Peripheral blood progenitor cell transplantation in lymphoma and leukemia using a single apheresis

Myeloablative treatment and peripheral blood progenitor cell (PBPC) transplantation are increasingly used for lymphomas and leukemias. We have sought to optimize conditions for priming, collection, and engraftment of the leukapheresis product. Fifty-four consecutive adult patients were eligible, 31 with high-grade non-Hodgkin's lymphoma of poor prognosis, 12 with Hodgkin's disease in chemosensitive relapse, and 11 with poor prognosis acute lymphoblastic leukemia. Filgrastim was administered after routine chemotherapy with VAPEC-B or HiCCOM to mobilize PBPC. A rapidly increasing white blood cell count was used to predict the time of peak PBPC release and plan leukapheresis. Forty- five patients underwent leukapheresis. A median of 14 L of blood was processed at a single apheresis. A median of 2.4 x 10(8)/kg mononuclear cells (MNCs), 1.04 x 10(6)/kg granulocyte-macrophage colony-forming cells (GM-CFCs), and 10.6 x 10(6)/kg CD34+ cells were obtained. Slightly fewer MNCs were obtained from the heavily pretreated Hodgkin's disease group. There were no other significant differences in the size or composition of the leukapheresis harvest in the three patient groups. Forty patients underwent high-dose therapy and PBPC transplantation. Filgrastim was administered by daily subcutaneous injection until the absolute neutrophil count was > or = 1 x 10(9)/L for 2 consecutive days. Rapid and sustained hematopoietic engraftment occurred in all patients. The median time to achieve a neutrophil count > or = 0.5 x 10(9)/L was 9 days (range, 8 to 16 days); to achieve a platelet count > or = 20 x 10(9)/L was 10 days (range, 6 to 88 days); and to achieve a platelet count > or = 50 x 10(9)/L was 15.5 days (range, 10 to 100 days). Neutrophil recovery was faster than that of a historical control group treated with autologous bone marrow transplantation and filgrastim, but platelet recovery times were halved in the PBPC group. There was no secondary engraftment failure. Requirements for blood and platelet transfusions, antibiotic use, and parenteral nutrition were similar in the three patient groups. The median number of days in the hospital was 13 (range, 10 to 55) in the PBPC patients, compared with 19 (range, 14 to 51) in the historical controls. Leukapheresis yields (MNC, GM-CFC, and CD34+ cell numbers) were not useful for predicting the times to engraftment. We have shown that sufficient PBPC for transplantation can be obtained at a single leukapheresis after mobilization with routine chemotherapy and filgrastim in patients with non-Hodgkin's lymphoma, Hodgkin's disease, and acute lymphoblastic leukemia, even those heavily pretreated.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cost-effectiveness of CD34+ dose in peripheral blood progenitor cell transplantation for non-Hodgkin's lymphoma patients: a single centre study

Intensive high-dose chemotherapy with peripheral blood progenitor cell (PBPC) transplantation is a common strategy for aggressive non-Hodgkin's lymphomas (NHL). A retrospective cost-effectiveness analysis of CD34+ cell dose was carried out. Between 1994 and 1998, 28 patients were included. Efficacy was measured by the length of aplasia. Data collection concerned the period from graft day until discharge from hospital, and the post-graft period until graft day +100. Patients transplanted using a cell dose greater than 5 x 106/kg were found to have a faster hematological recovery. Average length of post-graft hospitalization was shorter and fewer blood products were required for patients with more than 5 x 106/kg CD34+ cells transplanted. Hospitalization was the major cost driver. A large reduction in procedure cost was obtained with a CD34+ cell count higher than 5 x 106/kg (-US$2740, -11%). This difference was directly related to hospitalization (-US$860) and platelet units transfused (-US$1,340). A sensitivity analysis showed the robustness of results. Our findings indicated that a CD34+ cell dose higher than 5 x 106/kg was more cost-effective than a lower dose in NHL patients. The collection of 5 x 106/kg CD34+ cells appeared necessary to optimize the PBPC procedure.     

Transplantation of peripheral blood progenitor cells from HLA-identical sibling donors

Transplantation of peripheral blood progenitor cells (PBPCs) has largely replaced autologous bone marrow transplantation. The same might occur in the allogeneic setting if the favourable initial experience with allogeneic PBPCT is confirmed. We analysed all primary transplants utilizing unmodified PBPC from HLA-identical sibling donors reported to the European Group for Blood and Marrow Transplantation (EBMT) for 1994. 59 patients with a median age of 39 years received myeloablative therapy for acute myelogenous leukaemia (23 patients), acute lymphoblastic leukaemia (13), chronic myelogenous leukaemia (nine), lymphoma (seven), or other diagnoses (seven) mostly of advanced stages followed by transplantation of allogeneic PBPC. Three patients died soon after grafting, the others showed prompt haemopoietic recovery with median times to recover an absolute neutrophil count (ANC) above 0.5 and 1.0×10⁹/l of 15 (range 9–27) and 17 d (range 10–28) respectively. Time to platelet recovery above 20 or 50×10⁹/l was 16 (range 9–76) and 18 d (range 12–100) respectively. 27 patients (46%) developed no or mild acute graft-versus-host disease (GVHD). The incidence of moderate (grade II) disease was 27%; 24% of the patients developed severe acute GVHD (grades III or IV). 55% of patients who were alive 90 d after transplantation developed chronic GVHD, the probability to develop extensive chronic GVHD was 32% (95% confidence interval 22–42) with a median follow-up of 14 months. Overall and event-free survival (EFS) at 1 year were 54% (CI 48–60) and 50% (CI 43–57), respectively, the relapse incidence was 23% (CI 17–29). EFS was 67% (CI 55–79) in patients transplanted for acute leukaemias in first complete remission, chronic myelogenous leukaemia in first chronic phase, or severe aplastic anaemia. Transplantation of allogeneic PBPC resulted in prompt and durable engraftment. The incidence and severity of acute and chronic GVHD seemed comparable to that observed after allogeneic BMT. Overall and event-free survival in this cohort of patients, most of whom suffered from advanced leukaemia or lymphoma, is encouraging, suggesting that the high numbers of T lymphocytes and/or natural killer cells contained in a typical PBPC collection product exert a vigorous graft-versus-leukaemia effect. Further evaluation of allogeneic PBPCT is highly desirable.     

Peripheral blood progenitor cell (PBPC) transplantation with a single apheresis in patients with lymphoma,myeloma and solid tumors

Abstract: The aim of this study was to investigate if a single apheresis after peripheral blood progenitor cell (PBPC) mobilization can be used to rescue patients receiving high dose chemotherapy (HD.CHE) as treatment for an underlying malignancy. Eighteen consecutive patients who were admitted to the transplant unit for treatment were leukapheresed following mobilization with one of the following protocols: group I: rHuG–CSF alone, group II: conventional chemotherapy (C.CHE)+rHuG–CSF or rHuGM–CSF and group III: high dose Cytoxan (HD.CTX)+rHuG–CSF. The optimal day for leukapheresis was determined by following white blood cell counts (WBC), mononuclear cell counts (MNC) and CD34⁺ cell counts daily. Granulocyte – macrophage colony-forming cells (GM–CFC) assay was performed at the leukapheresis product and prior to reinfusion. All patients proceeded directly to ablative therapy according to their underlying malignancy. PBPC from single apheresis were reinfused to all patients and cytokines started 24 h after infusion. Hematologic recovery after HD.CHE was the parameter used to ensure successful engraftment. We have been able to recover adequate number of PBPC for transplantation with a single apheresis in all patients. The number of infused cells were for groups I, II and III: (1) median number of MNC 4.7, 3.58 and 2.79 × 10⁸/kg, respectively (2); median number of CD34⁺ cells 4.4, 2.8, 2.7 × 10⁶/kg, respectively. The median apheresis day was 6, 16 and 16, respectively. Recovery times to granulocyte count >0.5 × 10⁹/L was 9 d (range 9–12) and to platelets >20 × 10⁹/L was 12 d (range 1–135); 17/18 patients have engrafted successfully independent of the mobilization method used.These data suggest that sufficient PBPC can be harvested at a single leukapheresis for hemopoietic rescue after myeloablative therapy. Rapid hematologic recovery occurs when cytokines alone after conventional or HD.CHE are used for mobilization. Results of collection products and hematopoietic recovery are independent of the mobilization technique used.     

Characteristics of blood cells during peripheral blood stem cell mobilization following chemotherapy in patients with non-Hodgkin's lymphoma

The objective of our study was to obtain a predictor of the timing for peripheral blood stem cell (PBSC) collection using routine blood cell counts. For that purpose, we compared recovery kinetics of peripheral blood cells and CD34+ cells in non-Hodgkin's lymphoma patients who were given granulocyte-colony stimulating factor for PBSC collection after CHOP therapy. Peaks in the monocyte/WBC ratio and reticulocyte high fluorescence ratio (HFR) were observed 2 to 3 days prior to the peak CD34+ cell count. In addition, the appearance of immature granulocytes in peripheral blood correlated well with increases in CD34+ PBSC number. These findings suggested the peak monocyte/WBC ratio, HFR, and immature granulocyte count can be used as predictors of the timing for PBSC harvests.     

Ex vivo expansion of CD34-positive peripheral blood progenitor cells from patients with non-Hodgkin's lymphoma: no evidence of concomitant expansion of contaminating bcl2/JH-positive lymphoma cells

The aim of the present study was to evaluate the capacity to expand of hematopoietic stem cell (HSC) samples from eight patients with NHL, and to follow in parallel the fate of tumor cells in four of eight samples still containing bcl2/JH+ tumor cells after CD34+ or CD19-/20-/34+ cell selection. The presence of bcl2/JH+ cells was also investigated after expansion in four of eight samples, two of which were bcl2/JH at harvesting and two which were initially bcl2/JH+ but became bcl2/JH (below the level of PCR detection) after cell selection, to assess a possible reappearance of occult tumor cells after expansion culture. We used culture conditions that we previously had established to allow high level expansion of normal precursors, progenitors and LTC-ICs. In this study, particular attention was given to the role of Flt3-ligand, known to favor the growth of B cells. The expansion conditions were: 1.5 x 10(3) cells/ml in serum-free medium containing stem cell factor (SCF), interleukin-3 (IL-3), IL-6, granulocyte-stimulating factor (G-CSF), erythropoietin (Epo) +/- Flt3-ligand (Flt3-L) for 10 days. After culture, total cells, CFU-GMs, BFU-Es and LTC-ICs were expanded to a mean of 833-, 6.6-, 4.6-, and 1.8-fold, respectively with the cocktail of cytokines not including Flt3-L. When Flt3-L was added, the mean expansion values were 1095-, 31-, 15- and three-fold, respectively. Residual bcl2/JH+ cells present in four of eight samples before expansion were not detected after expansion. Similarly, no tumor cells reappeared after expansion of the two samples which had become negative after selection, as well as in the two samples which were bcl2/JH- at harvesting. These results suggest first that ex vivo expansion of hematopoietic stem cells in patients with non-Hodgkin's lymphoma is feasible without incurring the parallel risk of amplifying tumor cells; second, that Flt3-L did not stimulate the growth of tumor cells while it clearly favored the growth of normal progenitors.     

Natural killer activity and NK cytotoxic factors in peripheral blood and lymph node cells from non-Hodgkin's lymphoma patients

Natural killer (NK) activity and natural killer cytotoxic factors (NKCF) were found to be depressed in large granular lymphocytes (LGL) from the peripheral blood and lymph node lymphocytes (LNL) from untreated non-Hodgkin's lymphoma (NHL) patients. The LGL number was also reduced in NHL patients as compared to the normal subjects. The depression in all the activities mentioned above showed a correlation with the clinical status of the patients. Exogenous interferon-alpha (IFN-alpha) treatment of the effector cells could augment the NK activity to a comparable extent in normal as well as patient's LNL. The results indicate that the production of interferon may be affected in cases of NHL and therefore it would be worthwhile to test the tolerance and efficacy of IFN-alpha in these patients.     

Detection of minimal tumor cells in peripheral blood patients with non-Hodgkin's lymphoma by Southern blot analysis]

We studied peripheral blood mononuclear cells, bone marrow cells and lymph node cells from 30 patients with non-Hodgkin's lymphoma by DNA hybridization. Clonal JH or TCR beta gene rearrangements were detected in peripheral blood or bone marrow mononuclear cells from 15 of 30 (50.0%) patients studied, including 31.8% of those without evidence of tumor cells by morphological method. Four of 9 cases demonstrated identical clonal gene rearrangements at diagnosis and in remission phase in peripheral blood mononuclear cells. The presence of clonal gene rearrangements roughly correlated with the clinical stage of disease. And the proportion of clonal rearrangements was higher in the groups with small & medium sized cell types (64.3%) than in the group with large cell type (33.3%). So, we concluded that Southern blot analysis was more useful than morphological method to detect monoclonality of circulating lymphoma cells and minimal tumor cells.     

Feasibility of peripheral blood progenitor cell mobilization and harvest to support chemotherapy intensification in elderly patients with poor prognosis: non-Hodgkin's lymphoma

Mobilized peripheral blood progenitor cells (PBPC) are widely employed in the management of adult patients with high-risk non-Hodgkin's lymphoma (NHL), though their use in the elderly has received little attention. This study was mounted to assess the feasibility of the mobilization, harvesting, and reinfusion of PBPC in NHL patients aged >60. Twenty patients (median age: 67, range: 61-80) with poor-prognosis NHL entered the pilot study: nine others were discarded for various reasons. Thus, the program was applicable to 69% of potential candidates. Fourteen patients were at onset and six were being treated for refractory disease or relapses. Mobilization was induced with cyclophosphamide 4 g/m(2), followed by 5 micro g/kg per day granulocyte-colony stimulating factor (G-CSF) s.c. until PBPC collection or hemopoietic recovery. Sixteen patients (80%) displayed some signs of mobilization (CD34+: >5/ micro l). Maximum mobilization varied with median circulating CD34+ cells and colony forming units-granulocyte/macrophage (CFU-GM) peaks of 17.2/ micro l (range: 8.1-210) and 1,650/ml (range: 540-62,900), respectively. A median of two leukaphereses resulted in the harvesting of a median of 6.7x10(6) (range: 0.3-33.6) CD34+/kg and 21.1x10(4) (range: 1.2-209) CFU-GM/kg. Intensified therapy with intermediate-dose melphalan, associated or not with mitoxantrone, was delivered with autologous PBPC support to 13 patients and always resulted in rapid and stable hemopoietic reconstitution. The program was well tolerated and no treatment-related deaths occurred. Twelve patients are still alive with a 5-year survival projection of 59%. In conclusion, the results demonstrate the feasibility of using autologous PBPC to support therapy intensification even in elderly patients.     

Tandem transplant of peripheral blood stem cells for patients with poor-prognosis Hodgkins's disease or non-Hodgkin's lymphoma.

To improve the results of high-dose therapy with autologous stem cell transplantation, new conditioning regimens with acceptable toxicity must be developed. The aim of this study was to evaluate the feasibility and toxicity of two myeloablative regimens performed at a 2-month interval. After salvage chemotherapy and collection of peripheral stem cell progenitors (median CD34+ cells/kg: 11 x 106/kg), (n = 15) patients with aggressive non-Hodgkin's lymphoma with poor prognostic factors or refractory Hodgkin's disease (n= 9) received intensified regimens. The first conditioning regimen, consisting of BCNU-cyclophosphamide-VP16-mitoxantrone was followed by transplantation of a median number of 4 x 10(6) CD34+ cells/kg; then, after a median interval of 56 days, a second preparative regimen, combining busulfan-aracytine-melphalan or TBI + aracytine-melphalan, was followed by transplantation of a median of 4 x 10(6) CD34+ cells/kg. After regimens 1 and 2, respectively: median time to neutrophil recovery >500/microl was 11 days (both times); median time to platelet counts >50,000/microl was 14 and 36 days, but values > 20,000/microl were reached by days 13 and 16 (P = 0.9); mucositis grade III-IV was observed in 11 and 15 cases. The median number of days with fever >38 degrees C was significantly higher (7.8 days) after the second transplant (P <0.05). Three cases of veno-occlusive disease (VOD) were observed after the second transplant. At a median follow-up of 18 months, 14/24 (58%) patients remained in CR, seven patients had died (two of VOD and five after relapse) and two were alive in relapse. These results indicate that tandem transplants performed at a 2-month interval in poor risk lymphoma can be used with acceptable hematotoxicity. VOD remains the major drawback and hepatotoxic drugs, such as busulfan, should be used with caution. Longer term follow-up of a larger cohort of patients is needed to ascertain the overall efficacy.     

Feasibility and toxicity of high-dose therapy (HDT) supported by peripheral blood stem cells in elderly patients with multiple myeloma and non-Hodgkin's lymphoma: survey from a single institution

The aim of this retrospective study was to investigate the feasibility of high-dose therapy (HDT) followed by peripheral blood stem cell transplantation (PBSCT) in elderly patients with hematological malignancies. From April 1998 to November 2001, 40 elderly patients (defined as > or =60 years) with non-Hodgkin's lymphoma (12 patients) and multiple myeloma (28 patients) were evaluated. Seven lymphoma and one myeloma patients were in complete remission (CR), 27 in partial remission (PR), two had stable disease (SD), and three progressive disease (PD). The median age was 65 years (range 60-71). Thirty-nine patients were mobilized with chemotherapy plus granulocyte-colony stimulating factor (G-CSF) and one with G-CSF alone. Patients received HDT including melphalan alone in 32 cases or combined with other drugs in six and BEAM in two. The median number of collected CD34(+) cells was 12.4 x 10(6)/kg (range 2.0-68.9). The median number of re-infused CD34(+) cells was 9.9 x 10(6)/kg (range 2.0-68.9). All patients engrafted after PBSC and the median time to neutrophil recovery (N > 500/micro l) and platelet recovery (PLT > 20,000/micro l) was 8 days (range 5-18) and 6 days (range 5-18), respectively. Nonhematological toxicity was mild and no patient died from transplant-related toxicity (TRM). Median duration of hospitalization was 18 days (range 12-24). To date, 32 patients are alive and eight died from disease progression at a median follow-up interval of 24 months. HDT supported by PBSC is a feasible procedure in selected elderly patients, and an age of more than 60 years should not be considered a contraindication for HDT.     

Granulocyte colony-stimulating factor-mobilized peripheral blood stem cells in beta-thalassemia patients: kinetics of mobilization and composition of apheresis product

beta-Thalassemias are often associated with bone marrow expansion and immunomodulation in terms of lymphocyte subsets and cytokine levels in the peripheral blood. The mobilization of peripheral blood stem cells (PBSC) by cytokines in such a background has not been reported. If achieved, the apheresis product could be used as a stem cell back-up for beta-thalassemia patients prior to bone marrow transplant. PBSC collection may also become a means for providing stem and progenitor cells for gene manipulation and therapy of this disorder. The aim of the study was to assess the administration of G-CSF in mobilizing stem and progenitor cells in these patients and to compare the kinetics of CD34+ cells and lymphocyte subsets with those of healthy PBSC donors. Results showed that the CD34+ cells were effectively mobilized by G-CSF (10-16 micrograms/day per kg) in 20 thalassemia patients and 11 healthy donors. Although no significant difference was observed in levels of daily stem cell counts between the two groups of subjects, a 1 day delay in achieving peak levels of CD34+ cells was observed in the majority of thalassemia patients. The peak increase of CD34+ cells was 21.5 +/- 6.1-fold and 30.8 +/- 7.6-fold of the basal steady-state levels in thalassemia patients and healthy donors, respectively. Similar to the situation of healthy donors, G-CSF stimulated essentially the CD34+ cells and the myeloid lineage (granulocytes, monocytes) in thalassemia patients and had a slight effect on lymphocyte subsets (T-helper, T-suppressor, NK, and B cells) and activation (CD25, HLA-DR, and CD45RO). Compositions of the apheresis products, including CD34+CD38-, CD34+CD33+ and CD34+HLA-DR- cells, were similar in the two groups of subjects. Correlation studies showed that the level of CD34+ cells in the PB is a good indicator of that in the apheresis product (r = 0.88, p < 0.001). The study has demonstrated that under close monitoring of CD34+ cell levels in PB, the mobilization by G-CSF and collection of PBSC in beta-thalassemia patients are feasible.     

自体外周血造血干细胞移植治疗非霍奇金淋巴瘤182例临床分析

目的　评价自体外周血造血干细胞移植 (APBSCT)治疗非霍奇金淋巴瘤 (NHL)患者的疗效。方法　全国 34家单位采用APBSCT治疗NHL 182例。其中第一次完全缓解 (CR1)移植 112例 ,部分缓解 (PR)或复发期移植 70例。外周血造血干细胞 (APBSC)动员方案分为四组 :1组为大剂量环磷酰胺 (HD CY)联合粒细胞 集落刺激因子 (G CSF) 5 5例 ;2组为大剂量阿糖胞苷 (HD Ara C)联合G CSF7例 ;3组为增大环磷酰胺剂量的针对性化疗方案联合G CSF 10 2例 ;4组为单独应用G CSF 18例。预处理方案 :移植前处于CR1状态的 112例中 ,含有全身照射 (TBI)的预处理方案 39例 ,不含TBI的 73例 ;PR或复发的 70例中 ,含有TBI的预处理方案 2 9例 ,不含TBI的 4 1例。结果　四组所采集到的APBSC均可达到临床所需数量。四组间采集的单个核细胞数与采集次数之间无统计学差别。移植后WBC≥ 1 0× 10 9/L的中位数时间为 12 (10～ 30 )d ;血小板≥ 2 0× 10 9/L的中位数时间为 12 (0～ 181)d。患者移植后平均随访时间为 2 4个月。预期 3年无病生存率 (DFS)移植前达CR1期者 6 9 7% ;PR和复发期为 4 4 9%。在移植前达CR1期患者中 ,含有TBI和不含TBI的预处理方案的 3年DFS无统计学差别 (70 1%、6 8 0 % )。而对于PR或复发期患者 ,前者优于后者 (5 7     

Molecular analysis of patients with relapsed or refractory intermediate-high grade non-Hodgkin's lymphoma with bone marrow infiltration undergoing peripheral blood progenitor cell transplantation.

BACKGROUND AND OBJECTIVES: IgH gene rearrangement studies with a polymerase chain reaction (PCR) technique can detect the persistence of clonal cells at molecular level during the remission phase. This persistence of clonal cells can be used to establish the relationship between minimal residual disease (MRD) and clinical outcome. We have developed a three-step single strand conformational polymorphism PCR strategy which is able to detect clonal B lymphoid cells at a frequency as low as 1 clonal cell in 10(6) normal cells. DESIGN AND METHODS: Twenty patients with intermediate or high-grade B non-Hodgkin's lymphoma (NHL) were evaluated. Patients were pre-treated with a median of two (range 1-4) conventional chemotherapy lines before high-dose cyclophosphamide (HDCY). All patients had their bone marrow (BM) involved by disease (median 10%; range 5-50%). Nineteen patients were offered high-dose therapy followed by peripheral blood progenitor cells (PBPC) autografting. RESULTS: MRD analysis was performed for each patient at the end of conventional chemotherapy and every three months after high dose therapy. All these patients achieved complete response (CR) after high dose therapy (HDT). Six patients relapsed after a median time of 24.5 months. All the studied apheresis samples were positive at the molecular analysis. All 6 patients still positive at the molecular analysis after PBPC autografting relapsed. The remaining 13 patients who were negative maintained CR. INTERPRETATION AND CONCLUSIONS: Whereas the detection of clonal cells in the apheresis samples did not predict an unfavorable outcome, the disappearance of the clonal rearranged band from the BM sample after HDT proved to be a favorable prognostic factor and was associated with long-lasting disease-free status     

Isolation of large numbers of enriched human megakaryocytes from liquid cultures of normal peripheral blood progenitor cells

Investigations linking human megakaryocyte development and cell biology have been hindered by an inability to obtain large, relatively pure megakaryocyte cell preparations from in vitro stem cell cultures. We report here that such preparations can be generated from liquid cultures of normal human peripheral blood mononuclear cells stimulated by a serum source of megakaryocyte colony stimulating activity (Meg- CSA, the 0% to 60% ammonium sulfate protein fraction of aplastic canine serum). Adherent-depleted peripheral blood mononuclear cells are suspended at 5 x 10(5) to 10(6) cells/mL in supplemented liquid culture medium, platelet-poor human plasma 20% (vol/vol) and 1 to 2 mg/mL serum Meg-CSA protein. After 12 to 14 days of incubation, megakaryocytes constitute 3.0 +/- 2.9% (mean +/- SD, n = 8) of the unseparated cultured cell population. Megakaryocytes can be enriched by counterflow centrifugal elutriation to a purity of 58 +/- 14% (+/- SD) with a recovery of 13 +/- 7% and a viability of 67 +/- 19%. This algorithm results in the average isolation of approximately 3 x 10(5) enriched megakaryocytes from a 100-mL starting volume of peripheral blood. Cultured megakaryocytes exhibit normal light and ultrastructural morphology by Wright-Giemsa staining and electron microscopic analysis. After a 12-day culture interval, enriched megakaryocyte preparations exhibit morphologic stage distributions that are similar to normal human marrow. Stage distributions move rightward with culture duration indicating partial synchrony of megakaryocyte maturation. On cytospin preparations, megakaryocyte diameter averages 30.2 +/- 1.5 microns and increases with maturation stage. Flow cytometric analyses demonstrate the expression of platelet glycoproteins (GP) Ib and IIb/IIIa by the cultured megakaryocytes. The modal ploidy of the enriched cells at day 12 of culture is 16N and most remaining megakaryocytes are 8N or 32N. Liquid culture of serum Meg-CSA-stimulated human peripheral blood mononuclear cells represents a valuable investigative tool that should permit studies of human megakaryocyte biology that have not been possible in the past.