急性髓系白血病细胞诱导分化生成树突状细胞的研究

目的　将急性髓系白血病 (AML)原代细胞诱导成树突状细胞 (DC) ,并探索白血病免疫治疗的新途径。方法　分离初诊AML患者 12例和正常人 6例的骨髓单个核细胞 ,用重组人粒单核细胞集落刺激因子 (rhGM CSF) 10 0 0U /ml、重组人白细胞介素 4(rhIL 4) 50 0U/ml和肿瘤坏死因子α(TNF α) 50U/ml联合培养 10d ;经形态学 (Wright染色、倒置显微镜、透射电镜 ) ,免疫学 (CD80 、CD86 、CD83 、CD1a、HLA DR)鉴定 ,荧光原位杂交 (FISH)进行细胞遗传学分析 ,混合淋巴细胞反应检测功能。结果　细胞因子联合诱导后 ,呈现DC的典型形态 ,CD80 、CD86 、CD83 、CD1a的表达与对照组比较明显上调 (P <0 0 5) ,具有刺激T淋巴细胞增殖的能力。经FISH证实来源于白血病细胞的这类DC与正常DC在形态和免疫学表达方面相似 (P >0 0 5) ,但功能较弱。结论　在体外可成功的将AML原代细胞诱导分化成DC ,可望用于AML的免疫治疗     

米托蒽醌为主的化疗方案对CD34+高表达急性髓细胞性白血病疗效观察

目的：探索米托蒽醌(MTZ)在急性髓细胞性白血病(AML)化疗中的作用特点，提高AML的疗效和无病生存率(FDS)。方法：80例免疫分型中有CD34^ 抗原高表达的AML，随机选择(MA／MAE、DA／DAE和HA／HAE)方案，联合化疗1～2个疗程后分别比较CR率、骨髓抑制及其它毒副作用；同时对白血病细胞进行体外药物杀伤效应实验，分别比较MTZ、柔红霉素(DNR)、高三尖杉酯碱(HHT)对白血病细胞不同分化阶段的抑制作用。结果：CD34抗原高表达的AML中，1～2个疗程CR率，以MA／MAE方案最高。为80．0％(24／30)．白血病细胞体外药物杀伤实验显示，MTZ对CD34^ 高表达的AML的抑制显著高于DNR和HHT。结论：MTZ具有较强的抗AML活性，临床骨髓抑制明显上述特点可能与其主要作用于AML白血病细胞的分化较早阶段有关。     

Production of soluble CD34 by human myeloid cells

CD34, a glycophosphoprotein present in lymphohaematopoietic stem and progenitor cells, as well as in other cell types, exists in both transmembrane and intracytoplasmic forms. Transmembrane CD34 expression, which is high in the earliest haematopoietic precursors, decreases as cells mature. However, to our knowledge, there is no information on whether a decrease in transmembrane CD34 can also predict a release of the molecule from the cell membrane into the extracellular fluid. To investigate the above possibility, we studied conditions (incubation time, cell density and proliferative status) in human myeloid cells (lines KG-1a, KG-1 and cord blood-derived cells) that may cause a decrease in surface CD34 and the generation of a soluble form of the molecule. The latter, as demonstrated by Western blot analysis, adds more complexity to the proposed structural features and functional properties of CD34 in myeloid cells.     

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.     

The level of peripheral blood circulating CD34+ cells is higher in acute promyelocytic leukemia patients with adverse prognostic factors

Introduction: The increased flow cytometry enumeration of peripheral blood circulating CD34+ cells in patients with acute leukemia has been found in our previous work. In this study, we also demonstrated that acute promyelocytic leukemia (APL) patients not only had elevated CD34+ cell count, but also had some clinical features.

Methods: Fifty APL patients and 19 healthy volunteers were included in the study. The enumeration of circulating CD34+ cells, cytogenetic subgroup, immunophenotype analysis, and leukemic-related gene mutation detection were performed.

Results: Some APL patients with higher count of CD34+ cells (≤10 × 10⁶/l) usually possessed one or more poor prognostic factors (higher WBCs count, PML/RARa gene complex fusion, chemotherapy-related APL, normal karyotype/complex karyotype abnormalities, CD56/CD34 antigen positive expression, FLT3-ITD positive mutation, myelofibrosis, and marrow necrosis). A cut-off value of 10 × 10⁶/l CD34+ cells may have the power to distinguish APL patients with above adverse clinical prognostic factor from other APL subjects.

Conclusion: The circulating CD34+ cell count appears to increase in some APL patients and a higher CD34+ cell count may be indicative of inferior survival and serve as an adverse biomarker for APL.     

WT1基因及CD34在急性白血病中的表达及意义

目的研究WT1基因与CD34在急性白血病（AL）中表达的相关性及其临床意义。方法采用实时定量RT-PCR方法检测92例初治AL患者骨髓细胞WT1基因的表达,同时应用流式细胞仪测定骨髓细胞CD34的表达。结果初治AL患者WT1基因、CD34表达的阳性率分别为67．4％（62／92）、44．6％（41／92）,WT1基因、CD34阳性表达者的缓解率显著低于阴性表达者（P〈0．01）;WT1基因与CD34表达呈正相关（rn=0．5304,χ^z=25．88,P〈0．05）;WT1^＋CD34^＋、WT1^＋CD34、WT1-CD34^-AL患者第一次缓解率比较有统计学差异（P〈0．01）。结论WT1基因、CD34在AL患者骨髓细胞中的表达呈正相关,且阳性表达者的缓解率低、疗效差、预后不良。     

急性髓细胞白血病细胞诱导分化成为树突状细胞的实验研究

目的 :探讨急性髓细胞白血病 (AML)患者的白血病细胞体外是否可诱导分化成为树突状细胞(DC)。方法 :从 11例AML患者的骨髓或外周血中获取非贴壁细胞 ,利用细胞因子 (rhGM CSF、rhIL 4、rhTNF α)联合培养 ,每 12d收获细胞。培养前后分别用倒置显微镜、电镜观察细胞形态 ,用流式细胞术测定细胞表面标志 ,用MTT法检测收获细胞激发混合淋巴细胞反应的能力。结果 :8例AML标本分化成为具有典型树突状形态的细胞 ,培养后的白血病细胞的HLA DR、CD86、CD1a表达较培养前明显增高 ,差异有统计学意义 (P <0 .0 1)。在混合淋巴细胞反应中 ,DC具有强烈激发同种T淋巴细胞增殖的能力 ,且随数量增加而作用增强。M4/M5型AML DC的表面标志的表达率明显高于非M4/M5型AML DC(P <0 .0 1)。结论 :急性髓细胞白血病细胞可以诱导分化成为具有DC形态、表型、功能的细胞。     

慢性髓系白血病病期演变时CD_(34)抗原表达及其临床意义

目的　检测 CD34抗原在慢性髓系白血病 (CML)不同病期中的表达 ,并探讨其与临床化疗疗效及预后的关系。方法　采用流式细胞术检测 CML患者外周血和 (或 )骨髓单个核细胞(MNC) CD34抗原及 P1 70 糖蛋白的表达。结果　 CML慢性期、加速期、急变期外周血 MNC CD34抗原阳性率比较差异有非常显著性 (P <0 .0 0 1) ,随着治疗的有效 CD34阳性率下降 ;P1 70 阴性组与 P1 70 阳性组 CD34阳性率比较差异有非常显著性 (P <0 .0 1) ,治疗有效率比较差异有差异性 (P <0 .0 5 )。结论　CML慢性期患者 CD34抗原表达与临床疗效呈负相关 ,对预测患者进入急变期有一定临床意义 ;CML病期演变时 CD34阳性白血病细胞 P1 70 的高水平表达可能是其对化疗药物具有耐药性的原因之一     

Generation and functional characterization of human dendritic cells derived from CD34+ cells mobilized into peripheral blood: comparison with bone marrow CD34+ cells

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells (APC), specializing in capturing antigens and stimulating T-cell-dependent immunity. In this study we report the generation and characterization of functional DCs derived from both steady-state bone marrow (BM) and circulating haemopoietic CD34⁺ cells from 14 individuals undergoing granulocyte colony-stimulating factor (G-CSF) treatment for peripheral blood stem cells (PBSC) mobilization and transplantation. Clonogenic assays in methylcellulose showed an increased frequency and proliferation of colony-forming unit-dendritic cells (CFU-DC) in circulating CD34⁺ cells, compared to that of BM CD34⁺ precursors in response to GM-CSF and TNF-α with or without SCF and FLT-3L. Moreover, peripheral blood (PB) CD34⁺ cells generated a significantly higher number of fully functional DCs, as determined by conventional mixed lymphocyte reactions (MLR), than their BM counterparts upon different culture conditions. DCs derived from mobilized stem cells were also capable of processing and presenting soluble antigens to autologous T cells for both primary and secondary immune response. Replacement of the early-acting growth factors SCF and FLT-3L with IL-4 at day 7 of culture of PB CD34⁺ cells enhanced both the percentage of total CD1a⁺ cells and CD1a⁺CD14^? cells and the yield of DCs after 14 d of incubation. In addition, the alloreactivity of IL-4-stimulated DCs was significantly higher than those generated in the absence of IL-4. Furthermore, autologous serum collected during G-CSF treatment was more efficient than fetal calf serum (FCS) or two different serum-free media for large-scale production of DCs. Thus, our comparative studies indicate that G-CSF mobilizes CD34⁺ DC precursors into PB and circulating CD34⁺ cells represent the optimal source for the massive generation of DCs. The sequential use of early-acting and intermediate-late-acting colony-stimulating factors (CSFs) as well as the use of autologous serum greatly enhanced the growth of DCs. These data may provide new insights for manipulating immunocompetent cells for cancer therapy.     

Impaired generation of bone marrow CD34-derived dendritic cells with low peripheral blood subsets in patients with myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a stem cell disorder characterized by ineffective haematopoiesis and blood cytopenias. The present study investigated the potential of bone marrow CD34(+) progenitors in MDS patients to proliferate and differentiate into dendritic cells (DCs) in a cytokine-supplemented liquid culture system and analysed the status of blood DC subsets in these patients. CD34(+) progenitors had low potential to generate DCs in vitro, as the number of DCs obtained from one CD34(+) cell was significantly lower compared with controls (median value 0.2 vs. 4, P = 0.003). In patients, the survival and proliferation of CD34(+) cells in culture was not correlated to the degree of apoptosis. Phenotypically and functionally CD34(+)-derived DCs were similar in MDS patients and normal subjects. The percentage of both circulating DC subsets in patients was extremely diminished compared with controls (myeloid DC: 0.10 +/- 0.10% vs. 0.35 +/- 0.13%, P < 0.001; plasmacytoid DC: 0.11 +/- 0.10% vs. 0.37 +/- 0.14%, P < 0.001). In cases with the 5q deletion both CD34-derived DCs and blood DCs harboured the cytogenetic abnormality. Our results indicate that, in MDS, the production of DCs is affected by the neoplastic process resulting in ineffective 'dendritopoiesis' with low blood DC precursor numbers. This quantitative DC defect probably contributes to the poor immune response against infectious agents and to the escape of the malignant clone from immune recognition with disease progression towards acute leukaemia.     

不同来源的CD34^＋细胞归巢相关分子的表达

目的 研究不同来源CD34^＋细胞归巢相关分子（HRM）的表达情况。方法采用免疫磁珠法（MACS）分选不同来源的CD34^＋细胞，免疫荧光标记流式细胞仪测定HRM的表达。结果骨髓（BM）、动员后的外周血（mPB）及脐血（UCB）来源的CD34^＋细胞均高表达细胞黏附分子CD49d、CD49e、CD54、CD11a、CD62L、CD44、CD31。UCB来源的CD34^＋细胞表面表达的细胞黏附分子中，CD49e表达显著低于BM和mPB来源的CD34^＋细胞（P〈0．05），CD54表达显著低于mPB来源者（P〈0．05），CXCR4表达显著低于BM来源者（P〈0．05）。结论UCB来源的造血干／祖细胞归巢能力低可能是UCB移植造血重建延迟的原因之一。     

CD34~+ CD38~-细胞对异基因造血干细胞移植的影响研究

目的观察CD34+CD38-细胞对异基因造血干细胞移植术后造血重建和移植物抗宿主病(GVHD)的影响。方法分析2004年1月至2009年12月河南省人民医院血液科全相合异基因外周血干细胞造血干细胞移植78例,CD34+、CD34+CD38-细胞输入量与血缘全相合异基因外周血造血干细胞移植术后造血重建及GVHD发生率间的相关性。结果粒细胞、血小板恢复时间与CD34+CD38-细胞输入量呈负相关(r分别为-0.521、-0.448,P<0.01),与CD34+细胞输入量也呈负相关(r分别为-0.405、-0.371,P<0.05)。急性GVHD、慢性GVHD的发生与CD34+、CD34+CD38-、CD3+、CD4+、CD8+细胞输入量无相关性。结论输入高数量的CD34+CD38-细胞有利于移植术后的粒细胞、血小板快速恢复;对于预测术后造血恢复,CD34+CD38-细胞亚群输入量可能优于CD34+细胞总数。     

对过继免疫治疗中外周血单个核细胞采集术的探讨

目的观察细胞表面分化抗原CD117在急性髓细胞白血病(AML)与急性淋巴细胞白血病(ALL)的表达差异及其意义,评价其作为髓系抗原的特异性。方法采用CD45/SSC双参数散点图设门法进行三色流式细胞术分析。直接免疫荧光标记法标记20种细胞表面分化抗原,经流式细胞仪测定,对286例白血病患者骨髓或外周血白血病细胞CD117及其他表面抗原的表达结果进行分析。结果CD117在ALL中表达率极低,仅占2%,在AML中表达率为56.9%,2者差异有统计学意义(P<0.05)。在AML各型中,CD117在M3亚型中的表达率最低,为23.1%。本组数据统计结果显示CD117的髓系特异度为0.98(SE=0.014),髓系敏感度为0.57(SE=0.04),统计结果表明CD117比CD13、CD33更具髓系特异性(P<0.05)。结论与CD13和CD33相比较,CD117在作为髓系标记的敏感度不如前两者高,但它更具有髓系特异度,因而可作为排除ALL及辅助诊断AML的标志。     

Increased generation of pre-plasmacytoid dendritic cells in bone marrow of rheumatoid arthritis

Abstract

Objective. Plasmacytoid dendritic cells (pDCs) have been found to be accumulated in synovial tissues in rheumatoid arthritis (RA). Since pDCs originate from bone marrow (BM), we explored the differentiation of pDC in BM in RA and osteoarthritis (OA).

Methods. BM mononuclear cells (BMMNCs) of the posterior ileac crest from 25 RA patients and 22 OA patients were examined for the expression of BDCA2 and CD34 by flow cytometry. The degree of synovial proliferation was assessed on light microscopy in 10 of 25 RA patients.

Results. There were no significant differences in percentages of CD34 + cells or BDCA2 + cells within BMMNC between RA and OA. However, RA BMMNC contained higher percentages of BDCA2 + CD34 + cells (pre-pDCs) than OA BMMNCs. Accordingly, percentages of BDCA2 + CD34+ cells within BM CD34 + cells were significantly higher in RA than in OA. Finally, the percentages of BDCA2 + CD34+ cells within BM CD34 + cells were significantly correlated with the degree of synovial proliferation in RA.

Conclusion. These results indicate that the generation of pre-pDC from BM CD34 + cells is increased in RA compared with OA. Moreover, the data suggest that the increased output of pDC from BM might be involved in the synovial proliferation in RA.     

Cytokine mediated expansion of human umbilical cord blood CD34+ cells: comparison of the use of partially purified and pure CD34+ target cells

To determine the optimal cell population for cytokine mediated expansion, we compared the use of Magnetic Cell Sorting (MACS) system enriched CD34+ human umbilical cord blood (HUCB) cells with that of MACS enriched, flow purified CD34+ HUCB cells. Both MACS enriched CD34+ cells and MACS enriched, flow purified CD34+ cells (mean starting purity of CD34+ SC 51.27 ± 7.6% and 96.36 ± 1.34% respectively n = 6) were incubated for seven days with Interleukin-1 (IL-1)+IL-3+Stem Cell Factor (SCF) and showed a fold increase in the number of nucleated cells (10.02 ± 2.6 and 18.23 ± 4.73 respectively) and a reduction in the percentage of CD34+ cells (5.55 ± 1.23% and 12.21 ± 3.29% respectively). An increase in the absolute numbers of CD34+ cells (4.8 × 10⁴ ± 2.3 × 10⁴) was observed with MACS enriched CD34+ cells as compared to no change (1.3 × 10⁵ ± 8.8 × 10⁴) with MACS enriched, flow purified CD34+ cells. An increase in IL-3+GM-CSF+SCF responsive colony forming unit (CFU) (1.7 × 10⁴ ± 9.4 × 10³ and 1.6 × 10⁵ ± 7.7 × 10⁴ respectively) was also observed as compared with input values (1.5 × 10⁴ ± 1 × 10⁴ and 2.3 × 10⁴ ± 8.9 × 10³ respectively). We conclude that MACS enriched, flow sorted CD34+ HUCB cells have greater cytokine mediated expansion potential as measured by progenitor expansion, than MACS enriched CD34+ HUCB cells.     

In vitro differentiation of natural killer T cells from human cord blood CD34+ cells

Natural killer T (NKT) cells are involved in innate immune defence and also in the regulation of adaptive immune responses. However, the development of NKT cells in vitro has not been fully characterized and culture conditions have not been fully optimized. In the present study, we found that an NKT cell fraction developed during the in vitro culture of cord blood (CB) CD34+ cells, and this was subsequently characterized both phenotypically and morphologically. CD34+ cells purified from 10 human CB were cultured in the presence of several cytokines and analysed by flow cytometry, light microscopy and electron microscopy. The NKT cell fraction, defined phenotypically (CD3+CD16+CD56+CD94+) as expressing the invariant T-cell receptor Valpha24 and Vbeta11, appeared in the CD56hi fractions. Intracytoplasmic staining demonstrated that interferon-gamma and interleukin 4 (IL-4) were detected in the CD56hi fractions. IL-15 was essential and, in combination with either flt3-ligand (FL) or stem cell factor (SCF), was sufficient to induce the development of NKT cells. The phenotype of the NKT cell fraction was CD45RO+CD45RA- and CD4+CD8alpha+. Morphologically, they were very large, with either round or oval nuclei, moderately condensed chromatins, voluminous weakly basophilic cytoplasm and various cytoplasmic granules such as dense core granules, multivesicular bodies, and intermediate form granules. When CD34+ cells purified from bone marrow (BM) were compared with those from CB, the latter were consistently more efficient at generating CD56hi NKT cell fractions. In conclusion, IL-15 in combination with FL and/or SCF can induce the differentiation of NKT cells from human CB CD34+ cells.     

Correlation between CD34 expression and chromosomal abnormalities but not clinical outcome in acute myeloid leukemia

The hemopoletic stem cell marker CD34 has been reported to be a useful predictor of treatment outcome in acute myeloid leukemia (AML). Previous data suggested that CD34 expression may be associated with other poor prognosis factors in AML such as undifferentiated leukemia, secondary AML (SAML), and clonal abnormalities involving chromosome 5 and 7. In order to analyze the correlations between the clinicopathologic features, cytogenetic and CD34 expression in AML, we retrospectively investigated 99 patients with newly diagnosed AML: 85 with de novo disease and 14 with secondary AML (SAML). Eighty-six patients who received the same induction chemotherapy were available for clinical outcome. Defining a case as positive when ≥ 20% of bone marrow cells collected at diagnosis expressed the CD34 antigen, forty-five patients were included in the CD34 positive group. Ninety patients had adequate cytogenetic analysis. Thirty-two patients (72%) with CD34 positive AML exhibited an abnormal karyotype whereas 15 patients (28%) with CD34 negative AML had abnormal metaphases (P < 0.01). Monosomy 7/7q- or monosomy 5/5q- occurred in 10 patients and 8 of them expressed the CD34 antigen (P < 0.05). All patients with t(8;21) which is considered as a favorable factor in AML had levels of CD34 ≥ 20% (P < 0.05). We did not find any association between CD34 expression and attainment of complete remission, overall survival, or disease-free survival. In conclusion, the variations of CD34 expression in AML are correlated with cytogenetic abnormalities associated both with poor and favorable outcome. The evaluation of the correlations between CD34 antigen and clinical outcome in AML should take into account the results of pretreatment karyotype. © 1996 Wiley-Liss, Inc.     

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...     

Characteristics of haemopoietic progenitor cells related to CD34 epitope class expression

Haemopoietic progenitor cells (HPCs) express the CD34 molecule, a heavily glycosylated transmembrane protein displaying three main classes of epitopes. The CD34 epitope class expression may vary between different subsets of HPCs. The aim of this study was to characterise the subsets of HPCs expressing CD34 class II and III epitopes. The cells were studied for coexpression of activation-, lineage- and adhesion-associated molecules, and their clonogenic ability and morphological features were examined. CD34+ HPCs expressing class III epitopes outnumbered those expressing class II. Class III expressing HPCs were enriched for CFU-GM and BFU-E and cells coexpressing CD13, CD33, c-kit and CD71 compared to class II expressing HPCs. CD34+ cells exclusively expressing class III epitopes uniformly displayed CD13 and CD33; they had a high clonogenic capacity and morphological characteristics of promyelocytes and myelocytes. The data show that class III epitopes are distributed more broadly on CD34+ HPCs than are class II epitopes, and that lack of class II epitopes is confined to CD34+ HPCs at a late stage of myeloid differentiation. The higher number of class III expressing HPCs coexpressing c-kit and CD71 suggests that these cells exhibit a higher proliferative or differential potential than do HPCs expressing class II epitopes.     

Characterization and phenotypic analysis of differentiating CD34+human bone marrow cells in liquid culture

Abstract: Our current understanding of human haematopoietic stem cell biology is based in part on the characterization of human CD34⁺ bone marrow cell differentiation in vitro. CD34 is highly expressed on early stem cells and haematopoietic progenitor cells with clonogenic potential and is gradually lost during differentiation and commitment. However, CD71 (transferrin receptor) is expressed at low levels on early stem cells and generally increases during haematopoietic progenitor cell proliferation. We reasoned that the combination of these surface markers would provide a useful framework for the simultaneous analysis of multiple lineage differentiation of CD34⁺ haematopoietic progenitor cells in liquid culture. In this report, we identify the phenotype of distinct subpopulations of myeloid, erythroid and lymphoid cells in liquid suspension culture using differential expression of CD34 vs. CD71 in combination with specific lineage markers. Freshly isolated human CD34⁺ bone marrow cells were introduced into suspension culture and monitored over a 6-d period using 3-colour flow cytometry. This is the first demonstration that differential expression of CD34 vs. CD71 can be used to simultaneously monitor differentiation of multiple haematopoietic cell lineages in liquid suspension culture, facilitating the study of cytokine-, drug- or chemical-induced alterations in haematopoietic progenitor cell differentiation in vitro.