Analysis of immunohistochemical markers in bone marrow sections to evaluate for myelodysplastic syndromes and acute myeloid leukemias.

BACKGROUND: Accurate bone marrow (BM) blast counts (BCs) are essential for diagnosis (dx) of myelodysplasia (MDS), MDS/myeloproliferative (MDS/MPD) disease, or acute myeloid leukemia (AML), and may be difficult in hemodiluted bone marrow aspirates (BMAs). Erythroid precursors (EPs) may be indistinguishable from myeloblasts in BM sections (aspirate clots/cores). We compare the usefulness of immunohistochemistry (IHC) [ie, CD34, CD117, myeloperoxidase (MPO), Hemoglobin A1 (HbA1), and terminal deoxynucleotidyl transferase (TdT)] of BM sections (IHC-BM) with BMA, bone marrow touch preparation (BMTP), and flow cytometry (FC) BCs. DESIGN: The initial BC (48), percentage (%) of Eps (38) (both based on initial 100 to 600-cell counts), and FC expressions of CD34, CD117, Glycophorin A(GLY A), and TdT (44) were tabulated from 50 BMs (MDS, MDS/MPD, or AML). BMAs (48) and BMTPs (25) subsequently received 500-cell counts. IHC-BM was performed (45:formalin, 5:B5-fixed) [CD34 (46), CD117 (45), HbA1 (45), TdT (42), and MPO (45)]. RESULTS: Retrospective BMA BCs revealed a 31% (15/48) discrepant rate between the original/retrospective BMA BCs; 80% revealed an underestimated initial BC. There was a 28% discordance rate between the retrospective BMA and BMTP reviews; 77% showed a higher BMTP BC. IHC showed significantly higher BCs in 19% (9/47), resulting in a different dx (5). However, CD34 and CD117 IHCS revealed lower BCs in 38% and 48%, respectively. The CD34 IHC results were primarily due to CD34-negative blasts by FC. The CD117 IHC results were largely unexplained. EPs were CD34 and CD117-negative. CONCLUSIONS: (1) Evaluation for MDS/AML requires 500-cell counts of BMAs and/or BMTPs. (2) CD34 and/or CD117 blasts by FC indicate IHC-BM may increase BC accuracy. (3) CD34 is more reliable than CD117 by IHC; however, in combination, they are most reliable and should be performed on BM clots/cores due to variable reactivity.     

Comparison of CD34+ subsets and clonogenicity in human bone marrow, granulocyte colony-stimulating factor-mobilized peripheral blood, and cord blood

To compare the clonogenicity and distribution of CD34+ subsets in bone marrow (BM), granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood (PB) and cord blood (CB), we analyzed in vitro colony formation and CD34+ cells co-expressing differentiation molecules (CD38, HLA-DR), myeloid associated molecules (CD13, CD33), a T-cell associated molecule (CD3), and a B-cell associated molecule (CD19) from mononuclear cells (MNCs) in the three compartments. The proportions of CD34+CD38- cells (BM: 4.4+/-2.8%, PB: 5.3+/-2.1%, CB: 5.9+/-3.9%) and CD34+HLA-DR cells (BM: 4.7+/-3.4%, PB: 5.5+/-2.3%, CB: 6.1+/-3.7%) did not differ significantly among the compartments. In contrast, a significantly higher proportion of CD34 cells of PB and CB co-expressed CD13 (75.0+/-11.4%, 77.7+/-17.3%) and CD33 (67.1 +/-5.7%, 56.8+/-10.3%) compared with those of BM (43.0+/-6.3%, 27.6+/-5.1%) and a significantly higher number of granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were detected in MNCs derived from PB and CB compared with those from BM (p<0.01). The proportion of CD34+CD19+ cells was higher in BM (34.9+/-11.9%) than those in PB (5.6+/-3.0%) and CB (4.7=2.1%) (p<0.05). The proportion of CD34+CD3+ was comparable in all three compartments. In conclusion, our findings show that MNCs of mobilized PB and CB display similar phenotypic profiles of CD34+ subsets and clonogenicity, different from those of BM.     

Usefulness of anti-CD117 in the flow cytometric analysis of acute leukemia

We assessed the diagnostic usefulness of adding anti-CD117 to our existing flow cytometric profile in the analysis of 150 consecutive cases of acute leukemia (de novo or relapsed acute myelogenous leukemia [AML], AML arising in myelodysplastic syndrome, blast crisis of chronic myelogenous leukemia [CML], acute lymphoblastic leukemia, acute unclassifiable leukemia, and biphenotypic leukemia). CD117 was expressed on more than 10% of blasts in 64% of de novo AMLs (42/66), 95% of relapsed AMLs (19/20), 75% of AMLs arising from a myelodysplastic syndrome (6/8), and 25% of myeloid blast crisis in CMLs (1/4). CD117 was not expressed in acute lymphoblastic, acute biphenotypic, or unclassified leukemia or lymphoid blast crisis of CML. The specificity, positive predictive value, sensitivity, and negative predictive value of CD117 for AML were 100%, 100%, 69%, and 62%, respectively. CD117 is a specific marker for myeloblastic leukemias. Sensitivity is greatest in French-American-British M2 and relapsed AML. Intensity of CD117 expression is dim. Despite the high specificity and positive predictive value, the addition of anti-CD117 to our panel did not prove essential for the assignment of blast lineage.     

Homing-associated cell adhesion molecules and cell cycle status on the nucleated cells in the bone marrow, mobilized peripheral blood and cord blood

Homing-associated cell adhesion molecules (H-CAM) on the CD34+ cells play an important role for the engraftment process following hematopoietic stem cell transplantation (HSCT). However, it seems that not only CD34+ cells but also other nucleated cells (NCs) with H-CAM could be implicated in the engraftment process and the proliferation of hematopoietic stem cells. We investigated the differences of HCAM and cell cycle status on the NCs in cord blood (CB), bone marrow (BM), and mobilized peripheral blood (PB). The proportions of CXCR4+ cells within the NC populations were greater in CB than in PB or BM (p=0.0493), although the proportions of CXCR4+, CD44+, and CD49d+ cells within the CB CD34+ cell populations were same within BM or PB. A lower proportion of CD34+CD49d+ cells within the CD34+ cell populations was more noted in CB than in PB or BM (p=0.0085). There were no differences in cell cycle status between CB and BM or PB. Our results suggest that the migrating potential of CB would be enhanced with increased CXCR4 expression on the NCs, but the adhesion potential of CB CD34+ cells would be less than that of PB and BM. These findings may help explain why the lower cell dose is required and engraftment is delayed in cord blood stem cell transplantation.     

Leukemias resembling acute promyelocytic leukemia, microgranular variant

Acute promyelocytic leukemia (APL) should be distinguished from other subtypes of acute myeloid leukemia (AML) because of the increased risk of disseminated intravascular coagulation (DIC) and its response to arsenic compounds and retinoids. Some cases of AML seem morphologically similar to the microgranular variant of APL (French-American-British [FAB] AML-M3v) but lack the t(15;17). We evaluated 8 cases of APL-like leukemias for subtle morphologic, cytochemical, immunophenotypic, and cytogenetic differences compared with 5 cases of promyelocytic leukemia/retinoic receptor alpha (PML/RARalpha)-positive APL (FAB AML-M3v). We also evaluated both groups for the presence of DIC. No differences among the groups were noted in blast size, chromatin pattern, nuclear morphologic features, intensity of myeloperoxidase staining, or presence of Auer rods. Immunophenotypes were similar; both types of cases lacked CD34 and HLA-DR and were CD13+ and CD33+. Two cases of APL-like leukemias also were CD56+. DIC was present in 2 patients with M3v. Our study shows that there are no definitive morphologic, cytochemical, or immunophenotypic findings that can distinguish these cases from PML/RARalpha-positive APL.     

Quantitative expression of the adhesion receptors VLA-4, VLA-5, L-selectin, MAC-1, and ICAM-1 on the surface of CD34+ cells]

The aim of this work was to quantify by flow cytometry the main adhesion receptors on CD34+ cells. These cells were isolated from bone marrow (BM) or mobilized peripheral blood (PB). The proportions of CD34+/CD49d+ and CD34+/CD49e+ are weaker on PB cells, without quantitative expression variation. This phenotypic variation may induce CD34+ cells exist from BM into circulation, promoting the mobilization. The homing to the BM implicate the CD62L receptor, which expression was found more frequently and stronger on PB cells than on BM. The CD11b, CD18 and CD54 receptors are implicated in CD34+ cells adhesion to BM micro-environment. No significant variation in CD34+/CD11b+ and CD34+/CD18+ cells frequency was noted. Moreover, CD54 receptor was more frequently expressed on PB cells. Quantitative analysis revealed that CD18 was more strongly expressed on BM than on PB cells. This quantitative variation could promote progenitor adhesion by interacting with stromal cells. Finally, quantitative expression of the main receptors on CD34+ cells provides an original option for studying CD34+ cells during the mobilization, the homing or the adhesion to BM micro-environment.     

Immature leukemic CD34+CXCR4+ cells from CML patients have lower integrin-dependent migration and adhesion in response to the chemokine SDF-1

Chronic myelogenous leukemia (CML), a malignant myeloproliferative disorder originating from a pluripotent stem cell expressing the bcr-abl oncogene, is characterized by abnormal release of the expanded, malignant stem cell clone from the bone marrow (BM) into the circulation. Moreover, immature CD34+ CML cells have lower adhesion to stromal cells and fibronectin as well as lower engraftment potential in severe combined immunedeficient (SCID) and nonobese diabetic (NOD)/SCID mice than normal CD34+ cells. We report in this study that leukemic Philadelphia chromosome-positive (Ph+)CD34+ cells from newly diagnosed CML patients that express the chemokine receptor CXCR4 migrate in response to stromal-derived factor-1 (SDF-1). However, normal Ph-CD34+CXCR4+ cells derived from the same patient have significantly higher migration levels toward SDF-1. In contrast to their transwell migration potential, the SDF-1-mediated integrin-dependent polarization and migration of the Ph+CD34+CXCR4+ cells through extracellular matrix-like gels were significantly lower than for normal cells. Concomitantly, binding of these cells to vascular cell adhesion molecule-1 or fibronectin, in the presence of SDF-1, was also substantially lower. These findings suggest a major role for SDF-1-mediated, integrin-dependent BM retention of Ph+CD34+ cells.     

Cell cycle-dependent change of the adhesive character of CD34+ progenitor cells and their VLA-4 expression]

We identified the cell cycle status of CD34+ cells of steady-state bone marrow (BM) and peripheral blood (PB) obtained from healthy volunteers, and those of BM and apheresis PB samples collected from donors who had been administered granulocyte colony-stimulating factor (G-CSF). Regardless of whether G-CSF treatment was undergone, more than 10% of CD34+ cells in the BM was in the S + G2/M phase. In contrast, less than 2% of CD34+ cells in the PB was cycling. After co-culturing BM CD34+ cells with a monolayer of the stromal cell line MS-5 for 1 hour, some cells adhered to the stroma. The percentage of cells in the S + G2/M phase among these adherent cells was higher than that among the non-adherent cells. Flow cytometric analysis revealed that CD34+ cells in mobilized PB expressed less VLA-4 than those in BM and that in in vitro-cultured non-adherent cells exhibited a lower level of VLA-4 expression than adherent cells. In addition, CD34+ cells in the G0/G1 phase expressed lower levels of VLA-4 than those in the S + G2/M phase. These findings suggested that the reduced expression of adhesion molecules such as VLA-4 by the progenitor cells in the G0/G1 phase of the cell cycle result in the release of progenitor cells from the hematopoietic microenvironment to peripheral blood.     

CD7、CD56共表达对急性髓系白血病侵袭性的影响

目的:探讨CD7和CD56共表达免疫表型对急性髓系白血病（acute myelocytic leukemia,AML）侵袭性的影响。方法:采用多色流式细胞术检测AML患者免疫表型,对6例CD7⁺CD56⁺AML患者和6例CD7^-CD56^-AML患者进行临床资料比较和无病生存（disease-free survival,DFS）率随访。结果:CD7⁺CD56⁺AML在M₀+M₁分型中的分布比例、外周血血红蛋白、骨髓原始细胞比例、中枢系统浸润率均高于CD7^-CD56^-AML,差异具有显著统计学意义（P<0.01或P<0.05）;但平均无病生存期低于CD7^-CD56^-AML,差异具有显著统计学意义（P<0.01）。结论:AML中检出CD7、CD56的共表达的免疫表型意味着预后较差,需加强巩固治疗和中枢系统微小残留病灶监测。     

CDCP1 identifies a broad spectrum of normal and malignant stem/progenitor cell subsets of hematopoietic and nonhematopoietic origin

CUB-domain-containing protein 1 (CDCP1) is a novel transmembrane molecule that is expressed in metastatic colon and breast tumors as well as on the surface of hematopoietic stem cells. In this study, we used multiparameter flow cytometry and antibodies against CDCP1 to analyze the expression of CDCP1 on defined hematopoietic cell subsets of different sources. In addition, CDCP1 expression on leukemic blasts and on cells with nonhematopoietic stem/progenitor cell phenotypes was determined. Here we demonstrate that a subset of bone marrow (BM), cord blood (CB), and mobilized peripheral blood (PB) CD34+ cells expressed this marker and that CDCP1 was detected on CD34(+)CD38- BM stem/progenitor cells but not on mature PB cells. Analysis of leukemic blasts from patients with acute lymphoblastic leukemia, acute myeloid leukemia, and chronic myeloid leukemia in blast crisis revealed that CDCP1 is predominantly expressed on CD34(+)CD133+ myeloid leukemic blasts. However, CDCP1 was not strictly correlated with CD34 and/or CD133 expression, suggesting that CDCP1 is a novel marker for leukemia diagnosis. Stimulation of CD34+ BM cells with CDCP1-reactive monoclonal antibody CUB1 resulted in an increased (approximately twofold) formation of erythroid colony-forming units, indicating that CDCP1 plays an important role in early hematopoiesis. Finally, we show that CDCP1 is also expressed on cells phenotypically identical to mesenchymal stem/progenitor cells (MSCs) and neural progenitor cells (NPCs). In conclusion, CDCP1 is not only a novel marker for immature hematopoietic progenitor cell subsets but also unique in its property to recognize cells with phenotypes reminiscent of MSC and NPC.     

Rhodamine 123 efflux in human subpopulations of hematopoietic stem cells: comparison between bone marrow, umbilical cord blood and mobilized peripheral blood CD34+ cells

Hematopoietic stem cells (HSC) can be identified by the expression of the CD34 molecule. CD34+ cells are found in bone marrow (BM), umbilical cord blood (UCB) and in mobilized peripheral blood (PB). CD34+ cells express P-glycoprotein (Pgp), a product of the multidrug resistance (MDR) gene. Pgp activity can be measured by the efflux of the dye Rhodamine 123 (Rho 123) and can be blocked by verapamil. Transport activity in HSC suggests that Pgp could have a functional role in stem cell differentiation. This study compared the number of CD34+ cells with Pgp activity measured by efflux of Rho 123 in the hematopoietic population obtained from different sources. Samples were analysed for their content of CD34+ cells, and BM had a significantly higher amount of CD34+ cells compared to UCB, mobilized PB and normal PB. When the frequency of Rholow cells was studied among the CD34+ population, an enrichment of cells with Pgp activity was observed. The frequency in BM was significantly lower than that in UCB and mobilized PB. The low retention of Rho 123 could be modified by verapamil, indicating that the measurements reflected dye efflux due to Pgp activity. Although UCB and mobilized PB had a lower number of CD34+ cells compared to BM, the total number of CD34+ cells with Pgp activity was similar in the three tissues. The different profiles may indicate the existence of subpopulations of stem cells or different stages of cellular differentiation detected by the extrusion of the dye Rho 123.     

The incidence of trisomy 8 as a sole chromosomal aberration in myeloid malignancies varies in relation to gender, age, prior iatrogenic genotoxic exposure, and morphology

Although trisomy 8 as a sole change is one of the most common chromosomal abnormalities in myeloid malignancies, it is largely unknown if the incidence of this aberration is influenced by other factors of clinical importance. In the present study, the frequencies of isolated +8 in relation to gender, age, previous treatment with chemo- or radiotherapy, and morphologic subtype were ascertained in published, as well as in our own unpublished, cases of acute myeloid leukemia (AML; n=4,246), myelodysplastic syndromes (MDS; n=1,817), and chronic myeloproliferative disorders (MPD; n=530). The frequencies of +8 were higher in MDS and MPD than in AML (7.5% vs. 5.6%; P<0.01) and varied among the morphologic subtypes of AML and MDS (P<0.001 and P<0.05, respectively). Trisomy 8 was more common in women than in men with MPD (11% vs. 5.1%; P<0.05). Furthermore, the frequencies of +8 were higher in de novo AML and MDS than in treatment-related cases (6.0% vs. 2.8%; P<0.01 and 8.6% vs. 1.5%; P<0.001, respectively). The incidence also varied significantly with age in AML (P<0.001), being more common in elderly patients. Although the causes for this frequency heterogeneity remain to be elucidated, possible explanations may include different environmental exposures affecting the origin of +8 in AML, MDS, and MPD and the presence of different underlying cryptic primary aberrations.     

再生障碍性贫血患者淋巴细胞表型变化

目的：研究再生障碍性贫血（AA）患者骨髓（BM）及外周血（PB）淋巴细胞及其活化相关分子的表达及临床意义。方法：采用单色和双色免疫荧光标记法，流式细胞仪分析AA患者的BM和PB中淋巴细胞膜分子的表达。结果：AA患者BM和BP中CD8^ 细胞增加，CD4／CD8比例下降，BM在CD25^ 细胞和HLA－DR^ 细胞增多，急性AA增加尤为显著（P＜0．01），BM中CD16^ 或CD56^ 细胞也明显增多（P＜0．05），双标记分析提示T细胞主要为CD8^ 细胞：急性AA患者CD8^ -CD25^ 细胞显著增多（P＜0．01），AA患者BM中淋巴细胞活化相关分子表达增多，尤其4－1BB^ ,CD95L^ 和CD40L＋细胞显著增多（P＜0．01），结论：AA患者BM中淋巴细胞活化相关膜分子增多，是AA免疫功能异常及最终导致造血功能衰竭的原因之一。     

Successful remission rates and survival after lymphodepleting chemotherapy and donor lymphocyte infusion for relapsed hematologic malignancies postallogeneic hematopoietic cell transplantation

Few therapeutic strategies exist for hematologic malignancies relapsing post allogeneic hematopoietic cell transplantation. We present outcomes on 35 patients with nonchronic myelogenous leukemia (CML) hematologic malignancies, the majority having acute myelogenous leukemia (AML) or myelodysplastic syndromes/myeloproliferative disorders (MDS/MPD) (n = 22) receiving lymphodepleting chemotherapy followed by donor lymphocyte infusion (DLI) at 2 T cell dose levels (0.5 and 1.0 × 10(8) CD3/kg). Forty-nine percent of patients achieved complete remission (CR), with a median duration of remission of 6 months (range: 2-71+). CR rates were similar between the 2 groups. The incidence of acute graft-versus-host disease (aGVHD) of any grade was 49%. We saw a higher incidence of grade II-IV aGVHD, with a rate of 66% using the higher-dose DLI (grade III, 33% and grade 4, 20%) versus only 25% (10% grade III-IV) with the lower-dose DLI (P?= .06). Overall survival at 1 and 2 years was 30% (95% confidence interval [CI], 16%-45%) and 19% (95% CI, 8%-34%); however, for those achieving CR, 1- and 2-year survival was improved at 44% (95% CI, 20%-66%) and 28% (95% CI, 8%-52%) (P = .03), respectively. These results demonstrate that DLI after lymphodepleting chemotherapy for relapsed hematologic malignancies results in frequent CRs. The lower DLI dose regimen improved the tolerability of this therapeutic approach, with modest rates of severe aGVHD.     

The immunophenotype of 325 adult acute leukemias: relationship to morphologic and molecular classification and proposal for a minimal screening program highly predictive for lineage discrimination

Bone marrow cells of 325 adults with acute leukemia were immunophenotyped using a panel of monoclonal antibodies proposed by the European Group for the Immunological Characterization of Leukemias (EGIL). Of these, 97.2% could be assigned clearly to myeloid or lymphoid lineage (254 acute myeloid leukemias [AMLs], 48 B-cell lineage acute lymphoblastic leukemias [ALLs], 14 T-cell lineage ALLs), 1.8% as biphenotypic, and less than 1% as undifferentiated. Immunologic subtyping of ALLs revealed an association between early precursor phenotypes and coexpression of myeloid antigens, particularly CD15/CD65s coexpression and pre-pre-B cell-specific phenotypes and genotypes. The common ALL phenotype was associated with BCR-ABL translocation. Among AMLs, CD2 coexpression was almost exclusively restricted to French-American-British subtypes M3 variant and M4Eo and related molecular aberrations. The most valuable markers to differentiate between myeloperoxidase-negative AML subtypes M0 and ALLs were CD13, CD33, and CD117, typical of M0, and intracytoplasmic CD79a, intracytoplasmic CD3, CD10, and CD2, typical of B cell- or T cell-lineage ALL. Our results confirm excellent practicability of the EGIL proposalfor immunologic classification of acute leukemias. For myeloperoxidase-negative AMLs, we suggest a scoring system based on markers most valuable to distinguish between AML-M0 and ALLs.     

Pretreatment CD34+/CD38– Cell Burden as Prognostic Factor in Myelodysplastic Syndrome Patients Receiving Allogeneic Stem Cell Transplantation

Myelodysplastic syndrome (MDS) is a highly heterogeneous clonal hematopoietic disorder. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment and is of particular interest in patients at high risk for progression to acute myeloid leukemia (AML). In MDS, CD34⁺/CD38^– cells possess MDS stem cell potential, and secondary AML (sAML) clones originate from the MDS disease stage. However, the prognostic impact of the pretreatment stem cell population burden in MDS remains unknown. We retrospectively analyzed the prognostic impact of the pretreatment CD34⁺/CD38^– cell burden in 124 MDS patients who received allogeneic HSCT at our institution. A high pretreatment bone marrow CD34⁺/CD38^– cell burden (≥1%) was associated with worse genetic risk and a higher incidence of blast excess. Patients with a high CD34⁺/CD38^– cell burden had a significantly higher cumulative incidence of MDS relapse, a higher cumulative incidence of secondary AML, and a trend for shorter overall survival after allogeneic HSCT. In multivariable analyses this prognostic impact was shown to be independent of other clinical and cytogenetic risk factors in MDS. Patients suffering MDS relapse or progression to AML also had a higher pre-treatment CD34⁺/CD38^– cell burden as a continuous variable. The observed prognostic impact is likely mediated by MDS stem cells within the CD34⁺/CD38^– cell population initiating MDS relapse or progression to AML. New therapeutic strategies targeting MDS stem cells might improve outcomes.     

In vivo expansion of hemopoietic stem cells

Under conditions of steady-state hemopoiesis, a small fraction of immature hemopoietic cells, including stem cells, circulates in peripheral blood (PB). In rhesus monkeys, a median number of 1.2 x 10(7)/l CD34+ cells was observed as opposed to a median number of 1.5 x 10(9)/l in aspirated bone marrow (BM). The concentration of circulating CD34+ cells is therefore approximately two logs less than that in BM. Since a 4-kg rhesus monkey has an estimated number of 3 x 10(10) BM cells and approximately 300 ml of blood, the fraction of CD34+ cells that circulates can be estimated at approximately 0.4% of the total pool of CD34+ cells. During hemopoietic reconstitution following a cytotoxic insult such as results from a midlethal dose of TBI, PB CD34+ cell numbers appeared to be correlated to those of BM, suggesting that PB CD34+ cells may reflect reconstitution of BM CD34+ cells. Reconstitution of BM immature cells can be accelerated by treatment with pharmacological doses of growth factors, resulting in largely expanded immature cell populations within a few weeks after TBI. Growth factors observed to exert such an effect included, notably, thrombopoietin. Such an acceleration can be monitored by daily assessment of circulating CD34+ cells. Expansion of immature circulating cells indicates expansion of similar cells in the bone marrow rather than growth factor-induced selective mobilization of immature cells.     

Expression of leukemia-associated antigen, JL1, in bone marrow and thymus

The identification of immunophenotypic markers with restricted expression has long been a critical issue in diagnostic and therapeutic advances for acute leukemias. We previously developed a monoclonal antibody against a new thymocyte surface antigen, JL1, and showed that JL1 is expressed in the majority of acute leukemia cases. In this study, using multiparameter flow cytometric analyses, we found that JL1 was uniquely expressed in subpopulations of normal bone marrow (BM) cells, implying the association of JL1 with the differentiation and maturation process. Although CD34(+) CD10(+) lymphoid precursors and some of maturing myeloid cells express JL1, neither CD34(+) CD38(-/lo) nor CD34(+) AC133(+) noncommitted pluripotent stem cells do. As for the myeloid precursors, CD34(+) CD33(+) cells do not express JL1. During lymphopoiesis, JL1 on the earliest lymphoid precursors disappear in the CD20(+) sIgM(+) stage of B-cell development or after CD1a down-regulation in thymocytes. Despite the highly restricted expression of JL1 in normal BM cells, most of the leukemias express JL1 irrespective of their immunophenotypes. These results indicate that JL1 is not only a novel differentiation antigen of hematopoietic cells, but also a leukemia-associated antigen. Therefore, we suggest that JL1 be a candidate molecule in acute leukemia for the diagnosis and immunotherapy that spares the normal BM stem cells.     

The generation of human innate lymphoid cells is influenced by the source of hematopoietic stem cells and by the use of G‐CSF

NK cells play a central role in the haploidentical HSC transplantation (HSCT) to cure high‐risk leukemias. Other innate lymphoid cells (ILCs) have been proposed to exert a protective role in graft‐versus‐host disease and could also contribute to anti‐microbial defence and to lymphoid tissue remodeling. Thus, we investigated the ILC differentiation potential of HSCs isolated from BM, mobilized peripheral blood (PB), and umbilical cord blood (UCB). BM CD34⁺ cells are enriched in lymphoid‐committed precursors, while PB CD34⁺ cells preferentially contain myeloid precursors. In vitro differentiation experiments revealed that the highest and the lowest CD56⁺CD161⁺ ILC recovery was detected in UCB and PB HSC cultures, respectively. Among CD56⁺CD161⁺ ILCs, the ratio between NK cells and ILC3s was similar for all HSC analyzed. ILC recovery in PB CD34⁺ cultures was lower for G‐CSF‐mobilized HSCs (good mobilizers) than for G‐CSF+plerixafor‐mobilized HSC (poor mobilizers). Moreover, G‐CSF inhibited in vitro ILC recovery and the degree of inhibition was proportional to the time of exposure to the cytokine. Thus, although all common sources of HSC for transplant differentiate towards ILCs, substantial differences exist among different sources and G‐CSF may influence ILC recovery. These data offer new clues for a better understanding of the immune reconstitution after HSCT.