. Based on recent Eurocord data, which have shown safe engraftment using a threshold dose of 0.37 x 10(8) CB TNCs/kg body weight (BW), we calculated that six out of thirteen CB grafts collected by this method were sufficient to engraft adults. The CB derived CD34+ population contained two-fold higher numbers of committed HPCs (CFU-GM, BFU-E) and six-fold higher numbers of pluripotent HPCs [CD34+/CD38- cells, wk 5 and wk 8 cobblestone area forming cells (CAFCs)] than the CD34+ population of BM. Extrapolation revealed that BM grafts providing the threshold dose for allogeneic transplantation of 2 x 10(8) TNCs/kg BW contained nearly 3 times more pluripotent HPCs than CB grafts providing the Eurocord threshold dose. The assessment of CD34+/CD38(-) cell numbers in CB grafts was highly reproducible and correlated well with the in vitro performance of pluripotent HPCs, i.e. numbers of CAFCs. We conclude that CB grafts providing high numbers of TNCs have the potential to engraft adults and that the enumeration of pluripotent HPCs by flow cytometry may be a useful tool to define the ultimate threshold dose for CB transplantation.     

Growth factor receptor profile of CD34 cells in normal bone marrow, cord blood and mobilized peripheral blood

Growth factors regulate the proliferation and differentiation of hemopoietic cells. Their effect on hemopoietic precursors differs according to the ontogenic source of the cells. Cord blood and mobilized blood CD34(+) cells have a higher sensitivity for growth factors than bone marrow CD34(+) cells. This could be due to a higher expression of growth factor receptors. Therefore, we examined the expression of receptors for stem cell factor (SCF), interleukin-6 (IL-6), IL-3, granulocyte colony-stimulating factor (G-CSF) and IL-7 on the CD34(+) cells of cord blood, mobilized peripheral blood and bone marrow. The receptors were detected with monoclonal antibodies and flow cytometry. The majority of the CD34(+) cells in bone marrow clearly expressed SCFR; they showed a moderate positivity for IL-3Ralpha and a weak staining for G-CSFR and IL-6 Ralpha. Less than 10% of the cells were IL-7R positive. Cord blood CD34(+) cells showed a higher expression of SCFR and a lower positivity for G-CSFR and IL-6Ralpha. Mobilized blood CD34(+) cells showed a lower expression of SCFR and G-CSFR, and a higher positivity for IL-3Ralpha. This was not solely due to the presence of more myeloid precursors in mobilized blood, as the growth factor receptor profile did not correspond to that of early or late myeloid CD34(+) precursors in normal bone marrow. Changes induced by the mobilization procedure occurred as well. In conclusion, the higher sensitivity for growth factors of hemopoietic precursors in cord blood and mobilized blood cannot be explained by a general increase of the growth factor receptor expression on the CD34(+) cells.     

Peripheral and bone marrow CD34+ cell levels on chronic myeloproliferative disease

Purpose: The aim of the present study was to examine the relationship between peripheral CD34⁺ and bone marrow CD34⁺ levels and the clinicopathologic characteristics and laboratory parameters of myeloproliferative disease (MPD) patients.

Patients and methods: A total of 103 MPD patients were enrolled in this study. We examined the relationship between bone marrow CD34⁺ and peripheral CD34⁺ levels and the patients’ clinicopathologic and laboratory parameters.

Results: There were no significant correlations between the peripheral CD34⁺ levels and the JAK-2 V617F mutation, thrombosis, white blood cells (WBC), lactate dehydrogenase (LDH), transferrin saturation (TS), ferritin, or bone marrow cellularity. In addition, there were no significant correlations between bone marrow CD34⁺ levels and the JAK-2 V617F mutation, thrombosis, WBC, LDH, TS, ferritin, or bone marrow cellularity (P?>?0.05). We did not identify any significant relationship between peripheral CD34⁺ and bone marrow CD34⁺ levels (P?>?0.05). However, there were significant correlations between peripheral CD34⁺ levels and bone marrow fibrosis (P?+ levels and constitutional symptoms (P?+ levels and bone marrow fibrosis (P?Conclusion: We did not find any significant relationship between the clinicopathologic and laboratory characteristics and peripheral and bone marrow CD34⁺ cells from bone marrow fibrosis patients. There was also no significant relationship between bone marrow CD34⁺ cells and peripheral CD34⁺ cells. Some peripheral CD34⁺ cells may originate from the spleen rather than the bone marrow, which may given us different result of some parameters.     

Leukaemic blasts differ from normal bone marrow mononuclear cells and CD34+ haemopoietic stem cells in their metabolism of cytosine arabinoside

Different metabolites of cytosine arabinoside (AraC) contribute to its cytotoxicity including incorporation of AraCTP into DNA, the incorporation of AraUMP into RNA, inhibition of polymerase alpha and beta (AraCMP/CTP), an impairment of repair mechanisms (AraCTP), alterations of phospholipid metabolism (AraCDP-choline), a direct membrane interaction (AraC), the alteration of signal transduction pathways (AraCDP-choline, AraCTP) and the induction of apoptosis. Since little is known about the potential differences in AraC metabolism between leukaemic blasts and normal haemopoietic progenitor cells, the formation of all known AraC metabolites was determined in bone marrow samples from patients with acute myeloid leukaemia (AML), healthy volunteers and specimens of cellsorted CD34+ haemopoietic stem cells. Highly significant differences were found for phosphorylated AraC metabolites (AraCMP, -CDP, -CTP, AraUMP) between AML and normal mononuclear bone marrow (ng/107 cells respectively 1.30 v 2.66; 2.65 v 7.50; 33.68 v 99.0; 1.18 v 5.70). The highest differences were found for formation of AraCDP-choline (3.75 v 12.86) which might be relevant for the high efficacy of high-dose AraC regimens. In contrast, no differences were found in the deamination product AraU (2.01 v 2.91). Only minute amounts of phosphorylated AraU derivatives were detected, providing an explanation for the lacking contribution of AraU to cytosine arabinoside cytotoxicity. Results in normal CD34+ haemopoietic stem cells did not differ significantly from normal bone marrow mononuclear cells and therefore justify their use as a surrogate in determining AraC-induced haematotoxicity. These data suggest a metabolic basis for the relative selectivity of AraC cytotoxicity for AML blasts and provide a means to determine the role of different metabolites and their related mechanism of action for overall AraC cytotoxicity.     

Expression of adhesion molecules in endothelial cells during allogeneic bone marrow transplantation

Abstract: Endothelial cell activation during allogeneic bone marrow transplantation, mainly in acute graft-versus-host disease (aGvHD) was studied in 23 recipients and 5 controls using anti-von Willebrand factor (vWF) antibody, antibodies to endothelial leukocyte adhesion molecule-1 (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), and anti-HLA-DQ antibody, by immunohistological staining of skin. vWF extravasation, ELAM-1 and VCAM-1 expression were present in most recipients with a cutaneous rash which was confirmed as an aGvHD by histological examination (documented aGvHD) (p = 0.005 for vWF extravasation and ELAM-1 expression and p = 0.03 for VCAM-1 expression in comparison with the controls). In recipients with a rash, the cases displaying vWF extravasation and ELAM-1 expression were significantly more numerous in those with a documented aGvHD than in those without histological features of aGvHD (p = 0.01). vWF extravasation and ELAM-1 occurred concomitantly (p<0.01). This study demonstrates that, during the course of skin aGvHD following bone marrow transplantation, there is transient expression of ELAM-1 and VCAM-1 by endothelial cells and simultaneous vWF extravasation, indicating an intense inflammation with endothelial cell participation.     

Pancytopenia due to bone marrow necrosis in acute myelogenous leukemia: Role of reactive CD8 cells

Bone marrow necrosis is a rare clinical condition often associated with hematological malignancy. The mechanism by which malignant disease causes marrow necrosis is unknown. We present a case of a patient with newly diagnosed pancytopenia with bone marrow biopsy evidence of extensive marrow necrosis. Upon further work-up utilizing Tc bone scan directed bone marrow biopsy, a massive CD8+ T cell marrow infiltrate was discovered engulfing AML-M2 blasts. The role of Tc bone scans in the work-up of bone marrow necrosis as well as the potential mechanism of AML-M2 induced marrow necrosis in the setting of reactive CD8+ T cell infiltration is discussed. Am. J. Hematol. 59:74– 78, 1998. © 1998 Wiley-Liss, Inc.     

An in situ study of CD34(+) cells in human fetal bone marrow

The purpose of this study was to characterize the spatial distribution, number and size of CD34(+) cells in fetal bone marrow. Thin sections of normal fetal bone marrow from lumbar vertebrae were stained using CD34 antibody QBend/10. Sections were used under light microscopy with various eyepiece graticules to make measurements of CD34(+) cells in situ. Results showed that at mid- and late gestation, approximately 2% and 0.5% of fetal bone marrow cells were CD34(+) respectively. The mean distance of CD34(+) cells from the nearest trabecular bone surface was 61 +/- 4 and 46 +/- 4 microm, respectively, for mid- and late gestation. The mean distance to the nearest neighbour was 46 +/- 5 and 105 +/- 15 microm, and the mean distance to the nearest blood vessel was 13 +/- 1 and 17 +/- 2 microm respectively. The concentration of CD34(+) cells in the peripheral region was 6.5 times greater than that at the centre of the sections. Overall, the percentage number of CD34(+) cells decreased with gestational age. The cellular and nuclear diameters of CD34(+) cells remained unchanged throughout mid- and late gestation at 5.4 +/- 0.1 and 3.8 +/- 0.1 microm respectively. This information will be used to calculate the natural background alpha-radiation dose to haemopoietic stem cells.     

Antibodies to CD44 enhance adhesion of normal CD34+ cells and acute myeloblastic but not lymphoblastic leukaemia cells to bone marrow stroma

The role of CD44 in the adhesion of haemopoietic cells to bone marrow stromal layers has not been clearly defined in humans, although its importance in the murine system has been well documented. We have demonstrated that the CD44 antibody, NIH44-1, enhances the adhesion of haemopoietic cells to bone marrow stroma. Normal human CD34⁺ haemopoietic progenitors and blasts from patients with acute myeloblastic, but not lymphoblastic, leukaemia responded to NIH44-1. All CD44 antibodies tested which bound the same epitope as NIH44-1 also augmented haemopoietic cell adhesion to bone marrow adherent layers; however, antibodies which bound to other CD44 epitopes showed mixed responses. Augmented adhesion was independent of cell metabolism, suggesting that antibody binding resulted in direct activation of the CD44 molecule. However, hyaluronic acid was not the ligand for induced adhesion, nor could we show a role for other CD44 ligands including fibronectin, laminin, collagen or chondroitin sulphate proteoglycan. Similarly, none of the 22 CD44 antibodies tested inhibited the stimulatory effect of the NIH44-1. Expression of CD44 was not sufficient to determine NIH44-1 responsiveness since cell lines and leukaemic cells which failed to respond to NIH44-1 expressed high levels of CD44. Neither CD44 isoforms nor glycosylation patterns could be identified as predictive of response. CD44 antibodies enhanced binding of normal and leukaemic haemopoietic progenitors to bone marrow fibroblasts via an unidentified stromal ligand.     

Surface expression of HLA-DM on dendritic cells derived from CD34-positive bone marrow haematopoietic stem cells

HLA-DM has been known to be largely absent from the cell surface of antigen-presenting cells, accumulating instead in the intracellular compartment. In this study, we demonstrated that a population of HLA-DM-positive (HLA-DM+) dendritic cells (DCs) can be identified in an in vitro culture of CD34+ bone marrow haematopoietic stem cells. CD34+ bone marrow cells of healthy donors were used to generate DCs with the recombinant human cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), tumour necrosis factor alpha (TNF-alpha) and stem cell factor (SCF), both with and without interleukin 4 (IL-4). Flow cytometric analysis demonstrated that HLA-DM+ cells comprised 2.5 +/- 0.9% and 1.8 +/- 0.4% of the CD34+ cell-derived progeny in the presence of GM-CSF, TNF-alpha and SCF after 7 d and 14 d of culture respectively. The number of HLA-DM molecules expressed per HLA-DM+ cell on d 7 was significantly higher than that on d 14 (1410 +/- 47 versus 370 +/- 25, P < 0.05). The addition of IL-4 to the cytokines from the commencement of culture increased the proportion of HLA-DM+ cells and increased the number of HLA-DM molecules per HLA-DM+ cell significantly (P < 0.05). Although most of the HLA-DM+ cells expressed CD1a, CD80 or CD86 antigen, only a small proportion of CD1a+, CD80+ or CD86+ cells expressed HLA-DM. About half the HLA-DM+ cells expressed CD83. The addition of IL-4 resulted in a decrease in the expression of CD83 on the HLA-DM+ cells on d 7. Microscopic evaluations of sorted HLA-DM+ cells revealed the characteristic morphological features of DCs. Primary mixed lymphocyte cultures demonstrated that the HLA-DM+ cells elicited a vigorous proliferation of allogeneic T cells. The level of antigen-specific T-cell activation induced by antigen-pulsed, chloroquine-treated HLA-DM+ cells was substantially higher than that induced by HLA-DM- cells (P < 0.05). These results show that HLA-DM can be used as a useful DC lineage-specific marker, as well as a tool for the characterization of DCs and human immunotherapy.     

Exclusive expression of G-CSF receptor on myeloid progenitors in bone marrow CD34+ cells

Although granulocyte colony-stimulating factor (G-CSF) has been reported to act on cells of neutrophilic lineage, the administration of G-CSF to induce the mobilization of various haematopoietic progenitors into the circulation. We analysed the expression of receptors for G-CSF (G-CSFR) on human bone marrow and G-CSF-mobilized peripheral blood CD34+ cells, and examined the proliferation and differentiation capabilities of sorted CD34+G-CSFR+ and CD34+G-CSFR- cells using methylcellulose clonal culture. Flow cytometric analysis showed that G-CSFR was expressed on 14.9 +/- 4.9% of bone marrow CD34+ cells, most of which were included in CD34+CD33+ and CD34+CD38+ cell fractions. In clonal cultures, CD34+G-CSFR+ cells produced only myeloid colonies, whereas CD34+G-CSFR- cells produced erythroid bursts, megakaryocyte and multilineage colonies. When incubated with the cytokine cocktail for 5 d, CD34+G-CSFR- cells generated CD34+G-CSFR+ myeloid progenitors. In G-CSF-mobilized peripheral blood, CD34+ cells contained 10.8 +/- 5.8% of G-CSFR+ cells, most of which were also myeloid progenitors, although CD34+G-CSFR- cells contained a substantial number of myeloid progenitors. These results indicated that the expression of G-CSFR on CD34+ cells is restricted to myeloid progenitors, suggesting that the specific activity of G-CSF on myelopoiesis depends on the exclusive expression of its receptor on myeloid progenitors, and that the mobilization of various haematopoietic progenitors is not a direct effect of G-CSF in humans.     

Differences in the distribution of CD34 epitopes on normal haemopoietic progenitor cells and leukaemic blast cells

The CD34 molecule expressed on haemopoietic progenitor cells contains a large number of epitopes whose expression may be related to the maturation or function of the cells. Monoclonal antibodies specific for different epitopes have been reported to detect different numbers of CD34⁺ leukaemic blast cells. We wanted to confirm this observation and study whether parallel findings could be observed for normal haemopoietic progenitor cells. The cells were immunophenotyped by flow cytometry with a series of monoclonal antibodies reactive with different CD34 epitopes. Class III epitopes (resistant to enzymatic cleavage with neuraminidase, chymopapain and a glycoprotease from Pasteurella haemolytica) showed a broader distribution on normal haemopoietic progenitor cells and leukaemic blast cells than class I epitopes (sensitive to cleavage with all three enzymes) and class II epitopes (sensitive to degradation with glycoprotease and chymopapain, and resistant to neuraminidase). The subpopulation of normal progenitor cells which exclusively expressed class III epitopes had flow cytometric characteristics compatible with mature myeloid progenitor cells, whereas class I, II and III epitopes were equally expressed on cells enriched for immature subsets. No discordant epitope expression could be observed for the more immature leukaemias (AML-M0/1) and a higher percentage of the more mature leukaemic blast cells (AML-M3 and AML-M4/5) expressed class III epitopes compared to the percentage expressing class I and II epitopes. These data indicate that CD34 class III epitopes are more broadly distributed on normal haemopoietic progenitor cells and leukaemic blast cells than class I and II epitopes, and that class I and II epitopes may be down-regulated prior to class III epitopes during normal haemopoietic progenitor cell differentiation. These findings should be considered when selecting CD34 mabs for quantification and positive selection of haemopoietic progenitor cells for research and clinical purposes.     

Increased number of peripheral blood CD34+ cells in lithium-treated patients

Eight adult patients with bipolar disorder were prospectively examined to find whether lithium carbonate increased their peripheral blood CD34⁺ haemopoietic stem cells. Following lithium therapy for 3–4 weeks their neutrophil counts increased by a mean of 88% (from 4625 ± 1350 × 10⁹/l, mean ± SD pretreatment, to a peak of 8300 ± 3910 × 10⁹/l). Concommitantly, there was a significant increment in their CD34⁺ cells (from 0.11 ± 0.01% to a peak of 0.18 ± 0.08%). There was a significant correlation between the rise in neutrophil count and that of the CD34⁺ cells ( r  = 0.795, P  = 0.019). Lithium therapy may be used to mobilize peripheral blood CD34⁺ cells for marrow transplantation.     

Apoptotic bone marrow CD34+ cells in cirrhotic patients

AIM: To access the frequency and level of apoptotic CD34+ cells isolated from the marrow fluid of patients with post-hepatitis cirrhosis. METHODS: The frequency of bone marrow CD34+ cells and apoptotic bone marrow CD34+ cells in 31 inpatients with post-hepatitis cirrhosis (cirrhosis group), and 15 out-patients without liver or blood disorders (control group) was calculated by flow cytometry. Parameters were collected to evaluate liver functions of patients in cirrhosis group. RESULTS: The percentage of norm...     

Increased expression of Fas (APO-1, CD95) on CD34+ haematopoietic progenitor cells after allogeneic bone marrow transplantation

Up-regulation of Fas/APO-1 (CD95) on haematopoietic progenitors and Fas-mediated apoptosis have been suggested to occur in a possible pathological mechanism in some bone marrow failure syndromes. We examined the expression of Fas antigen and susceptibility to Fas-mediated suppression of donor-derived haematopoietic cells of allogeneic bone marrow transplantation (BMT) recipients. Cytofluorometric analysis revealed low expression of Fas on CD34+ bone marrow cells from marrow donors or healthy controls. However, significantly higher expression of Fas antigen was observed on CD34+ bone marrow cells of BMT recipients, in whom engraftment of donor bone marrow (BM) cells was confirmed. The addition of an agonistic anti-Fas antibody (Ab) (CH-11) to haematopoietic stem cell culture of BM cells more strongly suppressed colony formation from granulocyte-macrophage colony-forming units (GM-CFU) and erythroid burst-forming units (BFU-E) after BMT. Pretreatment by blocking anti-Fas Ab (ZB4) abrogated the Fas-mediated GM-CFU and BFU-E suppression. Purified marrow CD34+ cells from BMT recipients were also susceptible to the Fas-mediated colony suppression. Thus, donor-derived CD34+ haematopoietic cells increased their expression of Fas antigen and were susceptible to Fas-mediated haematopoietic suppression. These findings provide new insight for understanding the haematological condition after BMT.