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Extensive characterization of the immunophenotype and pattern of cytokine production by distinct subpopulations of normal human peripheral blood MHC II+/lineage- cells.

Dendritic cells (DC) represent the most powerful professional antigen-presenting cells (APC) in the immune system. The aim of the present study was to analyse, on a single-cell basis by multiparametric flow cytometry with simultaneous four-colour staining and a two-step acquisition procedure, the immunophenotypic profile and cytokine production of DC from 67 normal whole peripheral blood (PB) samples. Two clearly different subsets of HLA-II+/lineage- were identified on the basis of their distinct phenotypic characteristics: one DC subset was CD33strong+ and CD123dim+ (0.16 +/- 0.06% of the PB nucleated cells and 55.9 +/- 11. 9% of all PB DC) and the other, CD33dim+ and CD123strong+ (0.12 +/- 0.04% of PB nucleated cells and 44.53 +/- 11.5% of all PB DC). Moreover, the former DC subpopulation clearly showed higher expression of the CD13 myeloid-associated antigen, the CD29 and CD58 adhesion molecules, the CD2, CD5 and CD86 costimulatory molecules, the CD32 IgG receptor and the CD11c complement receptor. In addition, these cells showed stronger HLA-DR and HLA-DQ expression and a higher reactivity for the IL-6 receptor alpha-chain (CD126) and for CD38. In contrast, the CD123strong+/CD33dim+ DC showed a stronger reactivity for the CD4 and CD45RA molecules, whereas they did not express the CD58, CD5, CD11c and CD13 antigens. Regarding cytokine production, our results show that while the CD33strong+/CD123dim+ DC are able to produce significant amounts of inflammatory cytokines, such as IL-1beta (97 +/- 5% of positive cells), IL-6 (96 +/- 1.1% of positive cells), IL-12 (81.5 +/- 15.5% of positive cells) and tumour necrosis factor-alpha (TNF-alpha) (84 +/- 22.1% of positive cells) as well as chemokines such as IL-8 (99 +/- 1% of positive cells), the functional ability of the CD123strong+/CD33dim+ DC subset to produce cytokines under the same conditions was almost null. Our results therefore clearly show the presence of two distinct subsets of DC in normal human PB, which differ not only in their immunophenotype but also in their functionality, as regards cytokine production.

AC133 Antigen↗

Immunophenotyping of peripheral blood mononuclear cells collected by cytotoxic and cytotoxic/G-CSF mobilization.

We investigated surface immunophenotypes of peripheral blood mononuclear cells (PBMC) collected by cytotoxic and cytotoxic/G-CSF mobilization of peripheral blood stem cells (PBSC) from 38 patients with haematological malignancies in complete remission who underwent consolidation chemotherapy. PBMC were collected by leucapheresis during the haematopoietic recovery phase after intensive chemotherapy. G-CSF was used for mobilization of PBSC in 19 cases. Surface immunophenotyping of frozen-thawed PBMC was performed by flow cytometry. Our findings showed that monocytes and T cells were the two major cell components of PBMC. There were very few B cells in PBMC. Expression of CD45RO and HLA-DR was elevated in lymphocytes, suggesting that T cells in PBMC were activated. The percentage of CD34 positive cells were significantly increased in PBMC collected by cytotoxic/G-CSF mobilization (group 1) compared with PBMC collected by cytotoxic mobilization (group 2). There were significantly higher percentages of CD14 and CD33 positive cells in group 1 than in group 2. The percentage of CD4 positive lymphocytes positive for HLA-DR was significantly higher in group 1 compared with group 2. These observations indicated that PBMC contained a large number of monocytes and activated T cells, especially in cytotoxic/G-CSF mobilization.

Adolescent↗

Immunophenotypic and cytogenetic changes in acute leukaemia at relapse.

To gain more insight into the immunophenotypic and cytogenetic changes in acute leukaemia at relapse, 99 Korean patients treated at a single institution were studied: acute myelogenous leukaemia (AML, n=46), acute lymphoblastic leukaemia (ALL, n=44) and biphenotypic and mixed leukaemia (n=9). Immunophenotypic changes at relapse were observed in 51 of 99 patients (51.5%) with almost even distribution in AML and ALL. Overall expression of aberrant markers on leukaemic cells was more frequent at relapse than at initial diagnosis (P < 0.05), and this finding was most prominent in B lineage ALL (41.4% versus 10.3%, P=0.007). Gain of aberrant CD13 or CD33 at relapse of B lineage ALL was most frequently observed. Cytogenetic changes at relapse were observed in 28 of 46 patients (60.8%). The initially abnormal karyotypes were more frequently associated with clonal changes at relapse compared to initially normal karyotypes (78.3% versus 43.5%, P=0.016). Cytogenetic changes were more frequent in B lineage ALL than in AML (90% versus 47.8%, P=0.05). In ALL, patients showing cytogenetic changes at relapse were significantly younger than those showing no changes (mean age of 15.0 versus 38.8, P=0.002), whereas in AML there was no significant difference between the two groups. In conclusion, the gain of aberrant markers and cytogenetic changes at relapse, which are suggestive of clonal instability, are more prevalent in B lineage ALL compared to AML, and lymphoid leukaemic cells of younger patients are more susceptible to clonal changes at relapse.

Acute Disease↗

Immunophenotypic heterogeneity of hyalinizing trabecular tumours of the thyroid.

AIMS: We studied 12 cases of hyalinizing trabecular tumour of the thyroid gland (HTT) with the aim of reviewing the cytological, histological and immunophenotypic features and of investigating the relationships of HTT with other thyroid neoplasms. METHODS AND RESULTS: Eleven patients were female and one male, aged 8-74 years (median 58). Ten cases had a benign behaviour, while two cases were locally aggressive. Of the latter, one developed distant metastases and the other is a recent case. All patients are alive 6-311 months after diagnosis. Cytologically, HTT was characterized by hypercellular smears with aggregates of roundish cells having features of papillary carcinoma (nuclear grooves, vacuoles) and fragments of fibrous tissue. Histologically, prominent nesting, trabecular growth patterns and a hyaline stroma (partly positive for laminin and collagen type IV) were found. One case was associated with a papillary microcarcinoma. Two additional cases had extensive areas of papillary carcinoma. In one of these, hyalinized papillary stalks were observed. All tumours contained thyroglobulin but not calcitonin. High molecular weight cytokeratin (a marker of papillary carcinoma) was focally positive in 4/12 cases only and thyroperoxidase (a marker of follicular adenomas, but not of papillary carcinoma) was found in 3/12 cases. CONCLUSIONS: The immunophenotypic profile and the morphological features suggest that HTTs are an heterogeneous group of tumours, some of them probably representing variants of papillary carcinoma with hyalinized stroma.

Adenoma↗

Transitional cell carcinomas of the ovary and bladder are immunophenotypically different.

AIMS: Transitional cell carcinoma (TCC) of the ovary is a subtype of ovarian cancer whose main characteristic is its histological resemblance to TCC of the bladder. Thrombomodulin (TM), a surface glycoprotein commonly expressed in normal and neoplastic urothelium, has been proven to be a good marker for TCC of the bladder. To better define the phenotype of TCC of the ovary, we investigated TM, cytokeratin 20 and carcinoembryonic antigen (CEA) expression in 15 TCCs of the ovary and compared their phenotype with that of 20 TCCs of the bladder, and 20 serous and 10 endometrioid carcinomas of the ovary. METHODS AND RESULTS: Immunostaining was performed on formalin-fixed, paraffin-embedded tissue sections using the avidin-biotin-peroxidase complex method. All 20 TCCs of the bladder stained for TM and cytokeratin 20, and 13 stained for CEA. None of the TCCs of the ovary reacted for TM or cytokeratin 20, and only two expressed CEA. All of the serous and endometrioid carcinomas were negative for TM and cytokeratin 20. CEA positivity was observed in two of the serous carcinomas, but in none of the endometrioid carcinomas. CONCLUSION: The immunophenotype of TCC of the ovary is similar to that of other surface carcinomas of the ovary, but differs from that of TCC of the bladder. Since immunohistochemical procedures are often used in the diagnosis and classification of both primary and metastatic tumours, it is important to be aware of these differences in immunophenotype.

Biomarkers, Tumor↗

Monocyte-derived CD1a+ dendritic cells generated in two different culture systems: immunophenotypic and functional comparison.

Previous studies demonstrated that CD1a+ dendritic cells (DCs) could not be prepared ex vivo without using fetal calf serum (FCS). Recently, we developed a method of using heparin to induce differentiation of human monocytes into CD1a+ DCs without using FCS. In order to determine the potential clinical applicability of heparin-induced CD1a+ DCs, we conducted this study to compare both types of CD1a+ DCs, immunophenotypically and functionally. Our results showed that the expression of CD1a on heparin-DCs was lower than that on FCS-DCs. Both types of DCs expressed similar levels of CD11c, HLA-DR, CD40, CD83, CD80 and CD86 before and after lipopolysaccharide stimulation. Immature heparin-DCs and FCS-DCs had similar phagocytic activities. Heparin-DCs consistently secreted higher interleukin-10 (IL-10) and lesser IL-12 than FCS-DCs after activation. Mature heparin-DCs were slightly more active than mature FCS-DCs in stimulating the proliferation of allogeneic CD4+ T cells. Both types of mature CD1a+ DCs primed the naïve CD4+ T cells to produce large amount of interferon-gamma (IFN-gamma). However, naïve CD4+ T cells stimulated with FCS-DCs produced more IFN-gamma, while the naïve CD4+ T cells stimulated with heparin-DCs produced more IL-5. The results indicate that both types of CD1a+ DCs do not have identical function in the priming of CD4+ T cells and have minor difference in immunophenotypes.

Antigens, CD1↗

Atopic dermatitis: immunophenotyping of inflammatory cells in skin lesions.

BACKGROUND: The ever increasing incidence of atopic dermatitis (AD) has stimulated many researchers to use various diagnostic procedures to obtain new data to help elucidate the pathogenesis of the disease. AIMS: To perform cell immunophenotyping and to analyze the presence of inflammatory cell-surface markers in the biopsies of skin lesions from 15 AD patients and five healthy subjects. METHODS: Immunohistochemical analysis was performed in a group of AD patients and compared with that in a control group of healthy subjects. Avidin-biotin immunoperoxidase staining of paraffin-embedded, 4 microm skin sections, with semiquantitative counting of cells labeled with anti-CD3, anti-CD8, anti-CD20, anti-HLA-DR (HLA, human leukocyte antigen), and anti-immunoglobulin E (anti-IgE) primary antibodies, was used. RESULTS: The results of AD skin analysis showed a greater infiltration of CD3+ lymphocytes, especially of CD4+ subtype, compared with CD8+ lymphocytes. AD skin biopsy specimens also showed a higher intraepidermal HLA-DR+ Langerhans' cell count, the presence of HLA-DR on lymphocytes in the dermis, and higher intraepidermal expression of IgE+ cells compared with healthy controls. CONCLUSIONS: A statistically significant difference (P < 0.05) was found between the two groups for intradermal and intraepidermal CD3, CD4, and HLA-DR, intradermal CD8, and intraepidermal IgE+ cells. Immunophenotyping was found to be a useful diagnostic method in AD patients.

Adolescent↗

Possibilities of flow cytometric analysis for immunophenotypic characterization of canine lymphoma.

The purpose of the study presented here is to show the possibilities of flow cytometric analysis for immunophenotypic characterization of canine malignant lymphoma. Aspiration biopsies from lymph nodes of 30 dogs with multicentric lymphoma were stained by four dog-specific antibodies and three human-specific antibodies cross-reacting with canine lymphocytes, and analysed by flow cytometry. Twenty of the 30 lymphoma examined were characterized as B-cell-lymphoma and 10 as T-cell-lymphoma. Flow cytometry is a suitable method for the immunophenotypic analysis of canine lymphoma. Contrary to immunohistochemistry, no surgically produced lymph node biopsy is required and the results are available within a few hours.

Animals↗

Despite apparent morphologic and immunophenotypic heterogeneity, Waldenstrom's macroglobulinemia is consistently composed of cells along a morphologic continuum of small lymphocytes, plasmacytoid lymphocytes, and plasma cells.

We studied the clinical, morphologic, and immunophenotypic features of 26 Waldenstrom's macroglobulinemia (WM) cases, each with an IgM spike of >or=3.0 g/dL. The neoplastic cells were consistently composed of a spectrum of small lymphocytes, plasmacytoid lymphocytes, and plasma cells. Bone marrow (BM) involvement ranged from 10% to 90%, showed four histologic patterns (nodular [75%], interstitial [75%], paratrabecular [42%], and diffuse [4%]), two histologic subtypes (lymphoplasmacytic [87%] and lymphoplasmacytoid [13%]), and several cytologic variants (monocytoid [n = 2], signet-ring cell [n = 2], and hairy cell leukemia-like [n = 1]). By flow cytometry (FC), all cases expressed monoclonal surface immunoglobulin, CD19, and CD20. Most cases (58%) lacked expression of CD5, CD10, and CD23. However, variants such as CD5(+)CD10(-)CD23(-) (n = 3), CD5(+)CD10(-)CD23(+) (n = 1), and CD5(-)CD10(+)CD23(+/-) (n = 2) were seen. At last follow-up, 18 of 26 patients were alive (median survival, 94 months). Causes of death included WM (n = 1), large cell lymphoma (n = 1), acute myeloid leukemia (likely therapy-related [n =2]), and nonhematologic/unknown. When individual WM cases are compared, apparent morphologic diversity is suggested. However, every WM case is comprised of cells along a morphologic continuum from small lymphocytes to plasma cells, delineating a uniform, consistent pathology. As WM shows immunophenotypic heterogeneity, morphology must be the cornerstone of the diagnosis.

Aged↗

Immunophenotype of Down syndrome acute myeloid leukemia and transient myeloproliferative disease differs significantly from other diseases with morphologically identical or similar blasts.

BACKGROUND AND OBJECTIVES: Children with Down Syndrome (DS) have a 20-40 fold increased risk of developing acute myeloid leukemia (AML), mainly of the megakaryoblastic subtype (AMKL). Approximately 10 % of newborns with DS show transient myeloproliferative disease (TMD) which normally resolves spontaneously. The blast cells of both entities show megakaryoblastic/erythroblastic features (M7/M6) and cannot be distinguished by morphological characteristics. DESIGN AND METHODS: Blast cells of 62 children were analyzed by four-color flow cytometry and dual color fluorescence microscopy. RESULTS: The immunophenotype of blast cells from children with TMD and DS-AMKL is characterized by the expression of CD33 (+)/CD13 (+/-)/CD38 (+)/CD117 (+)/CD34 (+/-)/CD7 (+)/CD56 (+/-)/CD36 (+)/CD71 (+)/CD42b (+)/CD4dim (+)/TPO-R (+)/EPO-R (-)/IL-3-Ralpha (+)/IL-6-Ralpha (-). Non-DS children with morphologically related diseases, i. e. myelodysplastic syndrome (MDS), juvenile myelomonocytic leukemia (JMML), or AML-M6 and AML-M7, did not show this expression profile. CD34 expression was observed in 93 % of TMD, but only 50 % of DS-AMKL patients. The blast cells of all TMD and DS-AMKL cases were positive for TPO-R and IL-3R, whereas EPO-R and IL-6R were absent. CONCLUSIONS: Immunophenotyping by the use of surface antigens and growth factor receptors is a useful tool to discriminate TMD and DS-AMKL from diseases with morphologically similar or identical blasts. The absence of EPO-R on the blast cells might be a sign of the high expression of the mutated -- and less active -- GATA1 in DS. The higher amount of CD34 co-expression in TMD may be interpreted to indicate that TMD is a slightly more immature disease than DS-AMKL.

Acute Disease↗

Immunophenotyping of angioimmunoblastic T-cell lymphomas by multiparameter flow cytometry.

Angioimmunoblastic T-cell lymphoma (AITL) is a distinct form of peripheral T-cell lymphoma (PTCL) frequently involving lymph nodes, spleen and bone marrow, and is associated with systemic symptoms. Its histologic features may be subtle at an early phase and difficult to diagnose. Despite the success of flow cytometry (FCM) in diagnosing B-cell neoplasm, FCM has not been widely accepted as a useful method for establishing the diagnosis of PTCL. Recently, the neoplastic T-cells in AITL have been shown to express CD10. We prospectively applied multiparameter FCM immunophenotyping to three cases of histologically confirmed AITL and identified a small (5-7%) population of CD4+/CD10+ T-cells in two cases. In one case, the CD4+/CD10+ population lacked surface signals of CD3 and CD7, but strongly expressed CD2, whereas CD45 expression was very weak; partial loss of surface CD3 was observed in the other. None of the lymph nodes with reactive hyperplasia, B-cell lymphomas, or Hodgkin's lymphoma studied during the same time period contained the CD4+/CD10+ population. These findings suggest that addition of CD4/CD10 and CD3/CD10 to FCM immunophenotyping panels is useful in the diagnosis of AITL. To the best of our knowledge, this is the first report to demonstrate CD10-expressing T-cells in AITL by FCM.

Aged↗

Generation of inner ear hair cell immunophenotypes from neurospheres obtained from fetal rat central nervous system in vitro.

Neural stem cells are suggested to possess a highly plastic ability to differentiate into several specific cell types, not only neuronal lineages but also other germ layer tissue-specific cell lineages. To examine whether hair cell immunophenotypes could be derived from the central nervous system (CNS), we established cell cultures from embryonic day 16.5 fetal rat brain tissues, and analyzed changes in immunohistochemical features of the CNS cell cultures by induction of differentiation. The results of this study showed that neural progenitors obtained from fetal rat CNS generated hair cell immunophenotypes with expression of both epitopes of hair cell marker proteins Brn-3c and myosin VIIa in vitro. These findings indicate that immature neural progenitors possess the potential to differentiate into hair cell phenotypes. Immature neural progenitors may be useful as materials for cell transplantation therapy for replacement of damaged inner ear hair cells.

Animals↗

Thrombin generation in children with acute lymphoblastic leukemia: effect of leukemia immunophenotypic subgroups.

Elevated plasma concentrations of endogenous thrombin generation markers and thrombotic events have been reported in children with leukemia. The aim of this study was to evaluate the effects of cancer and its treatment on thrombin generation (TAT levels) in children with acute lymphoblastic leukemia (ALL). The authors evaluated 32 children (23 M, 9 F) aged between 1 and 15 years (mean 6) affected by ALL (immunophenotypic subgroups: 16 common, 7 T, and 9 pre-B type). In all patients TAT levels at onset and after 5-6 doses of L-asparaginase were evaluated. TAT levels were higher in patients both at onset (13.04 +/- 10.90 ng/L) and after the 5-6 doses of L-asp (19.41 +/- 11.05 ng/L) with respect to controls (4 +/- 1 ng/L) (p < .001 and p < .001). TAT levels after 5-6 doses of L-asp were higher than those at onset (p < .001). Factorial ANOVA showed that at onset there was a significant effect of leukemia immunophenotypic subgroups upon TAT levels (p < .05) and no effect of inherited thrombotic risk factors. These results indicate that in children with ALL an important role is played by acquired thrombotic risk factors, among which the indirect cancer procoagulant activity has its importance.

Adolescent↗

Childhood T-cell acute lymphoblastic leukemia with four distinct immunophenotypes representing different stages of T-cell development.

The authors report on a 14-year-old boy who developed T-cell acute lymphoblastic leukemia (FAB:L1) displaying 4 immunophenotypically distinct leukemic cell populations by 3-color immunofluorescence staining. Cytogenetic analysis at diagnosis showed 46,XY,add(4)(p16)[12]/46,XY[2]. A single rearrangement of the T-cell antigen receptor beta- and gamma-chain genes in these cells indicated monoclonality of the leukemic cells. These findings suggest that leukemic blast cells of monoclonal origin in this case were divided into 4 immunophenotypic populations, representing various stages of differentiation.

Adolescent↗

Immunophenotypic features of acute myeloid leukemias overexpressing the interleukin 3 receptor alpha chain.

In a previous study we have shown that the interleukin-3 receptor alpha chain (IL-3Ralpha) is over expressed in about 45% of acute myeloid leukemias (AMLs) and this phenomenon was associated with high blast cell counts at diagnosis, high rate of cycling of leukemic blasts and with a worse prognosis. Here we have investigated the immunophenotypic features of 125 AML patients subdivided into three groups (IL-3R(high), IL-3R(middle) and IL-3R(low)) according to the level of IL-3Ralpha expression. AMLs over expressing the IL-3Ralpha represent a subgroup of AMLs with a peculiar immunophenotype mainly consisting in the elevated expression of CD34 and several receptor membrane tyrosine kinases, such as c-kit and flt3, and in a usually low expression of myeloid-associated antigens such as CD11b, CD14 and CD15. These findings suggest that IL-3Ralpha + + + AMLs are blocked at an early stage of differentiation and express at elevated levels several growth factor receptors. It is proposed that these findings may further help to understand the mechanisms involved in the development of high-risk acute leukemias.

Acute Disease↗

Recurrent B-cell neoplasms after Rituximab therapy: an immunophenotypic and genotypic study.

Rituximab has been widely used to treat relapsing or advanced stage B-cell neoplasms with an efficacy of about 50%. However, approximately 40-50% of Rituximab treated patients will recur. It is not clear whether these recurrent diseases have the same immunophenotype as that of the original tumors. At the City of Hope, we treated 91 cases of CD20-positive B-cell neoplasms with Rituximab in combination with chemotherapy and hematopoietic stem cell transplantation between August 1999 and December 2000. Thirty-five of 91 patients (38%) experienced recurrence during the time period within one year from treatment. Tumor cells from all of the recurrent patients expressed one or more B cell antigens (CD19, CD20, CD22, CD45RA, or CD79a). However, thirteen of 35 recurrent cases showed aberrant loss of CD20 expression (37%) by immunohistochemical or flow cytometric studies. Pre- and post-Rituximab treated tumor cell DNA was successfully extracted from archival paraffin sections, hematoxylin and eosin (H and E) stained slides, smears, or frozen cells in 10 of 13 CD20 negative recurrent cases. PCR studies for immunoglobulin (Ig) heavy chain gene rearrangements were performed in all these cases. Five cases showed identical Ig heavy chain gene rearrangements in the paired specimens. PCR assay for Ig kappa (kappa) gene rearrangement was performed in the five paired specimens lacking detectable Ig heavy chain gene rearrangements; 2 of them showed identical Igkappa gene rearrangements. Three pairs showed unmatched Ig heavy chain and Igkappa gene rearrangements, probably due to poor quality of recovered DNA. Aberrant loss of CD20 antigens may be a mechanism of treatment resistance and should be considered in the immunophenotyping of recurrent Rituximab-treated B-cell neoplasms; therefore, a panel of B cell markers is recommended for the immunologic diagnosis of recurrent B cell malignancies after Rituximab therapy. Seven of ten pairs of recurrent CD20-negative cases showed identical Ig heavy chain and Igkappa gene rearrangements by PCR assay, strongly suggesting that the pre- and post-Rituxan treated B cell neoplasms are clonally-related.

Antibodies, Monoclonal↗

Immunophenotypic profile of AC133-positive cells in bone marrow, mobilized peripheral blood and umbilical cord blood.

AC133 is a molecule whose expression in the human hematopoietic system is restricted to a subset of CD34+ progenitor/stem cells with long-term repopulating ability. The antigenic features of these cells, like CD34+ cells, are described heterogeneous. The immunophenotypic profile of AC133+ cells, detected by means of dual-color flow cytometry, in bone marrow (BM), cytokine-mobilized peripheral blood (PB) and umbilical cord blood (UCB) was evaluated. The highest percentage of AC133+ cells was detected in mobilized PB despite not significantly different from that found in BM, but both are higher than that found in UCB. In addition, the highest percentage of CD34, HLA-DR and CD33 co-expressing AC133+ cells was observed in mobilized PB. Furthermore, UCB was found to be enriched in CD7+ and CD19+ cells and BM was found to be enriched in AC133+ cells co-expressing CDw90 and CD71. Our data confirm the immunophenotypic heterogeneity of cells expressing AC133 antigen, a promising new stem cell marker to be increasingly used as additional target for alternative identification and separation of early hematopoietic cells.

AC133 Antigen↗

Acute panmyelosis with myelofibrosis: clinical, immunophenotypic and cytogenetic study of twelve cases.

The clinical, cytogenetic, and immunophenotypic features in 12 adult patients with acute panmyelosis with myelofibrosis (APMF; ICD-0-3: 9931/3; C42.1) are reported (median age: 57 years; f/m = 1.4). The white cell count (WBC) was normal in 3 patients; 9 had leucopenia. The median hemoglobin value was 64.5 g/l, and median platelet count 12 x 10(9)/l. Bone marrow biopsy showed a hypercellular marrow in 10/12 patients with a significant infiltration of pathological blasts (range: 30 - 60%). All the cases had marked reticulin fibrosis. Immunophenotyping of bone marrow blast cells showed the expression of early (CD34) and lineage-unspecified antigens (HLA-DR) in 6/7, and 7/7 patients, respectively. "Early" myeloid antigens (CD13, CD33) were seen in 6/7 and 4/6 patients respectively. Monocyte antigen (CD14) was expressed in 3/7 patients. Megakaryocyte antigen (CD61) and erythroid cell antigen (GpA) were each expressed in only 1 patient. Two patients had expression of CD34, HLA-DR and "early" myeloid antigens by their bone marrow blast cells and 1 of these also had a co-expression of the antigens from a differentiated monocytic cell proliferation (lysozyme+, CD68+). Nonspecific chromosomal aberrations were recorded in 8/10 patients. The median survival was 2 months. These findings suggest an immature myeloid phenotype of blast cells in APMF. In 6/9 patients a leukemic cell differentiation into monocytic, megakaryocytic or erythroid lineage was also demonstrated.

Adolescent↗