急性非淋巴细胞白血病免疫表型分析

本文对一组急性非淋巴细胞白血病（ＡＮＬＬ）检测免疫表型，分析了不同抗原的表达情况，并且对其中部分病例追踪观察化疗后的缓解情况。结果发现，本组ＡＮＬＬ化疗后不能达到完全缓解的有关因素，除多药耐药基因（ＭＤＲ１、ｍＲＮＡ）高度表达外，尚有ＣＤ３４抗原阳性表达、ＣＤ３３／ＣＤ１３＜１及同时表达多种髓系相关抗原。     

老年人急性髓细胞白血病P-糖蛋白表达的临床意义

目的探讨Ｐ－糖蛋白（Ｐ－ｇｌｙｃｏｐｒｏｔｅｉｎ，Ｐ－ｇｐ）在初治老年人急性髓细胞白血病（ＡＭＬ）中的表达特点及其预后意义。方法采用流式细胞术（ｆｌｏｗｃｙｔｏｍｅｔｒｙ，ＦＣＭ）及抗Ｐ－ｇｐ细胞膜外区域单克隆抗体ＵＩＣ２检测了３７例初治老年人ＡＭＬ白血病细胞Ｐ－ｇｐ表达。结果１６例（４３％）患者Ｐ－ｇｐ阳性（Ｐ－ｇｐ＋），Ｐ－ｇｐ与干细胞或祖细胞抗原ＣＤ３４表达显著相关，与其它免疫表型无关。在可评估疗效的３２例中，Ｐ－ｇｐ＋１５例中的４例（２７％）获得完全缓解（ＣＲ），缓解率显著低于Ｐ－ｇｐ阴性（Ｐ－ｇｐ－）１７例中的１１例（６５％）（Ｐ＜０．０５）。ＣＤ３４阳性（ＣＤ３４＋）１４例中ＣＲ３例（２１％），也显著低于ＣＤ３４阴性（ＣＤ３４－）者１８例中１２例（６７％）（Ｐ＜０．０５）。Ｐ－ｇｐ－及ＣＤ３４－１３例中１１例（８５％）获得ＣＲ。结论Ｐ－ｇｐ阳性及ＣＤ３４阳性是老年人ＡＭＬ预后差的重要指标     

P—糖蛋白表达在急性非淋巴细胞白血病中的意义

为探讨成人急性非淋巴细胞白血病（ＡＮＬＬ）Ｐ－糖蛋白（Ｐ－ｇｐ）表达及其与临床、生物学特征的关系，用单克隆抗体ＵＩＣ２及流式细胞术间接免疫荧光法对１６９例ＡＮＬＬ（初治１５２例，难治７例，缓解１０例）患者Ｐ－ｇｐ进行检测。结果显示：初治者Ｐ－ｇｐ表达率为２９％，明显低于难治者的７１％，而缓解者无Ｐ－ｇｐ表达。ＡＮＬＬ亚型中以杂合型急性白血病及急性单核细胞白血病表达较高，阳性率分别为６７％及４７％。Ｐ－ｇｐ表达与ＣＤ３４、ＣＤ７、ＣＤ１４或ＣＤ４２ｂ／ＣＤ６１高度相关。细胞遗传学研究显示：Ｐ－ｇｐ在染色体预后差组表达最高（５４％），而在预后好组表达低（７％）。Ｐ－ｇｐ＋ＡＮＬＬ的完全缓解率为２３％，明显低于Ｐ－ｇｐ－者的７６％。结果提示：Ｐ－ｇｐ表达是成人初治ＡＮＬＬ化疗耐药的指标，综合免疫分型及核型分析可以更准确地判断预后及指导治疗。     

CD_(34)在急性非淋巴细胞白血病中的表达意义初步分析

ＣＤ34 是造血干祖细胞的特征性表面标记 ,一般认为ＣＤ 34急性淋巴细胞白血病预后较好 ,而ＣＤ 34 在急性非淋巴细胞白血病 (ＡＮＬＬ)中的表达意义尚不明了 ,我们回顾分析了 12 6例ＡＮＬＬ和 6例急性混合细胞白血病 (ＡＭｉｘＬ)ＣＤ34 、ＣＤ7、Ｐ170的表达情况 ,对比分析ＣＤ 34 和ＣＤ-34 两组在初诊时血象、骨髓象、ＣＤ7、Ｐ170 表达的差异 ,分析了ＣＤ34 抗原在ＡＮＬＬ各亚型的分布及对治疗的反应。一、资料和方法1 病例 :男 80例 ,女 5 2例 ,年龄 11～ 82岁 ,中位年龄 37岁 ,其中ＡＮＬＬ 12 6例 ,ＡＭｉｘＬ 6例。所有患者均符…     

急性白血病MDR1与分化抗原关系及其临床意义

目的：探讨急性白血病ＭＤＲ１＾＋／ＣＤ３４＾＋表型的临床意义。方法：采用流式细胞仪及对碘硝基四唑盐（ＩＮＴ）细胞毒检测法,分析了５１例初治及１７例复发急性白血病患者细胞的表面分化抗原及ＭＤＲ１＾＋基因编码的ｐ１７０阳性率,并用ＩＮＴ法的体外药敏试验进行对照。结果：ＭＤＲ１＾＋与ＣＤ３４＾＋有显著相关性（ｒ＝０．８４２,Ｐ〈０．０１）,而与ＣＤ１３、ＣＤ１４、ＣＤ１５、ＣＤ３３、ＨＬＡ－ＤＲ等其它髓系抗原无关;ＭＤＲ１＾＋／ＣＤ３４＾＋表型细胞较ＭＤＲ１＾－／ＣＤ３４＾－表型细胞缓解率、生存期、缓解期显著缩短。结论：急性白血病ＭＤＲ１＾＋／ＣＤ３４＾＋表型可作为白血病预后不良的指标。     

自体外周血干细胞的动员和采集及其移植效果的研究

对２２例自体外周血干细胞移植（ＡＰＢＳＣＴ）的三种动员方案、采集方法及移植的外周血干细胞（ＰＢＳＣ）数量与造血重建关系，进行了研究。２２例中急性白血病１１例，多发性骨髓瘤６例，非何杰金淋巴瘤４例，晚期乳癌１例。三组动员方案：化疗十四氢叶酸＋氟美松；化疗＋ｒｈＧＭ－ＣＳＦ（重组人粒巨噬细胞集落刺激因子）＋氟美松；化疗＋ｒｈＧ－ＣＳＦ（重组人粒细胞集落刺激因子）＋氟美松。用流式细胞计双染直接免疫荧光法测定ｒｈＧ－ＣＳＦ方案组中７例ＣＤ３４＋／ＣＤ３３￣＋细胞。结果表明：（１）ｒｈＧ－ＣＳＦ方案组的ＰＢＳＣ产率最高，平均每例ＭＮＣ（单个核细胞）（８．２９±６．１４）×１０￣８／ｋｇ，ＣＦＵ－ＧＭ（粒单系祖细胞集落生成单位）（２１．３５±１７．２４）×１０￣４／ｋｇ。（２）ＣＤ３４＋细胞数与ＭＮＣ及ＣＦＵ－ＧＭ数大致相关。ＣＤ３４￣＋细胞在动员前外周血中多为０或＜０．５％，动员后约在用ｒｈＧ－ＣＳＦ后６～８天明显增多，就可连续每日采集，如达到≥５×１０￣５／ｋｇ即可停止。（３）采集与回输的ＰＢＳＣ数量是决定造血重建的关键。     

CD7阳性急性髓细胞白血病免疫表型及临床特点

随着系列单克隆抗体的应用，白血病细胞免疫分型的广泛开展及其研究的深入，伴有ＣＤ７抗原表达的急性髓细胞白血病（ＣＤ＋７ＡＭＬ）不断被发现。有学者认为ＣＤ＋７ＡＭＬ是一类独特的急性髓细胞白血病亚型，具有与不伴有ＣＤ７抗原表达的急性髓细胞白血病（ＣＤ－７Ａ...     

慢性髓细胞性白血病病程进展中调节蛋白c-Myc、Bcl-2及Fas的表达变化

目的了解细胞程序死亡（ＰＣＤ）与慢性髓细胞性白血病（ＣＭＬ）急变的关系。方法采用流式细胞术，测定２１例ＣＭＬ及１２例正常骨髓标本单个核细胞的髓系免疫表型及三种与ＰＣＤ有关的调节蛋白——ｃ－Ｍｙｃ、Ｂｃｌ－２、Ｆａｓ的表达。结果与未治慢性期比较，加速／急变期膜抗原最显著的变化是ＨＬＡ－ＤＲ＋％的提高，ＣＤ＋１５％／ＨＬＡ－ＤＲ＋％比值倒置。正常骨髓及ＣＭＬ各期ＨＬＡ－ＤＲ＋及ＨＬＡ－ＤＲ－细胞几乎均表达ｃ－Ｍｙｃ，差别只在于表达量的多少，未治慢性期与正常骨髓组相似，加速／急变期组不仅显著高于未治慢性期组，其ＨＬＡ－ＤＲ＋细胞群的ｃ－Ｍｙｃ表达量亦显著高于正常骨髓组。Ｂｃｌ－２＋％在未治慢性期低于正常骨髓，加速／急变期组显著提高。Ｆａｓ在ＣＭＬ各期及正常骨髓均为低表达。结论处于未治慢性期的中、晚幼粒细胞的大量聚集似乎与Ｂｃｌ－２、Ｆａｓ的ＰＣＤ调节作用无关；而在加速／急变期组尤其是造血祖细胞不仅有增殖过旺，亦存在ＰＣＤ受阻     

免疫学无法分型的急性白血病细胞表面标记动态分析

为探讨缺乏系限抗原表达急性白血病的细胞起源，采用碱性磷酸酶抗碱性磷酸酶免疫酶法（ＡＰＡＡＰ），分析了２５例免疫学无法分型的急性白血病化疗后或复发后细胞表面标记的动态变化。结果：７例单纯表达ＣＤ３８抗原者，其中２例化疗后、３例复发后表达了Ｔ细胞标记；４例单纯表达ＣＤ９抗原者，化疗后或复发后均表达了Ｂ细胞标记；６例单纯表达ＨＬＡ－ＤＲ抗原者，化疗或复发后各有２例表达了Ｂ细胞标记；４例表达ＣＤ３８和ＨＬＡ－ＤＲ抗原者，各有１例化疗或复发后分别表达了Ｂ或Ｔ细胞标记；其余４例无任何分化抗原表达者，化疗后各有１例分别表达了Ｔ和Ｂ细胞标记。细胞表面标记的变异反映了白血病细胞克隆的演化和进展，动态研究有助于白血病细胞起源的判断     

MDS患者白细胞介素2受体表达研究

本实验以２８例ＭＤＳ（ＲＡ１８例、ＲＡＥＢ和ＲＡＥＢ－Ｔ１０例）和１０例ＡＮＬＬ为研究对象，采用ＡＰＡＡＰ和ＥＬＩＳＡ法检测患者外周血单个核细胞（ＰＨＡ刺激前后）的ＭＩＬ－２Ｒ和培养血清中ＳＴＬ－ＩＲ，结果表明：经ＰＨＡ刺激培养４８ｈ后，ＭＤＳ和ＡＮＬＬ患者Ｔａｃ抗原阳性率明显低于正常人（Ｐ＜０．０１）ＲＡＥＢ和ＲＡＥＢ－ｔ组Ｔａｃ＋率比ＲＡ低，与ＡＮＬＬ差异无显著性（Ｐ＞０．０５）；血清中ＳＴＬ－２Ｒ在ＭＤＳ各亚型中均高于正常对照组（Ｐ＜０．０５），其中以ＲＡＥＢ及ＲＡＥＢ－ｔ为著。认为ＭＤＳ患者免疫反应及监视能减弱；ＳＴＲ－２Ｒ与ｍＩＬ－２Ｒ无相关；ＩＬ－２Ｒ表达异常可能与造血抑制有关。     

Proliferation and maturation effects of in-vivo granulocyte-macrophage colony stimulating factor in acute non-lymphocytic leukaemia.

BACKGROUND: Granulocyte-macrophage colony stimulating factor (GM-CSF) can affect the treatment of acute non-lymphocytic leukaemia (ANLL) by supporting normal haemopoiesis and by enhancing the proliferation and the maturation of leukaemic cells. METHODS: A human recombinant E. Coli synthesized GM-CSF was administered to 7 patients with ANLL at a dose of 5 or 10 micrograms/kg/day for 7 days, prior to antileukaemic treatment. Peripheral blood neutrophil and blast cell count was monitored daily. Changes in marrow blast cell morphologic features, mitotic index, and the reactivity to a panel of monoclonal antibodies were assessed after 3 and 7 days of treatment. RESULTS: Peripheral blood neutrophil and blast cell count increased in 6/7 cases. The mitotic index of marrow cells increased in 6/7 cases. A significant maturation occurred along the granulocytic line (2 cases) and the monocytic line (1 case). Mild to moderate eosinophilia developed in 3/7 cases. Early stem cell markers (CD 34 and HLA-DR) were not lost, or actually increased. Myelomonocytic markers (CD 33, CD 13, and CD 14) rose and fell. Expression of the multidrug resistance-associated 170 kd glycoprotein remained stable. CONCLUSIONS: These data showed that in vivo GM-CSF more consistently enhanced the proliferation than the maturation of leukaemic cells.     

Immunological definition of acute promyelocytic leukemia (FAB M3): a study of 39 cases

Acute promyelocytic leukemia (FAB-M3) is a distinct entity among acute non-lymphoid leukemias (ANLL) with peculiar morphological, biological, clinical and prognostic features. An atypical form of M3 (M3v) could be confused with other FAB ANLL and therefore the diagnosis of this variant requires ultrastructural analysis and/or cytogenetic study and/or selective gene rearrangement studies. The immunological phenotype of blast cells in 39 APL patients was studied at diagnosis. The diagnosis of M3 FAB type was ascertained in 32 and the diagnosis of M3v in 7 cases. Using a large series of monoclonal antibodies (mAb), the APL blast cells were B and T cell antigens-negative, HLA-DR constantly negative, CD13- and/or CD33-positive, CD9-positive. Among ANLL this phenotype seems to be closely related to APL both in M3 type and M3v subtype. Because the diagnosis of APL (M3 or M3v) is important in order to establish the specific therapeutic approach, the discriminant capacity of the immunological typing to identify M3 and mainly M3v (hypogranular) could be determinant for a "quick" diagnosis.     

Determination of peripheral blood stem cells by the Sysmex SE-9500.

The Sysmex SE-9500 automated haematology analyser provides an estimate of immature cells, referred to as 'haematopoietic progenitor cells' (HPC). The aim of this study was to evaluate the reliability and usefulness of the SE-9500 HPC parameter as compared with the CD34 + cell count and to determine whether the HPC count was of value in predicting the optimal harvesting time for peripheral blood stem cells (PBSC). Studies were performed on 112 samples from 21 patients with haematological malignancies and 13 healthy donors undergoing progenitor cell mobilisation. Coefficients of variation for the HPC count were 30%, 23.8%, 12.4% and 8.3% respectively for samples with low (4 x 106/l), medium (13 x 106/l), high (250 x 106/l) and very high (2413 x 106/l) counts. There was good linearity for HPC measurement in both peripheral blood (PB) and purified CD34 + cell suspensions (r > 0.995), and no detectable carryover was observed. There was an acceptable correlation between HPC and CD34 + cell counts for PB samples (r=0.669) and for CD34 + cell suspensions (r=0.859). Analysis of purified CD34 + cells using the SE-9500 HPC mode revealed that they appear both in the blast cell area and the immature granulocyte area of the analyser cell display. Quantitation of CD34 + cells and HPC during PBSC mobilisation showed good agreement between these parameters with regard to the optimal time for PBSC harvesting. These findings suggest that HPC counting with the Sysmex SE-9500 may be clinically useful for optimising the timing of PBSC collection.     

CD34-positive cell selection by immunomagnetic beads and chymopapain.

BACKGROUND. Pluripotent hemopoietic stem cells, progenitors of all hemolymphopoietic lineages, and clonogenic cells from many patients with acute nonlymphocytic leukemia (ANLL) and chronic myeloid leukemia (CML) express the CD34 antigen on their surface. Isolation of these cell populations is of primary experimental and clinical importance. METHODS. Six bone marrow (BM) and 10 peripheral blood (PB) samples were obtained from 2 normal individuals, 3 patients with CML and 9 with ANLL. The CD34+ cell fraction was isolated using MY10 antibody, sheep anti-mouse immunomagnetic beads and the enzyme chymopapain. Indirect immunofluorescence and semisolid culture were employed to evaluate the percentage of CD34+ cells and that of clonogenic cells in each cell fraction. RESULTS. The frequency of CD34+ cells in the original unseparated populations was (mean +/- SE) 24.3 +/- 7.3%, and reached 85.0 +/- 2.7% in the isolated CD34-positive fractions; in the negative fractions it was only 2.7 +/- 1.7%. According to these results, the great majority of clonogenic cells was separated in the CD34-positive fractions and depleted in those CD34-negative. Moreover, chymopapain was shown to be non-toxic to the clonogenic cells. CONCLUSIONS. Positive immunoselection using My10 Ab, immunomagnetic beads and chymopapain is a method for isolating almost pure progenitors from the BM and PB of normal individuals and patients with myeloid leukemias.     

Infant leukemia: an analysis of nine Chinese patients

A study was made of the cellular and molecular characteristics of nine Chinese infants, consecutively presenting with acute leukemia. Five cases were acute lymphoblastic leukemia (ALL); four were acute nonlymphoblastic leukemia (ANLL). Hyperleukocytosis, hepatosplenomegaly, and poor response to conventional therapy were common features, and CNS involvement was detected at diagnosis in three cases. The blast cells from all five cases with ALL expressed early B-cell markers, i.e., HLA-DR+, CD19+, but CD10-. Terminal deoxynucleotidyl transferase (TdT) was present in blasts from four of the five cases and periodic acid-Schiff staining in blasts from two patients only. The leukemic cells of one patient also showed positive nonspecific esterase activity and expressed myeloid-associated antigens CD33 (My9), CD11 (OkM1), and CD14 (My4 and Mo2). Molecular analysis of leukemic cell DNA from this and two other patients showed rearrangement of the immunoglobulin (Ig) heavy-chain genes, but without any evidence of kappa light-chain gene rearrangement. T-cell receptor (TCR) genes remained in the germline configuration in these cases. Cytogenetic analysis showed translocation t(4;11) (q21;q23) in all four cases studied. In the group of ANLL, three cases belonged to the M4 and one to the M2 subtype. Chromosomal abnormality involving 11q23 was also detected in two patients: t(11;17)(q23;q11) and del(11)(q14q23) in each case respectively. Neither Ig nor TCR gene rearrangement was present in blast cells from patients with ANLL. The data indicate that chromosomal rearrangement of band 11q23 was quite common in Chinese infants with either form of leukemia, a finding that may have pathogenetic implications.     

Clinical significance of multidrug resistance P-glycoprotein expression on acute nonlymphoblastic leukemia cells at diagnosis.

To evaluate the clinical value of the expression of multidrug resistance P-glycoprotein (P-170) on the surface of acute nonlymphoblastic leukemia (ANLL) cells, we analyzed specimens from 150 newly diagnosed patients for staining with MRK16, a monoclonal antibody (MoAb) that binds to an external epitope of P-170. Other surface markers (CD13, CD14, CD15, and CD34) were studied by the same technique. A marker was considered positive when 20% or more cells were stained. Of 150 samples, 71 were P-170-positive. These cases did not differ from P-170-negative cases with regard to age, sex, initial white blood cell (WBC) counts, or French-American-British (FAB) type (except for M3 ANLL, which were more frequently negative). However, leukemias arising from previous myelodysplastic syndrome (MDS) and therapy-induced leukemias were more frequently P-170-positive. CD34 and P-170 expression were significantly associated. All patients were treated by intensive chemotherapy. Complete remission (CR) rates were significantly lower in P-170-positive (23/71, 32%) than in P-170-negative cases (64/79, 81%) (P less than 10(-5)). CD34 positivity was also associated with a low remission rate (P less than 10(-5)). Survival was shorter for P-170- and CD34-positive patients (P less than 10(-5)). The prognostic value of both markers was confirmed in multivariate analysis. CR duration was also shorter for P-170-positive cases, but the difference is less significant (P = .05). It is concluded that P-170 analysis may be an important tool for predicting the outcome of intensive chemotherapy in ANLL patients.     

Distinctive expression of myelomonocytic markers and down-regulation of CD34 in acute myelogenous leukaemia with FLT3 tandem duplication and nucleophosmin mutation

OBJECTIVE: Patients with acute myelogenous leukaemia (AML) show co-existing frequently internal tandem duplications of FLT3 (FLT3-ITD) and mutations of nucleophosmin (NPM1-Mt). We investigated the biological and clinical significance of FLT3-ITD and/or NPM1-Mt in this context. METHODS: We analysed 89 AML patients according to whether NPM1 and FLT3-ITD were single mutants, double mutants, or wild type for both. RESULTS: FLT3-ITD was detected in 19 of 89 patients (21.3%), while NPM1-Mt was detected in 19 of 89 patients (21.3%); eight of 89 patients (9.0%) carried both FLT3-ITD and NPM1-Mt. By multivariate analysis, white blood cell count and peripheral blood blast cell count at diagnosis were significantly higher in patients with FLT3-ITD but not in those with only NPM1-Mt. NPM1-Mt was significantly related to female gender, normal karyotype, and M4 or M5 disease according to French-American-British criteria. In addition, leukaemic blast cells with NPM1-Mt, FLT3-ITD, or both expressed CD34 less frequently than wild-type blasts (P < 0.0001 and P = 0.005 respectively), while myelomonocytic markers such as CD11b and CD14 were expressed more frequently in patients with NPM1-Mt. CONCLUSION: FLT3-ITD may increase potential for cell proliferation to produce a leukaemic population; NPM1-Mt may cause cells to develop along the myelomonocytic lineage. Extensive analyses and detailed experiments will be required to clarify how NPM1 and FLT3 mutations interact in leukaemogenesis.     

Modulation of leukaemia blast colony growth by steroid hormones

The effect of steroid hormones on in vitro colony growth of human myelogenous leukaemia cells was examined. β-Oestradiol, testosterone and 5-β-dihydrotesterone had little effect on HL60 promyelocytic leukaemia cells or blast colony forming cells (CFC) from eight patients with acute non-lymphocytic leukaemia (ANLL). These compounds inhibited blast colony growth at very high concentrations (10⁻⁶-10⁻⁴ M). In contrast, hydrocortisone (HC) had highly variable effects on blast colony growth. HL60 cells were resistant to HC at concentrations up to 10⁻⁴ M but blast CFC showed a wide range of response. Some patients were resistant to HC at all concentrations tested, while others were inhibited by concentrations as low as 10⁻⁸ M. The inhibitory effect of HC was also observed on ³H-TdR incorporation by stimulated peripheral blood blasts. Inhibition by HC was not blocked by progesterone, suggesting this effect was not mediated by specific hormone receptors. These data indicate differences in the response of blast cells in ANLL and normal progenitors to steroid hormones. Cells from patients with ANLL display variable inhibition by HC which is probably not mediated by specific receptors.     

Predictive factors for long-term engraftment of autologous blood stem cells

Data from 170 consecutive patients aged 19-66 years (median age 46 years) who underwent unmanipulated autologous blood stem cell transplant (ASCT) were analyzed to determine if total CD34+ cells/kg infused, CD34+ subsets (CD34+41+, CD34+90+, CD34+33-, CD34+38-, CD34+38-DR-), peripheral blood CD34+ cell (PBCD34+) count on first apheresis day, or various clinical factors were associated with low blood counts 6 months post ASCT. Thirty-four patients were excluded from analysis either because of death (n = 17) or re-induction chemotherapy prior to 6 months post ASCT (n = 13), or because of lack of follow-up data (n = 4). Of the remaining 136 patients, 46% had low WBC ( < 4 x 10(9)/l), 41% low platelets (<150 x 10(9)/l), and 34% low hemoglobin ( < 120 g/l) at a median of 6 months following ASCT. By Spearman's rank correlation, both the total CD34+ cell dose/kg and the PBCD34+ count correlated with 6 month blood counts better than any subset of CD34+ cells or any clinical factor. The PBCD34+ count was overall a stronger predictor of 6 month blood counts than was the total CD34+ cells/kg infused. Both factors retained their significance in multivariate analysis, controlling for clinical factors. In conclusion, subsets of CD34+ cells and clinical factors are inferior to the total CD34+ cell dose/kg and PBCD34+ count in predicting 6 month blood counts following ASCT.     

Determination of peripheral blood stem cells by the Sysmex SE‐9500

The Sysmex SE‐9500 automated haematology analyser provides an estimate of immature cells, referred to as ‘haematopoietic progenitor cells’ (HPC). The aim of this study was to evaluate the reliability and usefulness of the SE‐9500 HPC parameter as compared with the CD34 + cell count and to determine whether the HPC count was of value in predicting the optimal harvesting time for peripheral blood stem cells (PBSC). Studies were performed on 112 samples from 21 patients with haematological malignancies and 13 healthy donors undergoing progenitor cell mobilisation. Coefficients of variation for the HPC count were 30%, 23.8%, 12.4% and 8.3% respectively for samples with low (4 × 10⁶/l), medium (13 × 10⁶/l), high (250 × 10⁶/l) and very high (2413 × 10⁶/l) counts. There was good linearity for HPC measurement in both peripheral blood (PB) and purified CD34 + cell suspensions (r > 0.995), and no detectable carryover was observed. There was an acceptable correlation between HPC and CD34 + cell counts for PB samples (r=0.669) and for CD34 + cell suspensions (r=0.859). Analysis of purified CD34 + cells using the SE‐9500 HPC mode revealed that they appear both in the blast cell area and the immature granulocyte area of the analyser cell display. Quantitation of CD34 + cells and HPC during PBSC mobilisation showed good agreement between these parameters with regard to the optimal time for PBSC harvesting. These findings suggest that HPC counting with the Sysmex SE‐9500 may be clinically useful for optimising the timing of PBSC collection.